Liquid Rubber for Concrete Stone Molds

Ensuring you have the right liquid rubber material to make concrete stone molds is important to the success of your project. If you choose just any rubber to make your mold, it may result in damage to your casting or even the mold itself.

Artificial stone castings are not like any concrete project. You wouldn’t use the same rubber for a large formliner or stamping project. Because these materials are more delicate and detailed, they require material that can accommodate the complexity of the original design.

Polyurethane rubber is one of the best molding materials for these applications because of its abrasion resistance. It will hold up to repeated concrete casting without deteriorating quickly. However, as a versatile material, there are many formulas to choose from. You’ll need to look into the material properties to determine the best one for your concrete stone project.

What Properties Affect the Rubber You Choose?

Urethane rubber comes with a handful of important properties that you should look into, including:

• Shore Hardness – A standard tool called a durometer is used to determine a material’s resistance to deformation or indentation. The number tells you whether the rubber will be very soft, hard, or somewhere in between. Typically, for concrete stone projects, you will want to look at rubbers with a Shore hardness below 55 A. If you tried removing a delicate piece from a harder mold, you would most likely see some breakage from the force used to remove it. This force could ruin your casting and your mold. It could also break your original model when removing the mold from the mold box. While hardness is an important property, it’s not the only one that affects the function of the mold.
• Tensile Strength – This property determines how much force it takes to stretch a material before it breaks. Concerning Shore hardness, tensile strength tends to increase as the hardness increases. Having high tensile strength is important when making larger molds so the mold will hold up to large pours of abrasive materials. Molding rubbers with a hardness between 25-55 A will have a lower tensile strength. This isn’t as much of a concern for concrete stone molds, as the mold must be made with thicker walls to ensure durability.
• Elongation – This property determines the length the material can be stretched before it breaks. The elongation of a material is closely related to how flexible it is. Typically, lower durometer rubbers will have better elongation than higher durometer rubbers because they have better flexibility and stretchability. Since concrete stone molds need good flexibility, this would be an important property to consider.
• Tear Strength – This property determines the force needed to initiate a tear. It can be important for some molds if they are roughly handled in the demold process. Big molds or formliners that make concrete panels can tear more easily due to the pulling force initiated by the removal of the casting, which is why they require good tear strength. Because smaller concrete stone molds aren’t normally put through as much stress when demolding, tear strength is less important.
• Flexibility – This isn’t a property with standard testing; it is more so determined by the results of other properties, such as tensile strength and elongation. It’s also related to Shore hardness because if the rubber has a lower hardness or is softer, it will be more pliable. The most desirable thing about a flexible rubber is that it is better at capturing finer details that rigid molds might not be able to. The flexibility is also directly related to how thick you are pouring the rubber. A thinner pour will make a harder rubber more flexible. This is an important feature for most stone mold projects.

Why Use Urethane for Concrete Molds?

Urethane is a desirable material when casting concrete because it has a good variety of properties. These molds will typically be the most durable because of better tear strength and elongation. They also take less skill to make since they are a pourable formula.

They’re a more cost-effective alternative compared to making pourable molds out of materials like silicone. They are extremely reusable, as they can handle the abrasive effects of concrete. You can produce exact replicas of hundreds of artificial stone pieces from a single mold as long as the mold is properly cared for. You also don’t have to worry about shrinkage like you would with a latex mold.

Some silicone rubbers are more desired because they can be brushed onto surfaces to produce the highest detail possible and do not require release from stone. The problem is that it takes a lot more time to make these molds. Plus, they will always need to be backed with a mother mold for support when casting. So, if your concrete project doesn’t have certain requirements that prevent urethane and release from being used, a urethane mold is the way to go.

What Can Low Durometer Concrete Stone Molds Produce?

Liquid rubber is prized for being a versatile material because it can meet your design specifications. There’s not really a limit to the kinds of concrete elements you can produce, including:

Cast Stone

These elements produced from urethane molds are architectural building materials made to look like natural stone. They will typically be 3-dimensional decorative blocks, flat pieces, or other ornamental structures. They add beauty and dimension to homes, commercial buildings, gardens, parks, and plazas. Cast stone is only made for decorative purposes and will not usually offer structural support.

The rubber mold is produced from original stone pieces in the shape of quoins, keystones, cladding, window surrounds, corbels, columns, pillars, coping, capping, and more. Liquid rubber allows you to create a number of the exact same casting and is great for highly customized projects too.

VFI typically recommends using a rubber with a durometer between 25-40 A. Using a softer rubber is crucial for these projects because it ensures easy and complete removal of the casting from any intricate details, shapes, and undercuts without tearing or sticking to the mold.

Manufactured Stone

Manufactured stone castings are 3-dimensional, but typically flat-looking architectural elements. They are also called stone veneers as they are a thin layer of concrete used to decorate the exterior or interior of a building or structure.

These are not stand-alone products. They are applied to a surface like a concrete or wood wall, fireplace, or outdoor kitchen to create or match a desired aesthetic. They can easily be pigmented and will mimic the details of slate, limestone, granite, and other natural stones.

VFI typically recommends using a rubber with a durometer between 30-60 A. These molds are best for mass production of artificial stones. Unlike natural stone, these molds create a standard, repeatable pattern for homes, buildings, and other structures.

Architectural restoration

Architectural restoration projects are the replacement of natural stone pieces on historic buildings. They are extremely delicate, which is why most mold makers choose to use latex or silicone. These rubbers can be brushed onto surfaces to make a mold and do not adhere to the surface like urethane would.

However, VFI has developed Max Release Urethane Rubbers for these exact projects. In the past, you would have had to use enough release to ensure the rubber would demold from the architectural element. With this new formula, less release is required, and you won’t have to worry about damaging the original piece.

Apart from best-in-class release characteristics, the Max Release line also offers premium properties. These rubbers range in durometers from 25-50 A and help minimize damage during the casting process. They put less stress on the casting, allowing for breakage rates as low as 2-3%. So, you protect your castings and make the mold last longer for less material waste.

How Do You Prepare Concrete Stone Molds?

Models used to make urethane rubber molds typically need to be prepared differently than silicone or latex due to their release characteristics. Determine if your model needs to be sealed before you begin the molding process. Porous surfaces will need to be sealed with something stronger than release.

Since most models used to make stone molds are porous, you must seal the stone beforehand. VFI recommends using a combination of 80% mineral spirits to 20% petroleum jelly by volume. Several layers of the sealer should be applied before pouring the molding rubber.

Also, a release agent must always be used on any surface to ensure urethane demolds without issue. Apply the release agent to your model, mold box, and mold when casting.

Contact VFI if you need help choosing the best rubber for your concrete stone mold project.

Why Is My Urethane Mold Deforming?

So, you’ve done everything right in the process of making your mold, but after you’ve demolded it, it’s begun to deform. We’ve seen this happen to urethane rubber users periodically, and there can be several reasons this defect occurs. The biggest reason is time. You’re either demolding your mold or casting into it too quickly.

How you make the mold, use it, and store it can also affect its ability to hold shape over time. Once a mold becomes deformed, its usability is greatly reduced. This leads to a shortened lifespan, which increases production costs and downtime from having to remake the mold. The best way to maintain your mold is by reading the technical data sheet (TDS) and adhering to the instructions and guidelines listed by the manufacturer.

Reasons Your Mold is Deforming

1. Demolding Too Early

Many factors affect how fast your mold cures, including temperature, mold wall thickness, mold size, etc. If you don’t adhere to the recommended guidelines when making your mold, the pot life and demold time can change. If you lose track of them, you may run into issues.

If you demold too soon, the rubber might not have hardened enough to maintain its shape, causing it to warp or deform when you remove it from the mold box. Early removal can also cause damage because it is soft and prone to tearing. Even if the mold seems cured on the surface, it probably hasn’t cured internally.

At this point, since the mold is distorted, your future casting probably won’t be an accurate representation of the original object. If you want to demold it faster, you’ll have to use a faster material.

2. Casting Too Soon After Demolding

Many newer polyurethane users think that once the mold can be demolded, it’s ready to use. However, if you use it right after you pull it out of the mold box or form, you can deform or distort it.

Urethane initially cures after 16 hours and can be demolded, but it still needs to develop the necessary strength for various casting scenarios. Most manufacturers will recommend an additional waiting period after demolding before you use the mold. For products with demold time of 16 hours it is recommended to wait 72 hours.

Note: The longer you wait to cast into your newly made mold, the stronger it will be. Urethane develops full physical properties after 7 days. If you don’t want to wait, heating the mold can typically increase its physical properties faster.

3. Not Storing the Mold Properly

If you aren’t casting into your mold for a length of time, you’ll probably want to store it for later use. Do not store it vertically or on its side. Urethane can distort if it’s not stored on a flat surface. If a corner is curled, the mold is on top of another object, or something is lying on top of it, it may never go back to its original shape.

Also, don’t store it outside or in direct sunlight. Elevated temperatures and UV rays can negatively affect the mold. This may prevent you from getting accurate castings the next time you use it because the mold may have shrunk, expanded, or degraded.

4. Using the Mold in Extreme Temperatures

The type of deformation extreme temperatures cause will not ruin your mold, but it will change its shape. These extreme temperatures cause the mold to change because the rubber will expand and contract with the weather.

In most cases, this change might only be temporary. If the mold has expanded, it’s probably due to high temperatures, but if it has shrunk, it’s probably due to low temperatures. Dimensional changes often occur because you are not using the mold in the same conditions that you made it.

If you are constantly working in extreme temperatures, your mold may never return to its original size. This results in your castings being an inaccurate representation of the original model(s).

Note: Some solvent and oil-based release agents can also cause your urethane mold to expand. Unlike temperature, this will deform the mold permanently and cannot be reversed.

5. Mold Design Does Not Accommodate the Casting Material

Before you even begin to make your mold, you need to consider the design, what materials you are using to make it, and what materials you will be casting into it.

The thickness of your mold walls plays a big part in preventing your mold from distorting. We know you want to save money on material costs, but if you don’t make your walls thick enough, they may bulge in the casting process. Molds with complex shapes are prone to warping as well.

If you’re making a mold with thin walls, you must be sure it will hold up to the material you’re casting into it. Materials like concrete are heavy, and if your mold isn’t strong enough, it will distort during the casting process.

The hardness of the mold can also determine how it might deform if not designed well. If you use a softer rubber (25-45 A), you cannot pour the walls thinner than ¾ – 1 inch thick. Otherwise, it might not accommodate the weight of the casting material, especially if you are casting something big.

Also, thinner areas of the mold can take longer to cure. You might think you’ve given your mold enough time before casting, but it takes a little longer for thinner parts to gain the strength necessary to do so.

Solutions

Take your time, and don’t rush when demolding your newly made mold or casting into it. Check the manufacturer’s TDS to be sure you are following recommended cure times and temperatures.

When making the mold and casting, do so at room temperature (77°F) for the best results. All VFI products are tested with properties obtained at room temperature. Anything outside of that temperature will change the pot life, demold time, and dimensional stability of the rubber.

VFI recommends leaving your demolded urethane mold on a level surface at room temperature (77°F) for an extra 3 days. This will maximize the performance of the mold and allow it to gain enough properties for casting. You’ll be able to repeatedly cast into it without worrying about distortion.

A good rule of thumb is to use a harder rubber when making large castings. This way you can make the mold walls thinner because the rubber will have more tear resistance and can support heavier loads. On the other hand, if you use a softer material, make the mold with thicker walls to help cure it quicker and to give it additional structural support.

Urethane will cure quicker in thicker areas. Be sure you’re following the thickness requirements recommended by the manufacturer to withstand the pressure of casting materials. VFI’s recommended wall thicknesses are listed on every TDS. If you’re pouring under what’s recommended, you’ll need a rubber with a higher Shore hardness.

Since urethane rubber is meant to be reusable, you want to do everything you can to keep using it. The best way to extend the life of your mold is with proper care and storage. That means when you’re not using the mold, you want to store it flat, in a dry, temperature-controlled location, away from direct sunlight.

Do not stack urethane molds on top of or underneath other molds. They might stick to each other, which will require force to tear them apart and weaken the rubber. If you store them in contact with molds made of different materials, this can cause swelling, shrinking, and distortion from the transferring of oils or plasticizers.

Contact VFI if you are still having problems with your urethane mold distorting or if you have other technical issues.

Why Can’t I Remove My Casting from My Urethane Mold?

Some urethane rubber users have run into issues with being unable to remove their concrete casting from their mold. Major reasons this occurs is because a release agent was not used or not enough of it was used to prevent unwanted adhesion.

The casting will stick to the mold, which may lead to the piece breaking or the mold tearing if you have to use excessive force during the demold process. Overall, this results in increased breakage rates, material waste, production loss, and possible loss of the mold.

Reasons Why Your Casting Isn’t Demolding Properly

Reason #1: Not Using Mold Release

Urethane rubber is a unique molding material because of its adhesive characteristics. Unlike silicone or latex, it will adhere to anything. You need to create a barrier by using a release agent so it won’t bond with the surface of the casting.

If you do not use a release agent, you probably won’t be able to get your concrete casting out without breaking it. The adhesive effects of the concrete will also wear or tear your mold making it unusable.

Reason #2: Not Using Enough Mold Release

There’s a fine line between using too much and too little mold release. If you give your surface a light coat or mist of release, it might not be enough to prevent adhesion from occurring. If the mold has complex details or undercuts, you might miss some spots, which allows certain parts of the concrete piece to get stuck.

A torn mold can result from not using enough release because the concrete sticks to and pulls on the mold during removal. If your mold tears when you are demolding, you’re using too much force and stretching it beyond its limit to break the bond.

It’s also important to wait for the release agent to dry before you start casting. Once it is dry, it creates a smooth, effective barrier on the mold surface. If you don’t wait, the release agent might mix with the concrete, preventing the release agent from forming a barrier. Waiting also prevents residue from transferring onto the concrete, which could cause imperfections.

Reason #3: Using the Wrong Mold Release

If the specific release agent you have chosen is incompatible with your polyurethane mold or the concrete you’re casting, it can cause demolding issues. The casting may stick to the surface, tear the mold, or cause imperfections on the surface. Most release agents specify which materials they are compatible with, so it’s important to read the manufacturer’s instructions. Most solvent or oil-based releases will cause issues with urethane.

Reason #4: Choosing the Wrong Mold

Some key things to consider for your concrete casting project are the rigidity or flexibility and the complexity of the mold, including shape, size, details, etc.

You will typically have an easier time removing concrete castings from flexible, less complex molds. If you choose a firm rubber for a project with intricate details or undercuts, you might have trouble removing the casting, resulting in breakage. While most liquid rubbers stretch, over-stretching can cause tears in your mold.

Reason #5: Demolding Too Soon

Sometimes, issues with demolding are as simple as not waiting long enough for the concrete to cure. If the concrete doesn’t have enough time to gain its inherent strength before you demold it, it may be fragile and could break in the process. It also might still be sticky and leave residue in the mold that needs to be cleaned out.

Reason #6: Pigment

Depending on the casting, you may need to use pigment, and depending on the pigment, it can make it harder to demold. There are two styles of pigment, a powder and a liquid pigment. VFI always prefers the use of powder pigment over liquid pigment, because the liquid pigment is usually used for stamps and contains solvents that will attack the urethane rubber. Once the liquid pigment attacks the urethane rubber it will bind the concrete to the mold surface.

Note: Liquid pigment in concrete does not cause the same issue as applying liquid pigment to the surface of the mold.

Solutions

Always read the manufacturer’s instructions before using a product. They can be found on any product page or technical data sheet.

• Make sure you apply a release agent and use the correct kind. Using one will extend the life of your mold and decrease breakage rates. When casting concrete into a urethane mold, VFI recommends using one of Chem-Trend’s water-based releases specifically designed to release these materials from each other. We’ve seen great success with the dilutable CR-19597. The release agent should be applied before each cast to ensure the next one will demold without issue. Do not use an oil-based or biodegradable release, as these can cause the rubber to expand.
• Make sure you’re evenly coating the surface with a release agent, especially in complex and detailed mold areas. You need to find a balance where there’s enough on the surface to make the casting demold with ease but not too much so that it will make the surface shiny. VFI recommends spraying a few coats of a light mist over the mold. Allow the release agent to dry in between each coat and before casting. Consistent reapplication will also help prevent underuse.
• Use a Max Release urethane molding rubber. VFI released a series of low-durometer rubbers that have enhanced release abilities comparable to silicone. The benefit of using these rubbers is that you don’t need as much mold release on the rubber, and less effort is required to demold your casting. Since their hardness ranges from 25-50 A, they also provide better flexibility, allowing you to make more detailed castings without worrying about breakage. Check out the press release for more information.
• Allow the concrete to cure fully before removing it from the mold. The longer you let your material sit in the mold, the longer it has to gain strength. It can typically be removed within 24-72 hours.
• Go slow when removing your casting. People want the demold process to be quick and easy, but depending on the size of your casting, it might take more time and effort to get it out. Additional care should be taken if your casting is extremely detailed because you don’t want those details to break off when you pull the rubber away. Carefully work the edges of the mold to reduce the stress put on the rubber. Do not pull or twist the mold harshly.

Note: For increased reusability of your concrete mold, clean it after each use. Warm, soapy water is typically the best way to clean a urethane mold. It will remove residue and particle buildup, so you start with a clean surface when you’re casting next.

Contact VFI if you’re still having trouble demolding your concrete project so we can assist you.

Why Is My Urethane Rubber Mold Not Drying?

VFI has had customers using two-component urethane rubber come to us saying their material is not drying or curing. From experience and testing, we know this is typically an issue with mixing, mix ratios, or temperature.

To dry or harden liquid urethane, you must measure and combine a precise amount of each liquid component (A and B sides) before mixing thoroughly. The exact combination of materials is the mix ratio, which also helps the material achieve its formulated properties. It can be expressed by weight and/or by volume.

After mixing and once poured into a mold box or form, the material should be left to dry for at least 16 hours at room temperature (77°F) for best results.

Reasons Liquid Rubber Might Not Cure

Do not assume all mix ratios and mixing instructions are the same. The mix ratio varies per product because each material’s precise mixing formula provides the desired performance characteristics and allows it to dry.

If you mix with too little Poly (B side), the material can feel brittle and not as strong. If you mix with too little Iso (A side), the material can feel too soft, tacky, or gooey to the touch.

A change in final properties may occur from using too much or too little of one material. The off ratio mix may also be softer (lower hardness) than it was formulated to be.

Insufficient mixing can also cause drying issues. While some areas of the rubber may harden like normal, you may see tacky or soft streaks that are excessive amounts of A side material or excessive amounts of B side material. Also, it’s important to always premix your B side material to ensure you have an even weight per gallon. This makes it easier to achieve a uniform mix overall.

Also, temperature can play a huge role in the material’s ability to dry. Urethane rubbers cure best at room temperature (77°F). If your material, work area, or molding models are too cold, the mold rubber will take more time to dry. In some cases, it may not dry at all.

It’s important to read the product technical data sheets (TDS). The TDS includes mix ratios, mixing instructions, and molding guidelines. This information helps ensure you’re using the correct amount of each component, working in the best conditions, and mixing thoroughly to prevent drying issues.

Solutions

The best thing you can do if your urethane rubber isn’t drying is to start over. If it hasn’t dried after at least 3 days sitting at room temperature, odds are it never will.

One of the things you can do to limit issues is to pour your A side (Iso) first. It’s better to add more Iso than it is to add too much Poly (B side). If your mix is heavy on the Poly, you’ll never get the rubber off the master or out of the mold box.

An important thing to note is that tacky or sticky material should not ruin your master if the rubber is Iso-rich, and it will be reusable. You won’t have to restart the entire mold making process, which is a win.

To ensure that your material will dry in your second attempt, adhere to precise mix ratios. If you deviate from the suggested mix ratios, whether by volume or weight, your material will not solidify or reach its formulated properties.

Depending on your application, you may benefit from using a mix ratio by weight over a mix ratio by volume, or vice versa. Measuring by weight can have more accurate results as long as you use a working scale.

Bring the material to at least 65°F before use. Work in room-temperature environments with room-temperature equipment when possible.

VFI also recommends using the double bucket mix method when combining liquid rubber. Rather than mixing in a single container and then pouring, you should mix in one container and then pour the material into a clean container to mix again. This is the best way to ensure that unmixed material in the first mixing container will not appear in your final product.

The material should be left for a minimum of 16 hours before demolding. After demolding, allow the rubber to sit for 3 days before use. It will take at least 7 days for the material to develop final formulated properties. If the material is left to dry at lower temperatures, it may take longer.

Sticking to these guidelines will provide the best, most consistent results when pouring urethane molding materials. Plus, it will save you time and money if you don’t have wasted, unusable material.

Contact VFI if you have any further questions on the urethane rubber drying process. If you’re wondering why your urethane rubber mold is bubbling, check out our tech piece here.

Do I Need to Use a Release Agent with Urethane Rubber?

Release agents are required for any application when making a two-part urethane rubber mold to prevent the materials from adhering together. Urethanes have inherent adhesion, which means they stick to just about anything. They will chemically and mechanically lock without release. You would have to use extensive force to break them apart, which could likely tear the mold and break your masters.

A release agent will create a barrier between the liquid rubber and the molding surface. This allows the mold to release easily from the mold box and masters.

What Can You Use as a Release Agent?

The release agent you use when making a mold will depend on the materials you are working with. The release should be specifically formulated for your molding application. Most will be labeled with a list of materials they are compatible with.
When the appropriate material is used, it aids in the demold process, helps produce quality molds, and increases the working life of the mold. There are several types available, including:

• Water-based – environmentally friendly and suitable for a wide range of materials.
• Solvent-based – ideal for use on molds exposed to high temperatures and pressures.
• Silicone-based – versatile and compatible with various materials. When making urethane molds, silicone-based agents are typically used.
• Silicone-free – preferred if silicone interaction is a concern.

How Can Your Rubber Mold Benefit from Using Mold Release?

• Release agents make it easier to remove a newly made mold from a mold box or form. This ease prevents your mold from tearing in the demold process, preventing rework and material waste. An intact mold is important for manufactured stone and advanced detail form liner projects.
• You can also preserve the masters you are using, as these may be more delicate than the material you will be casting to make replicas. The release prevents breakage of the original piece for future use if you have to make new molds.

What Are Some Best Practices for Releasing a Mold Box?

First, use adequate personal protective equipment when making your mold. Gloves, safety glasses, and long sleeves can prevent skin and eye irritation. Follow safety guidelines and instructions provided by the manufacturer.

When making your molds, ensure that your molding surface is clean and dry. Dirt, debris, and other contaminants can affect the function of the mold release and the quality of the mold. The contaminants can transfer over to the finished surface when you begin casting.

Prepare the model(s) you are molding around. Determine if you need to use a sealing agent. Porous surfaces like wood, concrete, stone, plaster, etc., must be sealed first. This will prevent the urethane from penetrating the porous model(s). Allow the sealer to dry before applying release.

Different mold releases can be sprayed, brushed, or wiped onto the mold box or form. Typically, the best method is spraying (aerosol), especially when coating large mold boxes or forms. Brushing on liquid release can be suitable for small projects and detailed areas. However, it’s easy to overapply using this method.

You’ll want to apply several coats to ensure your mold releases from the details on the model(s) with ease. Allow the release to dry before applying another and before you begin pouring the rubber. Also, avoid touching the surface until it has dried, as this could cause defects in the mold.

After demolding, clean the mold with detergent or solvent to remove residue from the mold box or form. This will ensure that is ready for use when you begin casting.

What Are Common Issues When Making the Mold?

When making a urethane mold, do not use a water-based release, as urethane is sensitive to moisture and will bubble. We also recommend avoiding the use of shellac. We’ve seen issues with this material where users will also apply another solvent or mineral spirits, which makes the shellac soft. When the rubber is poured, it will bond with the shellac and fail to demold.

Avoid overapplying the release to the point where it is dripping or pooling. Using more is not better and can affect the quality of the mold. Common problems with overuse include air bubbles and a glossy finish. That glossy finish will then transfer over to your future castings.

What Release Agents Does VFI Recommend When Making the Mold?

VFI recommends the silicone-based MR-515 Mold Release for non-porous surfaces when making urethane molds. Sprayable materials are the easiest and least time-consuming to use.

Shake the can and hold it about 8-10 inches from the molding surface. Spray evenly in a sweeping motion to prevent unwanted adhesion. Generally, you should apply a few coats before pouring the rubber. This will protect and extend the life of your mold.

If your models are porous, use a sealer before the release agent. We recommend a combination of 80% petroleum jelly to 20% mineral spirits by weight to seal those surfaces. Apply several coats of the sealer with a chip brush. Wait for each coat to dry before applying another. Then, apply a light mist of MR-515 over the model(s) and the non-porous areas of the mold box or form.

Some polyurethane rubbers require less release. This is a desirable feature for projects like architectural restoration since using a certain amount can diminish intricate details. VFI offers a line of lower durometer urethane rubbers with enhanced demold characteristics. They are the closest you can get to silicone release properties in a urethane.

Check out our press release for more information.

Contact VFI if you need further assistance with mold release for urethane rubber.

Why Are There Bubbles in My Urethane Rubber?

We’ve come across urethane rubber users in the past who have wondered why there are bubbles in their molds. Bubbles can present themselves in urethane rubber for various reasons, with the biggest one being moisture.

Polyurethane is a very moisture sensitive material, so if it finds its way into your mold-making process, it can create issues. The good news is that most moisture sources that cause bubbles can be controlled.

Reasons Bubbles Form in Urethane Rubber

Bubbles that appear in your finished piece can diminish details and transfer over to future castings, which is why it’s important to prevent them from forming. The following should be avoided:

1. Humidity

Working in a hot, humid environment is not good for your rubber material. The second you open the A (Iso) and B side (Poly) containers, moisture will try to find its way in. The longer these materials are left to sit, even when unmixed, the more they will absorb moisture.

Humidity can be especially detrimental if the material has a long working time. If your rubber is left to cure in these conditions, the material will continue to react with the moisture in the environment, which will lead to foaming or bubbling. These defects will then remain in the rubber once it has dried.

2. Wet Molding Surface & Porous Masters

Again, because urethane is moisture sensitive, if you see bubbles on the surface of your rubber once you’ve demolded it, it means that something was on the surface that caused it.

If your molding surface is wet or you’re using porous masters (plaster, concrete, gypsum, etc.) without properly sealing them, you might discover bubbles on the surface of the rubber.

3. Wet Mixing Equipment

If your mixing equipment (buckets, mixing sticks, etc.) is wet when you pour your material into it, a moisture reaction will occur. You will notice air bubbles begin to form while you’re mixing.

Air bubbles can also form based on your mixing procedures. If you mix too quickly or for too long, you may introduce more air into your mix. If this happens, pour your material slowly in a thin stream to allow those air bubbles to pop, or degas the material before pouring.

4. Excessive Mold Release

If you see surface defects like tiny pinholes or champagne bubbles in your rubber, you may be using too much mold release. You may also not be waiting enough time for the release to dry before you start casting.

Alternatively, the mold release you’re using could be past its expiration date or poorly mixed, but this will appear as indentations in the rubber and not air bubbles.

Solutions

Always check the technical data sheet for recommendations before using the material. The best thing you can do to avoid bubbles in your material is to work in a room temperature-controlled (77°F) environment. You want the relative humidity to be as low as possible.

While vacuum degassing and pressure potting can be useful in certain mold-making scenarios, it’s not always possible, depending on how much material you’re casting and the size of the mold you are trying to make.

Before you mix and pour the material, make sure your forms and masters are properly released and sealed. VFI recommends sealing porous surfaces with a mixture of 80% mineral spirits to 20% petroleum jelly.

Some people have used polyvinyl acetate (PVA), or Shellac, to seal their masters. However, it is easy to remove it from the surface accidentally. So, if you forget to reapply it, your masters will not be sealed, leading to various issues.

Once any porous surfaces are sealed, you must apply a compatible release agent. VFI recommends Chem-Trend MR-515 or a similar silicone-based release for urethane rubber. Do not use a water-based release agent.

Avoid using too much release and allow it to dry before you pour your rubber. If you use too much release, bubbles may form, or the surface might appear glossy, which will then transfer over to future castings.

Use dry mixing equipment. Plastic and metal mixing equipment is less likely to hold moisture. Mix slowly so you don’t generate more trapped air in the mixture. Once fully mixed, pour it slowly in a thin stream into the lowest point of the form to minimize the formation of air bubbles. Let it flow naturally into the rest of the form.

Avoid repeated opening and closing of the containers as this can also introduce moisture into the A and B side materials. If you plan on storing unused material, you must nitrogen purge each material and close the containers as soon as possible after use. Store the containers in a cool, dry place.

Contact VFI if you have other mold-making issues or check out our other tech pieces.

How Much Liquid Rubber Do I Need to Make a Mold?

Before making a mold, the most important thing to consider is how much liquid rubber you’ll need. Several factors will affect the amount, including the complexity, depth, width, and length of your model(s). Also, consider how thick you want to make your mold to ensure longevity and reusability.

If you use too much rubber, you’ll end up wasting material, but if you use too little, you may run out during the mold-making process and have to scramble to mix up more.

Before you can begin estimating, the first step is making a mold box or form. You must determine how far apart to place your models if you’re molding over multiple objects and the overall mold wall thickness. Then, you’ll have a better understanding of the empty cavities that need filling.

Why Mold Thickness Matters

Mold wall thickness is a critical element in the design of your urethane mold. It considers the thickness of the sides and bottom of the mold. How thick you should pour the rubber is determined by if the mold is going to be supported in a mold box and the number of incuts and intricate details that are present.

All VFI molding rubbers have a minimum pour depth that can be found on our TDI specification sheet or the individual technical data sheet (TDS) for each product. Follow these specifications to have the necessary tear strength of flexibility for proper demold and use of the mold.

Lower durometer rubbers (20-60 A) are softer and more flexible, which is why they must be poured thicker. If they are poured too thin, they can be weak and prone to tearing. They are recommended to be poured ¾ of an inch to 1 inch thick. Molds made of these rubbers are typically used for cast stone and manufactured stone projects.

A thicker mold will prevent the mold from deforming during the casting process and increase tear resistance. Thinner walls might make a flexible mold bulge from the pressure of the casting material. The castings created will not be exact replicas of the original. To prevent this, you would need to build a mold box to keep the mold from deforming.

As the rubber’s durometer increases, the minimum pour thickness decreases. The material is less flexible but will have good tear strength. These higher durometer rubbers (70-90 A) are typically best for larger precast concrete projects like formliners, stamps, or rollers.

Thinner pours (between 3/8 of an inch to ½ an inch) use less material, which also keeps material costs lower. They can be very large, which is why mold makers want them to be as light as possible for easier handling during the casting process.

Note: Thinner pours of urethane can take longer to cure. When less material is used in certain areas, it creates a smaller exothermic reaction. The less heat generated, the slower the material will cure.

Also, as a rule of thumb, we generally recommend pouring at least half of an inch above the tallest point on your master. This will create a thick enough mold bottom that withstands the abrasive effects and weight of materials like concrete.

How To Calculate Mold Size

Once you’ve determined how thick you need to make your mold walls, you can assemble your mold box and find out how much material you need to fill it.

There are a few calculations used to determine how much material you need. First, you need to find the volume of the mold box in cubic inches. Most molds are square or rectangular in shape, so we use the simple math formula length x width x height to determine the volume.

• Formula: L x W x H = volume (cubic inches)

Ex.) Box dimensions: 11 ½ inches x 5 ¾ inches x 2 inches = 132.25 cubic inches (in3)

Once you find your mold box volume, you also have a model(s) inside that will take up space. This will reduce the amount of material you need to fill the space. You can calculate the volume of your model(s) using the same formula.

Ex.) Stone dimensions: 9 ½ inches x 3 ¾ inches x 1 inch = 35.625 in3

If you’re using multiple models, you’ll need to determine the volume of each. You can then add each model volume together to get an overall total model volume.

Once you have both volumes for your mold box and model(s), you’ll need to subtract them from each other to figure out how much of the space needs to be filled.

• Formula: Box volume (cubic inches) – model volume (cubic inches) = total volume of material needed (cubic inches)

Ex.) 132.25 in3 – 35.625 in3 = 96.625 in3

The next thing you’ll need to do is convert your volume into a weight measurement, like pounds (lb). The information you’ll need to do this is specific volume. VFI provides this property for all our products under liquid properties on each product page and technical data sheet. We typically recommend using 26 in3/lb. because it will accommodate some extra material in the event that waste occurs.

You’ll need to divide the cubic volume by the specific volume to determine the total weight of material needed, which means the combination of both A and B side materials.

• Formula: cubic volume ÷ specific volume = weight (pounds)

Ex.) 96.625 in3 ÷ 26 in3 = 3.7 lb. (Part A + Part B)

We would then round that number to a whole number (4 pounds). You would then look at mixed liquid density, also known as weight per gallon, to determine how much material to order. Most of VFI’s rubbers, with the A and B sides combined, are 8-9 pounds per gallon. Because VFI’s rubbers come in 1-gallon kits, 5-gallon kits, drums, or totes, we’d recommend a 1-gallon kit of material for this specific project.

Note: Many people have poured water into their mold box to determine how much material they need. However, this can be risky because urethane is sensitive to moisture. Getting your mold box and models wet can cause adhesion, curing, and bubbling issues. Some models will be very porous, so ensuring they are dry and sealed properly before pouring the rubber is essential.

Accounting for Waste

Material can be lost through accidental spills or as it clings to the sides of mixing containers and mixing equipment. Since waste occurs, it is recommended to add 5-10% more material to your estimate.

In most cases, having more material saves time and money when accounting for this waste. If you don’t have enough material, it might disrupt the mold-making process and create more waste than anticipated.

Contact VFI if you need further assistance determining how much rubber you need to make your molds.

Qwik Spray vs High Pressure Spray for Hard Coat: Which to Use?

The two most common spray methods VFI hard coat products utilize are Qwik Spray and high pressure spray. Spraying, in general, provides applicators with several advantages – speed, uniformity, and reduced labor costs – compared to roller and brush applications.

Those new to spraying can benefit by starting with a cartridge-based applicator. However, it can also be hard to know if it is the best application method for you. There may come a time when your production line could benefit from upgrading to a high-pressure spray rig. Maybe you started making small displays and signs for retail stores but have recently been contracted for bigger work by theme park and attraction companies. VFI has excellent technical and customer service support to guide you when making this important decision.

Note: Always wear proper protective equipment (PPE), including an approved respirator, regardless of what equipment you’re using. Also, utilize a well-ventilated spray booth where necessary.

Qwik Spray Gun Requirements

VFI-6171 70 D Qwik Spray Hard Coat is the cartridge-based polyurethane formula VFI recommends for protecting smaller EPS theming elements. To use the material, you will need a VFI-7500 Qwik Spray Gun capable of holding 750 mL dual cartridges, an air compressor that supplies clean, dry air at a minimum of 100 psi and 10 cfm of constant pressure, and GS-15 Static Mix Tips.

VFI-6171 is stored in cartridges with two separate chambers for the A (Iso) and B side (Poly) materials. The design of the cartridges ensures a precise 1:1 mix ratio by volume that achieves a quality protective finish. Once the trigger is pulled, the components are pushed into and mixed through the static mix tip, which initiates a chemical reaction that cures the material after it exits the tip. The GS-15s have an 11-inch mix tip with a 3/8-inch inner diameter, which creates a fine texture on surfaces.

High Pressure Spray Rig Requirements

VFI-6170 70 D Spray Hard Coat is the high pressure polyurethane formula VFI recommends for protecting larger EPS theming elements. To use this material, you will need a two-component air, electric, or hydraulic sprayer that runs at a minimum of 150-155°F and 2,500 psi of constant pressure, with heated lines. Some spray rigs that accommodate these requirements are:

• Graco A-XP1 air sprayer
• Graco Reactor 2 E-XP2 electric sprayer
• Graco Reactor 2 H-XP2 hydraulic sprayer
• Graco Reactor 2 H-XP3 hydraulic sprayer
• PMC PHX-2 hydraulic sprayer
• PMC PHX-25 hydraulic sprayer

Advantages of Using the Qwik Spray Gun

1. Portability

A big reason the Qwik Spray System is so desirable to many users is because all you need is the lightweight applicator and enough cartridges to cover your piece at the desired thickness. Since this method is typically recommended for smaller projects (under 90 square feet), you’ll probably only need a kit of material, which is just 6 cartridges. With improved portability of the material and equipment, you can go from job to job much easier and aren’t held down to a single location for spraying. Note: This will also be dependent on the size of your air compressor.

2. Cost-effective for Small Projects

If you’re spraying small sculptures, custom signs, scenery, or props for a museum, retail store, theater production, etc., the VFI-6171 formula is preferable. Small projects typically include pieces 4 feet x 6 feet and under. Anything over this size will generate a large amount of overspray. Other small jobs this material can help with are if you need to repair an existing hard coat that has become damaged or adhere large EPS pieces together for a larger project.

The Qwik Spray Gun is more affordable, and while the material might cost more, you’ll save a lot on equipment if you’re not hard-coating massive theming projects. If you want a quality spray rig, they can cost upwards of $20,000-$80,000 or more. The higher end would be for mobile rigs with compressors and generators, so your spray equipment is easier to transport.

3. Better for Minimal Spraying

Many applicators can’t justify the price that comes with high pressure machinery if they are not spraying frequently. The Qwik Spray System is a great alternative if your production only calls for spraying a couple of times per month. However, there are situations where applicators have justified upgrading even if they only spray once a month.

Someone might eventually switch to high pressure if their spray load increases substantially, as they would save upwards of 60% in material costs if they switched from Qwik Spray. Two cartridges are just under a gallon of material and are significantly more expensive than purchasing in gallons or drums.

4. Limited Training Necessary

Another reason users desire the cartridge-based applicator is due to ease of use. Because the machinery is less advanced, applicators don’t need as much training to use it. If you’re new to the Qwik Spray System, check out our how-to-use guide with pictures for easy assembly and tips on spraying.

VFI recommends this spray applicator to get users started when they don’t have any previous experience. It allows applicators who are used to applying coatings with brushes or rollers to experience a low pressure version of spraying. Note: If you’ve never sprayed before, it will take some practice to achieve a consistent, desirable finish.

5. Low Maintenance

A big perk about cartridge-based spray application is that there are no spray lines to clean after spraying. Empty cartridges and static mix tips can be thrown away after use, so there’s limited mess and maintenance. The cartridge-based applicator does not require frequent use to keep it in working condition.

On the other hand, high pressure spray equipment requires a lot of maintenance to prevent downtime from chemical buildup, corrosion, and other factors. You have to clean spray nozzles, pumps, lines, etc. frequently. VFI offers VFI-8005 Pump Flush for cleaning spray lines to prevent material from clogging the equipment. It also has more parts that can wear over time, so it’s important to inspect and replace them to ensure your equipment is in working order.

Advantages of Using a High-Pressure Spray Rig

1. Better for Increased Project Volume

If you’re suddenly spraying almost every day vs a couple of times per month, it may be time to upgrade to a high pressure spray rig. As mentioned, the material costs for a cartridge-based system are more substantial. When you start to notice that you’re buying cases upon cases of cartridges, switching over to drums or totes can make a huge difference.

Note: High pressure spray rigs must be used often to keep them in working condition. If you do not have plans to use the spray rig, you should flush the spray lines so that coating residue is not left to solidify or crystallize.

2. Better for Versatile Spraying

When you have a high pressure spray rig, there’s no limit to the types of jobs you can work on. Whether your carved EPS structure is small, medium, or large, the spray rig will accommodate it.

Another thing that makes high pressure rigs so versatile is that they can be used with different materials. Polyurethane and some hybrids are typically the only material that can be used with cartridge-based equipment. If you’re looking for a material that’s a bit softer than a polyurethane or hybrid coating for your theming project, high pressure polyureas have been used in their place.

3. Better for Fixed Location Spraying

While the portability of the Qwik Spray Gun is desirable, if you’re not going on-site to spray a hard coat, that portability doesn’t always matter. Many theming designers have workshops where they do it all: carve shapes and forms, spray hard coats, and paint over them. These shops typically also have a designated spray booth to contain overspray and protect their work environment and workers from harmful spray fumes.

4. More Control While Spraying

A negative part of the application process when using a Qwik Spray Gun is once you start spraying, you’re not supposed to stop. Continuous spraying is necessary because if the flow is stopped, the coating will clog up in the static mix tip. You need to plan your spray route ahead of time for a consistent, uniform finish. If you want to stop, you’ll have to switch applicator tips before you start again.

With a high pressure spray rig, you can start and stop when you need to. Having control also reduces the amount of material used, so there’s less waste.

5. Improved Cured Surface

Something that tends to be insignificant to some applicators but can save on time and labor costs is how the coatings cure. The high pressure hard coat formula comes out smooth, seamless, and free of blemishes due to the pressure and speed at which the coating exits the applicator. It has less time to interact with the environment, which could cause potential issues.

The Qwik Spray formula, on the other hand, is slower and doesn’t come out of the applicator with as much force. This gives it more time to interact with the environment, which creates a foaming effect from moisture in the air. While the surface irregularities aren’t that noticeable, it will be more textured. This might create more post-work, such as sanding before the application of a top coat can occur.

Contact VFI if you’re still trying to determine whether the Qwik Spray or high pressure hard coat is better for your unique project.

How to Use a Brushable Hard Coat + Testing for Recoat Window

Knowing how to use a brushable hard coat can save you money on labor costs and material waste. Before you begin working with new materials, always read the labels on the supplied containers. If it is difficult for you to read the labels, VFI offers technical data sheets with thorough instructions on every product page under resources.

If you’ve never worked with a brushable hard coat, you can also check out our detailed how-to video here.

Through this article, we will provide various tips for using one of these products. An important aspect of using a brushable hard coat is adhering to the recoat window. So, we also wanted to show you how we test for that.

Preparing Your Foam for Hard Coating

Typically, users apply these coatings to EPS foam. We recommend 2 PCF foam for the best cost-to-quality ratio. Allow the foam to age for 30 days minimum before coating it.

After carving the foam, it must be free of particles that might disrupt adhesion. Clean off the piece with a vacuum or compressed air. Also make sure the piece isn’t damp as this could also affect adhesion.

PPE for Applying Brushable Hard Coats

VFI recommends using personal protective equipment, including gloves, long sleeves, and safety glasses, when working with these materials. Please see the material SDS for more information.

Even though the coating is not sprayed, a respirator is required when sanding. Inhaling or ingesting these materials as particles can be toxic.

If you have a spray booth, it’s a good idea to work inside it while sanding. The fans will help keep the sanded hard coat particles inside the booth and away from your facilities.

Preparing Your Workspace

First off, these materials are sensitive to moisture. It is highly recommended that you work in a temperature-controlled environment around 72°F with low humidity.

If you don’t, bubbles will accumulate during mixing and application. These bubbles will then cure on and in the finished surface. The entire piece will require sanding and a new coat, depending on your desired finish.

Measuring the Materials

These are two component materials with a mix ratio of 1A:3B by volume. Since the B side is thicker and more of it is needed, we recommend measuring that material first. It’s much easier to pour the A side into the B side when ready.

We also recommend measuring how much of each material you need by weight rather than by volume. To do this, you will need an accurate gram scale. It helps you avoid making errors that could occur when measuring by volume.

Another tip when using these coating materials is to never use a full kit of material. Doing so will shorten the working time, which includes the time it takes to mix and apply it.

• VFI-2519 75 D Brushable Hard Coat has a mix ratio of 1A:3.44B by weight. To make calculations easier, we recommend using 100 grams of A side to 344 grams of B side. For an even smaller amount, use 50 grams of A side to 170 grams of B side.
• VFI-2626 65 D Brushable Hard Coat has a mix ratio of 1A:3.55B by weight. To make calculations easier, we recommend using 100 grams of A side with 355 grams of B side. For an even smaller amount, use 50 grams of A side to 175 grams of B side.

Note: when you’ve set aside the material you will be using, nitrogen purge both containers before closing them to extend the life of the unused material. You can find nitrogen purge kits on Amazon if you don’t have one readily available.

Mixing the Components

The second the materials touch, a reaction occurs, and the pot life begins. You’ll want to mix them using the double-bucket mix method. We recommend using a 1-gallon paint stir stick. You can find them at any home improvement store. Make sure to scrape the sides and bottom of the mixing container. Once you are done mixing in one container, pour the material into a new, clean mixing container and mix again.

It’s somewhat easy to tell when you’re done mixing because of how different the materials look. The Iso (A side) is very dark, and the Poly (B side) is very light. When the combined material is a uniform, neutral color, you’ve probably mixed it thoroughly and can begin applying it. You don’t want streaks of either material in the mix; otherwise, areas in the coating will be tacky and may never cure.

Applying the Brushable Hard Coat

When applying the material, use a non-shedding chip or foam brush. You can use a roller if you desire, but it must be a sponge roller, not a nap roller.

If you’re applying it to non-horizontal surfaces, you’ll want to wait a few minutes for the material to thicken so it doesn’t drip. If the coating does sag, you must sand it for a smooth finish.

Apply at least 60 mils to ensure a uniform film. Use a mil gauge to test the thickness of the layer.

If you plan to apply additional coats, you must stay within the recoat window. VFI-2519 has a recoat window of 4 hours at 50 mils. If you apply it at a greater millage, it may affect the recoat window. If you miss the recoat window, you must sand the coating before applying another layer.

Setting up to Test VFI-2519 for Recoat Window

While on the topic of recoat windows, we wanted to explain how we would test for this property. The test method is arbitrary, so there is no industry standard.

A recoat window is the time after an initial coating has been applied that a secondary coating can then be applied, ensuring a strong bond between the two layers.

For the test, we mixed up small batches of the VFI-2519. To ensure we had a sufficient amount of material, we used 206 grams of Poly (B side) and 60 grams of Iso (A side) by weight.

We applied the coating to a pre-sanded board of VFI-2538 70 D EPS Form Hard Coat, which is a similar urethane hard coat. We spread the brushable coating onto the board at 50 mils thick with a square film applicator.

The temperature was 75°F with a relative humidity of 70%. Because the humidity was so high, we immediately noticed bubbling in the mixing cup and the coating as it started to cure on the surface. This wouldn’t affect what we were testing for, but it is something to avoid if you want a smooth, bubble-free finish.

We didn’t think we would get good results if we tested the material in half-hour intervals at the start, so we applied a second 50 mil coat after the first had cured for 1 hour and 2 hours. These second coats were applied at 79°F with a relative humidity of 66%.

We also coated a second board to test in half-hour intervals from 2.5 to 4 hours. The first coats were again applied at 50 mils with the square film applicator. The temperature was around 71°F with a relative humidity of 70%. With the humidity still around the same as the first board, we noticed bubbling in the coating again.

We then applied another 50 mils on top of the first coat after it had been curing for 2.5 hours, 3 hours, 3.5 hours, and 4 hours. Note: A 5-hour test was also tacked on since we had room on the board.

The temperature was between 70-71°F with a relative humidity between 70-76%. The new layers also started to bubble. Increased bubble formation may have occurred because the previous coating was still off-gassing as well.

Testing Adhesion for Hard Coat Recoat Window

We left the boards to cure for the rest of the day before we could prepare them to test their intercoat adhesion for the recoat window.

The surface was sanded before we applied dollies from the Elcometer 106 Pull-Off Adhesion Tester to each test section with an epoxy adhesive. We left the adhesive to cure for 3 days to ensure the dollies were firmly attached to our testing surfaces.

With the dolly cutter (bimetal hole saw), we cut around the base of the dolly so lateral bonding wouldn’t interfere with the test. We then removed the excess coating and adhesive shavings.

The base support ring was placed over the dolly to ensure a flat surface. The tester claw was then clamped onto the dolly, and the wheel on top of the tester was tightened to apply a perpendicular force that would pull the dolly off. The indicator on the tester retains a PSI value at which the coating separates from the surface.

Results of the Recoat Test

We wanted to see two things from the pull-off test:

• An acceptable PSI for tensile strength
• The two coatings still adhered together

If we only saw one layer of coating and/or a low PSI, that would be a failure.

The 3.5-, 4-, and 5-hour samples failed at 200 PSI, while the 2.5- and 3-hour samples failed at 400 PSI. The 2.5- and 3-hour samples maintained intercoat adhesion, which was a success. While the 5-hour sample failed at 200 PSI, it maintained intercoat adhesion.

That’s how we determined that a second coating could be applied at 50 mils up to 4 hours after the first. We also determined that reapplication 1-2 hours after applying the first coat is not recommended. The recoat window can always change depending on the film thickness, application surface, and temperature.

Applying VFI-2519 after 4 hours will compromise the adhesion between coats. After this time, the initial coat would have to be sanded and/or primed before another could be applied.

Contact VFI if you need more assistance when applying multiple coats of a brushable hard coat.

Why Is My Hard Coat Cracking?

Hard coats are supposed to be durable protection over surfaces like EPS foam for theming, so why are customers experiencing cracking? Cracking is a stress-related failure, which stems from substrate movement, lack of flexibility, extreme temperatures, and improper application.

Reasons Hard Coats Crack

Reason #1: Substrate Issues

Using the incorrect substrate for a hard coat can cause future issues. A general rule of thumb is you cannot apply a rigid coating to a surface that is softer or more flexible than the coating.

Hard coats are high on the Shore hardness scale. VFI’s hard coats are 65-75 D, which makes them feel very plastic-like, similar to a hard hat. Since these coatings have higher hardness properties that limit their flexibility.

Certain surfaces are more flexible and will expand and contract in extreme environments. Because the coating is rigid, it won’t be able to bend and flex with a surface that is more flexible than itself. This lack of flexibility makes them more susceptible to cracking from substrate movement.

Reason #2: Environmental Factors

Your hard coat’s ability to handle stress is closely associated with the environment. If your theming project is exposed to extreme temperatures, sunlight, humidity, and impact, it will degrade eventually.

Hard coats traditionally do not handle thermocycling or weathering very well. Our hard coats have a heat deflection temperature of 107°F, which means they will start to distort under stress at that temperature. This is a reason they need to be supported by a surface. The good thing about using EPS foam underneath is that the coating will hold strong unless the foam fails.

However, if you are installing the project in a location like Las Vegas where temperatures are high year-round, expect cracking to occur over time on dark surfaces. While substrates like EPS foam have good thermal stability, once they reach above 170°F they will start to fail. The failure of the substrate is what causes the coating to also fail and crack.

Reason #3: Improper Application

Coatings can fail if they aren’t applied correctly. If the surface is dirty or contains contaminants before the coating is applied, it can affect adhesion. If the coating is not properly adhered to the surface, it can delaminate, peel, or crack.

Applying the coating outside the recommended thickness range can also cause issues. If the coating is applied too thick or too thin, it has a greater chance of cracking. It will be very brittle unless it reaches a certain thickness.

Solutions

No one wants their hard coat to crack. These failures lead to extra costs, material waste, and project delays. The best way to prevent cracks is to use the right coating system and substrate for your environment.

If temperatures get above 170°F, a hard coat over EPS foam is not the recommended material. For a hard-coated project to last as long as possible, it should be placed in a relatively temperature-stable environment.

There is an alternative to using a hard coat. You can use a softer, more flexible coating. Softer coatings provide the needed flexibility to accommodate stresses and impacts without affecting the underlying surface. You may also need to use a different substrate.

VFI offers several products that will work for various application needs. VFI-3119 70 A Polyurea Hybrid Spray Coating or VFI-3131 65 A Polyurea Hybrid Spray Coating are softer coatings that can be applied to flexible surfaces like flexible foam. They offer great resistance to thermocycling and outstanding durability in diverse climates.

We’ve also seen theming fabricators use other substrates to create more durable structures. EPS foam is only going to get you so far with its thermal stability. If you created your structure from a material like metal or wood, it would have better thermal and structural stability.

VFI typically recommends a polyurea hybrid coating like our VFI-542 High Pressure Spray Bedliner for metal surfaces. It’s a cost-effective material in comparison to some polyurea and polyurethane coatings on the market. At 40-50 Shore D, our bedliners have more of a rubber-like feeling. They also have the ability to withstand cracking, warping, and peeling in extreme hot and cold temperatures.

A few other tips to remember to prevent cracking include:

• Ensuring proper surface preparation and application of your coating.
• Following the manufacturer’s instructions listed on the technical data sheet.
• Remember that if you apply paint as a topcoat, it has to be more flexible than the coating beneath it, otherwise it will crack.

Contact VFI if you need assistance finding the right hard coat material for your specific theming project. We also have recommendations for what you should and should not use to repair hard coat cracks.

How to Fix Holes or Cracks in Urethane Hard Coat?

Accidents can happen when using urethane hard coats over EPS foam shapes, signs, and props. We’ve had customers call in about cracks, holes, and dents on their sprayed hard coat layer and are looking for a fix. While we’ve heard of many DIY options, such as Bondo, plaster, and other polyester resins, the best repair material is a brushable urethane hard coat.

What Is the Problem with Other Repair Materials?

The biggest reason you shouldn’t use other materials to repair a hard coat is because they won’t be as compatible. A brushable material like VFI-2519 75 D Brushable Hard Coat has similar capabilities as a sprayable material like VFI-6170 70 D Spray Hard Coat.

At their core, these coatings are both polyurethanes. When properly prepared, a new coat of urethane bonds extremely well to a previous coat. The brushable hard coat can create an effective seal on the old hard coat, so the repair appears seamless. The ability to sand and paint the hard coats is comparable as well, so it’s easy to blend the repair in with the rest of the coating.

Patching materials like Bondo or plaster won’t be able to behave exactly like a hard coat. Bondo is commonly used for autobody, boat, and home repairs on surfaces like wood, metal, concrete, and more. Plaster is typically used as a building material or to patch cracks and small holes in walls and ceilings. These materials may not adhere well to polyurethane coatings.

Another reason to use a brushable urethane hard coat is that it will be able to match the properties of the existing coating. At around the same hardnesses (70 D vs 75 D), they offer similar abrasion, impact, and wear resistance. While they are formulated to be rigid, they also have good flexibility to prevent cracking. They offer these benefits whether you apply them by spray or by brush.

While Bondo and plaster are very rigid after they have cured, they won’t allow for the same amount of movement. If the hard-coated foam surface moves when temperatures are elevated, the repair material will move with it. Eventually, the Bondo or plaster repair will crack or fail over time, which defeats the purpose of using it as a repair. Also, polyester can melt the foam underneath, which is more trouble than it is worth.

Because the hard coat is meant to be painted, Bondo will cause issues with the topcoat. When paint is applied to the polyester resin, it will off-gas and wreck your paint. If these repairs are large, your overall piece might not look good.

Ultimately, these materials are too dissimilar to the original polyurethane hard coat to stay bonded together and undamaged. A urethane-based material will offer better adhesion, durability, and flexibility for repairs.

Solution

So, while you can use Bondo or other materials to repair cracks and holes in your coating, it’s better to use a brush-applied hard coat repair like VFI-2519 or VFI-2626. VFI-2626 has fire retardant in its formula, so it’s the better choice for indoor projects.

How to Use the Repair

When repairing an existing hard coat, you will need to remove any broken-off pieces in or around the damaged area. You will also have to sand in and around the damaged area to ensure adhesion of the repair material to the previous coating. Once the damaged area is prepared, mix up your repair material by weight or volume.

Before using the repair material, it is best to let it sit in the cup and heat up a bit so it gets thicker. This will make it easier to fill the hole or crack. An alternative to this method is to add fumed silica to your mix. This addition will make your mix very thick, like a paste, so it fills holes or cracks even better.

Fill the crack or hole until it is level with the rest of the hard-coated surface. We recommend using a rubber scraper to smooth and remove excess material when it’s still in a tacky state. Allow the patch to cure before sanding or painting it for theming purposes.

Contact VFI if you need assistance using a brushable hard coat repair or if you have any other questions.

Why Is My Hard Coat Project Failing?

In the past, we’ve had customers think they could use a hard coat in a casting capacity for theming projects. They spray the hard coat into a mold and demold it once cured to create a lightweight part without adding support beneath it. The most likely explanation for why the coating is failing is that it was left in high temperatures without support.

Reasons Unsupported Hard Coats Fail

By definition, coatings are materials designed to create a layer over or cover the surface of an object or substrate. Hard coats are best at creating durable, protective films over EPS foam. They are not made to be a casting material or to create hollow shapes to save money.

You might think that since hard coats are hard and durable, they can create three-dimensional shapes without a supportive surface underneath. However, they lack the structural rigidity and strength to support themselves. Without a support structure, they are thin, slightly flexible, and won’t last long due to various conditions.

An unsupported hard coat will eventually weaken and deform when exposed to high temperatures and UV rays. This can lead to a ruined project or noticeable imperfections in the piece. A support structure can help the coating maintain its dimensional stability, preventing warping, cracking, and distortion.

Outdoor temperatures can surpass the coating’s heat deflection temperature (HDT). HDT is a property that measures a material’s resistance to distortion under a given load at an elevated temperature. In other words, it will tell you how well your coating can handle a high-heat environment before it will deform.

Hard coats with a lower HDT than the environment they are being installed in will need to be fully supported. An example of this would be if you were to use an EPS hard coat in an outside environment. The hard coat gets structure from the EPS at high temperatures. If you are installing your project in a location where temperatures get above the HDT and you are not supporting it, that hard coat is not recommended.

Depending on what it is used for, a hard coat can also deform from impacts. They’re sprayed thin (up to 120 mils or a 1/4 of an inch), so they can be susceptible to cracking under impact. A support layer will absorb some energy from the impact, reducing the risk of damage to the hard coat.

Solutions

Polyurethane is a versatile material that can accommodate a variety of applications. Its properties can be adjusted to make it hard or soft. Depending on the raw materials used, it can be made into a foam, coating, rubber, or plastic. Hard coats have a similar feeling to plastic, which is why they may be useful in some casting scenarios.

• The first solution to prevent your hard coat from deforming is to spray over a surface that will support the coating. These coatings are typically sprayed over EPS foam to harden it. They create a durable, weather-resistant finish without diminishing the details of the underlying structure. EPS foam has good heat and thermal stability, so the hard coat shouldn’t fail unless the foam fails. Using foam also doesn’t add too much weight to the piece. Plus, it is cost-effective, so it won’t increase the price too much, either.
• Another solution is to spray the urethane coating into a mold, treating it like a fast-setting plastic. It must be backfilled with expanding foam once it has cured. A material like urethane foam is lightweight like EPS and will provide the support the hard coat needs. There is a range of urethane foam options with varying densities to accommodate your specific project.
• Rather than use a hard coat, you could use a urethane plastic with a high heat deflection. These high-performance plastics are good for high-impact applications and can be exposed to environmental temperatures up to 205°F (96.1°C) without deforming. The only downside is that you’d need more material to make these castings, so they will cost more.
• One last option would be to use a urethane plastic capable of being rotocast and then backfill it with expanding foam for support. Using this material will depend on your intended application. Not all plastics have high heat deflection temperatures, so you’ll want to be aware of that, too.

Contact VFI for more information on our urethane sprayable plastic coatings and plastics.

Why Isn’t My Urethane Hard Coat Drying?

Customers of urethane hard coats have called VFI asking why their urethane hard coat isn’t drying. Mix ratio, poor mixing, application thickness, and temperature can all cause urethane to not dry.

Urethane coatings can sometimes be hard to work with if you’re new to the material. Read the material technical data sheet (TDS) before you begin working to avoid errors.

Reasons Urethane Hard Coats Might Not Dry

Issue #1: A hard coat customer reached out about the coating not drying correctly over EPS foam. After talking through his issues, we discovered the problem. He was trying to use the hard coat more like paint. He sprayed in several thin passes at less than 20 mils per pass.

For a urethane hard coat to dry properly, a minimum amount must be applied to the surface. When applying to EPS foam, it must be sprayed thicker, or it won’t fill the foam in and will have a popcorn-like finish.

Issue #2: Another issue we’ve seen urethane hard coat users run into is using the wrong mix ratio. This is typically not an issue for those using spray rigs with proportioners. It is more likely for brushable hard coat users.

If you’re weighing the material by volume, you can mistakenly read the lines on your measuring cup wrong. Using too much of one material or not enough of another can result in your hard coat not drying.

Issue #3: You may notice the coating has some sticky spots after allowing it to dry for a few hours. The tackiness is unmixed material. Failure to thoroughly mix the material creates these spots.

Again, this is typically a problem for brush-applied coatings. However, off-ratio spots can happen in sprayed coatings if the proportioner becomes off-ratio at any point. When using cartridges, the mix may be off-ratio at the beginning or end of the tube as well.

Poor mixing can occur because users are worried about the working time and are in a rush. If you are using large amounts at once, your working time is reduced, which can also cause mixing errors.

Issue #4: Another factor that controls the drying time of a hard coat is temperature. This means temperature of the environment, application surface, and material. If you work in cold conditions, it can take your coating much longer to dry. In freezing conditions, the hard coat may never dry correctly.

Solutions

If your coating isn’t drying, you may have to start over or do large-scale patches. Follow the manufacturer’s instructions on the technical data sheet. Surface preparation, mixing, application, and drying instructions should all be included.

Work in a temperature-controlled (77°F) location. Warming up your material to at least 65°F can help it perform to standards. Avoid storing or applying in very cold or hot conditions for optimal results.

When weighing out your material, VFI recommends using the mix ratio by weight instead of volume. It’s easier to notice if you go above or below the amount of the material needed on an accurate scale.

Mix up your material in smaller amounts. This will help you avoid poor mixing by extending the working time of the material. Mix the material in one container until it is a uniform color. Scrape the sides and bottom of the container while mixing. Pour it into a new, clean container and mix again to ensure all parts are sufficiently mixed.

If you are using hard coat cartridges, make sure to spray on a disposable surface before spraying onto your piece to ensure no off-ratio material is used. When your cartridge is almost empty, spray onto the disposable surface again.

VFI recommends applying urethane spray hard coats at a minimum of 40 mil passes to create a uniform film that protects the piece. The minimum application rate for a brush-applied hard coat is a little higher at 60 mils. Depending on the application, you may want to increase the thickness for better impact resistance.

Increasing the temperature after application can help the material cure faster. Make sure the relative humidity is low so the coating doesn’t bubble.

Contact VFI if you have more questions about troubleshooting hard coat issues.

Why Should You Hard Coat EPS Foam Props?

There are several reasons that you should hard coat EPS foam props. If they are being used or moved around frequently and are getting dinged, dropped, or even smashed in the process, they won’t last.

If these props are meant for outdoor use, they will wind up broken and damaged from weather conditions, including rain, sunlight, and extreme temperatures.

Even if your props aren’t meant for close human interaction, accidents can happen. If you plan to reuse your props or need them to last the entire production, they can’t be left unprotected.

A way around this has often been with fiberglass, but this material is expensive and time-intensive to use. An alternative is to harden your foam props and set pieces with a high-strength, protective EPS theming hard coat.

What Is EPS Foam?

EPS foam is often called styrofoam by many prop designers, but they are not the same. Styrofoam is a brand name for extruded polystyrene (XPS), whereas EPS is expanded polystyrene. While they use the same polystyrene base, the manufacturing process for each type is different.

Other foams can be used for props and set pieces, but EPS tends to be the easiest to work with, making it the most desirable. Compared to other materials like wood, metal, or concrete, it is also more affordable. It can be purchased in blocks or sheets at varying densities if it needs to be tougher for the desired project.

It is most recommended for props if they are to be moved around, which is frequently needed for movie, television, and theater productions. The lightweight nature of the foam makes it the obvious choice for creating large, oversized props. It allows productions to be more dynamic and efficient for smoother movement and transitions between scenes.

How Do You Make EPS Foam Props?

These days, most of what we see on our screens in terms of movie props and sets is computer generated. CGI took the industry by storm, but audiences are reverting to the desire for authenticity in media. Physical sets and props can bring back that authenticity. Making physical props is more affordable and easily customizable when you hard coat EPS foam. The prop making process goes like this:

• Designers and prop artists typically start by creating and mapping out a design using a computer program. They can be as creative as they want, which is helpful for designing realistic or imaginative props and set pieces.
• Following the creation of the prop design, foam is then carved using a number of methods, including CNCing, milling, hot wire cutting, etc. Shaping the foam is the most delicate part of the prop making process because of how fragile the foam can be, especially when adding extreme detail.
• Once you’ve gotten through the hard work of carving or machining the foam, a hard coat should be sprayed or brushed onto the surface. As a coating, the material adapts to the contours, curves, and edges of the foam without diminishing the details.
• After the hard coat has cured, the surface is sanded to a smooth finish to accept paint or a topcoat. Painting is the part of the prop making process that allows designers to enhance the aesthetic appeal of the prop to look real and life-like. It can even make the prop look like other materials, including wood, metal, and stone. Even with a lower budget, prop masters can make high-quality props with foam and hard coats.

Best Hard Coating Material for Foam Props

While there are several ways to harden EPS foam props, VFI has seen the most success with polyurethane hard coats. At 65-75 D Shore Hardness, these coatings create a strong, seamless shell over foam props. Hard coatings come with many benefits, including:

• Fast cure – Other hard coating materials for foam props can take much longer to apply and dry. For example, fiberglass is durable, but epoxy or polyester resin has to be applied by hand. The resin then dries slowly, so projects take time to finish. Urethane sprayable plastic coatings are applied quickly and cure after a few hours, which makes them better for quick project turnarounds.
• High durability – Foam can be pretty fragile on its own. When hard-coated, it’s shielded to resist scratches, dents, chipping, etc., from movement or actors interacting with the prop. The coatings are also flexible enough to not crack from environmental extremes. They can be formulated with varying physical properties for long-term protection of the prop.
• Versatility – Urethane hard coats are versatile in many ways. They can be applied to large and small props made of various materials, including other foams like XPS and polyurethane. They can also be applied in different ways for different application needs. VFI specifically offers brushable, high pressure, and Qwik Spray hard coatings. These coatings can be used for indoor or outdoor projects as well, depending on if they have fire testing.
• Fire testing – Because many props and set pieces are used indoors, they may need to adhere to strict fire safety regulations. VFI’s urethane hard coats can pass ASTM E84 Class A fire testing. Class A is the highest classification these coatings can achieve under this test. In the event of an accident, the coating will not add to flame spread and can minimize damage.

What Kind of EPS Foam Props Can You Hard Coat?

Handheld props are often the most common props made of EPS foam. Since they are small and can be held, a brushable hard coat is typically the preferred coating to protect them. The only issue is that you must work in an environment with low humidity when applying brushable urethane to prevent bubbling.

If you are only making handheld props, the cost of a high pressure spray rig may be out of the question. Otherwise, if you’re making small props frequently, you might want a hard coat that can be sprayed through a cartridge-based gun.

On the other hand, the best way to hard coat oversized props and large set pieces is with a high pressure spray coating. If your set needs a rocky landscape, sculptures, or furniture, a brushable hard coat will not be able to accommodate the size of the piece. It’s also more cost-effective for a company that creates a lot of large foam props to get a high pressure spray system or a Qwik Spray Gun.

Hard coats can even adhere large foam pieces together, so brushable and spray applied coatings can be used in conjunction. Even if you are mostly spraying, it can be a good idea to keep some brushable hard coat around in case you need to make repairs.

Other props that designers may not realize could also be made of hard coated foam are architectural accents and custom signs. Foam makes an excellent alternative to stone and wood when making these features. We’ve even seen success with foam columns, trim, molding, shutters, corbels, signs, and more on the outside of actual homes. If these materials are used for decorative architecture, you know they’ll be able to withstand various conditions on movie and theater sets.

Contact VFI if you’d like to learn more about our hard coatings or need help determining the best one for you.

Why Is My Urethane Hard Coat Bubbling?

Customers of polyurethane coatings have called VFI about bubbles forming while mixing their material or when the material is curing. Bubbles can form for a handful of reasons, but when it comes to urethane, it’s usually due to moisture.

Urethane is a two-component material, and its A side (Iso) is very sensitive to moisture or water. Wherever there’s moisture in the environment, it will react with the coating and form carbon dioxide gas, which causes foaming or bubbling.

Reasons Bubbles Form in Urethane Coatings

Bubbles can occur regardless of your application method (high-pressure spray, Qwik Spray, or brush-applied). Some methods with a longer application time will be more sensitive than those with a shorter gel time. In most cases, bubbles are usually small and not always visible. However, it is best to avoid the following:

1. Humidity

Sprayable coatings don’t have much time to react with moisture in the air, but if the humidity is relatively high, you might experience bubbling. This is also true if you apply the coating while temperatures are fluctuating.

Brushable coatings like some urethane hard coats are a slowed-down version of a typical sprayable urethane. Their longer pot life and cure time allow for more moisture absorption to occur during the mixing, application, and curing process. When you start mixing the components in a humid environment, bubbles will form and continue to form as the material is applied and left to cure.

Spray coatings formulated to be sprayed through cartridge guns can also experience moisture issues. The material reacts slower and comes out at a lower pressure, so it can’t avoid a moisture reaction.

Products like VFI-6171 70 D Qwik Spray Hard Coat and VFI-2538 QS 70 D EPS Form Hard Coat are known to create a finish that is lighter in color and with more of a surface profile. That texture is a result of the material foaming as it interacts with moisture, even at a lower humidity.

2. Wet or Porous Surface

If you put a non-breathable coating over a wet or porous surface, any moisture underneath will be trapped. Hot temperatures can cause the surface to expand and increase pressure, and the coating will form bubbles or blisters.

Allow the surface to dry before application. If you’re working with a porous surface, you may need to seal it with a primer. For example, wood surfaces should be dry and contain less than 11% moisture; otherwise, they should be primed or mist-coated.

However, the coating may bubble if the foam isn’t allowed to age for 30 days after it has been manufactured. By coating the foam too early, you might seal gases within it, which could cause it to bubble as it cures.

3. Wet Application Equipment

For spray coatings, be cautious about water getting trapped in the spray hoses. A moisture reaction could occur if water gets in from humid or cold weather. The A side will react with the water and cause it to cure in the line. The B side will take in the water causing a foam interaction when sprayed. When the mixed material comes out of the gun, you’ll notice bubbling defects in the finish.

If the formula allows it, some applicators use chip or foam paint brushes to apply hard coats. Make sure that the application equipment doesn’t absorb moisture from the environment.

Solutions

Work in temperature-controlled conditions with low relative humidity. We recommend applying the material around 72°F. Cold weather can slow the coating’s cure, which could allow more bubbles to appear in the finish.

Avoid using hard coatings over wet or damp substrates. Make sure your surface is dry and prepared. Porous surfaces like wood might need to be primed. If you apply it over wood, it should contain less than 11% moisture. If you’re working with foam, allow it to sit for 30 days for any gas to escape.

If you’re spraying, ensure your lines are clear of moisture contamination. They should be cleaned after each use with a compatible pump flush or lube like VFI-8005 or VFI-8011. For brush applications, it’s best to use non-shedding chip brushes to avoid moisture absorption that could occur in foam ones.

If the coating is hard enough, bubbles can be sanded to achieve a smooth, uniform finish. Work with 120-grit or finer sandpaper to scuff-sand the bubbles. You’ll want to apply another coat to cover those defects after sanding.

Contact VFI if you need other technical assistance with urethane coatings.

Differences Between Silicone, Latex, and Urethane Molding Rubber

Learning the differences between silicone, latex, and urethane molding rubbers can help you determine which material is best for your next project. Regardless of the material you choose, they are all flexible and capable of producing highly detailed, durable molds. Their unique features can make one better for a certain application compared to another.

What Is Silicone Rubber?

Silicone is a synthetic rubber used to make brush-on or pour molds. It is a two-component material, and these parts are combined to cause a chemical reaction that converts the liquid into an elastomer.

Its main structure is composed of siloxane chains (silicon and oxygen). The manufacturer can adjust these chains to enhance the rubber’s properties for a desired project.

It is the most expensive rubber molding material. There are two common catalysts used to cure silicone:

Platinum-based

This type of silicone is also known as addition curing and uses a platinum catalyst. It’s a premium molding rubber that lasts longer than tin-based silicone but is also the most expensive.

This material can be formulated for various uses, including brush or pour application, skin-safe application, or food-safe projects when needed. Little shrinkage occurs when making molds, plus the material has great temperature stability and chemical resistance.

Tin-based

This type of silicone is also known as condensation curing and uses a tin catalyst. The tin catalyst makes it less expensive than platinum silicone.

It is used for general mold-making and prototyping, but it is not as long-lasting as other materials. As it ages, it will wear, lose elasticity, and become brittle.

Unlike platinum-based silicone, it is not prone to cure inhibition and can be used with most materials. It can create fine and intricate details for polyester, epoxy, gypsum, wax, concrete, and plaster casting. However, it is not suitable for skin application, even after curing.

It is prone to shrinking over time and as it cures. Its shrinkage partially comes from the release of methanol during the reaction. So, the bigger the mold, the less stable it will be. Fillers can make it more stable, but it will lose tear strength and become heavier.

Benefits of Silicone Rubber

• Its most appealing feature is that it does not require a release agent, so it demolds easily from most materials. It will also be able to withstand several casts without wearing significantly.
• Silicone can have varying properties, including Shore hardness, elasticity, working times, and curing times. This versatility makes it easier to choose one that meets your needs.
• Silicone is mostly formulated on the Shore A hardness scale. A lower hardness and ability to replicate details make them a great choice for historic restoration. There is a reduced chance of damage to the original or master.
• Regardless of where you need to make your molds, silicone works well for molding on or off-site. Various formulas offer fast cure times for easier in-field molding.
• It is not sensitive to moisture, so you can work in various conditions without worry of bubbles forming in your mold.
• It is desirable as a brush-grade material because it gets thicker better than urethane. Brushable formulas also replicate complex designs for specialty projects more easily. It is best for creating what’s known as a skin or glove mold. These molds will need wood or plaster backing.
• If you need your mold to withstand high temperatures, silicone works better in these environments.

Cons of Silicone Rubber

A downside to using silicone molds is that with repeated use, they will not last very long. Depending on the mold, they start to disintegrate or tear. They also lose their detail over time.

Because of cost, silicone molds are usually made with mold boxes or additional support, which will take added time and experience to develop.

These molds have poor abrasion resistance, so they’re not always recommended for casting concrete or materials like it. If you cast concrete, they work for low-volume production.

What Is Latex Rubber?

Latex is naturally sourced from rubber trees and was the first widely used rubber. It’s typically composed of rubber particles, water, proteins, and sugars, which all work together to provide a unique set of properties.

Compared to other molding rubbers, it is a thin material that can be brushed onto surfaces or sold as a sheet good. A brush-on mold can be desirable compared to solid molds as it saves on material costs.

Unlike other room-temperature vulcanizing rubbers, latex cures by evaporating the water and ammonia in its formula. Once cured, it leaves a highly elastic, durable mold that replicates perfect detail.

Benefits of Latex Rubber

• It’s the most affordable molding rubber and is extremely durable, so you benefit from a more cost-effective, long-lasting product.
• It has good strength, tear resistance, and flexibility, which all contribute to its longevity. It will last a long time in production if maintained and stored properly.
• In terms of ease of use, as a single-component material, it does not require measuring and mixing. Like silicone, little or no release agent is required to prepare the molding surface. It’s also water-based, so cleanup is easier and faster.
• Due to its abrasion resistance, it is good for casting abrasive materials like concrete and cement as well as wax and plaster. It is perfect for making flat molds for ornamental concrete projects like stone veneer and two-dimensional architecture. It can also be used for limited resin casting.
• Like silicone, it makes a good thin-walled glove mold but cannot be applied to the skin during or after application. By applying it with a brush, you can create molds with irregular shapes or very intricate molds with fine details.
• It is biodegradable, which makes it more environmentally friendly. This also means that, over time, when exposed to the elements, it can rot, degrade, and crumble.

Cons of Latex

Latex has a strong ammonia smell, which is undesirable during the extensive application process. When it’s not in use, it has to be stored at room temperature. If it freezes, it is unusable and must be disposed of.

While latex is strong, it has a high shrinkage rate as it cures. It can shrink as much as 10-20%, which causes it to lose fine details. It’s generally not recommended for casting urethane, polyester, or epoxy resins.

Because this material is used to make thin-walled glove molds, it requires rigid backing or a support mold. An unsupported latex mold will deform and stretch out of shape while casting.

Like silicone, certain materials can inhibit its cure like Vaseline and sulfur-based clay. Touching the surface of one latex layer before you add another can prevent it from curing. It’s also known to cause allergic reactions in some people upon skin contact.

Even though it is the cheapest molding rubber option, its multiple thin layer application method increases labor costs. Since only one layer can be applied at a time, and many coats are needed, it may take several days or weeks to make a single mold.

What Is Urethane Rubber?

Urethane rubber is another synthetic molding material for use in a variety of molding and casting applications. Like silicone, it is 2 part rubber that must be measured and mixed accurately. The chemical reaction occurs between an isocyanate and a poly. It is best for concrete casting.

Polyurethane is an affordable molding material. It is also more versatile because it can be formulated into different materials like plastics, foams, and coatings. It ranges between the A and D Shore hardness scale to accommodate various application needs.

Benefits of Urethane Rubber

• It has excellent physical properties that make it tougher than other molding materials. High properties include elongation and tensile strength for extended wear and tear, which are also customizable to meet specific performance requirements.
• Urethane is more dimensionally stable than silicone or latex, which means low shrinkage when making molds. It also maintains stability after substantial pressure is applied for consistent castings.
• It is more versatile than silicone or latex. Due to its range of property options, it’s used for a wide variety of projects. It can be formulated harder than other rubbers, which is better for tooling projects like stamps and formliners.
• Because it is highly durable, it can be reused over and over, especially in abrasive applications. Its reusability makes it the best material for high-volume production.
• Its ability to transfer pigment is better than other molds, which makes the color of the casting more vivid. It’s also more friendly to in-mold coatings and other modifications like painting. This ability is important to enhance the look of casting materials.
• Since urethane molds are thicker and solid, they typically don’t need rigid backing like silicone and latex glove molds. However, wood backing can be beneficial for large, flat molds to prevent shrinking in extreme temperatures.
• While release is required to prevent urethane from sticking to other surfaces, VFI offers a line of urethane rubbers that demold more easily. They have best-in-class release characteristics and are proven to lower breakage rates by 80%. This can be especially beneficial when demolding from delicate undercuts and details.

Cons of Urethane

The biggest downside of urethane rubber is that it requires a release agent before casting. It is highly adhesive and will bond to any surface. When making the mold, porous surfaces, including wood and natural stone, also have to be sealed properly.

Another downside of urethane is that it is moisture-sensitive in its liquid form. This can make it hard to work in warm and humid environments. If moisture finds its way into the mixture, it causes bubbles to form, which may affect your final mold surface.

Which Molding Rubber Should I Use?

What material you choose depends on several factors, including:

1. What is your budget?
2. What is your model or master made of?
3. What properties do you require? (i.e., high tear strength, high hardness)
4. What level of detail do you require? (i.e., extreme vs simple detail)
5. What material are you casting into the mold?
6. How many castings do you need to produce, or how long do you need your mold to last?

Molding Material Comparison Chart

VFI Coatings to Protect Flexible Surfaces

Volatile Free, Inc. has formed a niche line of softer coatings that provide certain applications with much-needed flexibility and strength. Almost 30 years ago, we started offering a diverse line of polyurea and hybrid coatings for the protection of various surfaces.

These coatings are versatile and used by industry experts across North America. Since they are softer, they have higher elongation, which means they have a better ability to stretch and flex. Due to this property, they withstand various conditions without breaking, protecting surfaces in the long term. On the other hand, they will have lower tensile strength.

The Versatility of a Flexible Polyurea Coating

Polyureas are desirable due to their adaptability and high properties. VFI’s two-component VFI-270 70 A Polyurea Spray Coating is no exception. It is a high-quality material with excellent abrasion and chemical resistance. Like most polyureas, this coating is fast-setting for high builds on vertical surfaces without sagging. The quick cure also allows for quick turnarounds on projects.

While polyurea can be used over a handful of surfaces, VFI-270 is best applied to flexible surfaces like a flexible foam. This is because the material itself is flexible and rubber-like at 72 Shore A hardness. The lower hardness also lends itself to resisting impacts better than harder coatings. Over foam, the coating creates an elastomeric surface without adding too much weight to the entire piece. Unlike other polyurea coatings, the film can be applied smoothly with no texture.

Typically, this material is used instead of other coatings due to its low moisture sensitivity. It can be used in various conditions, including high temperatures and high humidity. The only benefit it doesn’t provide is UV stability.

Uses: VFI-270 makes an incredible protective skin for foam parts and pads. This product has been used for artificial rocks, walls, and tree bark, amusement ride pads, spray-on cushioning, and to reinforce self-skinning foam. Depending on the thickness at which it is applied, you have control over what poundage of foam you back it with. It takes tint incredibly well, so you can color it to your desired aesthetic.

Polyurea Hybrid Flexible Coatings with High Properties

While polyureas are great, they don’t work for every situation. That’s where polyurea hybrids come in. Hybrids are a combination of polyurea and polyurethane, so they behave like a balance of both. Many of VFI’s flexible coatings are polyurea hybrids, including VFI-3119 70 A Polyurea Hybrid Spray Coating and VFI-3131 65 A Polyurea Hybrid Spray Coating.

These coatings work in a similar capacity to VFI-270. They are rather unique as hybrids due to their higher tensile strength, tear strength, and elongation compared to the polyurea. Both are rubber-like with hardnesses between 65-70 A but are incredibly tough and durable against impacts and cuts over soft or flexible surfaces. VFI-3119 is unique because it sprays like polyurea but wets out and flattens for a non-textured surface.

Like polyureas, they are fast enough to be applied vertically without dripping. Once applied, they set quickly and provide a soft yet durable protective film. They have outstanding durability in diverse climates, whether used indoors or outdoors, with a UV stable flexible top coat.

Uses: These coatings can be used in high-impact applications with foam as the substrate. Surfaces requiring high rebound with good structural strength can also use these protective coatings. They have been used as wear and waterproof membranes and protective skins on furniture and seat cushions. Other potential applications include artificial tree bark, flexible brick panels, and faux animal skins.

VFI Flexible Coating Property Comparison

A coating’s properties strongly influence its performance in various applications. Because the coating may be subject to physical stressors over its lifespan, it needs a good balance of properties to withstand extensive damage. Below is a comparison of the mentioned coatings for more insight into their capabilities.

Benefits of Using a VFI Flexible Coating

Polyurea and polyurea hybrids can be formulated to achieve a range of properties. They are desirable for many reasons, including:

• Flexibility. The most special attribute of these coatings is their inherent flexibility, even at low temperatures. They will expand and contract with the surface due to temperature variations or vibrations, unlike thin, less flexible coatings. This ability allows them to flex, bend, and stretch without cracking, peeling, or delaminating from the surface for long-lasting protection. They accommodate movement without compromising their structural integrity.
• Durability. How durable a coating is will be one of the most important properties to consider when formulating it for protective purposes. These coatings should have the necessary properties to resist breaking, deforming, wearing, and tearing from high mechanical loads and stresses. These stressors can be caused by abrasion, impact, weather, and chemicals. Their toughness and strength ensure the longevity of the structure.
• Weather resistant. Humidity, low temperatures, and rain can degrade, crack, and discolor bare surfaces. These coatings are seamless once applied, creating a barrier to protect surfaces from substantial damage. The coating prevents water and other debris from passing through, reducing the likelihood of surface damage. Also, if moisture were to get through to the substrate, it could cause mold, mildew, and rot.
• Rapid cure. Because these coatings set up quickly, projects can be placed into service the same day. This is very desirable for applications that require quick turnaround times. Other materials, such as hand-applied polyurethane and epoxy, take much longer to cure, with epoxy taking days to be ready for service. VFI coatings dry within 4-6 hours and can withstand heavy-duty use within 24-48 hours, reducing downtime. The rapid cure also allows adequate coating thickness to be built in a single pass.

Contact VFI for more information on flexible industrial coatings. We can help you figure out the best material for your unique project.

Understanding the Properties of Industrial Polyurea and Hybrid Coatings

Understanding the properties of industrial polyurea and hybrid coatings is essential for proper use. Some industrial coatings enhance or protect surfaces, while others improve something as simple as aesthetics. Polyurea and hybrids are used almost solely for their protective purposes. VFI compiled information about the most important properties of these materials so you are better equipped to choose the right one for your project.

What Physical Properties Are Important?

When it comes to properties, there is a bit of a difference between polyurea and polyurea hybrids. Pure polyureas tend to have consistently higher physical properties than hybrids. However, both vary by formulation.

There are certain applications where polyurea is more desirable, such as environments where moisture is a concern. If moisture isn’t a concern, hybrids still have advantages and can be more cost-effective. The following physical properties are important to know regardless of coating type:

Shore Hardness

Test method: ASTM D2240

Definition: Shore hardness tests the resistance of a material to localized deformation or indentation. The material is tested using a durometer tool and is ranked on different scales between 0-100. Which scale is used is determined based on the material’s qualities.

Importance: Hardness is an adjustable property. Materials can come in different hardnesses to suit a customer’s needs. Industrial coatings will protect underlying surfaces when the correct hardness is chosen based on the specific application.

Polyurea or hybrid coating hardness is typically measured on the Shore A or Shore D scale between 40 A and 80 D. Materials on the A scale are typically softer, while materials on the D scale become much harder. For example, VFI-270 70 A Polyurea Spray Coating will be more flexible and rubber-like, while VFI-2622 68 D Polyurethane Spray Coating will be more firm and almost plastic-like.

A harder material is desirable for its resistance to scratches, dents, or gouges from abrasion. This is important in applications that experience daily wear and tear, such as truck bed liners, secondary containment, speaker boxes, table edging, and more. Lower hardness provides more flexibility and is desirable for applications like reinforcing foam for amusement ride padding due to higher impact resistance.

Polyurea and hybrids typically offer a good balance between hardness and flexibility to prevent cracking. They can bear weight or maintain their shape under various stresses. They will also resist punctures and penetrations.

Note: Most VFI products will have their Shore hardness in their name, specifying whether they are on the A or D scale, to make it easier to find what you’re looking for (ex. VFI-200 50 D Slow Polyurea Coating vs. VFI-3119 70 A Polyurea Hybrid Spray Coating).

Tensile Strength

Test method: ASTM D412

Definition: Tensile strength is a property that tests the maximum pull a material can withstand without tearing or breaking when being stretched. It is expressed in pounds per square inch (psi).

Importance: High tensile strength increases a coating’s ability to resist pulling forces, providing a higher tolerance to stress.

Good tensile strength is essential where surfaces experience impacts, expansion, contraction, or vibrations. In the instance of impacts, high tensile strength will help absorb the impact energy and prevent damage or deformation from occurring on the surface.

Like hardness, tensile strength also works with flexibility. A highly rigid coating could be prone to cracking, even with impressive tensile strength. That’s why polyurea and hybrids often offer a balance between all these properties to prevent failure. Certain hybrids might have a lower tensile strength, but this can be the trade-off for other desired properties like increased elongation.

Elongation

Test method: ASTM D412

Definition: Elongation is tested with tensile strength by stretching a material and measuring the increase in length it will achieve before breaking. It is expressed in a percentage (%) of the original length.

Importance: Industrial coatings can have high elongation, which is important for applications that encounter impact. Polyurea’s inherent flexibility is a factor that contributes to its ability to elongate and move with the surface without cracking or losing adhesion. They are formulated to be strong and flexible, which is dissimilar to other coatings that may break from movement or vibration. Elongation can also help absorb impacts, which is beneficial for applications like truck beds, recreational vehicles, trailers, or work trucks.

A higher elongation will mean a lower tensile strength, which makes it more elastic than rigid. If it is highly elastic and stretches easily, it might lack the hardness needed for certain applications. Polyurea offers a good balance of elongation with other properties to provide desired flexibility and durability. Hybrids might have lower elongation, but this can be made up with other higher properties.

Tear strength

Test method: ASTM D624 C

Definition: Tear strength tests the maximum force required to start a tear in a direction perpendicular to the stress. It is also known as tear resistance and is expressed in pounds per linear inch (pli).

Importance: Tear strength is another critical property for coating users. It tells you how well a coating will resist tearing and maintain its integrity as a protective barrier. High tear strength will prevent small punctures and abrasions from turning into large tears that could compromise the coating’s ability to protect the surface.

Even in an application with abrasive wear, the higher tear strength will prevent minor abrasions from turning into large tears that expose the underlying surface. In the event of impact damage, tear strength prevents the development of tears from a forceful blow.

Polyurea provides good tear strength and flexibility. Hybrids may have lower tear strength, but what they lack in one property, they can make up for in another one.

Water Absorption

Definition: Water absorption is the amount of water absorbed by a material. It is measured as a percentage (%) of the weight of water absorbed to the weight when dry. It can also be called moisture absorption or water swelling.

Importance: One of the most desirable uses for industrial coatings is waterproofing. They produce a seamless, impermeable barrier, preventing moisture from reaching the underlying surface. You will see a low percentage (under 5%) of water absorption if the material works well as a water-resistant barrier.

Polyurea and hybrids are non-porous, which helps prevent them from absorbing liquids. If water is absorbed and then freezes, it will expand and cause the coating to crack. High water absorption can also cause swelling, which results in dimensional change, loss of strength and adhesion, delamination, or fracture.

Water absorption will also tell you if a coating is suitable for interior and exterior use. A low absorption rate is necessary in outdoor applications, especially in climates with heavy rainfall or freeze-and-thaw cycles. If it has low water absorption, its strength and durability will be maintained over time with water exposure.

Water Vapor Permeability or Permeance

Definition: Water vapor permeability is the rate at which a material allows water vapor (water in its gas form) to pass through. It is stated in perms and is often also called permeance or breathability. Lower numbers indicate a lower permeability. It is not directly related to water absorption.

Importance: Along with water absorption, permeability can impact the performance and durability of coatings in waterproofing applications. A high permeability controls the rate at which water vapor passes through, preventing moisture build-up that could lead to mold growth, blistering, bubbling, and delamination.

Low permeability can also prevent corrosion, discoloration, and other forms of damage. If a coating with high permeability is applied to a metal surface, trapped moisture could accelerate the formation of rust. If the coating is breathable, the water vapor can escape, reducing corrosion.

Permanent Set

Definition: Permanent set refers to a point where irreversible deformation of the material occurs even after stress is removed. The property is recorded as a percentage of the total deformation compared to the original length.

Importance: Permanent set can be affected by various factors, including the type and amount of stress applied, temperature, and stress duration. Knowing a material’s permanent set will help you understand its behavior and properties under stress. It can be reduced by using materials with higher strength and stiffness and by controlling the temperature and duration of stress.

Cold Temperature Flexibility

Definition: Cold or low temperature flexibility is the ability of a material to resist cracking when flexed in low temperatures. This property is not listed for every material but will receive a pass or fail as a test result.

Importance: Though temperature and weather are out of our control, manufacturers can control how well their products hold up in these conditions. Polyurea and polyurea hybrids are unique because they withstand the fluctuating temperatures of various climates. Even in low temperatures, these coatings can maintain their durability and properties. Other materials might have impressive strength, but they can become brittle at low temperatures, which leads to cracking or failure.

Good cold temperature flexibility means the coating has enough flexibility and elongation to stretch without breaking over a mandrel bend. Flexibility is essential for the coating to expand and contract with the surface in low temperatures.

Adhesion Strength

Definition: Adhesion strength measures a coating’s resistance to separation from a surface when perpendicular tensile force is applied. It may also be called bonding strength. It is expressed in pounds per square inch and is typically tested for prepared steel and concrete surfaces.

Importance: Adhesion is one of the most, if not the most, important properties for a coating. It ensures that the material will adhere to the surface for long-term protection. It will do so even in the most aggressive conditions.

Polyurea or hybrids have excellent adhesion to several substrates, including concrete, steel, foam, and wood. Bonding increases with proper surface preparation. Cleaning the surface is always necessary to prevent adhesion failure. While not always necessary, priming the surface can provide the best adhesion results. Factors that may cause poor adhesion include temperature, cure time, moisture, and inadequate surface preparation.

Poor adhesion can cause peeling, flaking, blistering, and delamination, allowing substances to penetrate underneath. It can compromise the coating’s effectiveness in waterproofing, impact resistance, chemical resistance, and other properties. These problems can be costly to fix, so you’ll want to find a coating with good adhesion to your specific surface.

What Liquid Properties Are Important?

Unlike most manufacturers, VFI differentiates between physical and liquid properties. This differentiation helps tell you which properties pertain to the coating when it is in its liquid state vs its solid, cured state. Liquid properties help more during the application process, while physical properties tell you how it will perform throughout its lifespan. The following are important liquid properties:

Solids by Volume

Test Method: ASTM D2697

Definition: Solids by volume is a measure of the total volume that remains on the surface once the material cures, expressed as a percentage (%).

Importance: Low solids content means there is solvent within the product. Solvents evaporate as the coating dries and can be harmful to applicators since they may be volatile organic compounds (VOC). The evaporation of the coating significantly reduces the amount of material that cures on the surface. That’s why several coats must be applied to have the same thickness as a 100% solids coating.

A coating with high solids will have a higher concentration of solid components. They are more environmentally friendly because little to no solvents are emitted during cure. Also, they maintain the same level of thickness once cured. Not having to apply multiple coats means less material and less time are needed during application. There’s also a reduced risk of adhesion problems if extra coats are not required.

A great characteristic of polyurea and hybrids is that most are 100% solids. This makes applying them much easier because you know the amount of material you are putting down is the amount of material that will remain. You don’t have to worry about applying or buying more material to make up for the thickness that would evaporate if you used a low solid coating. Also, because there are no solvents, this contributes to a faster cure for reduced downtime and quick turnarounds.

A common misconception is that all solvents are VOCs. A common solvent that disproves this is water and it contains no VOCs. A solvent is part of the total solution and acts as a carrier for the entire system.

Mix Ratio by Volume

Definition: A mix ratio is assessed for liquid materials that require two or more components to be mixed together to produce a chemical reaction that will allow them to cure. Mix ratio by volume uses exact proportions, expressed as a ratio (ex. 1A:1B), measured using equal-sized containers.

Importance: Some coatings may have a mix ratio by weight, but due to the speed of polyurea and hybrids, there is not enough time to mix them together before they cure. They are applied by high-pressure spray rigs where the material is pumped through lines and mixed right at the gun tip so the reaction can occur without clogging the lines or gun.

Exact mixing proportions must be followed for proper curing. Too much or too little of one component can inhibit the cure. It might feel too soft or sticky and won’t offer the desired properties to protect a surface. It might never develop full physical properties, which wastes time and material if reapplication is necessary. Being off ratio could also affect adhesion and lead to peeling, flaking, or delamination from the surface.

Viscosity

Test method: ASTM D2196

Definition: Viscosity measures the resistance of a liquid to flow, or rather, the relative thickness/fluidity of a liquid. It will be listed on a technical data sheet in centipoise (cps) for each liquid component and sometimes for the mixed material. To better understand viscosity, below is a list of household items and their relative viscosities:

Importance: Viscosity can directly affect how a coating behaves during application. Because polyureas are applied by high pressure spray, they are most desirable at a lower and similar viscosity. The lower viscosity is desirable because it enhances the workability of the coating and makes application easier. The speed at which they are applied and their low viscosity can also reduce the amount of trapped air in the finish.

Low viscosity is also needed to evenly distribute the coating for smooth and uniform application. A higher viscosity would be desirable for brush applications because it prevents dripping and sagging.

Polyureas will not typically list a mixed viscosity. It’s hard to assess the combined viscosity while it is still a liquid because it cures quickly once combined.

Gel Time

Definition: Gel time is the time it takes for a material to stop flowing or become gel-like. A tack free time might also be listed for some products. Tack free is when the material is no longer sticky.

Importance: Polyureas and hybrids are incredibly fast setting, so their gel time typically happens within seconds of application. The speed is desirable for most users because the faster they gel, the quicker they cure and can be placed into service.

Their fast reaction time also means they are less likely to react with humidity and moisture in the environment. Low sensitivity to moisture allows them to be applied over cold or damp steel, concrete, wood, or foam surfaces.

Gel time can also affect the surface finish. As the material is sprayed, the gel time can make it come out fine and smooth or heavily textured. The texture can be further altered by adjusting the air pressure or gun tip size.

Their speed can also be a bit of a hindrance. Because they are so fast, they are a bit harder to work with. They are typically only sprayed through high-pressure rigs, and you must have adequate training to apply them effectively. The quality, thickness, uniformity, and texture may vary depending on the applicator’s experience. Sometimes, they can be slowed for a smoother flow on intricate surfaces.

Recoat Time

Definition: Recoat time is specific to coatings and is the time frame an applicator has to apply a subsequent coat or topcoat with ensured adhesion. It can also be called the recoat window.

Importance: Some coatings are applied in single passes, but multiple coats must be applied to build thickness. You must apply those extra coats within the recoat window. The longer the first layer cures, the less likely a subsequent coat will adhere to it.

If the recoat time passes, using a primer can ensure adhesion to the original coat. In some cases, roughing up the surface by sanding or grinding before applying the next coat can also increase adhesion. If you don’t adequately prepare the recoat surface, it can lead to peeling, cracking, or delamination between layers.

Place into Service

Definition: Place into service tells you the amount of time needed for a material to cure before it is ready for use.

Importance: For polyurea and hybrid coatings, the place into service time frame can be the same day (within 4-8 hours) or the next day (at least 24 hours). This is due to the speed at which they cure. Once they cure to a point where they have enough of their properties, they can be used.

The place into service time can vary based on application. If the coated surfaces will be in contact with chemicals, the material may need more time to cure. In other circumstances, such as truck bed liner, the coated surfaces might be ready for light use in a shorter amount of time, which can be desirable for faster turnaround.

Full Cure

Definition: Full cure is the time it takes for a material to develop full strength and properties for repeated daily use.

Importance: No material develops full properties upon initial cure. Most have to sit for a few days at room temperature to obtain full strength, hardness, and other properties listed on technical data sheets. This property is typically listed so users understand that failure can occur if too much pressure is put on it before it obtains its properties. Once the full cure time has passed, the material will perform as per the properties listed. Full cure can be affected by many factors, including temperature.

Where to Find Material Properties?

Once rigorous testing has been conducted on a product, our lab staff generates the physical and liquid properties. It’s important that customers can easily find properties for all our products. We list them on all technical data sheets and product pages. To find the technical data sheet, you can navigate to any product page, and it will be off to the right-hand side under the resources tab. For mobile users, the resources tab is at the bottom of the product page.

Contact VFI for more information on properties so you can find the best material for your project.

When to Upgrade a Qwik Spray Gun to a High Pressure Spray Rig

For those who have been spraying two-component polymer coatings for a while, you may be wondering if it’s time to upgrade your Qwik Spray Gun to a high-pressure spray rig. The Qwik Spray Gun is VFI’s cartridge-based spray equipment for use with specific coatings that have been on the market almost since the beginning of the company. In fact, we were one of the first to sell a cartridge-based spray system for spray on truck bedliner and EPS theming hardcoats. It has been desirable to many due to low maintenance, portability, and ease of use.

Even though the pneumatic cartridge gun comes with many benefits, there might come a time when you’ll need something else. There are several things to consider that can make the decision to switch to high pressure much easier.

Why Switch to a High-Pressure Spray System?

1. Better for Spraying Large Pieces or Areas

Maybe you started spraying small props, custom signs, truck beds, or other equipment but have since been offered bigger projects. VFI’s Qwik Spray Gun and similar cartridge-based equipment on the market are recommended for small to medium-sized projects. If you’re spraying a piece or area larger than 4×4 or 4×6 feet, a cartridge-based system will not be as efficient. The size of the project can be extended, but it is not recommended. These projects are also pretty flat, with a limited amount of detail.

Those who do use cartridge-based equipment on larger projects accept that they will encounter a lot of overspray. That overspray will cause more required post-work as the piece will probably need to be sanded, depending on the desired finish for the project. Otherwise, this can be avoided by spraying in smaller passes, but the application will be more labor-intensive and time-consuming.

2. Better for Increase in Project Volume

Another reason applicators typically stick to the Qwik Spray System is due to the amount they are spraying. This equipment is desirable for custom jobs where applicators work on one small project at a time or are only spraying a couple of times per month. It doesn’t make sense to spend money on an expensive spray rig. However, if you’re spraying more than you initially were, purchasing high pressure equipment can save you money in the long run due to material costs.

For example, businesses that spray less than 10 truck beds a month would benefit from spraying cartridges of VFI-544 Qwik Spray Bedliner, but if you’re seeing more traffic come through, you’ll probably need an upgrade to accommodate. VFI-542 High Pressure Spray Bedliner sprayed through high pressure equipment is recommended if your business is growing and you’re taking on more projects.

Also, high pressure equipment, because of the increase in pressure and temperature, cures coatings faster. A faster cure is extremely desirable for applicators who need to spray at high volumes so they can get onto the next project quicker.

3. Better if You’re in a Fixed Location

With the Qwik Spray Gun, as long as you have air pressure, you can take the equipment anywhere. However, if you’re not taking your spray gun to various locations for spray jobs, you don’t need portable equipment.

High pressure equipment is not as easily transported, which is why it’s not the go-to for many new sprayers or those who do low-scale, low-volume jobs. Once you know that the location you’re spraying at will be permanent and you have enough space, upgrading your equipment is ideal.

4. Increased Control

A downside of the Qwik Spray Gun is the lack of control when spraying. Once you pull the trigger, you must keep going until the cartridge is empty. If you were to stop midway through the application, the material would become clogged in the static mix tip because it is mixing the material as it exits.

While training is required to use high pressure equipment, once you get the hang of it, you have complete control while spraying. The trigger on the spray gun allows you to start and stop when needed. This is because a mechanical proportioner is typically used to meter out the correct ratio of material and mixes only what is necessary. It’s also desirable because it can pump, mix, and apply coatings with short pot lives very quickly.

5. Increase in Material Options

Not every material is offered in a cartridge-based format; in fact, most materials aren’t. The cartridge-based system, due to its low pressure outlet, is typically used for polyurethane and polyurea hybrid materials. However, urethane and polyurea hybrid formulas will not all work in the Qwik Spray Gun either. If you’re itching to try something new, you may need to get the application equipment to accommodate it. When you switch to a high-pressure spray rig, you get access to more materials and more formulas.

Polyurea is an incredibly fast setting material and requires high-pressure, high-temperature equipment to apply it. Cartridge-based spray guns typically only spray at a maximum of 100 psi and 10 cfm of constant pressure to push material through a static mix tip. If you use a fast material like it in a pneumatic, air-driven gun, the material wouldn’t provide a good mix without gelling and clogging the tip, so it would not have enough time to exit the gun.

6. Improved Cured Surface

While not exactly a catalyst for switching from a cartridge gun to high-pressure, there is also the benefit of having a more uniform, smooth surface. A downside of the Qwik Spray equipment is that you’ll never get as desirable of a finish as you would with high pressure equipment. Due to the lower pressure and atomizing tip on the cartridge, the material reacts more as it exits the gun. The Qwik Spray System’s reaction occurs slower, which allows the moisture in the air and the environment to create foaming. The foaming is the reason it comes out less smooth, with a bit of texture.

For example, the VFI-6171 70 D Qwik Spray Hard Coat is lighter and has a subtle splotchiness in its finish. In comparison, the VFI-6170 70 D Spray Hard Coat, sprayed through high-pressure equipment, comes out more uniform and slightly darker.

As mentioned before, if you are spraying VFI-6171 on larger projects, it will require more post-work than a high pressure spray. If the foaming reaction is not an issue for you, it’s best to stick with the Qwik Spray Gun, especially if your project size and spray volume have not increased.

High-Pressure Equipment Recommendations

VFI manufactures polyurethane, polyurea, and hybrid materials that are mostly applied using high-pressure industrial spray equipment. We recommend finding a high-pressure, plural component spray rig that can run at 130-155°F and 2,500 psi of constant pressure with high pressure heated hoses and 10ft whip hoses. Gun tips will vary by the project and will need to be adjusted on-site. The following machines are capable of meeting these specifications:

• Graco A-XP1 air sprayer (up to 3,500 psi, 170°F, 1.5 gal/min output, & 210 ft hoses)
• Graco Reactor 2 E-XP2 electric sprayer (up to 3,500 psi, 190°F, 2 gal/min output, & 310 ft hoses)
• Graco Reactor 2 H-XP2 hydraulic sprayers (3,500 psi, 190°F, 1.5 gal/min output, & 310 ft hoses)
• Graco Reactor 2 H-XP3 hydraulic sprayers (3,500 psi, 190°F, 2.8 gal/min output, & 410 ft hoses)
• PMC PHX-2 or 25 hydraulic sprayers (up to 3,000 psi, 190°F, 2 gal/min, 210-410 ft hoses)

Graco equipment can be used with Probler P2 or Fusion guns. PMC equipment can be used with AP-2 Air Purge, PX-7 Mechanical Purge, or Xtreme Spray Gun.
Whether you’re using the Qwik Spray Gun or high-pressure equipment, you must always wear proper personal protective equipment. Also, spray in a well-ventilated spray booth whenever possible.

Contact VFI if you need technical assistance when deciding if you should make the move to a high pressure spray rig.

Understanding the Properties of Urethane Hard Coats

Understanding the properties of urethane hard coats is essential to picking the best material for theming projects. They are designed to harden surfaces like Styrofoam or EPS foam to protect architectural shapes and forms, custom signs, and props. If you’re new to hard coatings, you may not know what properties are essential to look at compared to other coatings. VFI has put together a comprehensive guide to help you learn more about them and how they function due to their properties.

What Physical Properties of Urethane Hard Coats Are Important?

Physical properties will tell you how the material will perform when cured. Most users look at these properties to help them decide if the coating will withstand the demands of their unique project. These properties are tested using standardized methods from the American Society for Testing and Materials (ASTM). The most prominent ones listed can include:

Shore Hardness

Test method: ASTM D2240

Definition: Shore hardness is a material’s resistance to indentation or compressive forces. It’s measured using a tool called a durometer and rated on various scales depending on the characteristics of the material. The most common scales for polymer materials are Shore A, which rates softer materials, and Shore D, which rates harder materials.

Importance: Hardness is a property that will tell you a lot about a urethane hard coat’s wear resistance, strength, and service life. It directly impacts the material’s ability to protect an underlying surface from scratches, abrasion, and other physical damage. A harder material will give more strength, while a softer material will give more flexibility.

Polyurethane hard coats most often use the Shore D hardness scale. They will typically be in the 65-75 D range, which has a similar feeling to a plastic hard hat. When they drop below this range, they feel more flexible or rubbery. When they go above this range, they will have high resistance to deformation but can also be brittle unless they reach a certain thickness.

Achieving a good balance of hardness and flexibility while also maintaining good weathering characteristics is important. Coatings with a higher hardness have less flex and can be more susceptible to cracking when applied to surfaces that expand and contract as temperatures change. Because they have less flex, they have a limit on substrate usage and are best applied to EPS foams for theming projects. Hard coats are not recommended for surfaces softer than themselves. However, other properties can contribute to them having more flex, even at a higher hardness.

Note: All VFI EPS theming hard coats list their hardness in the product name (ex: VFI-6170 70 D Spray Hard Coat) to help you find what you’re looking for.

Tensile Strength

Test method: ASTM D638

Definition: Tensile strength is the maximum amount of stress that a material can withstand before it fails when being stretched. It subjects a test specimen to an applied force or load until it reaches its breaking point. That force is then measured and expressed in pounds per square inch (psi).

Importance: Tensile strength is an important property that determines if a urethane hard coat is suitable for your application. It can tell you a lot about structural integrity and durability. Coatings with high tensile strength should be capable of withstanding significant force without breaking or deforming. They are often used to protect and support delicate substrates from heavy loads. Demanding applications that would require high tensile strength include EPS foam projects within touching distance of people.

The strength of a hard coat helps it maintain its integrity under stresses such as wind, vibrations, and pressure to prevent deformation. Even small impacts can cause stress, but high tensile strength helps it absorb those forces, preventing damage from occurring.

Elongation

Test method: ASTM D638

Definition: Elongation is a property that measures the percentage (%) increase in length of a material before it breaks when stretched. It has an inverse relation with tensile strength and uses the same test method (stretching force).

Importance: Elongation is a very important property for urethane hard coats due to their rigidity. Their job is not necessarily to resist stretching force, which is why they will have high tensile strength and low elongation. However, this property ensures some flexibility and complements the strength offered by hardness and tensile strength. It is the balance of all of these properties that allows hard coats to perform the way they are designed.

Elongation will provide some necessary give to the hard coat to resist cracking even with high tensile strength and hardness. It will absorb some energy from impacts and distribute stress more evenly. Elongation with a high tensile strength also provides thermocycling capability that would not be possible with high tensile alone.

Tear Strength

Test method: ASTM D624

Definition: Tear strength or tear resistance is measured by assessing the maximum force required to tear a material in a direction perpendicular to the direction of the stress. More simply put, it is a measure of how well a material can resist tearing. It is expressed in pounds per linear inch (pli).

Importance: Tear strength is another property that can tell you about the durability and lifespan of lower durometer urethane hard coats. In a hardcoat, tear strength is a hard property to obtain unless the coating is under 65 D, but it is a good sign for thermocycling if the tear strength is high with good elongation.

After damage has been endured, the tear strength will tell you how the material will hold up. It will also tell you about its resistance to rips, punctures, and cracks. Minor nicks, scratches, and cracks can be a starting point for bigger issues if tear strength is too low. Tear strength makes the coating more resistant to damage, preventing a problem from occurring that compromises its ability to protect the underlying substrate.

Elastic Modulus

Definition: Elastic modulus is a material’s resistance to elastic deformation when stress is applied. Elastic deformation is the temporary change a material goes through when under stress, so the material will return to its original shape or size once the stress is removed. This property is expressed in pounds per square inch (psi).

Importance: Elastic modulus is a material’s ability to bear loads without significant deformation (temporary bending or indentation), which can be very important for urethane hard coats. The stiffer the coating, the higher its elastic modulus will be.

A high elastic modulus will allow it to perform effectively by handling impacts and other forces without cracking, scratching, or denting. This is because these coatings can store more elastic energy before deforming. So, the hard coat will absorb the impact energy from a blow and prevent it from transferring to the substrate.

A lower elastic modulus will allow a coating to deform rather than crack. This is useful when an object might be kicked or something sharp will hit it. It will also allow the coating to deform and not break to protect the foam. This is also important if water and outdoor elements are a concern.

Impact Resistance Unnotched/Notched Izod

Test method: ASTM D256

Definition: Impact resistance is a test that measures a material’s resistance to impact from a swinging pendulum. Unnotched Izod tests do not make a premade notch in the test specimen, so the impact energy is focused on the entire test piece. Not creating a notch will test the overall toughness of a material. The value, in pounds per inch (lb/in), will be a less accurate representation of real-world impact situations and give an elevated number. An alternative test method is a notched Izod impact resistance test with a preset notch to accurately direct the force.

Importance: Urethane hard coated projects, especially ones placed outdoors, may experience sudden forces, shocks, or blows throughout their lifespan. Impact resistance provides an understanding of whether the material has the toughness needed to protect theming applications long-term. High impact resistance will help shield the substrate from damage by absorbing the blow, preventing the coating from cracking or chipping.

Softer coatings are better at taking impacts because they have more flexibility but have a low impact strength. Usually, softer coatings will not have an impact strength tested because they will flex out of the way and provide a low number as a result. However, impact resistance is only one property that will help determine the material’s toughness. Consider the tensile strength, hardness, and elongation for a better understanding of the material’s strength.

What Liquid Properties of Urethane Hard Coats Are Important?

Not all manufacturers divide up their properties between liquid and physical. VFI does this so our urethane styrofoam hard coating users know which properties apply to the material when it’s in a liquid state versus when it has fully cured. The following are liquid properties we typically list:

Solids by Volume

Test method: ASTM D2697

Definition: Solids by volume or volume solids is the percentage (%) of the total volume of a material that remains once cured. In the context of coatings, it’s how much material will remain on the substrate and how much will evaporate into the air.

Importance: The amount of volume solids lets applicators know how much material they’re actually putting down, which is important when trying to build it to a certain thickness. Some manufacturers specify a millage that must be applied to achieve optimal protection, so making sure you know what you’re putting down is that much more important.

Luckily, most urethane hard coats are 100% solids, meaning no material evaporates during cure. The amount of material you apply to a surface is guaranteed to be the amount that remains once cured. Because of this, you also don’t have to worry about calculating wet and dry film thickness using the solids by volume.

Note: Be careful of shrinkage on extremely long parts as it can change depending on your thickness causing your part to warp.

Mix ratio

Definition: A mix ratio is a ratio that entails the exact measurements needed from multiple components to be mixed to produce the needed chemical reaction for a material to cure (ex: 1:1 or 2:1). A mix ratio can be expressed in two ways:

• By weight: Uses an accurate scale to measure the amounts of each component needed to cure. This property will typically only be listed for hard coats that can be applied by brush or roller.
• By volume: Uses same-sized mixing containers to measure the amounts of each component needed to cure. This property will typically be listed for sprayable and brushable hard coats.

Importance: Urethane is a very touchy material. If you don’t follow the mix ratio properly, then it might not cure to the desired effect. Adding too much or too little of one component can make the coating feel sticky or goopy rather than plastic-like when it sets. Typically, when this happens, it won’t develop physical properties, so it cannot effectively protect the substrate it is applied to. Affected physical properties can include hardness, adhesion, and resistance to abrasion or impact. The coating might be softer and not adhere to the substrate, leading to peeling or flaking.

Incorrect mixing of the components can also lead to material waste. Not only are you wasting material from each mixed component, but you may also have to scrap the entire project you’re working on and start fresh. This problem can be costly as these foam pieces take time to carve, so you don’t want to mess up.

Off ratio material will also affect the final finish of the project. When you try to paint over a hard coat that has iso-rich spots, you might be able to get away with it. However, the paint might peel off more easily when placed in the sun. When you try to paint over a hard coat that has poly-rich spots, the paint might react more with the sun and cause the paint to bubble because it is not breathable.

Viscosity

Test method: ASTM D2196

Definition: Viscosity is a fluid’s resistance to flow or change in shape and describes the internal friction of a moving fluid. It is often referred to as the thickness of a liquid and is measured in centipoise (cps). Viscosity can be listed for each component (A and B sides) and the material when combined. To understand viscosity, here is a list of household items and their relative viscosities:

Importance: Viscosity will tell you a lot about how a urethane hard coat will perform. It determines how easily the coating can be brushed, rolled, or sprayed onto a surface. With a very high viscosity, they can be hard to spread evenly but prevent dripping or sagging. On the other hand, a material with a very low viscosity might not provide adequate coverage because it is too runny.

The ideal viscosity will depend on the application method and desired film thickness. When a material is applied by brush, the viscosity will be higher to allow easy application without excessive dripping or running. The higher viscosity also allows for better control when using this application method. When using spray equipment, lower viscosity coatings are required for even distribution, fine atomization, and a desirable finish. A similar viscosity A and B side is also highly critical to maintaining a nice even spray. Not considering the viscosity when choosing your application method can result in surface defects, such as brush marks, orange peel texture, or uneven coverage.

Viscosity affects the final thickness of cured coatings. Higher viscosity materials will generate a thicker film build, while lower viscosity materials will have thinner builds. A lower viscosity also ensures that the material can level and flow effectively to minimize imperfections in the surface finish.

Air bubbles are also typically generated in the application process. High viscosity materials are more prone to trapping air bubbles, which can create imperfections in the cured finish. Low viscosity materials allow more of the trapped air to come to the surface and escape before cure. Because the bubbles leave easier, you’ll achieve a smooth, uniform finish.

Pot Life

Definition: Pot life is the length of time a material can be used. Depending on the material, pot life can be as quick as seconds or as long as hours.

Importance: Pot life is not a property that is listed for every urethane hard coat. Since a chemical reaction happens much faster for spray coatings, you’ll see it as a property for brushable ones. It’s specific to these coatings because you need to know how much time you have to brush or roll the material onto the surface before it becomes unworkable.

Within the pot life window, your mixture maintains a viscosity for smooth and efficient application. Once the pot life ends, viscosity increases, making it hard to spread. Ensuring you have adequate time to apply the coating will minimize defects in the finish, such as orange-peel texture, air bubbles, and incomplete coverage. Also, mixing more material than can be used within the pot life leads to material waste. In some cases, mixing less material can even extend the pot life. Finding a coating with an acceptable pot life for your project is crucial for optimal protection over your theming project.

Tack Free

Definition: Tack free determines the amount of time after mixing that a material will no longer feel tacky (sticky). Depending on the material, this can happen in seconds or minutes.

Importance: Unlike pot life, this property is usually listed on sprayable coatings because it tends to happen shortly after the pot life. After a hard coat is sprayed, it needs some time to cure and become tack free so it will no longer adhere to dust, debris, or other objects that come into contact with it.

This property is essential to know for handling and assembling a coated project. If it is still tacky, it can pick up contaminants that compromise its appearance and performance. These contaminants can come from airborne dust or someone touching the surface before it has solidified enough. The material then traps these particles, marks, or smudges once cured.

Most users will want a fast tack free time. The speed will allow further processing, such as sanding or painting, to occur much sooner. It also helps if the coated component needs to be assembled with other parts. The faster an applicator can post-work their project, the faster their production cycles are. However, a fast tack free time can limit the working window, especially for larger projects.

Note: A long tack free time also creates a great window for recoating and will help with better adhesion. Always check your technical data sheet (TDS) for recoat windows to prevent bad adhesion or additional sanding.

Cure to Handle

Definition: Cure to handle is the time until a material can be handled after application. It usually comes between the tack free time and the recoat window since the material has not completely cured. Most cure to handle times happen minutes after application.

Importance: Cure to handle time directly affects how soon you can handle a coated object after application. It can also tell you how soon it is ready to be sanded, painted, or assembled without compromising the final properties.

It needs sufficient time to cure and develop its properties. If you handle the coated project too early, the surface can crack or become damaged by touch. Handling it too soon can also lead to uneven curing, weak spots and inadequate protection of the underlying surface. Different urethane hard coats will have different cure to handle requirements.

Recoat Window

Definition: The recoat window is a property specific to coatings as it is the time frame between which a previous application can receive a subsequent coat or topcoat. Depending on the coating, a recoat window can extend from minutes to hours and may have different requirements based on the specific formula.

Importance: Some urethane hard coats must be applied in layers to build the thickness. Adding layers is usually done for more adequate protection of the underlying surface. During the recoat time, you can be sure the subsequent coat will have excellent adhesion with the prior one. This property is also important if you must paint over the coated surface for theming purposes. You can be sure that the paint will stick to the hard coat.

If you apply a new coat outside the recoat window, there will be weak adhesion between the coats. That weak bond can compromise the overall integrity of the coating, making it more likely to peel, crack, or delaminate. Poor adhesion can also compromise scratch resistance, impact protection, and other properties. In some cases, the initial coating can be sanded or scuffed to create better mechanical adhesion for the second coat. A strong bond between them will allow them to perform consistently across the entire project.

How to Find Urethane Hard Coat Properties

Because material properties are so important for users to know before they purchase a product, we display them accurately after meticulous testing and review. They can be found on technical data sheets or product pages of any product. Technical data sheets can be found under the resources tab on any product page.

Contact VFI if you would like more information on properties to determine the best product for your project.

Sprayable Plastic Coatings for Theming & Attractions

The main job of a sprayable plastic coating for theming and attractions is to protect foam surfaces from various environmental elements. When you create a new themed environment out of EPS or Styrofoam, you’ll want it to last. That won’t happen unless you have the proper protection. Even though this part is unseen by the audience, it’s one of the most important steps. This step also prepares the surface for priming and painting to create a more uniform and professional finish. So, you need to find the best material to do so.

What Is a Themed Environment?

Themed environments are physical spaces that should transport guests and visitors to different times and places. An effective way to do this is by creating an immersive world using architectural sets, lighting, sound, and technology. If done right, your environment should invoke emotion, engage the senses (sight, hearing, touch, etc.), entertain, and give your audience a reason to want to come back.

These themed environments can help businesses differentiate themselves from the crowd. An environment like this can also foster a good work culture. Businesses can even get brand exposure from people taking pictures or videos and sharing them online, helping bring in more people. Themed environments are not limited to theme parks like Disney World and Universal Studios; you can create a unique experience for showrooms, restaurants, stores, and more as well.

What Makes up a Themed Environment?

Just about every part of queue areas, theme park rides, and even the streets of a theme park can be themed. Theming elements can be as simple as faux rocks and trees or as extravagant as large 3D sculptures. The following are used to add to the overall theme in amusement parks:

• Sculptures: While not always directly surrounded by an environment they’re meant to be in, theme parks can use larger-than-life 3D character sculptures throughout the park to further connect with guests, elicit nostalgia, and generate photo opportunities.
• Props: Many theme parks, as added entertainment, put on stage productions that use various stagnant and handheld props. These props create much-needed visual elements for stories. Without props, costumes, and sets, much is left up to the imagination. When props are used, it further enhances the imaginative experience.
• Scenery: The architecture is meant to engulf your audience in a new world with visual elements that captivate them the second they enter. Setting a scene can include a handful of things, including simple architectural elements like columns, shutters, crown molding, etc. or, memorable objects, sets, and characters that tell a story.
• Signage: Signs are typically the first thing an audience sees as they approach a building. They may even help them decide if they want to continue into a location, whether that be a shop, restaurant, or ride. It also directs them where to go since they’re high up in places everyone can see.

How to Design a Themed Environment?

The type of materials you use to create a themed environment will depend on several factors, including:

• What is your budget?
• Will the project be for indoor or outdoor use?
• Will people be able to touch it?
• Is it a one-time project or long-lasting?
• What are your safety requirements?
• Is there a weight requirement?

While various materials have been used to create themed environments in the past, it has become much more common for designers and artists to use foam to make massive landscapes, sculptures, signs, and more. This material is desirable because of its cost-effectiveness and lightweight nature. Compared to other building materials like natural stone, wood, and metal, foam is much more affordable and easier to move or transport to a permanent location.

The most common foam used in these instances is EPS (expanded polystyrene). XPS/Styrofoam (extruded polystyrene) and polyurethane foam have been used as well. EPS is much easier to cut, shape, and mold using CNC, hot wire cutters, and wire brushes, among other tools. This method allows designers to create pieces with less skilled artistic labor and more easily than if they used heavy, solid, and expensive materials.

How to Protect EPS Foam Theming Projects

While foam is an excellent material for theming, it can’t be placed in an environment without a protective shield because it’s not very durable. Without protection, it would be exposed to the sun, wind, rain, and other weather conditions that could cause damage. The foam could also become damaged from transport or during installation if unprotected. Also, if you want to be able to sand, prime, and paint the foam, a rigid material that creates a smooth surface is needed. The best thing to do would be to harden the foam.

A sprayable plastic coating like urethane is a good material that hardens and protects foam for indoor and outdoor use. It is versatile and can be formulated with varying properties, including Shore hardness and tensile strength. The recommended durometer is around 65-75 D and will provide a plastic-like appearance and feeling while not being able to shatter or crack.
When undertaking large-scale projects or many small projects, the best application method is by spray. There are two distinct spray methods VFI recommends:

• High pressure – For high volume projects, artists and applicators use a sprayable plastic coating through a two-component high pressure spray rig on large projects. VFI recommends VFI-6170 70 D Spray Hard Coat, as it provides a durable shell over large structural shapes made with EPS foam. A benefit of this material is that it is Class A fire tested to meet strict indoor and outdoor safety standards.
• Qwik spray – An alternative to expensive spray equipment is to find a sprayable plastic coating formula that is applied with a cartridge-based applicator gun. This method is best for portability if you must take your projects on the go. It is also only recommended for smaller projects under 4 feet. Otherwise, you’ll have to spray in much thinner passes and must be comfortable with the overspray it will generate. VFI-6171 70 D Qwik Spray Hard Coat is VFI’s cartridge-based hard coat compatible with the VFI-7500 Qwik Spray Gun.

Interested in a brushable hardcoat? Check out VFI’s blog for more information.

Benefits of Using a Sprayable Plastic Coating

While foam is lightweight, the coating is also fairly light, so it doesn’t add too much weight to the entire piece, making it just as easy to move and transport finished objects. This solves a lot of logistical problems with large pieces that have to be hung up or mounted above the ground.

Because the coating forms a seamless finish, it is able to withstand damage from weather, which is essential if the foam piece is placed outside. Its hardness makes the foam incredibly strong and resists cracking, so it’s capable of lasting long-term. It is also impact and abrasion resistant, so it holds up in the event that people are constantly touching, leaning against, or sitting on it, which is expected in theme park environments where children are present.

Polyurethane, as a sprayable coating, is incredibly versatile in what it can be applied to. It conforms to curves and does not diminish details as long as it is not sprayed on too thick. While the finish typically comes out smooth, it can be sanded to enhance aesthetics before applying a paint or top coat.

Contact VFI if you are interested in any of our EPS theming hard coats and need assistance choosing the best one for your project.

What Is Polyurea Hybrid?

Polyurea hybrids have been closely confused and mistaken for a polyurea. While they have some components of polyureas, they are vastly different in some major categories, including price, properties, and moisture sensitivity. They are generally two-component systems where a blend of polyols and amines react with an isocyanate.

The chemical backbone of a hybrid is composed of both urethane and urea linkages. These linkages are made of a reaction of amines with isocyanates (urea) and polyol with isocyanates (urethane). However, not all hybrids are equal. Some formulas can be 99% urea linkages to 1% urethane mix, while others can be the complete opposite at 99% urethane to 1% urea. These content variations will change the properties and other features substantially.

Urethane linkages contribute to a more favorable price point compared to polyurea. The amine content, linked to polyurea, makes it less sensitive to moisture compared to urethane, because it does not require catalysts to promote a water reaction. Pure formulations are very limited in the compounds they can use for the B-side. A hybrid’s urethane side allows for more versatility.

They can be specially formulated into tough, elastomeric coatings for industrial and commercial applications. They can handle complex designs over surfaces, such as metal, foam, and concrete when applied by spray. Most are aromatic in nature, which means they do not resist UV rays.

Hybrid vs Polyurea vs Polyurethane

Hybrid Advantages

• Their fast-setting ability makes them suitable for spraying on horizontal and vertical surfaces. Some formulas are also capable of being sprayed overhead without sagging. This fast-curing time also provides projects with a quick return to service.
• These coatings are tough and durable, with properties that allow them to resist impact, abrasion, wear, and tear. Other properties that help them resist damage include chemical and corrosion resistance.
• Using a spray-applied method, the material creates a seamless film. Since there are no seams, the coating prevents water penetration that could cause damage to the underlying surface.
• Since these coatings are very versatile, they can be adjusted to fit the needs of the application. Hardness can range from 40 to 75 D on the Shore Hardness scale, which is rubber-like to extremely hard.

How Is It Applied?

Proper preparation of the substrate is important to ensure the coating will perform how it should. Moisture and humidity should be monitored as they could cause issues in the application process.

The two-component materials are typically mixed through a proportioner. With either high-pressure, low-pressure, or cartridge-based spray rigs, the coating is sprayed directly onto the surface to protect it from external damage. Temperatures and pressures of the machines must also be taken into consideration.

• High-pressure spray rigs are the most common application method. They are plural component machines capable of heating the material and maintaining a specified psi. This equipment is best suited for high-volume and continuous coating applications. Vehicle producers, film-set creators, and theme-park sculptors typically benefit from these systems.
• Low-pressure spray rigs are used when coatings have slower gel times and longer cure times. The longer cure time allows easier spraying when going through a machine, using less pressure to push the material. Sometimes, it’s not necessary to have an expensive high-pressure rig, especially if you have flexibility in your project timeline.
• Cartridge-based spray systems offer the benefit of being able to spray while being less of an investment. The cartridges make the application portable and suitable for lower-volume applications. Based on frequency of use, a vehicle repair shop would benefit from cartridge-based coatings, whereas a vehicle manufacturer would probably need a high-pressure system. The maintenance on the machine is also much easier than a high-pressure system and does not require skilled labor to maintain.

Common Polyurea Hybrid Applications

Since hybrid coatings are highly customizable, they are the best choice for a wide range of applications. With a good cost-to-benefit ratio, they’ve been used in the following commercial settings:

• Below-grade waterproofing. The coating creates a seamless, leak-free membrane, which makes it a suitable option for waterproofing surfaces. With fast-curing properties, it is much faster and easier to apply than other materials. The barrier not only protects a building’s foundation against moisture but also against other contaminants in the ground.
• Tank pad coating / secondary containment. Hybrids work to create impermeable barriers in areas where preventing hazardous materials from reaching an environment is critical. These coatings are highly resistant to chemicals and solvents, so in the event of a spill, they keep the material contained. They work great over EPS foam for tank pad coatings.
• Truck bedliner. At a relatively low cost, hybrids form a durable, water, and air-tight barrier for exterior protection of pickup trucks, dump trucks, and utility vehicles. These spray-on coatings are easy to clean and maintain with the bonus of abrasion, scratch, and skid resistance. They are your best bet for vehicle part protection, especially from rust and corrosion.
• Theme park and decorative design. The coatings can form hard shells over EPS foam, wood, and other structures that need long-term protection from abrasion and physical wear. Sculptors and set makers have used them to make characters, artificial rocks, themed environments, and more.
• Joint filler. They also make great materials for filling concrete joints in industrial and commercial settings. Rather than spraying, they are injected into the cracks between concrete panels and cure quickly for a fast return to service. They are excellent at protecting concrete joint edges from damage due to heavy traffic.

VFI High Performance Polymers

VFI manufactures a handful of coatings for industrial and theming projects. From our bedliners (VFI-542, 543, and 544) to our specialty coatings like VFI-206, we have options for any circumstance. Also, ask about our polyurea coatings for other industrial applications. If you don’t see something you’re looking for, contact the VFI team for assistance.

Cast Stone vs Manufactured Stone Veneer: Which Should You Use?

You may think the architectural elements you see on commercial and residential buildings are made of real stone, but it is becoming more common for them to be made of concrete. It is hard to tell if an accent wall in a lobby or the columns on a front porch are made of natural stone because man-made products are so realistic.

For years, natural stone was upheld as a premier building material for its beauty and stability. The reason why people are turning to other building materials is due to cost, weight, and sourcing difficulties. Manufactured stone and cast stone were created as solutions to these problems.

What is Natural Stone?

Natural stone is a durable material that is obtained from the earth. It has been used for centuries due to its strength and longevity. To make it an effective building or decorative material, it is cut down, shaped, and finished for an assortment of projects. Though, it is much more difficult to cut than man-made products.

A desirable feature of natural stones is their uniqueness. As a product of nature, no stone will have the exact same pattern, look, texture, or coloring. There is an abundance of natural stone types, including limestone, granite, marble, slate, etc. While each natural stone’s distinct graining and coloring give it character, it prevents uniformity and consistency throughout a project.

What Is Natural Stone Used for?

• Natural stone was once used to create some of the most famous historic structures, monuments, and sculptures around the world, and still is.
• It can be used as decorative architecture on interior or exterior floors and walls. An example could be an accent wall or a fireplace.
• For larger outdoor projects, it can be added to your landscape when designing fishponds, patios, outdoor kitchens, or boundary walls, among other things.
• Natural stone can even be used for furniture like countertops or showers to give your home a makeover. Granite and marble are most favored for these projects as they create elaborate displays that are easy to clean and maintain.

What Is Cast Stone?

Cast stone is a man-made concrete building material whose main purpose is to replicate natural stone at a lower cost. It is used to create complete architectural elements. Cast stone is often mass-produced, meaning you’ll likely find identical pieces across one project, which creates a uniform appearance with consistent quality. Its availability is also not limited by geographical factors, which means it is accessible wherever you are.

It has unmatched design flexibility as it can be molded into various shapes and sizes to achieve your desired aesthetic. It can also be pigmented to match and blend with other building elements. Cast stone can have intricate details, replicating diverse textures, shapes, and patterns without the need of skilled labor carving the shape each time.

Because it’s made of a synthetic material, it often costs less and is lighter than natural stone. As a lighter-weight material, transporting and maneuvering concrete pieces on a site is much easier, especially for larger projects. The manufacturing and installation processes are easier, with less time and labor needed. And even though it is lighter, it is still durable and has high strength as a concrete product.

How Is Cast Stone Made?

Cast stone can either be wet-cast or dry-cast concrete. The wet cast method is commonly used for casting large, structural, and complex elements. A mixture of Portland cement, aggregate, and pigments is combined and poured into molds. The texture of the material will be similar to natural stone and produce finishes that are difficult to distinguish from the original material.

Cast stone can be molded using various materials, including wood, fiberglass, plastic, or rubber. The material you should use depends on the architectural element being replicated and the amount of detail required.

One of the best mold materials is liquid urethane rubber due to its abrasion resistance and tear strength. It handles concrete well without breaking the cast piece and can produce as many as 100 pieces in a single mold with the same consistent detail.

By first casting over an original model, these molds will easily replicate the original piece’s features into the concrete. Due to their flexibility, they are also great for elements with deep undercuts. For most cast stone projects, a 20-30 A material is recommended to obtain desired shapes and details.

What Is Cast Stone Used for?

• It is often used in architectural restoration projects because it is able to replicate and replace the old and deteriorated stone on historical buildings.
• It is popular for decorative elements, trim, ornaments, or facings for buildings and other structures, such as columns, porticos, balusters, pier caps, copings, watertables, window surrounds, door entries, and more.
• It makes great concrete furniture and décor, including tables, benches, plant pots, etc.
• It is found on and in homes, condos, churches, banks, courthouses, and more.

What Is Manufactured Stone?

Manufactured stone veneer is often called a handful of other names, including faux stone, artificial stone, or cultured stone. Like cast stone, it is a man-made material designed to replicate the look of natural stone at a lower price and weight. It differs from cast stone because it is veneer, a thin layer of molded concrete applied to another surface, like wood or flat concrete. It is often used for non-load-bearing decorative detailing, as it does not provide any structural support.

Stone veneer products offer an array of shapes, sizes, and color options that are indistinguishable from natural stone unless closely inspected. As a concrete material, they are strong and durable to be used in indoor and outdoor spaces.

They are not the same thickness and weight that a natural stone would be, making them easier to install in hard-to-reach places. A faux stone can be 15 pounds or less with no support needed when applied to various surfaces.

How Is Manufactured Stone Made?

Manufactured stones are typically pre-cast using wet-pour concrete. Like cast stone, they are made of water, cement, superplasticizers and lightweight aggregate materials. This mixture makes them durable and able to withstand the elements. It is the coloring and molding of the concrete that makes them look like natural stones. When poured into molds with pigment, the concrete mixture is able to resemble marble, granite, limestone, and other desirable stones.

The actual process begins by making a mold. The mold is typically created as the negative of a real stone, so the concrete can mimic the look and texture accurately. When urethane molds are used, the veneer stone will pick up all the details of the stone it is replicating. When making the molds, a 30-50 A urethane material is recommended, as it provides more strength than a lower durometer rubber would.

A small mold of one stone can be made, as well as a large mold with multiple stones that vary in size, which are then packaged together. As a veneer, it is typically cast at about 1 inch thick. Some of the stones will have repeated textures and designs, but that ensures your project will be consistent in quality and appearance.

Manufactured stone veneer will have a flat back for easy installation over a variety of surfaces. While cast stone is typically custom-made, manufactured stones can be laid out and cut to suit the project.

What Is Manufactured Stone Used for?

• The main use of manufactured stone veneer is to create exterior facades and unique statement walls.
• They can be used both indoors and outdoors to elevate the architecture and appearance of office buildings, restaurants, roadways, hotels, medical facilities, etc.
• Due to their flat-back nature, they can be installed over metal, wood, masonry, brick, or poured concrete to add a decorative element to various spaces.
• They are used to elevate the architecture and appearance of various buildings. They can be placed around fireplaces, fire pits, outdoor kitchens, water features, walkways, patios, and more.

If you’re interested in cast stone or manufactured stone, VFI makes a variety of 2 part urethane rubbers that make perfect molds for these projects. Contact us today for assistance in finding the best material.

Urethane Molding and Casting Materials

Industry professionals can greatly benefit from various molding and casting materials when it comes to making structural and architectural concrete elements. Among some of the best materials to use are urethane rubbers.

They are very versatile two-component kits that can be used to make molds, formliners, and stamps for sturdy, functional, and artistic concrete projects. Their versatility comes from the ability to be formulated with varying properties, including a range of Shore hardnesses, which allow the materials to be used for small, detailed projects as well as large structural projects.

What Is a Concrete Mold?

Concrete molds, also called forms, are a type of molding and casting material used to shape fresh, liquid concrete. Once hardened and left to strengthen, these concrete pieces are demolded to be used as building components, decorative elements, or artistic displays.

A concrete mold must be sturdy and abrasion-resistant to ensure it won’t deform during the casting process and the concrete will demold without damage. Molds can be made of various materials, including rubber, plastic, silicone, latex, wood, and metal. Urethane rubbers are among one of the most robust materials for concrete casting. These molding and casting materials can be made into a range of shapes and sizes with various designs and textures. These details are transferred into the wet concrete to influence the final finish of the piece.

The hardness of the mold is an important factor to consider when casting concrete and depends on the piece you intend to produce. The softer the rubber, the easier it will release from a complex, detailed concrete piece. However, softer rubber is not as durable as harder rubber. As urethane’s hardness increases, it is less flexible but more durable. This is why more detailed stone molds (ones with more incuts and the need to compress) use 20-50 A material and large form liners and stamps use 70-90 A material.

How Is It Used to Cast Concrete?

A single urethane mold can be used to make repeated concrete castings that mimic natural materials. It captures high surface detail and can be reused over and over, making it the material of choice for high-volume production. These molds are used to cast concrete in many different ways, including:

• Precast panels – Harder rubber is typically used to make larger structural elements. The concrete material is poured into massive flexible form liners off-site, in a controlled environment. These detailed liners can then make decorative panels, fences, retaining walls, and more.
• Manufactured Stone – Rubber ranging from 30-50 A is great in general assembly lines to make molds for lightweight concrete stone facades and/or decorative exterior elements. Urethane rubber’s dimensional stability is perfect for the repeated casting process required. These stones are used on homes, restaurants, and more.
• Cast Stone – Urethane rubber is made primarily for wet cast stone and is used to create corbels, wall caps, crown molding, and other advanced shapes. Urethane rubber is mainly used in cast stone when compression of the mold is required.
• Hardscape – Rubber stamps or rollers are capable of turning wet concrete into natural-looking, textured pieces that mimic real brick, flagstone, slate, etc., for outdoor decks, patios, walkways, and more. Rather than using expensive natural stone, stamping concrete with urethane can create pavers, steppingstones, small retaining walls, and curb walls for less.
• Décor & furniture – Concrete can be cast into molds to make large statues or art pieces for decoration or even functional elements like benches, countertops, planters, fireplaces, and outdoor kitchens. These creations can utilize stone veneer as a finish or cast stone for complete pieces.
• Architectural Restoration – Softer urethane rubbers are great for restoring old stonework on buildings. The lower durometer makes it easier to demold around complex shapes and undercuts without damaging the original piece.
  Whatever your project is, it is important to use an appropriate mold release when casting concrete. While urethane is an extremely durable material, it can also create strong bonds with many surfaces.

Not using release can have disastrous effects on the mold and concrete pieces. Even with a release, you may have to use a tool to pry the piece out of the mold if it’s stubborn. VFI, however, has developed new easy-releasing urethane rubbers for ease of use and reduced breakage when used with release.

Are there Alternatives to Urethane?

Choosing the right material is essential to ensure it will meet the needs of your project. And while urethane does come with great benefits, there are alternatives that might be better for your application. Other materials must be non-porous, non-reactive with concrete, and rigid enough that the mold won’t change shape once the concrete is cast.

1. Silicone rubber molds

Silicone is another flexible molding and casting material that produces intricate designs and textures on concrete elements. It has outstanding demolding characteristics that don’t require mold release. It works well for architectural restoration since it is able to keep the original model intact without damaging it.

However, polyurethane has more variety when it comes to hardness so it can be used in a variety of concrete applications that silicone may not be able to. Silicone is also more expensive and not great for large-scale, high-volume concrete casting. Shrinkage is another major concern with silicone when repeatedly casting concrete.

2. Plastic forms

If you desire a more affordable material, various plastics like ABS have been used to cast concrete for decorative and artistic pieces. They can offer high detail in the cast part, producing complex shapes and fine textures. They are also relatively easy to use due to their lightweight nature. However, making these molds requires certain skills and techniques you don’t need with urethane. Most plastic molds will need to be purchased from a manufacturer and will have a preset design. They also will not last as long as other materials, producing only about 10 castings per mold.

3. Wood forms

Wood molds can be custom-made and are easy to construct for large-scale structural elements. They are versatile, tough, and strong, and because wood is readily available, they can be more affordable for certain projects. However, these molds are not as durable as other materials and are not suitable if you want intricate designs or curves in the concrete. To increase the usability of these forms, a form coat epoxy can be used to protect the casting surface from abrasion.

4. Metal forms

Most metal molds are made from either steel or aluminum and can be used for structural or decorative concrete purposes. They are durable, made to last, and, like wood, produce smoother finishes. Similar to making plastic molds, metalworking requires specialized tooling and skills for precision. Metal is ideal for repeated, high-volume use when making concrete pieces for larger industrial projects that require strength and durability over aesthetics. Most metal molds will be small because of cost restrictions. A form coating epoxy can be used for long-term protection of these forms as well.

5. Latex molds

Because of its low viscosity, latex is applied to a model by brushing on multiple thin layers until the desired thickness is met. Having to apply multiple layers is a big drawback to using this material. Some latex molds can take as long as 2 weeks to finish because they don’t cure as quickly as silicone or polyurethane. So, if you require quick production, this is probably not the material you want to use. Also, due to latex being used as a thin film, you will always need a rigid backer mold for casting. However, it is probably the strongest and most resilient material, leaving you with long-lasting molds for years.

Why is Polyurethane Rubber Better?

• It is a long-lasting, reusable molding and casting material. Due to its high abrasion resistance and strength, it is more durable than other materials.
• It creates highly detailed and accurate concrete pieces that mimic natural materials. With high flexibility, the material is able to form around complex undercuts and other details to make perfect copies of the original.
• It is easy to work with. While it requires a release agent for demolding, it requires little effort to separate it from delicate details once the concrete has set. There are also easy-releasing urethanes available at VFI, which makes using these materials more desirable when heavy release cannot be used.
• It can be a cost-effective option compared to silicone and metal molds. Silicone has a few benefits that urethane lacks, but they’re fairly equal in their abilities. While it is more expensive than wood or plastic, it makes up for that cost in its longevity, flexibility, and reusability.
• It is an extremely versatile material that can come in a range of hardnesses to complete both large and small projects. There’s really no limit to what urethane molds can be used to create.

VFI manufactures a variety of urethane rubbers for various concrete casting projects. Contact us today if you need help finding the best material for you.

What Is a 2 Part Polyurethane Rubber Kit?

A 2 part polyurethane rubber kit, or 2K polyurethane, is commonly used in the construction industry as a molding and casting material or precast concrete product. The material is packaged into two separate containers, which are meant to be combined just prior to use.

Most urethane rubber kits are categorized in terms of hardness. Since urethane rubbers are called elastomers, they use the same hardness scale, which is the Shore A Scale. A lower number on the scale means a softer, more flexible rubber. A higher number on the scale means a harder rubber that provides greater durability and long-term use. Soft rubbers are best for making molds with complex shapes or details, while hard rubbers are best for making tough, flat molds, formliners, or stamps.

2 part polyurethane rubber kits are excellent for casting concrete. They are mainly used to make molds for manufactured stone, cast stone, sculpture and décor reproduction, architectural restoration, and more.

Why Does Liquid Urethane Rubber Come as a Kit?

Urethane rubber comes as a 2-part kit because it requires precise mixing of each part so it can undergo a controlled chemical reaction to cure. The kit includes an A side and a B side; the A side is an isocyanate blend, and the B side is a poly/amine blend. Mix ratios of the A and B side materials can vary, with 1:1 or 2:1 by volume being the most common.

The chemical reaction can only occur once the A side and B side components are combined and mixed. When mixed, the two components chemically link, creating an irreversible exothermic reaction. The material will cure at room temperature to a flexible rubber with formulated properties. Being a liquid material at the start allows you to mold it into any shape you require.

Advantages of using a pourable urethane rubber kit include:

• Ease of use: 2 part urethane rubber kits are easy to use, as many users like to measure their material by volume, so no scales are required.
• Controlled pot life: By keeping the components separate until use, you can prepare everything else for molding before you pour the rubber.
• Controlled cure time: Since the components are separate, they won’t start curing until they are mixed. You can ensure that your material will cure at the desired rate for your application.
• Custom formulations: Varying the ingredients and the mix ratios of the two components creates different formulas. This allows for versatility in properties to meet requirements for various applications. Flexibility in formulation is much easier to achieve with two component kits.

How Do You Mix the A Side and B Side?

Before mixing, ensure your material, mold boxes or forms, and working area are at a proper working temperature. At VFI, we typically recommend temperatures above 65°F for the material to cure properly. Always check the technical data sheet provided by the manufacturer for specific instructions.

Not all urethane rubber products have the same mix ratios or handling procedures. Check the mix ratio before you start, as they can be listed by volume or weight on the technical data sheet. Following the mix ratio is crucial for your material to achieve the full formulated properties once cured.

Before mixing, prepare the equipment you’ll need. Spray release on your mold box or form for ease when demolding. We recommend having two clean, dry mixing containers, such as plastic buckets, and a hand mixer or mixing sticks. Depending on how you plan to measure your material, you may also want a scale. Also, wear proper PPE, including gloves and safety glasses, to avoid contact with the material. Once you are set up in a well-ventilated area, proceed with the following:

• First, mix the B side. Some B side material may have settled in transit or storage, so we require mixing before pouring it into a clean container.
• Weigh or measure the B side into a clean mixing container.
• Weigh or measure the A side and pour it into the same mixing container. Once the A side material has been added to the B side material, your work time/pot life has begun.
• Mix the A and B sides together using a hand mixer or mixing stick. Make sure to scrape the sides and bottom of the container while mixing to ensure a homogenous mix. Mix slowly to prevent air bubbles from forming in the material.
• Pour the mixture into a new, clean container for a second mix. The double mix method will ensure that no unmixed material is used. Continue to scrape the sides and bottom while mixing.
• After thorough mixing, the rubber should be immediately poured into a mold or form to cure.

If you do not use all your material, a nitrogen purge can help extend the shelf life of both the A and B sides. Do not save any material that has already been mixed. Only unmixed A and B sides can be purged.

How is 2-Part Urethane Different?

A 2 part polyurethane rubber kit allows for versatility and customization that other single and two component materials can’t provide. Chemistry can be adjusted to provide different properties, making them suitable for applications in various industries.

Urethane’s properties contribute to an increased lifespan of molds and forms made with the material. It has better abrasion resistance with excellent strength, durability, and dimensional stability. These properties are why urethane rubber is one of the most commonly used materials to cast concrete.

Its elastomeric properties allow it to be bent or compressed and still return to its original size and shape. This flexibility is vital for abrasive molding conditions since it results in less damage to the mold and casting. VFI has even developed a Max Release Molding Rubber series for easier demolding and reduced breakage rates. This is similar to the characteristics of silicone, but much better for concrete casting.

Also different from other materials is urethane’s ability to provide consistent performance under repeated casting. Many materials are only good for a few uses, while a single urethane mold is capable of producing up to one hundred castings. They are also typically less expensive than other similar rubber kits like silicone.

How Do I Find a Liquid Polyurethane Supplier?

The first step in finding a liquid polyurethane supplier is to conduct an online search. Search engines like Google can offer a vast amount of information when searching key terms like “liquid polyurethane rubber suppliers.”

Attending trade shows, exhibitions, and conferences is also a great way to connect with polyurethane manufacturers and suppliers. Look for events related to industries where the material is typically used. These events will generally have polyurethane companies showcasing their products so you can connect with them or other professionals who use the material.

Alternatively, you could also reach out to professionals in your industry who may use polyurethane. They may be able to guide you in the right direction or recommend reliable suppliers based on their experience.

VFI is a manufacturer of urethane rubbers, plastics, and coatings. Contact us today if you’re interested in hearing more about our products.

Advantages of Using a Form Coating Epoxy

There are several advantages of using a form coating epoxy over expensive precast forms, surfaces, and molds. Forms are essential for casting concrete, as they hold and shape the wet material as it cures. However, if you want to repeatedly use these forms without damaging them, you’ll need to apply a form coating. This protective coating will contribute to the long-lasting success of the casting surface.

With an understanding of how to use a form coating epoxy to protect surfaces from abrasive damage, you can create an abundance of quality precast products from a single surface or form. Here are several advantages:

• Extended protection – Using an appropriate form coating epoxy will ensure that the surface can withstand the weight and abrasive characteristics of the casting material during the pouring and demolding process. While rigid, it is also formulated with some flexibility so it will limit cracking without fabric or polyester reinforcement. The coating minimizes abrasion, impact damage, wear, and chemical or moisture exposure to enhance the quality, durability, and life of the surface.
• Reusability – Some materials are more durable than others. After repeated use, the casting surface can deteriorate. When a form coating epoxy is applied, it makes the surface durable, lengthening the life of the form so it can be used over and over without damaging the underlying surface. The coating is also repairable. It can be sanded and reapplied for continuous protection.
• Smooth finish & improved quality – Applying a form coating can improve the overall quality of the casting. It creates a self-leveled surface that is flat enough to distribute the casting material evenly. The coated surface also ensures that the final precast product will have clean edges and smooth surfaces. Without the coating, there may be a rough, uneven texture on the surface of the cast piece. So, you’re not only lengthening the life of your form, but you’re also improving the aesthetics of the finished product.
• Easier casting removal – While a release agent is recommended before casting, the surface will be smooth and non-porous when the coating is applied. The casting mixture will not seep into the surface beneath the coating, which allows it to detach from the surface more easily. The easier release means less effort is required to remove the casting. The coating also prevents waste since the casting will come out intact, and the surface is undamaged for reuse.
• Versatility – A form coating epoxy is extremely versatile as it can be applied to a variety of surfaces using a roller. It bonds well to metal, wood, and foam. It should be able to contour to corners and edges no matter the shape or size of the form.
• Reduced maintenance – Because the epoxy is a smooth, non-porous material, it is easier to clean surfaces between castings. There’s no worry about debris, dust, or moisture slipping beneath and contaminating the form, which means faster turnaround times.

Types of Forms That Can Benefit

When deciding the type of material to use for your form or mold, there are a few things you should take into consideration. The surface material should be non-porous, non-reactive with the casting material, level, and rigid. A desirable form material would also be capable of accepting a coating that could reduce the adhesion between the surface and the casting material. Some common molding materials that could benefit from using a form coating include:

Metal

These forms are typically made of steel due to their reusability. They’re rigid, durable, and provide a smooth surface for casting. Simple, preformed metal surfaces make practical molds for casting. They will be more expensive than other materials due to their extended durability.

However, not covering the molding surface with a form coating epoxy can cause the metal to deteriorate faster than anticipated. Casting abrasive materials, like concrete, that contain alkalis directly onto a metal surface can cause corrosion. When the coating is used, it will prevent direct contact between the surface and the casting material. This barrier will protect the surface from developing imperfections that will affect the final cast quality.

Another reason a form coat epoxy should be applied to metal is so the casting material won’t bond to the surface and cause damage in the removal process. Because these forms are so expensive, it’s important to protect them for long-term use.

Wood/Sheet Goods

Wood and sheet good forms are the most basic and can be made of timber, plywood, particle board, or MDF. They will generally be simple, rectangular, and flat. Although these materials are easy to work with and cost-effective, they have a relatively short lifespan and won’t offer the same reusability as other materials.

Casting materials will stick more easily to an uncoated surface, which makes cured pieces difficult to remove. This adhesion can damage the surface, preventing the mold from being reused, and it will need to be repaired after each use. When a form coating epoxy is applied to a porous surface, it reduces the chance of adhesion or moisture absorption and increases the reusability of the form. If the surface absorbed some of the moisture from the cast material, it could cause it to swell and warp, leading to a poor cast. The absorption could also promote rot as the wood would absorb moisture and promote fungal growth.

The coating also, if necessary, can prevent the casting from copying the natural grain texture from the wood. When applied to the wood surface, it covers the texture and any imperfections, so the casting surface is smooth and non-textured.

EPS Foam

Foam forms are typically chosen for the ability to use a machine to create a specific shape without the additional labor of making them by hand. A machine-made foam part is used when a low-weight and highly precise mold is necessary. Since the foam is fairly delicate, it’s usually made for a single use or limited use based on the shape.

Solid blocks of foam can be carved to achieve a desired shape for casting. Foam pieces can also be glued together to create walls to pour casting materials into. However, the only way EPS is capable of being a casting surface is if a durable form coating is applied. The coating will make the foam more rigid and capable of withstanding abrasion and wear. This option also tends to have a lower cost than other materials because foam is inexpensive.

How to Prevent Form Failure from Occurring

Before pouring your casting material, prepare the surface to avoid issues. Certain factors can cause the form to fail. There are several ways to prevent that failure from occurring:

• Ensure adequate strength of the form – A strong form is essential to withstand the weight and abrasion of various casting materials, like concrete. Even the toughest surface will be prone to failure if you overfill the mold. That’s why a form coating is applied over the surface. It is rigid and takes on some stress during casting, so the surface is stable and reusable. Make sure the weight is distributed evenly, which can be done by vibrating the form. An adequate amount of coating will need to be applied based on the form material and thickness of the cast.
• Be cautious when using old materials – A form coating epoxy will wear over time due to the abrasion and wear caused by the casting material. The great thing about using one is that it can be reapplied. Look for signs of deterioration in the coating after each cast. If it’s time for a new application, sand the original coating and apply a new coat. It takes much less time to restore the coating than it would to replace an entire form.
• Don’t neglect maintenance – Conducting regular maintenance will prevent future failure due to deterioration of the coating. The coated surface should be cleaned after each casting is removed to maintain its integrity. Maintenance includes removing any casting residue before it is stored for future use. Ideally, you’ll want to store your forms indoors in a controlled environment.
• Take your time and be patient – Allow the concrete to cure properly before it is removed to prevent failure of the form. If you try to speed up the demolding process, you may end up with subpar castings or a damaged form.

If you want to protect your precast forms, contact VFI for information about our VFI-4385 82 D Form Coating Epoxy. We also have a polyurethane alternative: VFI-2538 70 D EPS Form Hard Coat.

Why Is My Urethane Rubber Mold Expanding?

Liquid urethane rubber molds shrink from low temperatures, but problems also arise if they are used in warm and humid climates. Pourable polyurethane rubber may expand in high temperatures due to its elastic properties. While these properties are beneficial, you must follow certain application procedures to ensure they work how they’re supposed to.

The dimensional stability of our urethane rubbers is tested using the ASTM D2566 method for thermoset casting systems. This is the percentage of linear shrinkage when subject to changes in temperature or humidity during cure. At room temperature, all VFI TDI urethane rubbers maintain dimensional stability below 0.001 in/in.

Once temperatures rise above 77°F, users may begin to see temporary expansion in their molds and forms due to weather.

Testing for Rubber Expansion

To prove that urethane expands when exposed to heat, we conducted a series of tests in our on-site lab. Using several samples of our own pourable urethane rubber and a few competitors’, we observed what happened when we adjusted the room temperature.

Once cast, cured, and demolded, we put the samples in an oven for 2 hours at 125°F. After the allotted time, we measured them and noticed they expanded by 1-3% on each side.

We then pulled the samples out of the oven and allowed them to sit for 2 hours at room temperature (77°F). We measured them again and noticed they returned to nearly the exact size of the molds they were cast in.

Results of our testing: If your mold or formliner has expanded due to a temperature change, it should return to its original size once it is brought back to room temperature.

Solutions

We’ve seen this kind of dimensional change occur when people work in warm, humid climates. If you plan to operate at a warm temperature, you’ll need to cast the mold in the same conditions. So, the liquid rubber and the environment temperature will have to be relatively the same as the temperature you plan to use the cured mold in. Also, as a note, please see our urethane shrinkage blog if you are using molds at a temperature that has dropped substantially from what it was molded at.

Urethane rubber must sit at room temperature for 16-24 hours before it can be demolded to prevent deformation. Keep the material at room temperature for an additional 3 days before use so it has time to gain strength and properties. The rubber will typically develop full physical properties after 7 days.

Casting the rubber against a rigid backing material can also prevent it from expanding due to high temperatures. We typically recommend using some type of wood, like plywood. Urethane’s high adhesion properties will form a strong bond with the surface.

We recommend pouring the urethane over the lip of the surface, allowing the material to grip onto it. When formed around and bonded to something more dimensionally stable, it won’t expand unless the substrate expands. Expansion or contraction of a sturdy substrate like plywood is very unlikely.

Contact VFI if you require further assistance with urethane rubber issues. We can also help you find the best material for manufactured stone, cast stone, and concrete stamps.

Understanding the Properties of Liquid Urethane Rubber

It is always essential to look at the properties of liquid urethane rubber when choosing a material for any project. If you’re new to urethane, you may not know what properties are most important to look at. The answer will vary based on what you plan to do with the material. This is a comprehensive guide to help you understand which ones are important to know and why.

What Physical Properties Are Important?

The physical properties of urethane molding rubber will tell you a lot about what the material is capable of. You’ll want to understand these properties to decide if the material you’re looking at is best for your project. These properties are tested using various methods from the American Society for Testing and Materials (ASTM). The most prominent physical properties listed for molding rubbers include the following:

Shore Hardness

Test method: ASTM D2240

Definition: Shore hardness uses a standard testing tool called a durometer to analyze a material’s resistance to localized deformation or indentation. The durometer determines the hardness of a material relative to materials with similar qualities on unitless scales.

Importance: This is one of the first properties users look at when determining if a material is suitable for their application. Hardness is a good indicator of properties, and generally speaking, the harder the material, the greater the properties.

Hardness factors into how easily a mold will demold from a model or casting. A softer material is much better when creating molds of delicate or detailed originals. Rubbers within the 20-40 A range are great for cast stone, while the 30-60 A range is great for manufactured stone. These types of applications use small and delicate original pieces that have the potential to break during the molding process, so softer molds will help demold more easily. Lower hardness is also recommended for architectural restoration projects as well.

Interested in reducing your product breakage rate? VFI has new polyurethane rubbers with release characteristics similar to silicone.

On the other hand, harder rubbers are better when you’re making large, flat, and simple molds. Their hardness makes them more abrasion resistant and capable of handling heavier loads, which helps lengthen the mold’s life. Rubbers within the 50-70 A range are great for detailed concrete formliners, while the 70-90 A range is great for simple formliners and concrete stamps. They also provide more strength so they can be used on casting beds.

Note: When looking at VFI urethane molding rubbers, you will notice that they all include the Shore hardness in their names to make it easier to find what you’re looking for (i.e., VFI-2143 45 A TDI Molding Rubber).

Tensile Strength

Test method: ASTM D412

Definition: Tensile strength uses a standard test to determine the maximum load or amount of stretching force a material can withstand before it breaks. The higher the tensile strength, the more force it can withstand. It is measured using pound-force per square inch (psi).

Importance: Tensile strength is one of the properties that tell you something about the durability of urethane. Generally, it will increase as hardness increases, but there are exceptions when custom formulas are created to achieve other higher properties at a lower hardness. With high tensile strength, the material can withstand loads, forces, and impacts without breaking or warping.

For mold making, the material should withstand the stretching forces exerted by the casting material. Having good strength is essential if you are making large molds that need to hold up to abrasive materials and large pours. Since urethane molds are meant to be reused, having good tensile strength allows them to endure repeated stress without failing. When demolding, the mold may be pulled, bent, and twisted to release the cast part, so this property helps it handle these forces and produce successful castings in high-volume production runs.

Elongation

Test method: ASTM D412

Definition: Elongation is tested to determine the maximum length a material can be stretched before it breaks. It is measured using a percentage of the final length compared to the original length of a tested material. It is also an inverse relationship with tensile strength as it uses the same test method.

Importance: While elongation isn’t a main concern for mold making, it’s still one of the physical properties users should know. If you require your molding material to have more stretch and flexibility, you’ll want to look at elongation. A mold with higher elongation will have a lower tensile strength, allowing you to demold from the master or the cast piece easier. Harder materials have lower elongation because they’re less flexible and have greater tensile strength, meaning they don’t have the same ability to stretch.

Tear Strength

Test method: ASTM D624 (Die C)

Definition: Tear strength, also called tear resistance, tests the maximum amount of force required to initiate a tear in the material. It is measured using pounds per linear inch (pli). Die C is the most common test type for urethane, and the test specimen is not nicked. The force acts parallel to the tab ends of the test specimen or at 45° to the 90° center.

Importance: Tear strength is considered one of the most important physical properties of urethane molding rubber. The reason for this is due to rough handling in the demold process. When removing castings from molds, tears or punctures can occur due to the pulling force when trying to break the tension between the mold and the cast part. Higher tear strength keeps the mold from tearing for easier part removal and a longer-lasting mold.

Tear strength is an important property and is loosely tied to the tensile strength of the material. Usually, the higher the tensile strength, the higher the tear strength. This means that when you have a high elongation, you will have a lower tear strength.

Dimensional Stability

Test method: ASTM D2566

Definition: Dimensional stability is tested to find a material’s ability to maintain its dimensions (size and shape) when it cures. It measures linear shrinkage expressed in inches per inch (in/in) between the cured material and the mold box or cavity it was molded from when cured at room temperature (77°F).

Importance: All two component urethane rubbers experience an exothermic reaction that generates heat as they cure, which causes the material to shrink. The degree to which this shrinkage occurs depends on the material, amount of exotherm, thickness, and geometry of the piece or mold. If more material is used to make large molds, you may notice a difference in the mold’s dimensions from the mold box or form it came from due to a larger exothermic reaction. This can also be an issue when casting thicker mold walls because it will generate more heat, leading to greater shrinkage.

If a mold material has good dimensional stability, it will retain its shape through the casting process. If the mold shrinks too much, cast pieces may be different sizes and may not fit together, especially in the case of manufactured stone.

Cast the rubber on a rigid backing material like wood to combat shrinkage when making larger molds. If you pour it around the lip of the backing material, it will create a better grip on the surface edge, making it harder for the material to shrink. Also, work at a consistent temperature so your environment doesn’t affect the material’s dimensional stability.

What Liquid Properties Are Important?

Not all companies split their properties into separate sections, but VFI specifies properties for urethane in a liquid state and when it is in its cured solid state. The following properties pertain to the unmixed and mixed liquid components:

Specific Volume

Definition: Specific volume is a property that relates to the volume of matter divided by the amount of matter or the reciprocal of its density to determine how much material is needed to occupy a given space. It is measured in inches cubed per pound (in3/lb). Simplified, this means that you can use the specific volume to determine the weight of product needed for your project.

Importance: Specific volume is an important property to know to calculate the amount of material you need to make a mold. First, the volumes (length x height x width) of your mold box and master must be calculated and subtracted from each other. Once you know the volume needed to fill the remaining space, you can divide it by the specific volume to convert it into weight. This number will be the total weight of urethane needed (Part A + Part B). Calculating this number ahead of time saves you from the risk of mixing extra material and generating waste or not having enough during the molding process.

Liquid Density

Definition: Liquid density is the weight of a material in a specified volume. It equals the mass of the liquid divided by its volume and is commonly measured in pounds per gallon (lb/gal).

Importance: Looking at a liquid density can tell you if there are useless fillers in the mix to increase the bulk and reduce costs. These fillers will notably change the weight of the material. As a standard, the liquid density of urethane rubber is around 8.5-9.5 pounds per gallon. If filler is included, you may see the liquid density range between 11-13 pounds per gallon.

Mix Ratio

Definition: The mix ratio is a property for liquid materials with several components that must be mixed to create a final product. It tells you how much of each part needs to go into the final mixture to produce the proper chemical reaction. It can appear in two ways:

• By volume: Mix ratio by volume is expressed as a ratio (Ex: 1A:1B) and is the exact proportions of Part A and B that must be combined and is not dependent on the weight. It is measured using equal-sized containers and is mostly used when processing through automated dispense equipment.
• By weight: Mix ratio by weight is expressed as a ratio (Ex: 51.50A:100B) and is the exact proportions of Part A and B that must be combined and is not dependent on volume. It is measured using an accurate scale, but if the user does not have one, selecting a material with a convenient mix ratio by volume is more desirable.

Importance: Most urethane rubbers are two-part systems (resin and hardener), and when mixed, they cure at room temperature. Staying on ratio for both parts ensures the material will cure successfully and achieve the desired properties.

If the mix ratio is not followed correctly, it can impact the final product. If you mix it with too little resin (B side), the material may become brittle. If you mix it with too little hardener, the material may become soft, tacky, or gooey to the touch. In some cases, not adhering to precise mix ratios can inhibit the cure, and the mold will never develop full physical properties, and it will be unusable.

Viscosity

Definition: Viscosity is the measure of a liquid’s resistance to flow. It will generally show up three times on a property sheet as Part A, Part B, and the mixed liquid viscosity. It is measured in centipoise (cps). For reference, below is a list of common household items and their viscosities so you are better equipped to understand the viscosity of urethane.

Importance: Urethane can come in a wide range of viscosities depending on processing needs, but pourable urethane will typically be between 200-3,000 cps. This property affects how easily the rubber can be mixed and poured into a mold. Less viscous rubber is easier to mix and pour, especially when using more complex molds. It will flow more readily into details, corners, and pockets. Rubbers with a lower viscosity are also less likely to trap air bubbles in the finished molds.

On the other hand, high viscosity materials are thicker and have a greater resistance to flow. There is a higher chance that the rubber will cure with air bubbles that create imperfections on a mold’s surface. A great way to combat air bubbles in thicker rubbers is to vacuum degas the material before pouring.

Having material components with similar viscosities that must be combined is also important to maintain a uniform mix. This varies when trying to incorporate a thinner material into a much thicker material because it requires a longer mixing time than if they had similar viscosities.

Pot Life/Work Time

Definition: Pot life or work time refers to the time it takes for the material to reach a viscosity where it is deemed too difficult to work with. For molding rubber, it is essentially the time after you start mixing that the material is pourable.

Importance: Understanding a material’s pot life is essential for having control and flexibility in the mold making process. It will tell you exactly how much time you have to mix, vacuum degas, and pour the material into a mold.

Depending on certain working conditions, the pot life may be shortened. Temperature is the number one factor that affects this. If the material, the environment, or the mold temperature is increased, pot life will decrease. It’s important to work at room temperature (77°F) or cooler temperatures. However, working in warmer temperatures will have the benefit of reducing the cure time if you need to process your molds faster.

The amount of material you use at one time can also affect the pot life. When you use more material, the extra mass causes more heat to be generated through the exothermic reaction. This heat then causes the rubber to become more viscous quicker. Heat is also a problem for thick-walled molds. More material concentrated in one area will cure much faster than thin sections.

Pot life is even more important if you’re making large molds or form liners. You’ll want to find a material with a long enough pot life that will allow you to mix and pour into the mold before it starts to solidify. Most urethane users will use dispensing equipment for this exact reason.

Demold Time

Definition: Demold time indicates the amount of time a material should cure before being removed from a mold, mold box, or form. Depending on the cure speed of the material, it can vary from minutes to hours.

Importance: You must wait until the material has solidified enough before demolding; otherwise, it may cause distortion or deformation. All cure times are based on room temperature (77°F) unless otherwise stated, and temperature will play a major role in demolding. The mold can be left in an area warmer than room temperature to speed up its demold time.

When the mold is removed from the mold box or form, it does not mean that it is ready for use. Polyurethane rubbers need up to 7 days to obtain final physical properties; however, they can be used for casting about 72 hours after they have sat at room temperature. Using the mold before this time can also result in deformation from casting pressure or increased difficulty when demolding.

Place Into Service

Definition: Place into service is the amount of time before a material is ready for use. It is measured in hours or days.

Importance: Not every manufacturer lists the place into service time for their urethane materials. However, it is a good property to know because it provides a time frame for when you can start using the mold for casting.
Urethane can usually take several days to develop desired properties, so a newly made mold can’t be used right after its initial cure. After sitting outside of a mold box or form at room temperature for a few extra days (72 hours minimum), the mold should have enough properties for casting.

Where to Find Material Properties?

Volatile Free, Inc. and most manufacturers list physical and liquid properties on product pages and technical data sheets or bulletins. We know the value of expressing these material properties accurately, so you can trust that the product you’re using will perform to specification. We use various standard ASTM test methods to determine a product’s properties and only publish them once they have gone through multiple reviews. Technical data sheets can be found on any product page under the resources tab.

How to Seal Styrofoam for Outdoor Use

There are several ways to seal styrofoam for outdoor use. You should prioritize weather-resistant materials to seal the foam, ensuring the longevity of your piece. Whether it’s rain, sun, impact, or other outdoor factors, styrofoam requires extra protection to maintain its structural integrity, especially if it will be placed in storefronts, public spaces, or outdoor events.

Protection is important, not just for styrofoam, but other foams too. Most foam sculptors in the industry are actually using expanded polystyrene (EPS) over styrofoam (the brand name for extruded polystyrene (XPS)). This is because EPS is made in large blocks, and XPS is made in sheets.

Regardless of which styrene foam you use, both are inexpensive and easy to work with but can become damaged if not protected with a durable hard shell.

Does Foam Last Outside?

Styrene foam is not designed to withstand extended outdoor conditions. One reason foam should be sealed is because it is highly sensitive to UV rays. The plastic material will break down into a discolored powdery substance or become brittle upon long-term exposure. It can fully break down in a few years, which is bad for the environment if not disposed of properly.

In addition to this degradation, excessively heating the material can break down its chemical structure, causing it to leach. Small amounts of styrene will seep out and contaminate surrounding surfaces, which means if your foam piece is within reach of people, it’s not safe. The foam may also lose its thickness during this process.

While it is water resistant, it’s not waterproof. Over time, it will absorb moisture from rain, snow, or spills. Extra water may also be stored causing mold and mildew growth. In addition, there are also a handful of solvents that can melt or break down polystyrene . Impacts from various environmental conditions can also damage uncovered foam. If you want to protect it from damage, it is crucial to apply some sort of coating or sealant.

Options for Sealing Styrofoam

When you seal styrofoam for outdoor use, the material you choose will depend on how long you need the piece protected. While many people use DIY methods because they’re more cost-effective, there are specialized hard coats for styrofoam that lengthen the life of your project.

Polyurethane is the top suggestion for sealing styrofoam. These coatings are two component, semi-rigid materials that are plastic-like and impact resistant when they harden. When applied, they provide the durability and flexibility needed to protect the surface underneath without cracking. Most are applied by high pressure spray equipment, but there are also brushable options, such as VFI-2519 75 D Brushable Hard Coat, for smaller projects. For lower cost spray options, there are even coatings in a cartridge format, such as VFI-6171 70 D Qwik Spray Hard Coat.

Polyurea coatings are a similar alternative but come with premium properties at a lower hardness in comparison. These properties will make the cost slightly higher, but they do offer more in the way of protection in the form of impact and thermocycling. They are usually fast setting and they’re also a great alternative if you work in environments where moisture is an issue. One downside to a polyurea material is that it is normally harder to sand, because they tend to be softer than a urethane hardcoat.

Epoxy is a coating with similar characteristics to polyurethane and polyurea. It acts as a protective barrier for any type of foam but is applied in several thinner coats. Epoxy is also mostly brush-applied or roll-applied, which makes it time-consuming to work with, so it’s typically used for smaller projects. If you plan to sand the material, particles get into the air and can create toxic dust, so an approved respirator should always be used. The main benefit is the ability to work on large projects without the need for a full spray booth.

Fiberglass has a more time-intensive application process, but it is an effective way to protect an outdoor foam piece. Layers of the material are placed over the foam with intermittent applications of epoxy or polyester resin that will impregnate the fiberglass fabric/fibers. These layers are applied until the desired thickness is achieved providing strong impact resistance that is reinforced by layers of fabric. Resins that are not a full 100% solids will melt the foam, so you must be careful in choosing the right one.

Benefits of Sealing Styrofoam for Outdoor Use

• Protection – There are several things a hard coating can protect outdoor styrofoam projects from. The coatings resist moisture and water damage, UV radiation (when a compatible paint or topcoat is applied), and other weather conditions. They also resist impact and abrasion from people sitting on, climbing up, or touching these structures. Some coatings can also provide fire retardant characteristics to meet fire safety requirements where necessary.
• Long-term durability – Because a coating can offer incredible protection, it keeps your foam piece in good condition, especially outside. If you were to just paint your foam piece and call it a day, there’s no doubt that it would deteriorate quickly and not look very smooth. When your project is resistant to external factors, it lasts longer and saves you money in the long run.
• Versatility – There’s no limit to the shapes and projects you can use a hard coat for. Because spray coatings are the most used and recommended application option, the coating gets into all the curves and crevices on a piece. These coatings adhere well to all types of foams, so you gain protection no matter what material you use.
• Easy to apply & work with – Most hard coatings are relatively easy to work with, as long as you have experience with high pressure spray equipment. Most formulas also come in 1:1 mix ratios for ease of setup. If spraying is not your thing, brush and roller applications are also available. After application, coatings are easy to post work. Fast setting coatings can leave a smooth surface perfect for top coating or painting, especially when spray applied.

Outdoor Applications for Sealed Styrofoam

Due to the adaptability of sealed foam, a handful of outdoor applications benefit by using these materials. These materials are used to fabricate signs for outdoor store displays, theme park rides, restaurants, and more to enhance brand recognition and draw customers in. Nothing elevates an aesthetic like a custom sign that stands out from less creative materials.

Companies may also use foam to create large-scale 3D figures or characters to attract visitors and create magical environments. They can be seen at outdoor festivals, concerts, parks, gardens, etc. With a hard coat, your creations will be protected for years.

Sometimes, these materials are used for realistic outdoor hardscaping, such as stones, edging, boulders, rocks, and more. Foam hardscape objects can be more cost-effective since natural materials are more expensive and difficult to install. Heavy machinery is typically not required when installing hard-coated foam pieces, reducing labor costs.

Outdoor amusement parks rely heavily on custom props to immerse customers and enhance their experience. Hardened foam can be used as themed elements in ride queues, in the rides themselves, or throughout the park. The protection these hard coats offer keeps your projects in good shape for a long time.

Contact VFI today to see if you could benefit from using a hard coat on your next foam project.

How to Use a Form Coat Epoxy

Learning how to use a form coat epoxy is important for generating multiple quality castings when using abrasive casting materials. Creating a stable surface to pour concrete will help control and shape it as it cures. These qualities help ensure that the material will set properly and maintain its strength, durability, and longevity when transported and installed at building sites.

However, bare wood, foam, and metal surfaces will not last long without a form coating, so it’s crucial to protect your investment with a strong barrier. Using an appropriate coating will ensure that the surface can withstand the weight of rough casting materials for multiple uses without becoming damaged.

What Is a Form Coat Epoxy?

Form coat epoxies are also called mold coats or bed coats in the precast industry. This is due to their versatility, as they are used to protect large formwork, casting beds, or molds for precast, tilt-up, slip form, and cast-in-place applications. The castings produced from these forms include beams, columns, walls, etc., made of cementitious materials.

A form coating creates a tough, rigid surface that adheres well to wood, steel, and even EPS foam. It acts as a barrier to protect these expensive molding forms from the abrasive effects of various casting materials. The coating will act as a shell over the surface to prevent it from absorbing the casting material, which would otherwise have a hard time releasing from the form or surface. The smooth coated surface is then used to create multiple identical and flat building materials for parking structures, bridges, highway walls, retail shopping centers, and more.

Specially formulated epoxy coatings work well for this application. They are rigid but are formulated to also have the flexibility to resist cracking or deforming from regular use. Because these coatings have outstanding properties that make them strong, they become almost unbreakable, reducing the risk of damage to the underlying surface. Epoxy coatings require minimal maintenance and will endure heavy wear and tear before they need to be recoated.

Importance of Surface Preparation

For excellent adhesion to the following surfaces, you must ensure they are free of dirt, debris, and other foreign materials.

• Wood forms – Sand new wood panels for good mechanical adhesion of the coating. Clean off the sawdust with a vacuum. Though the coating is moisture insensitive, ensure the surface is relatively dry before application.
• Steel forms – If the metal contains rust, mill scale, dirt, and other contaminants, you will want to conduct abrasive blast preparation by sandblasting to SP6. Once finished, clean the metal shavings off the surface with a vacuum or broom.
• EPS forms – While EPS is typically not used for large-scale production, it can be used for casting smaller pieces. The foam must be aged at least 30 days to allow any gas to escape. The higher the density of the foam, the nicer the finish, but any foam between 1-3 PCF is acceptable. The foam should be clean and dry before applying the coating. The coating will not deform the mold shape.

The Form Coating Epoxy Application Process

Materials needed: VFI-4385 82 D Form Coating Epoxy, nap roller, wet film thickness mil gauge, large industrial orbital or rotary sander

Because epoxy can be toxic when inhaled, swallowed, or in contact with skin, use the material in a well-ventilated area. Wear the necessary personal protective equipment (PPE) to avoid exposure.

It is always recommended to work with the material at temperatures between 60-80°F. Remember, you will have a shorter working time when the temperature is higher. After preparing your casting surface, follow the steps below to create a protective barrier on your molding surfaces.

• Once you have mixed the components together, pour the material onto the surface.
  • Note: Leaving it in a mixing container can cause it to over-generate heat, which causes the material to thicken faster and cure faster. Do not leave material in a mass to cure. Mix up only what is needed to prevent excess.
• Begin rolling the material evenly at a rate of about 20 mil passes. It can be back-rolled to help achieve a uniform thickness. Coverage will vary in the first application due to the porosity of the surface.
• Check the thickness with a wet film thickness mil gauge. The coating should self-level.
• Allow it to cure overnight (minimum of 16 hours).
• Once cured, power sand the surface to smooth out imperfections or bubbles. Clean the surface of dust and debris from sanding.
• Apply a second coat following the same instructions. Repeat the process until the overall desired thickness is achieved.
  • Note: Total thickness should not be thicker than 250 mils.
• Before casting, spray a release agent to prevent unwanted adhesion between the form coat and casting material.
• Pour the casting material into the coated form and allow it to harden until it can be removed, typically after 24 hours. The surface can then be reused for future castings if the surface is clean, free of dust, and dry.

Once the original form coat becomes worn, a new coat can be applied. All you need to do is sand down the existing coating to remove any previous casting residue and improve surface adhesion for the new coat.

VFI Compatible Products

VFI-4385 82 D Form Coating Epoxy is VFI’s exclusive product for precast manufacturing purposes. It has a convenient 2A:1B by volume mix ratio for easy application with a roller. It is moisture-insensitive, so it can be applied to damp surfaces with no effect. At 82 D Shore hardness, the cured coating will produce a highly rigid yet flexible surface perfect for repeated concrete casting. Contact VFI if you are interested in protecting your wood, steel, or foam surfaces.

Volatile Free, Inc. Releases Form Coat Epoxy for the Protection of Precast Forms

Brookfield, Wisconsin – (May 16, 2024) – Volatile Free, Inc. announced the addition of a new form coating epoxy to its molding and casting line today. The Midwest-based company said this product adds long-lasting protection to the expensive steel and wood surfaces used to make precast concrete products. Because the coating acts as a barrier on these forms, it takes on the abrasive damage caused by concrete in the molding process. As an epoxy, the product is highly rigid and moisture-insensitive, making it strong and capable of being applied over damp surfaces. Once it is worn, it can be sanded and reapplied for consistent protection over molding surfaces.

Michael Sullivan, the Technical Director at Volatile Free, Inc., said, “Our intent was to create a product that would support our existing polyurethane formliner material and EPS form coats, but as we began to talk to different customers, we realized the need for something different than the available options. The performance characteristics of the epoxy being reported during field testing is telling us we’re on the right path.”

Volatile Free, Inc. also manufactures polyurethane rubbers and plastics used by concrete producers across North America. Learn more about their product lines at https://volatilefree.com.

Contact Information:
Volatile Free, Inc.
(800) 307-9218
Info@volatilefree.com

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Fire Tested Foam Hard Coat for Indoor and Outdoor Use

Fire tested foam hard coats are designed to protect and harden foam sculptures, parts, and components against external impacts and environmental elements. There have always been strict building code requirements, so it is important to protect foam projects that will be used indoors with a hard coating that will pass Class A fire testing.

While these requirements are essential inside buildings, they are slowly beginning to expand to outdoor areas as well. So, it’s best to make sure your foam project is compliant with safety standards by using a fire tested foam hard coat, no matter where you plan on placing it.

What Is the Difference Between Retardant and Resistant?

Many people don’t realize that there is a big difference between fire retardant and resistant coatings. Though both are considered passive fire protection, they will respond very differently when exposed to heat and flames, so it’s important to know which one your project requires.

A fire retardant coating’s job is to reduce the rate of flame spread and smoke over combustible materials such as wood, plastic, and foam. They are not used for structural protection, which is why they’ve found a place in the theming industry for foam projects. Fire retardant coatings can be applied by brush, roller, or spray and are formulated to look similar to paint. The standard test these coatings must pass is known as the ASTM E84, which tests for a much shorter time frame than ASTM E119. Most of these coatings are only rated based on their ability to not contribute to a fire. Others may provide some resistance to prevent the flames from reaching the substrate or keep it contained in one area for a longer period.

Fire resistant coatings are materials that resist catching fire or are self-extinguishing. When exposed to extreme heat and flames, they will not drip or melt but form a char layer that acts as a barrier. It takes much longer for these types of coatings to burn. Their thickness varies to meet certain requirements, and they are either brushed, sprayed, or troweled onto load-bearing surfaces like walls, columns, floors, and beams. The standard test for these coatings is the ASTM E119. Their rating is determined by how long they offer protection before they ignite, usually tested up to 2 hours. Adhesion, char integrity, and char growth are closely observed. Because they offer greater protection than retardant coatings, they typically contain more ingredients, making them more expensive.

Neither coating type is fireproof, as they will burn once they reach a certain temperature. Another important note is that fire and flame are interchangeable. So, if you hear these coatings referred to as flame retardant or flame resistant, they will mean the same thing.

What Is the ASTM E84 Test?

The ASTM E84 is a standard fire testing method developed by the American Society of Testing and Materials and applies to many industrial and commercial projects. It assesses the surface burning behavior of a material by observing flame spread and smoke emission.

Flame Spread Index (FSI) and Smoke Developed Index (SDI) metrics are evaluated to help rank and determine a material’s fire retardant classification. FSI is determined by the speed at which the flames progress across a surface. SDI is calculated similarly and measures the amount of smoke the material emits as it burns.

The test runs for 10 minutes, and within that time, the FSI and SDI are measured and compared to a standard. Fire retardant materials can fall into three categories: Class A, Class B, and Class C. Class A is the highest classification a material can achieve, with an FSI under 25 and an SDI under 450.

Types of Fire Tested Hard Coats for Foam

Fire tested coatings are used because they do not contribute to making a fire worse. There are several types of coatings formulated to do this, including oil-based, two-part mixes, epoxy solvent-based, and water-based. However, if you are specifically hard coating foam, we recommend using a two component polyurethane that is Class A fire tested. A unique coating like this complies with indoor and outdoor safety codes, providing flame-spread protection.

Why Is It Important to Use a Fire tested Foam Hard Coat?

Many building codes require materials used in public areas to meet fire safety standards. A coating’s retardant properties allow you to comply with these codes and ensure they pass inspection.

By definition, they are designed to “delay or hold back” flames. When a fire retardant coating is applied to foam projects in theme parks, theaters, venues, and more, it is less likely to ignite or spread fire. Since the spread is slowed, this provides people with more time to leave unsafe areas and reduces the risk of accidents and injuries.

Apart from protecting people, another benefit of these coatings is that they help protect your property. By slowing the flame spread, the coating can minimize the destruction caused by fire to a smaller area.

These hard and durable coatings do more than enhance the fire safety of a foam project. They also become seamless barriers that prevent damage from physical impact, weathering, moisture, etc., to extend the life of the entire structure.

VFI Fire Tested Foam Hard Coats

VFI was the first in the industry to formulate an ASTM E84 Class A fire retardant polyurethane hard coat in a cartridge based format (VFI-6171 70 D Qwik Spray Hard Coat). The hard coat is also available in a high pressure format (VFI-6170 70 D Spray Hard Coat) for larger spray jobs. Contact VFI if you need assistance finding a coating that meets indoor or outdoor safety requirements.

What Is a Brushable Hard Coat for Foam?

A brushable hard coat for foam is a coating formulated to be applied by brush or trowel rather than through spray equipment. These coatings are used to protect fragile surfaces such as Styrofoam, EPS, and XPS.

Using a brushable hard coat heavily depends on your unique project. If you’re a sculptor who works on small EPS foam projects for theme parks, film and theater, or art exhibits, you probably don’t require large, expensive spray equipment. A brushable coating can be much more effective for these applications because, as the name suggests, all that’s needed is a paintbrush.

Types of Brushable Hard Coatings

While various hard coatings exist, most are not formulated for brush application. This is because most hard coatings are fast curing, meaning they dry or become tack-free in under a minute. Due to this speed, a spray method is the best approach. A brushable coating has a slowed pot life with good hang to allow applicators ample time to apply it to foam and other surfaces.

Two specific formulas of brushable hard coats for foam that will provide the best protection are polyurethane and epoxy. The material you choose will depend on the surface you’re protecting, the shape of the structure, the required finish, budget, environment, and turnaround time.

Urethane

Urethane brushable hard coats for foam feel almost like smooth plastic when they cure and are generally tougher than epoxies. Similar to sprayable hard coats, they encapsulate the entire foam piece, making it water and impact resistant. It’s recommended to apply these coatings a bit thicker for thorough protection. With a high thickness, the coating will hang vertically in up to 40 mil passes without sagging. The longer you’re working with the material, the more it will thicken as well.

While they are not UV color stable, this isn’t normally an issue since they are typically top coated with primers and paints in the finishing process. Once cured, they can also be sanded if the surface is not as smooth as desired from brush application.

When using a polyurethane brushable hard coat, a big limit compared to sprayable coatings is it has a longer cure time. Sprayable coatings can cure in a few hours while a brushable urethane can take a minimum of 8 hours.

VFI offers two different formulas for brush application:

• VFI-2519 75 D Brushable Hard Coat. At 75 D hardness, it’s about 10 D durometer higher than VFI-2626. As a harder and stronger polyurethane coating, this material offers higher tensile and tear strength for extended protection from impacts. This coating is not fire tested and has no fire retardant or resistant properties.
• VFI-2626 65 D Brushable Hard Coat. While this material has similar qualities to VFI-2519, it has slightly lower tensile and tear strength at a lower durometer. The coating is recommended over its counterpart in indoor applications, as it is capable of passing the UL 94 V-0 combustion test.

When applying one of these hard coats, you can mix up the material in smaller quantities, so you won’t overuse material. Mixing smaller quantities also helps extend the pot life.

Epoxy

Epoxy brushable hard coats form a solid, plastic-like surface over foam to protect it from impact and weathering effects. Because epoxies can be hazardous when sprayed, they are usually only applied by brush or roller. They’re also applied in thin layers, so they won’t always provide as much protection as urethane coatings.

It’s recommended to use them on projects that are kept out of reach and won’t endure heavy impact. Too much impact can make these coatings crack or break. However, they are a more desirable option if you are working in environments where moisture and humidity are a concern. Their neutral-colored surface can easily be sanded, primed, and painted over.

Like all brushable hard coats, epoxy cures slowly. It’s even slower than urethane brushable hard coats and can take almost double the time to cure at about a 16-hour minimum.

Why Use a Brush Method Over Spraying?

The choice between using a brush on or spray on coating will depend on your project’s needs, including your budget, the size of your project, the surface texture you desire, and turnaround time requirements.

• Cost-effective – High pressure spray equipment can cost thousands of dollars, so buying brushes is an inexpensive option. While it can be labor-intensive to use a brush, it is recommended for small projects, so material and time waste is not an issue. However, if you consistently work on larger projects, spraying may be the more desirable method. To achieve the effects of spraying at a lower cost, there are quick spray alternatives, such as VFI-6171 70 D Qwik Spray Hard Coat.
• Excellent control – Spraying can be great for larger projects, as it covers them quickly and evenly, but it’s not always suitable for small pieces. It can hinder details, whereas a brushable coating would be better for small corners, intricate designs, and specific curves. Because you don’t have much control over where the material goes when spraying, you must mask and prepare adjacent surfaces to protect them from overspray. Also, more material is used due to overspray, but brush application allows you efficient control over material used.
• Even, uniform coverage – Those with limited experience using spray equipment may encounter overspray, drips, runs, and uneven spots where material is too heavily built up or too thin, offering little protection. Brush application is much more straightforward, so you achieve consistent coverage for long lasting protection. Brushes are also better at getting into hard-to-reach, tight corners where spray coatings can’t.
• Easier application and cleanup – Applying coatings with spray equipment requires training, so you know how to spray at a consistent distance for smooth application. When brushing, you don’t have to be concerned with spray techniques, chances of overspray, or cleaning spray lines once you’re finished. Cleanup is even more effective if you use disposable paintbrushes. Also, if the coating cures with any brush marks, the surface can be sanded before it is primed or painted.

Applications for Brushable Hard Coats

When protecting foam, a brushable coating is most advantageous for smaller, delicate, and detailed projects. We’ve seen our polyurethane coatings used on custom signs, film and theater props, holiday décor, art sculptures, and more because of their strength and durability. Even when working on larger projects, you can brush the hardcoats onto smaller pieces before assembling them into the final structure.

Brushable hard coats for foam also work as a good repair material. While these coatings are durable, they aren’t foolproof. Before extensive damage can happen to the foam being protected, it’s best to patch up areas as quickly as possible. Rather than spraying a new coating layer, brushing material onto small cracks and punctures is easier and saves material. Material can be mixed in small batches, and you won’t have to worry about cleaning spray lines.

Contact VFI if you need assistance finding the best hard coat material for your foam project.

VFI Styrofoam Hard Coating to Protect Against Elements

Volatile Free, Inc. has been manufacturing styrofoam hard coatings since the start of the company almost 30 years ago. We manufacture these products on site at our Brookfield, Wisconsin facility, and distribute them to theming professionals across the United States.

These sprayable plastic coatings form durable “shells” on various surfaces, but most popularly over lightweight foams. Other than providing a durable surface, they are fast curing, so you’ll be able to sand and paint over them shortly after application. Depending on the formula, they can be applied by brush, quick spray, or high pressure spray.

Brushable Hard Coats for Smaller Projects

A hard coat that can be applied with paint brushes or trowels, like VFI-2519 75 D Brushable Hard Coat, is a go-to when working on small custom projects or repairs. Unlike spray coatings, this polyurethane material cures slower, so you have more time to work with it. Due to its thixotropic nature, it can hang vertically in up to 40 mil passes. The further into the working time you get, the better it is able to hang without sagging as well.

The best way to use this product is in small batches to extend the material’s pot life. A full mix of the material will yield a pot life of about 8 minutes, but if you mix 200 g batches, the pot life can be extended to 15-20 minutes. It’s also crucial that you use exact proportions; otherwise, the material may not set up correctly.

Using the brushable coating can be more time-consuming than spray materials since it’s more labor-intensive. Because it’s slower, it’s also not immediately ready for post-work after application. Depending on coating thickness, temperature, and other factors, it may not be ready for sanding or painting until the next day.

Convenient Qwik Spray Cartridges for Hard Coating

If working with a brushable hard coat is not your forte but you don’t want to invest in high pressure spray equipment, VFI has just the alternative. We manufacture a urethane styrofoam hard coating for convenient spraying in a cartridge format known as VFI-6171 70 D Qwik Spray Hard Coat.

The Qwik Spray System allows for hassle-free setup and is desirable for its low startup cost and portability. It utilizes 750 mL dual cartridges of the material with the VFI-7500 Qwik Spray Gun to make spray coatings more accessible to smaller companies and applicators. To run the equipment, it requires 10 CFM of dry air at 100 psi of constant pressure. The gun comes with all the other accessories needed to spray, including static mix tips. The standard tip size for this product is GS-15, but other spray tips are available upon request.

Another benefit of the Qwik Spray System is how easy it is to clean up after using it. The cartridges and static mix tips can be thrown away once you have finished spraying for a completely disposable process without additional cleanup.

High Pressure for Big Jobs

For those who spray larger pieces and/or at a higher frequency, the quick spray hard coat also comes in a high pressure formula, VFI-6170 70 D Spray Hard Coat. The coating is sprayed using a high pressure, plural component spray rig at a recommended pressure of 2,500 psi.

However, the difference in application methods does not change the physical properties of either material. Both have consistent tensile, tear, and elongation. The only property that differs between the two is that the cartridge version sets a bit slower in comparison.

Applications for Styrofoam Hard Coating

There’s not much of a limit to what kind of projects can benefit from a hard coating. Foam is the main surface these coatings are applied to because it applies rigidity to an otherwise fragile surface making the foam itself more versatile. Due to their high versatility, we’ve seen creatives use them for:

• Prop making & set design – A low-cost way to make realistic props and set pieces for theater, movie, and television productions is using a lightweight foam that is then hard coated. Hard coats not only make these creations durable but they can be painted to help increase the realism of the prop or set. You can protect handheld objects all the way to large set pieces.
• Custom signs – An effective alternative to plastic, wood, and stone signs is EPS foam with a hard coat. These signs will be just as durable but are much easier to transport to final destinations because of their lightweight nature. Regardless of where they will be placed, they are able to endure both indoor and outdoor conditions.
• EPS theming hardcoats – Just like how they can be utilized for set design, museums, art shows, and amusement park rides can benefit from using these coatings to protect displays, models, and themed environments. They are especially helpful if the piece will be within the reach of people and children who may touch, step on, or sit on them. As fire tested formulas, they can be used in indoor and outdoor environments without deteriorating.
• Architectural shapes – While many outdoor architectural pieces tend to be made of stone, there’s a cost-effective alternative way to make them. Foam is shaped to look like faux window shutters, columns, arches, crown molding, etc., and then hard coated for protection. Because the hard coat is durable, it can withstand outdoor conditions similar to stone materials.
• Hard coat repairs – Hard coat is incredibly durable, but wear and tear can happen over time or in production. The best solution for fixing damaged areas is to use a brushable hard coat. You save money on material, and it should easily blend in with the rest of the coating that is intact so you can sand and paint over it.

Why Choose VFI Hard Coatings?

There are several benefits to choosing VFI hard coat products. The main objective of these coatings is to harden styrofoam because it requires added strength for protection against various variables. As it encapsulates the piece, it protects against moisture, impact, and other environmental factors.

Because some of the pieces that theming professionals create are placed indoors, the coatings must pass certain fire regulations. We have several sprayable hard coat options that are capable of passing the ASTM E84 Class A test or have passed it for fire retardance. Having this certification allows the coated material to be placed indoors and outdoors where strict fire safety is essential.

Because these coatings are typically painted over, they are protected from UV rays. This protection then allows them to be used indoors and outdoors without worry of yellowing or color change. They also boast good weathering characteristics, which also makes them desirable for outdoor placement.

Contact VFI if you need assistance figuring out which styrofoam hard coating would work best for your project.

Why Is UV Stability Important for Spray-in Bed liner?

UV stability is important to prevent your spray-in bed liner from deteriorating. Spray-in bed liners provide a durable, sealed surface that prevents damage from dirt, moisture, chemicals, and other debris. They also protect against abrasion and impact damage from heavy loads and weathering effects.

What Do UV Rays Do to Bed Liner?

Ultraviolet light can be produced by high temperatures from various sources but most commonly comes from the sun. Though only a small percentage of UV rays make it to the earth’s surface, they are still harmful to non-UV stable objects. When the weather changes, the sun’s rays might be the last thing on your mind, but UV rays are damaging to humans, objects, and materials all year round, even if you can’t see it happening.

With too much exposure, non-UV stable bed liners can fade, change color, chalk, and yellow. In some cases, they may begin to lose strength, become less flexible, warp, crack, and deteriorate over time.

The molecular makeup of the material is what becomes damaged or affected by UV rays. The chains of molecules will begin to break down, which ultimately causes both physical and chemical property changes.

Whether the liner is made of a coating, plastic, or rubber, if it cracks, moisture penetration can occur and cause rust. Drop-in bed liners and bed mats especially encounter issues because they aren’t UV stable, and it is not easy to add UV stability to them. Unlike with spray-in coatings, there’s no solid solution to fix the UV stability problem for drop-in liners and bed mats.

What Is UV Stability?

UV stability refers to the ability of a material to resist the effects of ultraviolet light from the sun. In certain coatings, it is a feature that prevents degeneration, and it provides more than just retention of color over time.

UV-stable coatings prevent UV rays from breaking down the material’s composition. They are able to do this because of the UV stabilizers added to them. UV stabilizers are chemical compounds that improve a polymer’s resistance to degradation. Sunlight can break down polymer chains, but these stabilizers absorb UV light, reducing the amount that reaches the material. This helps extend the life of the coating and prevents its color from changing or dulling until the UV absorbers are fully used up.

What Are Aliphatic Spray-in Bed liners?

These coatings can be polyurea, polyurea hybrid, or polyurethanes in chemical makeup and use an aliphatic isocyanate. They are a premium product due to their use of higher quality raw materials. The property that makes these coatings so desirable is their UV color stability. They exhibit great weathering characteristics and block harmful rays to prevent fading and color change.

They are used either as a whole system or to top coat aromatic bedliners. In the case that they are used to top coat an existing coating, they are applied thinner in a clear or black coat to preserve the layer below.

While aliphatic coatings provide the extra longevity and protection many truck owners desire, those qualities lead to higher prices. They are also more toxic and require more safety procedures during use. These reasons ultimately make applicators and truck owners turn to aromatic spray-in bed liners.

What Are Aromatic Spray-in Bed liners?

These coatings can be a polyurea, polyurea hybrid, or polyurethane in chemical makeup and use an aromatic isocyanate. They are seen as a workhorse in the coatings industry because they perform extremely well and are more affordable than aliphatic coatings. However, because they contain aromatic rings that UV light can attack unlike the linear chains of aliphatics, they are affected by UV rays.

Spray-on bedliners can come in a variety of colors, the most common being black. For aromatic coatings, black will have the least notable fade when exposed to sunlight. Other brighter colors will fade much more noticeably to a yellow shade unless they are protected.

To remedy the lack of UV color stability, aromatic coatings are applied as a base coat in a thick, durable layer. Then, a thin layer of a clear or tinted aliphatic top coat is added to protect them from sunlight. The combination of the two coatings makes a durable system that is UV-stable, chemically resistant, and long-lasting.

How to Protect Them From UV Rays

If you don’t want to pay for a premium aliphatic bedliner, the next best option is using a UV-stable top coat. Aliphatic top coats are essentially like permanent sunscreen for bed liners. VFI offers an exclusive coating called VFI-2580 Aliphatic Top Coat. Our top coat is chemically UV stable to protect and extend the life of existing polyurea and polyurea hybrid coatings. It preserves the original coating’s color and gloss, so you can be confident in the coating’s appearance as the years pass.

If you’re unsure whether you have an aliphatic or aromatic bedliner, store your truck out of direct sunlight. Because the truck bed is flat, sunlight radiates directly on it when there is no coverage. This may help for a little while, but over time, you still may see fading if it’s not covered while in use. An alternative is getting a tonneau cover, which would also shield it from the sun.

You should also regularly clean your truck bed when it gets dirty. If you’re actively using it to haul and transport various items, it can accumulate a lot of grime. Cleaning with soap, water, and a stiff bristle brush is the best option. Be careful bringing your truck to commercial car washes, as they may be bad for your bed liner since the wax they sometimes spray can build up and also cause chalking and fading.

VFI Compatible Products

VFI-2580 Aliphatic Top Coat can be applied to various polyurea and polyurea hybrid coatings to protect them from UV rays. This includes our VFI-542 High Pressure Bedliner, VFI-543 Low Pressure Bedliner, and VFI-544 Qwik Spray Bedliner. If you’re worried about UV color stability, contact VFI to see if using an aliphatic top coat is the best solution for you.

How to Repair Spray-in Truck Bedliner

Spray-in truck bedliner is a useful accessory for protecting pickup truck beds, work trucks, and recreational vehicles from damage caused by weather, cargo, employees, or daily use. However, they aren’t made to last forever, and while it is a rare occurrence, they can experience damage over time.

The good news is that spray-on bedliner can be repaired. Since most are made from polyurea, polyurea hybrid, or polyurethane, repair materials are made of the same materials to bond with the original liner. VFI specifically offers bedliner repair to repair scratched, cracked, or gouged spray-in truck bedliner. The material blends in to make it seem like the damage was never even there in the first place. With proper surface preparation, it will adhere to existing polyurea or hybrid coatings.

You’ll only need a minimal amount of material to patch up small, damaged spots, as long as the integrity of the liner isn’t compromised. If the damage is too extensive, which isn’t usually the case, you can always restore the old liner by applying a completely new layer of material or tearing out the old material.

How Does Bedliner Damage Occur?

While bedliner is a tough, long-lasting material, it is not invincible. Regular maintenance can help prevent damage from occurring, but there are many things that can cause damage. Specific causes include:

• Weather & UV exposure: If you’re using and storing your truck outside, both hot and cold temperatures can have a negative effect on the bedliner. You may notice cracks start to form from extreme weather, which could warrant repair. The material is also consistently exposed to direct sunlight. UV radiation is actually harmful to most truck bed liners because they are aromatic, which means they are sensitive to sunlight. Over time, you’ll start to see your truck bedliner’s color fade and degrade if it isn’t UV-stable.
• Daily wear: Depending on what you’re hauling in your truck, heavy loads can tear or gouge the liner. Different types of cargo have a chance of getting caught and puncturing it. This can cause impact and abrasive damage, depending on how gentle you are when loading and unloading. Cracks or tears can also cause bigger structural issues if moisture or debris slips beneath.
• Incorrect installation: Depending on who installed your liner, they may not have taken the appropriate care to install it properly. If the surface is not thoroughly prepared, the bedliner can experience adhesion issues that lead to damage. Signs of an incorrectly installed bedliner can include bubbling, flaking, peeling, cracking, and uneven application.
• Liquid spills: If water, grease, oil, or other harsh chemicals spill and are left to fester in the truck bed, they can cause stains on the bedliner. While most bedliners are made to withstand chemical exposure, they don’t hold up against all harmful chemicals and can begin to wear if not cleaned.

To ensure your truck bed liner continues to provide long-term protection, you’ll have to decide whether to repair, recoat, or replace it when damaged. If you decide to completely recoat the liner, hire a professional to ensure the new material is properly applied.

Importance of Surface Preparation

While polyurea and polyurea hybrid coatings bond to themselves, it’s still wise to thoroughly prepare the surface before making any repairs. Doing so will ensure the repair material will bond to the existing coating.

Make sure you are in a well-ventilated area and use proper personal protective equipment when working with chemicals. Read the manufacturer’s safety data sheet for hazards and precautions before using the material.

The truck bed should be cleaned to remove debris, oil, detergents, or other grime. Clean the surface around the damaged spots with acetone. Sand and rough up the area with a wire cup brush sander, 40-grit sandpaper, or steel wool to create proper adhesion. Cut out blisters or other unadhered, damaged material.

The Bedliner Repair Process

Materials needed: VFI-520 QS Bedliner Repair, paint brushes or VFI-7500 Qwik Spray Gun, wire cup brush sander or 40-grit sandpaper, acetone, and texture mats

Prepare the surface as mentioned above. The temperature should be above 50°F. Small repairs do not require spray equipment. When using VFI-520, there are two different application methods.

Brush Application:

• If you are applying the repair by brush, combine 1A:1B of the material by volume in a disposable cup.
• Mix the material until it turns into a thick paste that is capable of hanging on vertical surfaces.
• Using a chip brush, work quickly to apply the repair material to all damaged areas. A wide wooden popsicle stick can also be used to spread and flatten the material.
• Apply texture to the repair areas using a texture mat. Add pressure to ensure the texture imprints into the repair material. This will ensure a consistent finish with the rest of the surface.

Qwik Spray Application:

• When using the cartridge version of the repair material, it does not need to be mixed. Only shake the cartridge if there is visible separation.
• When loading the material into the application gun, keep the cartridge vertical with the label facing up.
• The material is shot as a stream. Apply it to all damaged areas in need of repair.
• Place a texture mat over the material to achieve a consistent finish with the rest of the surface. Add pressure to ensure the texture imprints into the repair material.

How to Prevent Future Damage From Occurring

Proper care and maintenance should be given to your spray-in truck bed liner to prevent damage from occurring. Regularly remove dirt, debris, and grime buildup, as not doing so can lead to the degradation of the protective layer. You can use a hose or pressure washer to wash the liner, and soap and water can clean rougher areas. Avoid using harsh chemicals that may damage the material.

Also, conduct inspections every so often as the liner can become worn and damaged from extended or heavy use. Inspections should help you catch small cracks, chips, and gouges from turning into bigger issues. Be careful when loading and unloading sharp and heavy objects, as they can leave behind unwanted damage. If you notice any damage, repair it quickly so your bed liner remains intact and continues to perform as it should.

Ensure your bedliner was applied correctly to begin with. Rigorous surface preparation before application can ensure the liner won’t develop bubbles or detach from the OEM surface. You should also ensure that the liner was applied evenly at a high enough thickness across the entire bed. This makes it so the liner isn’t easily cut or gouged.

Applying a UV-stable topcoat is the best way to ensure your bedliner is sealed from fading or discoloration over time. This will keep the material looking great for longer, so you don’t have to worry about applying a whole new coat of bedliner. Make sure the topcoat you use is made to go over polyurea and hybrid coatings to ensure adhesion between the two layers.

VFI Bedliner Repair and Other Materials

VFI-520 QS Bedliner Repair works incredibly well with our polyurea hybrid coatings: VFI-542 High Pressure Spray Bedliner, VFI-543 Low Pressure Spray Bedliner, and VFI-544 Qwik Spray Bedliner. Once repairs are complete, we also recommend applying a UV stable top coat such as VFI-2580 Aliphatic Top Coat to prevent the repair patches from fading.

Differences Between Spray-on Bedliners

Understanding the differences between spray-on bed liners is important to determine the best protection for your truck. No matter the type, a good bedliner should provide the durability and toughness needed to extend the life of the truck bed. They come in different formulas with processing methods to suit the needs of all truck owners. They can be altered to accommodate price, properties, texture, colors, and convenience.

• Cost – Price will depend on the application method and coating formula. Compared to all other bedliner options, spray-on liners are expensive upfront but more cost-effective over time. They offer better protection and aesthetic.
• Durability – One formula may be stronger than another based on properties such as hardness, tensile strength, and elongation. A softer bedliner is going to handle impact better. Coatings with high tensile strength and elongation will also endure high impact before deteriorating.
• Appearance – Depending on the application method, you could have a smooth or heavily textured finish. High-pressure sprays have a more uniform texture than low pressure. More texture can also be added if desired.
• Ease of application – Some formulas require professional installation using specialized equipment, whereas some can be applied by applicants relatively new to spraying. Depending on the equipment used, there are also slight speed differences that can make one easier to use than another.

What Is Bedliner?

Bedliner is a popular truck accessory that acts as an extra layer of protection for truck beds. A typical bedliner will cover the floor and sides of the cargo area, safeguarding the original metal surface from scratches, dents, and abrasive damage. It also offers protection from weathering, moisture, rust, and corrosion.

Apart from spray-on coatings, other common materials used are plastic coverings or rubber mats that offer similar protection at a lower cost. All these materials can revitalize old metal truck beds that are scratched and worn. They also provide a textured or gripped surface to prevent cargo from sliding around.

What Types Are There?

• A spray-on liner is a protective coating that you can apply with pressurized spray equipment. As a spray, it will adhere to every contour of the truck bed. It forms an air and watertight seal to reduce maintenance. It is the only material that will provide long-term protection.
• A roll-on liner is a protective coating that you can apply using rollers. While it is a good method for DIYers and those on a budget, the application process is much more time-consuming. Roll-on bedliners will typically have to be applied in more than one coat for optimal protection, and the cure time is longer. You may also notice roller marks in your textured finish.
• A drop-in liner is a cost-effective sheet of plastic cut to the size of a truck bed. It usually covers both the sides and floor, much like spray coatings. However, drop-ins do not provide the same seal that spray-ons do. Debris and moisture can still get trapped underneath, which makes maintenance excessive. It’s not the recommended method for long-term protection and should be chosen by truck owners who use their beds sparingly to prevent frequent replacement.
• A bed mat is a simple, soft rubber mat that only covers the floor of the truck bed but is the cheapest alternative for protection. These mats reduce damage from impact due to their softer quality. Like drop-ins, water and other debris can easily get underneath, which could cause rust and other damage. It is easy to clean but will require constant maintenance to remove buildup.

What Are Spray-on Bedliners Made Of?

Most industrial bedliners are aromatic. Aromatic means that the coating is sensitive to UV light and will fade over time, but it is more cost-effective than aliphatic. Various manufacturers offer multiple formulas to provide variations in 3 main material properties: hardness, tensile strength, and elongation.

• Polyurea hybrid is a polymer formula that is a mix of polyurea and polyurethane. A cheaper and more effective alternative to the higher cost of polyurea, which can have higher properties and lower moisture sensitivity. It creates a secure and durable coat of material designed to last for years.
• Polyurea is another polymer formula that creates a rigid, strong coating resistant to abrasion and impact damage. It provides truck beds with high tear strength, tensile strength, and elongation. The tear strength contributes to its strength, while tensile strength and elongation make it more resistant to abrasion and tearing. It’s the most expensive coating formula because it uses high-quality raw materials and specialized application equipment.
• Polyurethane is a two-component polymer formula that is the most sensitive to moisture and UV degradation. It is able to maintain 1 or 2 properties that are high but does not have the all-around property strength of a polyurea hybrid or polyurea. It still offers tough and long-lasting protective properties.

What Are the Application Methods?

Apart from chemical makeup, bedliner variations also center around the application process. All are based on two-component materials that undergo an irreversible exothermic reaction when spraying.

1. High Pressure

Some bedliner formulas require high pressure and temperature to spray and are the superior choice for most applications. They are applied using a spray rig capable of pressure of at least 2000 psi and temperatures up to 145°F.

The material is extremely fast, setting within 3-5 seconds of application, and should be sprayed by professionals. Coatings produce an ultra-tough sealed liner with a fine, uniform texture resistant to dents and dings.

The high-pressure system is recommended for businesses that spray a lot of bedliner. Upgrading to high pressure can help increase profits and expand your business.

2. Low Pressure

Using similar equipment to high-pressure systems, low-pressure bedliner is applied with less pressure and at lower temperatures. The equipment needs to be capable of between 500-700 psi and is typically more affordable than high-pressure rigs. Due to this low pressure, the coating flows and takes longer to set.

You can typically tell the difference between low- and high-pressure bedliners by texture and appearance. Low-pressure texture is less consistent and a bit larger, but some of this can be mitigated with different tip sizes. Some people appreciate this texture because it provides a softer, rubbery grip for better skid resistance. The friction will keep cargo from sliding around as much.

The low-pressure spray system is recommended when an applicator/company is not ready for the full investment into high pressure machine. Despite its longer cure, it will still provide great protection for your truck bed.

3. Cartridge System

A newer method of spraying bedliner is using an air-driven cartridge-based spray system. An applicator gun attached to an air compressor that can maintain 100 psi and 10 CFM of pressure and can hold 1500 mL cartridges is used to spray. Like the other spray bed liners, this is a two-component system that combines the material in a static mix tip as it is sprayed. It is a continuous spray process that cannot be stopped until the cartridge is empty, or it will clog the tip.

Cartridges are easy to remove and dispose of, so no material goes to waste. There’s also no need to replace equipment parts due to material setting in the gun or spray lines like in heavy-duty rigs.

Spray-on bedliner is ideal for mobile applications where large equipment can’t go and for those looking to ease into spraying bedliner. It is a cost-effective system that produces results just as good as high- and low-pressure systems.

Comparing VFI Bedliners

Below are some notable differences between our polyurea hybrid spray-on bed liners. We offer low-pressure, high-pressure, and cartridge-based formulas. Contact VFI for help choosing the best one for your truck bed.

VFI Is More Than Just Spray in Truck Bedliner

Volatile Free, Inc. has been manufacturing polyurea hybrid spray in truck bedliner since our beginning—which was almost 30 years ago. This material is manufactured onsite at our Midwestern facility, where our team takes time to ensure quality in every batch. While you may not have heard our name before, that may be because we have primarily sold private-label products to distributors around the US. So, it’s very likely you have seen or used our product before.

These polyurea hybrid coatings are most known for protecting truck beds, but they can also be used for a handful of other applications. They offer durability, anti-slip protection, and resistance to chemicals, rust, and corrosion over various surfaces, including metal, wood, and concrete. These coatings come in 3 different versions for various processing needs: high-pressure, low-pressure, and Qwik Spray.

Convenient Qwik Spray Cartridges for Spray on Bed Liner

Did you know that VFI developed a spray on bed liner in a convenient quick spray cartridge format? In fact, we were one of the first, if not the first, to take cartridge-based spray bed liner to market. It typically only takes one full case (6 cartridges) to completely cover and protect a truck bed.

The cartridge-based system was created based on the desire for small-scale spraying with low startup costs. Using the VFI-7500 Qwik Spray Gun, users now have an easy, portable method for spraying truck bedliner. The spray gun only requires 10 cfm of dry air at 100 psi of constant pressure to operate, which is much less than a high- or low-pressure system requires. It comes with static mix tips and all the gun accessories needed to spray.

A perk about this product is that it doesn’t sacrifice the quality of a traditional high-pressure, spray in truck bedliner. It has all the same benefits, including durable watertight protection from rust, corrosion, impact, and abrasion. Another perk is how easy cleanup is. Since the material comes in disposable cartridges, all you have to do is throw them away when you’re finished spraying.

Because polyurea hybrid coatings are so versatile, these QS cartridges are used for:

• Low-cost bedliner applications. Coatings are used to protect truck beds from damage for an extended lifespan and increased resale value. Due to a spray-on application method, they are versatile for sealing truck beds of any make or model. Unlike drop in bedliner, there’s no shifting or rubbing that causes noise. Also, dirt, moisture, or debris do not accumulate underneath.
• Speaker box coatings. They are used to protect speakers from abrasion and impact damage that can occur from indoor or outdoor use. The textured surface adds a unique visual appeal, improving not just aesthetics but functionality of the equipment.
• Recreational coatings. They are a great option when your ATV, UTV, boat, or other recreational vehicle is expected to navigate through rough terrain. Polyurea hybrid coatings provide long-term protection from abrasion and impact caused by mud, dirt, debris, rocks, and more.
• Theming and attractions projects. While polyurea hybrid coatings are not the first choice for most of these projects, they can serve as a cost-effective alternative to polyurea or polyurethane. These coatings work for many applications if a textured, black, paintable surface is desired.
• Work trucks. These coatings can be used on a handful of utility vehicles and commercial fleets. They rely on polyurea and polyurea hybrid coatings to protect them against extreme weather and rough road conditions during transport. They also use this protection to prevent heavy loads from causing impact, abrasion, or chemical damage as they move around, rub against surfaces, or leak.

VFI Also Makes Polyurea Coatings

While polyurea hybrid coatings are extremely versatile materials, there are applications where pure polyurea might work better. Polyurea is a premium product due to its higher properties, better chemical resistance, and improved moisture resistance. Our general-purpose option is VFI-201, with VFI-200 and VFI-202 being slow and fast versions, respectively. These coatings are used in applications such as:

• Secondary containment. This is an application that requires the use of polyurea coatings as temporary containment for chemical, oil, and other liquid spills that break through primary containment. Polyurea’s robust properties and fast setting abilities support their use in various settings.
• Sacrificial coatings. They are used as temporary protection where mechanical abrasion is present. Our general-purpose polyurea is best utilized for these applications. It creates a barrier between abrasive materials and the substrate and is reapplied as it wears away.
• Kennel floor coatings. They protect not only the surfaces they’re applied to but also the safety of pets. They are durable, slip-resistant, and prevent bacterial growth. With a seamless surface, there’s no way for moisture or other debris to accumulate beneath the material.

What Makes VFI Different Than the Competition?

1. Accurate Properties

Publishing accurate, comprehensive physical properties for products plays a vital role in the customer experience. Your polyurea or polyurea hybrid coating is expected to perform the way it is supposed to according to its properties, and it can be a nuisance when it doesn’t.

This is why our products go through in-house and third-party testing to ensure physical properties are posted correctly. Our lab staff uses industry-trusted ASTM testing methods to determine the physical properties of each product. We then post technical data sheets with this information, which go through multiple reviews before they are published.

Some important physical properties we list for spray in truck bedliner and polyurea coatings include hardness, tensile strength, tear strength, elongation, elastic modulus, permanent set, and adhesion strength. We also list liquid properties for gel, tack-free, recoat, and full cure so you know the material working time and when your project will be ready for service.

2. Continuous Batching

Large companies tend to make big batches of material in which one product is made in a single production run. The material is then stored until it’s ordered, and another product goes into the production process. This can typically cause longer lead times for setup and production, which can slow down the time the product gets to customers, especially if the stock runs out and another batch isn’t scheduled for production soon after.

A benefit of working with VFI is that we do continuous batching. This process allows us to consistently make smaller batches, so you not only get fresher material, but you also get products delivered to you faster. Having more control over inventory and flexibility with the batching process allows for higher customization in our materials as well. We are also capable of making larger batches if needed.

3. Technical Insight

We have an onsite lab, staffed with knowledgeable chemists as well as field technicians who are able to talk customers through their problems. Both teams work together to come up with valuable solutions. With years of experience, our chemists research and evaluate the coatings market to determine customer needs before they occur. They are consistently developing new, innovative formulas that benefit unique projects. And when needed, you’ll have access to direct technical support.

4. Customized formulas

When you need a nonstandard polyurea or polyurea hybrid coating with specific properties to meet your specifications, the VFI team can provide unique solutions. We work with you to create a formula with the properties you desire for improved performance. We start by asking you questions to understand your situation so we are better equipped to get you what you need.

If there is a polyurea or polyurea hybrid coating that we offer that is close to what you’re looking for, we will work from that formula to develop something that matches your requirements. With a custom formula, we can adjust cure speed, coating texture and finish, or other properties for extreme conditions. It’s also always possible that you may be looking at the wrong product entirely, and we’ll be able to guide you towards one of our available solutions.

5. Customer-driven

Above everything else, we take pride in servicing our customers with a personalized approach. We’re dedicated to getting you answers quickly when you need help finding a specific product, placing an order, or using our coatings for the first time. Our staff is always happy to troubleshoot issues that customers run into when using our products.

We take time to evaluate the feedback we get from customers and aim to improve existing products or create new ones based on it. We want to lead you to a solution that will be the best for your project. If you still can’t find what you’re looking for, we’ll work with you to develop a custom formula.

Vacuum Degassing vs Pressure Potting: Are They Necessary?

Vacuum degassing and pressure potting are techniques professionals use to get clear, bubble-free molds and castings. Either process removes or reduces these weak spots and imperfections from liquid materials that would otherwise affect the look and durability of the final product.

Many new casters use an open pour method that involves mixing A & B components together, pouring them into a mold, and then allowing them to cure at room temperature. The issue is that hundreds of tiny air bubbles are introduced into the material and will be visible in the final casting.

While using a vacuum chamber or pressure pot may seem unnecessary or costly, for those who create molds and parts regularly, it is almost essential to achieve professional results. If you are in a situation where it is critical to make bubble-free castings, using both will ensure a clean mold and part. Various industries use these processes to ensure purity, structural integrity, and performance.

What Causes Bubbles in Liquid Materials?

Air or gas becomes trapped in liquid resins and creates nodules, cavities, and hollow parts in the finished cast for several reasons:

1. Mixing two components (resins and hardeners) together quickly can introduce air into the material. While mixing faster may save time during the rest of your molding process, it can produce voids in your final product. Use a gentle folding method to prevent air from getting trapped during this process.

2. Depending on what they’re made of, mixing sticks and mixing containers can play a part in introducing moisture and air into your material. It’s best to use plastic and metal mixing tools, especially with polyurethane rubber or plastic.

3. Air can also become trapped due to improper casting techniques. If you pour your material too quickly or in thick streams, it can lead to bubble formation. To combat this, pour the material into the mold or form in a high, thin stream. Trapped air escapes more easily when the material is poured this way.

4. If the material or environment is too cold, it can increase the viscosity of the resin. Thicker viscosity materials with high surface tension have a harder time releasing trapped air since they have more resistance to flow. Using thinner viscosity and warmer materials is generally recommended. Warming the material can reduce the viscosity, making it easier to mix without introducing extra air.

5. Over-applying a release agent in your mold box or mold can also cause champagne bubbles or pinholes in your cured material. Be sure to let your release dry before casting, or use one that you can gently brush onto the surface.

What Is Vacuum Degassing?

Vacuum degassing is a process that uses a vacuum pump to pull air out of a closed chamber to reduce and remove trapped air in materials for a higher-quality product. In the controlled environment, the air pressure is reduced, which pulls the bubbles in the material to the surface, where they foam over and pop or release. For the best results, the vacuum pump should be capable of pulling up to 29 inches of mercury (Hg).

The vacuum chamber is usually a steel container with a clear lid for visibility while vacuuming. These chambers can come in various sizes and designs to accommodate a range of projects.

How It Works

Degassing is done after mixing and before pouring the material into a mold. Some casters choose to degas individual components after dispensing the amount needed and then also degas the combined mixture.

The container placed in the chamber should be large enough to allow for as much as five times the expansion of the material. If this space is not supplied, the material may spill over, leaving the mold or container only partly filled. While stopping and starting the chamber can prevent this, you would have to pay close attention during the degassing process.

The speed of this technique and how easily air escapes will depend on the viscosity of the material used. High-viscosity materials take longer for all bubbles to release. Vacuum degassing can also be more time-consuming, which is why certain fast-cure resins cannot be degassed traditionally before pouring.

Since degassing happens before you pour the material into a mold, you must be careful not to introduce air back in. If you are worried about bubbles forming in the pouring process, a pressure pot may be used instead or after degassing.

When to Use and Not Use

This method is best for materials with longer pot lives because quicker setting materials may cure with a foamy texture if they start curing while degassing. It also works well for materials with high viscosities and high surface tension. Even if the material is thick, if it has a long pot life, there should be enough time for the bubbles to rise and escape.

It’s an effective way to remove air bubbles from hard and flexible rubber materials. It’s also good for materials that must form intricate designs and complex shapes on the surface.

An important note is that materials that have a flash point under 200°C are prone to flashing off during the degassing process. This causes the product to be inconsistent and can release harmful vapors. So, any materials that contain solvents are not recommended for degassing.

Materials that can be degassed: silicone rubber, urethane rubber, urethane resins, epoxy resins, etc.

What Is Pressure Potting?

Pressure potting is a process that uses an air compressor to push air into a concealed chamber to create bubble-free molds and castings with liquid rubber and plastics. Depending on the material, the amount of pressure added is between 40-60 psi and should not exceed the pressure limit of the pot to prevent safety hazards from occurring.

Adding pressure will alter the viscosity and flow characteristics of the material. The pressure forces the material into tight spaces, ensuring cavities are filled and minimizing surface imperfections. Unlike degassing, the pressure pot will not completely remove the trapped air but shrinks it, so bubbles are invisible to the naked eye.

How It Works

Pressure potting must be done after mixing, degassing, and pouring the material into a mold. Most people will fill the mold outside the pressure pot before they transfer it. The lid is then tightened on the chamber, and air is slowly introduced through the attached air compressor line. The material and mold will sit in the pressure pot to cure before the pressure is released. If the pressure is removed before full cure, it will not work and may increase the number of imperfections.

Note: Ensure your air compressor line is dry. Bubbling or foaming may occur if there is moisture in your line, especially if you are using urethane resins or rubbers. Also, molds must be made under the same conditions, including pressure, as the casting material or deformation may occur.

A way to combat spillage is to fill your mold outside the chamber about ¾ of the way. Fill it the rest of the way once it is transferred into the pot. You’ll also want to make sure the mold fits inside the container before you start pouring. A pressure pot can also be used on its side, depending on manufacturer’s specifications.

When to Use and Not Use

A pressure pot should be used if you need a perfectly clear, bubble-free casting. Materials that can be pressure potted are those that cure to a solid or hard state.

Pressure pots can remove bubbles from materials that have either a long or short pot life. Using materials with short pot lives is better since they must cure while still in the pressure chamber, so you can process your parts faster than if you used a vacuum chamber.

When using a silicone mold, a pressure pot is almost mandatory for urethane parts. This is due to the surface tension on the silicone causing bubbles in the urethane. Additionally, urethane will cure better when pressure potted.

It typically does not work as well for materials with thicker viscosities. When a material has a low viscosity, bubbles are able to rise faster. Some liquid resins have relatively low viscosities, which makes them ideal for pressure potting.

Benefits of the Equipment

• Bubble reduction: Either method will eliminate bubbles from your castings. This is especially helpful for clear, transparent materials that must be perfect or nearly there throughout.
• Improved surface finish: By eliminating any bubbles in opaque materials, you gain parts and castings with smooth finishes and zero to minimal imperfections on the surface.
• Enhanced material quality: Both methods are crucial to achieve high-quality castings. They will reduce defects like porosity, voids, and other surface imperfections for better reliability of your finished products.
• Enhanced material properties: The material properties may be slightly modified as pressure potting occurs. The castings exhibit better performance characteristics as the material is better fused together with minimal voids, if any.
• Extended lifespan: When materials don’t have trapped air, gases, or impurities, they are less susceptible to degradation over time.

VFI Molding Rubbers and Plastics

VFI has various molding and casting materials that can be degassed, pressure potted, or both. We recommend using either or both of these methods with our materials if you want a bubble-free cast. Our VFI-4580, 4581, and 4582 clear plastics require you to degas and pressure pot to achieve perfect castings. If you have any questions about these processes, reach out to VFI today.

Why Is My Urethane Rubber Mold Shrinking?

Urethane rubber is often called an elastomer because it comes with elastic properties. These properties can be very beneficial, especially when casting and demolding concrete. However, they also come with downsides. One of these downsides is that it is susceptible to shrinking if you’re working in a cooler temperature.

All of VFI’s polyurethane rubbers have a dimensional stability of under 0.001 in/in at 77°F, which is the percentage of linear shrinkage when subject to changes in temperature or humidity during cure. This is tested using the ASTM D2566 method for thermoset casting systems.

With temperatures dropping rapidly across the US, more users may begin to have a temporary shrinkage problem due to the weather.

Testing for Rubber Shrinkage

We conducted a series of tests in our on-site lab to further prove our hypothesis that shrinkage happens due to the weather. We cast, cured, and demolded our own samples of pourable rubber along with competitors’ and observed what happened when we adjusted the room temperature.

First, we stuck the samples in a freezer at 20°F for 2 hours. Once they sat for the allotted time, we measured them and noticed that they shrunk 1-3% on each side.

We then pulled them out of the freezer and allowed them to sit for 2 hours at room temperature (77°F). We measured the samples again and noticed that they returned back to approximately the exact size of the molds they were cast in.

Results of our testing: If your mold or formliner has shrunk due to a temperature change, it should return to its original size once it is brought back to room temperature.

Solutions

Regardless of the temperature you plan to operate at, you’ll need to cast the liquid rubber in the same conditions. This works for people who cast urethane in warmer conditions, but if you’re someone who works in a colder climate, you may run into some issues. Urethane must reach a certain temperature for it to cure, so we do not recommend casting or using it in cooler conditions if you want to prevent shrinkage. Also, as a note, please see our urethane expanding blog if you are using molds at a temperature that has risen substantially from what it was molded at.

All VFI urethane molding rubbers, and most urethane rubbers on the market, must be allowed to sit at room temperature for 16-24 hours before demolding. A minimum of 3 days at room temperature is required before use. A full cure typically occurs after 7 days, and the rubber will develop full physical properties.

Another solution to prevent shrinkage from occurring if you can’t get around working in cold temperatures is casting the rubber on a rigid backing material. We typically recommend casting over some type of wood, like plywood. Urethane can form strong bonds with most surfaces, so it should have no trouble adhering to the wood.

When casting over a backing material, we recommend pouring it over the lip of the surface, allowing the urethane to grip onto it. Because the material has formed around the edges of the surface, it will have a much harder time shrinking. The plywood would have to break in order for any substantial shrinkage to occur.

Contact VFI if you have more questions on urethane rubber or need help finding the best material for your project.

What Is Polyurethane?

Since the 1930s, polyurethane has become a popular material used in a handful of applications. Polyurethane is chains of urethane linkages called monomers that make larger polymers. Polyurethane starts as two components that need to be combined to form a new solid full of polymers. The new polyurethane polymer will have properties varying in strength and elongation that come from the base monomers to provide a custom fit for an application.

Urethane linkages form with the reaction of two components: a poly (B side), an alcohol group and an isocyanate (A side), the backbone of the material. Based on the type of compound used, which will typically be polyol, you will be able to determine the properties of the final product. The polyol’s relative molecular mass, number of reactive functional groups per molecule, and molecular structure contribute to the formed material. The isocyanate is extremely reactive but becomes stable after the reaction has occurred.

Due to its flexible yet tough nature, it has been called plastic and rubber but is neither. More accurately, it is capable of having both elastic properties and high rigidity based on its formulation and final end use. It can be molded into various shapes and enhances surfaces with wear resistance, strength, and protection. Hardness, cure time, and physical properties can all vary to fit a specific need.

What Is Thermoset?

Thermoset urethanes are polymers that start as two-component liquids, and once combined, they cure into a solid. Due to cross-linking, additional heat will cause them to soften, not melt or reform, so they cannot be recycled. Thermosets are a good alternative to thermoplastics when you are unable to invest in high-end molding equipment, have an uncontrolled environment, or need alternative processing methods.

What Is Thermoplastic?

Thermoplastic urethanes are polymers that begin as a solid bead but, when heated, can be melted and molded into a specific shape. Since they have no additional cross-links, with the addition of more heat, they can be reformed into new shapes or recycled. Thermoplastics are great for repeated high-volume applications and do not require another reaction that could affect their final properties. However, they do require advanced molding processes and techniques that limit their use and in-field functionality.

Types of Polyurethane Materials

1. Elastomers

Polyurethane, when made as an elastomer, is best used in places where natural rubber would fail. It has great rebound that allows it to return to its original shape after being bent, stretched, or compressed. Compared to silicone, it is a cost-effective mold-making option for advanced part making. It captures extreme detail that will transfer to each casting for repeatable use. Other benefits the liquid urethane rubber can provide include resistance to impact, shock, cuts and tears, and bacteria.

2. Coatings

When formulated into a coating material, it is typically sprayed onto surfaces for protection. The coating will resist harsh chemicals, corrosion, abrasion, and impact. It can also be used for weathering protection, antibacterial properties, and many other purposes. With the ability to adhere to many surfaces, it offers flexibility and tough, long-lasting protection.

3. Foams

Thermoset polyurethanes are one of the only alternatives to expanded or extruded polystyrene foam. Using a chemical blowing agent or water, a polyurethane foam can produce a wide variety of options. Depending on the needed application, they can be rigid, semi-flexible, or flexible and have high impact strength. These two-component foams begin expanding once combined and cure to the predetermined weight and density. They are best used in void-filling applications to reduce the material costs of parts and structures. They’re also a great material for the protection of products during transit and can also be used as insulation foam.

4. Plastics

Polyurethanes, when made into a plastic, are rigid and smooth and are a good option if high strength and durability are important for the part being made. The plastic can take on extreme details of the mold it is poured into. Whether the surface is smooth, glossy, or matte, it will take on those exact qualities. As a thermoset material, it can be formulated with high heat deflection for use in high-temperature environments. It is also useful for prototyping parts and industrial part-making and can be made to be user-friendly without the need for high-end equipment.

Benefits of Polyurethane

• It is a very versatile material since it can be manufactured as an elastomer, coating, foam, or plastic. These materials can be soft and flexible or tough and rigid. With flexibility in design, manufacturing one-off parts, prototypes, and high-volume runs is convenient. You also gain versatility that can be used in various indoor or outdoor applications and produced on job sites.
• Unlike other rigid materials, it has high elasticity and easy moldability when needed. This molding quality allows you to create complex shapes at relatively low tooling costs.
• It possesses high properties such as high tear resistance and high tensile strength for optimal protection. When sprayed onto surfaces, it offers protection against scratches, scrapes, and other damages that occur over time. It also resists abrasion, has substantial impact tolerance, and does not support fungal growth.
• Compared to thermoplastic materials, it has a relatively short cure time. Most types are fast curing, which allows for increased part production and quick return to service. You’ll be able to sand, machine, and paint a lot faster than you would with other materials.

Alternative Materials

Polyurethane is commonly used for its low cost, but this low cost comes with downsides. When applying polyurethane, it is unsuitable for areas with high levels of moisture or humidity since it is sensitive to moisture. The material will bubble and leave a flawed surface. Some polyurethanes are not UV Stable, meaning UV rays can also cause degradation, so it must be protected with paint or a topcoat for indoor or outdoor use.

An alternative for coating applications would be to use polyurea. This material is much better in environments where moisture is an issue. It has improved properties that polyurethane may lack but uses high-end raw materials that make it more expensive.

An alternative to polyurea is polyurea hybrid. The hybrid material is a mix of polyurea and polyurethane. It has the benefit of being less expensive than polyurea, with better moisture resistance than urethane.

VFI High-Performance Polymers

VFI manufactures various polyurethane-based materials for various applications. Our casting rubbers and plastics are great for part-making. With different chemistries, our molding rubbers are great for making molds and forms. We’ve seen our hard coats and spray coatings used in various theming and industrial applications. Our foams can be formulated into rigid or semi-flexible structures for void-filling and high-end packaging, among other applications. Contact VFI today if you’d like to learn more about all our high-performance polymer products.

What Is Polyurea?

Polyurea is a two-component polymer produced through a process known as step-growth polymerization. This process is the chemical reaction between an isocyanate (A side) and a resin compound (polyamine, B side). The polyamine causes it to produce urea linkages.

Not many other materials can combine polyurea’s mechanical, physical, and chemical properties. Many industries use it as a protective coating, casting, or sealing material. As a coating, it is applied as a liquid and can conform to any shape or texture. It produces a strong yet flexible shell over many surfaces, including concrete, metal, and wood. The material can also be applied in a range of temperatures and environments. The primary use is in aromatic nonlight stable version, but color-stable versions are available in the form of an aliphatic.

What Is an Aromatic?

This material is a type of polyurea based on an aromatic iso. It is a workhorse in many industries when used as a base coat. It offers high properties at a low cost compared to aliphatics. Aromatics are also more chemically resistant.

One disadvantage is that it is not UV stable, which means it will change color from extended exposure to sunlight. However, the discoloration and loss of shine does not indicate a loss of properties or mechanical strength.

What Is an Aliphatic?

This material is a type of polyurea based on an aliphatic iso. Due to high-cost raw materials and complicated processing, it is a more expensive, premium product. It is UV stable, so it won’t change color when exposed to sunlight, and UV will not degrade its properties.

It can be used as a topcoat in indoor and outdoor applications to improve aesthetics and endure weathering. It can also be applied over aromatic polyurea at lower film thicknesses, so you use less of the high-cost material during application.

Aliphatic materials require advanced safety procedures above and beyond the aromatic polyureas, because the molecule is smaller and more toxic than an aromatic compound. An aliphatic molecule is a linear molecule while an aromatic molecule has a ring structure, making it much larger and less toxic than a similar sized aliphatic material.

What Are the Advantages of Polyurea?

Based on application needs, it can be formulated to achieve a range of properties.

• Depending on whether a hard or soft material is needed, the hardness can vary by changing the durometer. Most range from Shore 80 A to Shore 80 D, with the A scale classifying the hardness of flexible to somewhat harder materials and the D scale classifying hard and rigid materials. The higher the durometer gets on each scale, the harder the material.
• It is known for its durability and resilience as it protects against abrasion, chemicals, and other damaging effects.
• A unique feature is that it sets within 5-15 seconds of application. Its molecular structure makes it less sensitive to moisture, so it does not react with water in the environment. Because it makes a urea linkage, the isocyanate targets and reacts with the amine groups first, generally before it can even get to the OH (hydrogen/water) groups, as the chemical reaction occurs.
• It doesn’t degrade easily, even in the harshest conditions, so your surfaces remain protected. With a high-end combination of tensile strength and elongation, it is less likely to crack under pressure from flexing and movement.

How Is It Applied?

Surface preparation is critical to the material’s success in adhering to the surface. Oily contaminants and dirt affect the coating’s durability and longevity, so they must be removed first. A proper surface profile and/or primer are required to ensure long term adhesion and prevent expensive failures.

Polyurea is fast-reacting, so it needs to be applied with equipment that can handle its unique features. The application process uses high-pressure at a minimum of 2500 psi with heated, plural component spray equipment. The fast-setting speed requires advanced operating techniques, so applicators also must be trained to use the spray rigs.

Alternative applications are available for areas that are not able to be sprayed. A roller method is popular for industrial and residential application, because of the ease of application and limited access restrictions. Polyurea can also be mixed with a static mix tip to fill cracks and voids or applied with a brush for repairs or extremely small sections.

Where Is Polyurea Used?

Polyurea has properties that make it useful in applications where protection and strength are fundamental to the life of the surface. It is adaptable for use in a variety of applications, including:

• Mining & excavation. Mining and construction equipment encounter abrasive materials like coal, stone, and metallic ore. It can be used to protect conveyors and rollers that transport or come into contact with these materials. Coatings allow the equipment to survive harsh working conditions.
• Work and utility vehicles. It’s a great material for protecting and extending the life of work and utility vehicles. Coatings can be applied anywhere on these vehicles, from bumpers to truck beds, so they’re able to endure road wear. Choosing the best protective spray coating can help maximize the longevity of vehicles and their accessories. As a waterproof barrier, it can also protect metal parts from corrosion.
• Commercial flooring. Polyureas can be used in flooring in two different ways. It can be formulated into a multi-purpose joint filling material. A joint filler creates a flexible, durable, and water-tight seal for various building joints. Its elasticity allows it to remain intact even during expansion and contraction between joints. It also can be used as a finish coating on a concrete floor to provide long-term protection and aesthetics. The polyurea’s flexible nature and high elongation allow for a continuous monolithic layer that is not prone to chipping.
• Oil & gas. Fossil fuels and chemicals can be dangerous to the environment, so setting up proper containment is important. Many industries have turned to polyurea for primary and secondary containment in sensitive areas. This includes spraying over tank pads and geotextile fabric in containment fields to protect against leaks and spills. It has excellent chemical resistance, protects against corrosion, and withstands daily wear and tear.

Alternatives to Polyurea

No coating system can replace polyurea in all respects due to its unique physical properties and durability. While there are alternatives, some will not provide the same protection. They may also cause additional downtime during application.

1. Polyurethane

Polyurethane is closely related to polyurea, their main difference being in their resin sides. Urethane uses polyol and a catalyst rather than an amine. Without the amine acting as a curing agent, polyurethane is more versatile and can have specific high properties depending on the application.

While it can be less expensive than its counterpart, it doesn’t provide the same combination of high properties. It is sensitive to moisture and may cause foaming and/or pinholing when applied to damp surfaces. Because polyurethane is more sensitive to the environment and curing conditions, it is not recommended for sensitive environments.

2. Polyurea Hybrid

A Hybrid combines isocyanate, an amine, and polyol. The polyol contributes to its urethane component while the amine contributes to its polyurea component. It is a cost-effective solution but won’t obtain all high properties (elongation, tensile strength, tear strength). However, it provides a more polyurea like cure and less sensitivity to moisture compared to urethane.

3. Epoxy

Epoxy is a material that can be used for similar applications, such as floor coating. Spraying is not the preferred application of epoxy, as it is normally rolled or brushed on to a surface. Compared to polyurea, it is not flexible, takes longer to cure, but is more chemically stable. An epoxy’s adhesion is very dependent on surface profile, so it will cause continuous issues if not prepared properly.

VFI High-Performance Polymers

VFI is a 25+ year-old manufacturer of high-performance polymers for coating and joint-filling applications. Check out our high-pressure polyurea coatings, VFI-200, 201, 202, and 270, for optimal protection from chemicals, abrasion, and impact. Contact VFI for assistance in finding the right material for you.

Spray-on vs Drop-in Bedliner: Which Is Better?

Spray-on and drop-in bedliners offer truck beds extra protection from daily use and abuse. Whether you’re using your truck for work hauls or just moving equipment around for a friend, it pays to keep every part of the vehicle in tip-top shape. Great truck bed liners will preserve the truck bed for the entire life of the vehicle.

Now the question is, which type is best for you: spray-on or drop-in? While each comes with pros and cons, which one you choose will ultimately depend on how you use your truck bed, how often, and how much you’re willing to pay for protection.

What Is Spray-on Bedliner?

It is a paint-like protective coating, generally made from polyurea, polyurethane, or hybrid chemistry. These coatings are sprayed on the truck bed using high-pressure, low-pressure, or cartridge-driven spray equipment. Most coatings are fast curing for a quick return to service in as little as one day. Polyurea coatings come with excellent physical properties that make them the premium product for spray on bedliners.

Benefits:

1. One and Done Solution

Coatings are a simple and mostly permanent solution to protect your truck bed. When sprayed, they adhere directly to the metal, forming an airtight bond. They won’t slip, shift, fall out, or cause damage to the truck bed from an improper fit. They should last the entire life of the truck when applied correctly.

2. Durability

They offer excellent protection from daily wear and extreme temperatures with impact resistance and abrasion resistance. Since the surface is sealed, moisture and other debris cannot get beneath the liner to the bare metal, reducing the risk of rust and corrosion. They also have excellent chemical resistance. They keep the truck bed looking new without warping, cracking, or breaking.

3. Aesthetically Appealing

If you’re concerned about the appearance of your truck, not only does the spray-on bedliner provide protection, but it also looks great doing it. Coatings mold to the contours of the bed without looking bulky, and very minimal maintenance goes into keeping them looking great for years.

Texture can also be applied for a finish that suits your needs. A grittier texture can provide traction to prevent cargo from sliding around the truck bed.

4. Versatility

Applied by spray, these coatings fit all-size truck beds with no custom fitting needed. They are also not limited to just truck beds as they can also offer protection to a handful of other industrial applications. You can cover bumpers, fenders, trims, and entire vehicles with spray-on liners. We have also seen them used on ATVs, emergency vehicles, utility vehicles, boats, and more.

5. Increased Value

Your truck starts depreciating the second you take it off the lot, so why not protect it with the best? Spray-on liners are a worthy investment and offer better value for your money. Since they don’t need to be replaced, the one-time installation costs are paid off in the long term. This added protection keeps the truck bed in great condition, increasing the value when it is time to sell.

Disadvantages:

While durable, these coatings can be expensive and time-consuming to apply. Most require expensive spray equipment and special training to use. They also rely heavily on surface preparation, which can be a meticulous process. You must make sure the truck bed surface is thoroughly scuffed, cleaned, and taped up to avoid overspray and adhesion issues. However, if you can get past the initial costs, they are more cost-effective in the long run.

Also, you must be aware that these coatings may fade depending on the chemistry. Colors fade much faster, which is why black is popular since the fade isn’t as noticeable. Consider applying a UV-stable topcoat for optimal protection.

What Is Drop-in Bedliner?

It is a plastic or rubber sheet that you “drop into” the truck bed. The best-installed drop-ins are custom-designed to fit the make and model of the truck. Some offer a universal fit, which means they’re made for a wide variety of truck beds. While this may be appealing, it may cause issues later.

Benefits:

1. Cost-effective

They are more affordable because of the materials they are made of and the do-it-yourself installation. They are a great option for truck owners who use their truck beds sparingly since they likely won’t offer the long-term protection desired.

2. Easy Installation

Unlike spray coatings, you don’t have to worry about a full cure time. They are easy to install from home without the help of a trained professional. Extensive prep work is not required, so your truck bed gains an extra layer of protection in under 30 minutes.

3. Removable

If you’re looking for a temporary solution, drop-in liners are the perfect option since they just sit in your truck bed. Some require you to drill holes to secure them down, but for the most part, they should be custom-made to fit securely in the vehicle. When it’s time to sell your truck, it can be easily removed and transferred to a vehicle with similar dimensions.

4. Covers Previous Damages

Coatings conform to every curve of a truck bed, so prior damage to the metal is more visible. Drop-ins hide the damage that the truck bed accumulated before installation. Since most are made of hard plastic, they are resistant to impacts, so you can load large objects into the bed without damaging them.

Disadvantages:

While the price may be lower, it typically means the material is of lower quality and looks like it too. Frequent replacement is more likely to occur when using a plastic drop-in liner. It is vulnerable to cracking, breaking, and warping over time. You’ll have to replace it several times across the lifespan of your truck because they don’t last as long as spray-ons.

If it’s not custom-fit, it can scuff the paint and cause dents on the metal bed. There is also the potential for water and other debris to slip under gaps and get trapped. Moisture and dirt on the bare metal will allow rust and corrosion to form.

When driving at high speeds, wind can get under the plastic and cause it to vibrate. The vibration causes it to hit the sides and floor of the truck bed, creating a lot of noise. Constant rattling from a loose bedliner could become quite annoying and it may cause cracking to occur.

It doesn’t have the same traction support as spray bed liner, especially when wet. The surface can be slippery, which makes sliding equipment into the truck a breeze, but you should also expect cargo to slide around while driving. A slippery surface can cause damage to the truck bed and its contents.

Bed Mats & DIY Bedliners

Bed mats are a type of drop-in liner that only covers the floor of the bed. They’re usually made of rubber and fit specific truck makes or models. They are preferred when truck owners want a soft material that provides shock absorption and impact protection. They require more maintenance as you’ll need to remove them often to clear the debris or moisture that builds up over time.

Aerosol sprays or roll-on coatings are more affordable and appeal to do-it-yourselfers who want a quick and easy solution from home. While you get a low-cost product, you also sacrifice quality. These products aren’t as thick, so they may need to be applied a few times for damage protection. Using a DIY product can also be much more labor-intensive since they take longer to apply.

VFI Coating Solutions

VFI’s protective spray materials are time-tested for quality assurance. We offer solutions from high and low-pressure formulas to our patented Qwik Spray System for low-volume application and those new to the industrial coating industry. Contact VFI today about any of our spray-on bedliner products.

What Can You Spray on Styrofoam to Make It Hard?

There are plenty of sprayable materials you can use to harden Styrofoam. Styrofoam is a lightweight material that is easy to CNC and create custom shapes, but it does not provide any strength or rigidity for long-term use. Using a sprayable hardcoat to make the Styrofoam “hard” and durable for use in almost any environment is a necessity. A hardcoat will solve your impact and environmental problems by encapsulating the Styrofoam, leaving only a paintable surface.

These coatings are designed to protect against impacts as well as wind, moisture, sunlight, or anything that may degrade the foam structure. They will not erase any details carved into the foam, as they tend to be applied in multiple coats to build protection.

What is Styrofoam?

Styrofoam is a brand name for closed-cell extruded polystyrene (XPS) foam used in a variety of industries. It’s commonly confused with EPS (expanded polystyrene) foam since people use the brand name to generalize all polystyrene foam. Both types of foam are lightweight yet sturdy and easy to sculpt or carve, making them desired for architectural and theming applications.

Styrene foam is also cost-effective compared to other materials like wood or metal. There’s not a project too big that foam isn’t able to handle since you can carve a single piece or assemble multiple pieces together. Once a three-dimensional object is completely carved, it’s hard-coated to provide a desired finish that is paintable and durable in any environment.

Types of Foam Hardening Materials

The type of method you choose to harden foam will depend on the shape of the structure, the needed finish, budget, and turnaround time. These are typically not the best methods for crafty DIYers who use Mod Podge, PVA glue, adhesives, and paint to protect their smaller projects. If you want your project to last, the following materials are your best bet:

1. Polyurea Coating

Polyurea coatings are durable and flexible coatings with premium properties, allowing you to have great tear strength, tensile strength, and elongation. They are extremely fast setting for quick turnarounds on your foam projects. If you want a foam structure that can be placed indoors or outdoors and withstands abrasion, chemicals, and impact, this is the ideal option. It also provides substantial moisture resistance for use in moisture sensitive environments.

Polyurea coatings must be sprayed through plural component equipment since they cure quickly. Their speed can also make them a little tricky to work with, so special training and equipment are required.

2. Polyurea Hybrid Coating

Polyurea hybrid coatings are made of both polyurea and polyurethane to be strong yet maintain flexibility when applied to foam surfaces. They cure rapidly, so the surface is sandable and paintable within a day. They can also be sprayed over plastic, cardboard, wood, cement, metal, and other prepared surfaces. They are most recommended for indoor and outdoor use, spraying large areas, or use in areas with a lot of traffic. Some coatings can also be fire retardant to meet safety requirements when needed.

These coatings also must be sprayed through plural component spray equipment, which requires training to use. However, they allow you to cover large surfaces quickly compared to other techniques that are more labor-intensive, such as fiberglass.

3. Polyurethane Coating

Polyurethane coatings are also strong, durable, and watertight when applied to various surfaces. They can be applied directly to foam, and unlike polyester resin or other solvent-based materials, they will not melt it. They’ve been used in a variety of foam projects, from architecture to theming and art. Other than foam, they can also be sprayed over fabric, metal, plastic, wood, etc.
They are a bit slower than polyurea hybrid coatings but still cure within hours for sanding and painting the next day. Like polyurea hybrid coatings, they also must be sprayed through plural component sprayers. However, some are offered as a cartridge-based spray system for ease of spraying and low-volume applications. Their chemistry makes them the more cost-effective option compared to hybrids.

4. Epoxy Coating

Like the aforementioned coatings, epoxy coatings form durable, hard-shell finishes over EPS foam. Most of these coatings, however, are not sprayed but brushed or rolled onto the surface. This can make the application process more labor-intensive. Epoxy is also applied in thinner coats, which makes it a bit more fragile than other coatings. Heavy impact could break or crack the coating, but it is a more economical solution.

Epoxy coatings also typically need to be sanded after they cure to create a smoother texture for priming and painting. They are most recommended for limited outdoor use or short-term applications over foam signs, logos, and props.

5. Fiberglass

Fiberglass is a process where once the foam is carved, successive layers of fiberglass mats are laid over the surface and wet out with resin until the desired thickness and strength are reached. This process can be messy and labor-intensive but makes the surface strong and durable as the fiberglass will bond to it.

Using polyester resin with fiberglass mats will melt Styrofoam, so the surface will either need to be covered with something else first, or a different resin will have to be used. Epoxy is the resin typically used in place of polyester. Polyurethane foam can handle either epoxy or polyester resins.

Examples of Hard Coating Foam

• Theming – Polyurea or polyurethane hard coats can protect foam sculptures, props, sets, and signs for amusement parks, movie sets, or art shows. These coatings must be able to endure a lot since people will probably put their hands on them, children might play on them, and the weather might affect them if they’re placed outside.
• Construction – Replacing stone architecture with foam is a possibility, but the foam must be hard-coated to withstand the molding process and additional weight.
• Decorative Accents – Foam hard coats can be used for decorative purposes to mimic crown molding, trim, window shutters, pillars, columns, and more. They can also be used as garden décor for faux boulders, stones, tree bark, and more.
• Transportation – Depending on the hardness, polyurea hybrid and polyurethane coatings can be made more flexible for seat cushion covers for aircraft, boats, and automobiles. They can also be used as covers for pads on amusement park rides for safety as well as comfort.

VFI Hard Coat Products

VFI manufactures a line of hard coat products for foam applications. These polyurea hybrid and urethane coatings range in hardness from 70 to 95 A and 50 to 75 D, making them durable for indoor and outdoor environments. As a premium option, some of our hard coats will pass Class A fire testing for optimal safety in any application. While most of these are meant to be sprayed, we also offer a brushable hardcoat option.

• VFI®-2519 75 D Brushable Hard Coat
• VFI®-2626 65 D Brushable Hard Coat
• VFI®-6170 70 D Spray Hard Coat
• VFI®-6171 70 D Qwik Spray Hard Coat

Contact VFI to learn more about protecting your foam project with a hard coat.

How to Use the Qwik Spray System (W/ Pictures)

The Qwik Spray System is VFI’s exclusive applicator gun and cartridge system used to help businesses with entry-level or low-volume applications of polyurea hybrid and polyurethane coatings. It is a cost-effective option that provides the same quality finish as high- or low-pressure spray equipment.

The gun is easier to operate than other systems as it requires no special training to use. It also automatically mixes the material in the static mix tip during the spray process and offers increased portability. There is minimal overall equipment maintenance, and cleaning after use is easy since cartridges can be thrown away once they are fully used.

Importance of Surface Preparation

All surfaces to be sprayed must be properly prepared beforehand to ensure coating adhesion. Remove debris, oil films, or detergents, and make sure the surface is dry before spraying. Some surfaces should be sanded and primed to create proper adhesion. Cover surrounding areas you’re not spraying to ensure there is no chance of overspray.

How to Set up the Applicator Gun

Equipment needed: VFI-7500 Qwik Spray Gun, air regulator kit with air supply hose, and air compressor (not included, must be capable of 10 CFM at 90 psi)

1. Remove the VFI Qwik Spray Gun from the box and plastic bag. Remove the air regulator and air supply hose from the smaller box.

2. Screw the quick-connect hose coupling (included with the gun) onto the bottom of the T-fitting to the right of the air regulator. Then, screw the top of the T-fitting onto the compressed air connection below the trigger handle of the spray gun.

3. Insert the air supply hose into the push-to-connect fitting on the left side of the regulator.

Note: When disconnecting, press the push-to-connect fitting to release the hose.

4. Attach the provided handle to the blue front plate of the spray gun. There are six different spots to screw the handle into for optimal comfort when spraying.

5. Connect an air compressor hose to the quick-connect hose coupling.

6. On the rear of the gun, you will find the air pressure regulator that controls the coating flow. Adjust by twisting the knob clockwise for increased flow or counterclockwise for decreased flow.

7. The brass forward/reverse rod near the regulator allows you to move the plungers forward while spraying and backward to remove empty cartridges.

How to Use the Qwik Spray System

Equipment needed: VFI-7500, 750×750 ml disposable cartridges, and static mix tips

1. Remove the cartridge from the box and plastic bag. If material separation occurs, shake the cartridge until uniform. Heat material slowly to at least 75°F. It should be elevated slowly to operating temperatures. Do not microwave.

Note: Do not store the cartridge nose up for long term periods to prevent leaking from the plunger seals.

2. Keep the cartridge nose up to prevent the components from mixing.

3. Remove the red safety cap from the threading.

4. Slowly remove the white anti-separation cap. (The material may come out if the product is too warm or heated unevenly.)

5. Place the provided static mix tip on the plastic threading and hand-tighten the attached nut to the base.

6. The static mix tip should sit snug on the threading with no gaps and without cross threading.

7. Load the cartridge into the gun frame label side up by placing the rear of the cartridges over the plungers and lowering the front of the cartridges into the front plate.

8. Keep the cartridge and applicator nose up so the static mix tip stays vertical to prevent the A and B side material from crossing and flowing in the static mix tip. (If using joint filler material such as VFI-5011, skip steps 8-10.)

9. Connect the elbow push-to-connect fitting on the air supply hose to the static mix tip for atomization during application.

Note: When disconnecting, press the push-to-connect fitting to release the static mix tip.

10. Turn on the atomizer by opening the ball valve.

11. Twist knob on the regulator to adjust for the desired texture. VFI recommends starting between 60-90 psi, but the psi can be increased based on the texture you desire. You can leave the setting for spraying future tubes.

Now, you can begin spraying by pulling the trigger on the handle.

Tips for Spraying

• Use proper personal protective equipment (PPE). We recommend using a full-face mask/supplied air respirator, coverall suit or equivalent, and chemically resistant gloves.
• The application area must be well-ventilated, like an approved spray booth, as these materials are hazardous to ingest, inhale, or come into physical contact with.
• Consider your spray pattern before you start spraying. Once you begin, the entire cartridge must be fully discharged to keep the static mix tip from clogging.
• Start spraying off the surface onto a disposable area to ensure the material is fully mixed. Monitor the level of material in the cartridges as you’re spraying. When the cartridge is nearly empty, spray off the surface to prevent off-ratio material.
• Begin spraying within the recoat window of the product where you previously stopped to maintain uniform coverage across the entire surface.
• You may apply texture by spraying over but not directly onto the surface until a desired finish is achieved.
• Clean the gun of all coating residue after use with MEK or xylene, and do not soak it in solvent.

Compatible VFI Materials

The VFI-7500 Qwik Spray Gun works incredibly well with the VFI-6171 70 D Qwik Spray Hard Coat and provides the same quality as any low- or high-pressure system. It is also compatible with VFI’s other cartridge-based systems, including VFI-544 Qwik Spray Bedliner, VFI-5011 80 A Expansion Joint Filler, and VFI-2538 QS 70 D EPS Form Hard Coat. Contact VFI today if you are interested in getting started with our portable, easy-to-use spray system. You can also check out our Qwik Spray instructions in video format by clicking here.

Is Polyurethane Rubber or Plastic?

While there has been some confusion on the matter, polyurethane is neither rubber nor plastic. It often looks and feels like either material, which is why people often ask for polyurethane rubber or plastic. It also has properties that make it behave like a strong, rigid plastic with the elasticity of a rubber.

Polyurethane is strong and more durable than natural rubbers or thermoplastics, and it outperforms in highly abusive environments. It is a more cost-effective material in the long run for its long-lasting capabilities. The material is cast as a liquid, so production prices are lower than heat and pressure-molded materials. Being a liquid at the start also allows it to bond well to other materials when needed.

What is Urethane?

It is categorized as a polymer used to produce materials that behave like plastics and rubbers. Polymers are made of long, repeating chains of monomers. These highly cross-linked structures produce a thermosetting material. Thermoset polyurethanes, once hardened, cannot be melted or reformed.

While one polyurethane may look and feel different from another, they all essentially have the same chemistry. The material is made by mixing two or more liquid chemicals to produce a reaction. In this case, it is the reaction of a monomer and an isocyanate. Urethane has to be an isocyanate reaction with an alcohol functional group (OH). The choice of iso and monomer is how the properties of the material can be altered. Using different compounds is also how polyurethane is able to imitate other materials. Its range of durability, flexibility, and resilience make it highly valued across industries.

The material first became a replacement for rubber during WWII. Since then, many industries have preferred to use it in place of wood, metal, thermoplastic, and rubber. It offers many advantages and embodies aspects of each material. Based on its chemical structure, it can be a coating, adhesive, foam, or molding and casting material, making it versatile for a wide range of applications.

Benefits Compared to Rubber

There are two distinct types of rubbers: natural, harvested from the latex of rubber plants, and synthetic, made of petroleum byproducts. They are classified as elastomers as they are moldable and flexible, like polyurethane. There are several advantages to using urethane over rubber:

•  It has notable resistance to abrasion, impact, and scratches. It’s best used when a material needs plenty of strength and resilience to endure continual stress and stretching.
• While rubber is cheaper, polyurethane has more affordable tooling costs as it is easier to produce complex parts. It’s also more cost-effective in the long term since it is made to outlast rubber.
• It excels at resisting cuts and tears better than rubber. It also has great load-bearing capacity to handle more weight without breaking, resulting in longer product life.
• No matter the hardness range, it maintains its properties, whereas rubbers will have limited properties. It also maintains its properties over a wide range of temperatures and other conditions. Whether hot or cold, it stays flexible and functional. Rubber will typically become brittle and lose its elasticity over time due to these stresses.
• It can be used for a handful of applications, as different formulas offer a broad range of properties, durometers, and colors, whereas rubber is more limited.

Benefits Compared to Thermoplastic

Thermoplastics have chain-like polymer molecules and can be made of various chemical compositions. Standard thermoplastics include polyethylene, PVC, nylon, and ABS. There are several reasons polyurethane would be used in place of these materials:

• It is an ideal material for products that are subject to high impact or sudden forces and shocks. Thermoplastic is unable to handle repetitive impact, and it is more likely to break, abrade, or degrade.
• It outperforms thermoplastic because of its durability, abrasion resistance, and wear resistance. This makes it a suitable material for applications that experience constant friction.
• It maintains its strength, even at higher hardnesses. Thermoplastics are more limited in their durometers and properties, which makes them crack and break under heavy loads and stress.
• You have more freedom in your production process when using the material, especially when making complex shapes. Thermoplastics are usually heated and injected into a mold, while polyurethane can be cast or reaction injection molded at both room and high temperatures.

Benefits Compared to Metal

Polyurethane has often been used in place of metal for its unique properties and advantages such as:

• It has better shock absorption and noise reduction abilities. This is important for applications where a quieter environment is required.
• It is a lightweight material, which is an advantage for applications where reducing the weight of parts is essential. Its lower weight also makes it easier to work with and handle.
• It’s the preferred material when exposure to moisture or chemicals is possible. It can handle abrasive and corrosive environments, so you get more life out of your parts. Metal may rapidly break down when exposed to certain chemicals and moisture, making the life of parts much shorter.
• It offers reduced tooling costs, as it is typically less expensive to machine, cast, and mold into complex shapes. This allows for custom designs that are difficult to achieve with metal. There’s also no need for expensive welding or machining processes, as it cures at room temperature.
• Metal does not have the ability to flex under stress, but urethane can be compressed and still rebound to its original shape and size.

VFI Polyurethane Materials

VFI is experienced in the manufacture of various polyurethane products. We offer coatings, foams, rubbers, and plastics for a vast number of markets. Depending on the material, they can be sprayed, injected, or poured and customized to your specifications. There’s no limit to what they can be used for, as they are very versatile and adaptable. If you need help finding a solution for your project, VFI is happy to help. Contact us today for assistance with your urethane needs.

Polyurea vs Polyurea Hybrid: How to Tell the Difference

Polyurea and polyurea hybrids are used for a similar purpose, as they are both sprayable coatings that form seamless, protective barriers on virtually any surface. Once cured, they have excellent resistance to abrasion, corrosion, and impact damage. They can also be sprayed through the same type of high- or low-pressure equipment.

Polyurea is considered a premium product due to its higher properties and chemical resistance, whereas hybrids are a cost-effective option with qualities of both polyureas and polyurethanes. The one big difference between these coatings is moisture resistance, as it does not react with water like a urethane or hybrid would. This allows it to be used in extremely sensitive conditions.

A common misconception in the industrial coatings market is that some products claim to be “pure” polyurea, but do not reflect it in cost or properties. These coatings may also boast a high percentage of polyurea content to make them seem superior to typical hybrids. It’s believed that the higher the content, the better the product. Due to this, many applicators ask for the polyurea content in any given product.

However, percentages mean nothing if they are not verified by a third-party testing agency. The truth of what the product is lies within the physical properties. If you look at the properties, you’ll usually be able to determine where the material falls on the polyurea to hybrid spectrum.

The Truth Is in the Physical Properties

To determine if a polyurea is “pure” or a hybrid, you’ll want to look at three main properties: tensile strength, elongation, and tear strength. It is a combination of the three that allows you to tell the difference between the coating types. These three properties will typically all be high for polyurea, but you will see variations for hybrids. Only one or two may be on the higher end for a hybrid while the other(s) are relatively lower, which is how you’re able to decipher its polyurea content.

Note: these properties are averages for 50-60 D materials. Properties will change if the durometer is increased or decreased.

Tensile strength is the strength of a material (in this case, the coating) to withstand pulling force tension before it fails. It is usually listed as the pound-force per square inch (psi) at which the material fails on average. This is determined using standardized mechanical testing.

• What to expect for polyurea tensile strength: Typically, above 2,500 psi

Elongation is the maximum strain or stretch a material (the coating) can withstand before it fails. It is listed as a percentage found by comparing the final and original length of the tested material. Elongation is tested using the same standardized mechanical testing as tensile strength. It is important to know the relationship between tensile strength and elongation to understand the point at which failure or deformation may occur.

• What to expect for polyurea elongation: Typically, above 300%

Tear strength is the amount of force required to rip a material (the coating) or continue tearing it along the vertical axis. It is usually listed as the average tested force in pounds per linear inch (pli) needed to rip the material. If the material was cut or punctured, the value represents how much force along the axis is needed to continue the tear. These values are based on a standard ASTM test method and die shape (ASTM D624, Die C).

• What to expect for polyurea tear strength: Typically, above 350 pli

Tensile Strength vs Elongation vs Tear Strength

Let’s compare the properties of VFI-201 vs VFI-206 and VFI-542. Other people in the industry would potentially consider VFI-206 a pure polyurea, but its properties show that it has just enough urethane content to make it a hybrid (shown in its lower elongation).

How to Choose Between a Polyurea and a Hybrid

Knowing the difference between a true polyurea and a hybrid will help you choose the best coating for your application. Your choice will depend on the intended use and potential exposure to the elements.

While polyurea coatings are the premium option, you should determine if you actually need one. Its moisture resistance makes it the common choice, but it is misconceived that a hybrid needs more moisture resistance than required. If you have a moisture problem during application, you may be looking for an entirely different product.

It is also important to know the differences in setting speed for successful application. Polyureas tend to be rapid curing with about 4-6-second gel times, while hybrids gel at about 8-10 seconds. A polyurea’s faster setting abilities can make it tricky to work with and ensure adhesion.

Polyurea hybrids are super versatile, providing a good balance between properties, moisture insensitivity, and price. VFI recommends our hybrid solutions as they are cost-effective and can be custom-formulated to fit your needs. Contact us today to find the right coating for you.

Thermoset vs Thermoplastic: Which is Better?

When looking at thermoset vs thermoplastic, choosing the best material for your project will highly depend on the application, needed properties, and your overall budget. Both materials have been used to create products for everyday use and even specific purposes. There are many applications where either material will work, but some require the use of one over the other.

The main difference between thermosets and thermoplastics is what happens in the curing process and how they behave when heat is applied. They are also different regarding their properties, applications, and how they’re manufactured or processed.

Thermosets handle heat incredibly well after curing, as they do not melt when exposed to additional heat.

Thermoplastics begin as solids and are then heated and melted to be formed into new solid shapes once cooled. Unlike thermosets, if heat is applied to the material after it has cured, it will melt back to its liquid state.

What Is a Thermoset?

A thermoset is a high-performance polymer that cross-links during its curing process to form irreversible chemical bonds. At room temperature, it is a liquid and then hardens when heat and/or pressure is applied to make the material undergo a chemical reaction. The chemical change prevents the material from returning to a liquid state, making it impossible to reshape, recycle, or remold.

The chemical bonds also make the material stronger and more heat-resistant than its thermoplastic counterpart. The higher the cross-link density, the better the heat and chemical resistance they have. They can also be more rigid or flexible depending on the length and number of cross-link chains.

The main molding process used to make thermosets is reaction injection molding (RIM). Some materials can also be poured or sprayed. True to their name, they are set with permanent physical properties after the initial cure.

Common materials: epoxy, polyurethane, polyurea, polyaspartic, silicone

Advantages & Weaknesses

Advantages: 

• Durable. Thermosets are a good choice for parts that require dimensional stability and structural integrity at various temperatures. Due to their strong chemical bonds, they retain their strength, form, and shape in any condition, which makes them more durable.
• On-site uses. Thermosets can be applied to be cured on site without heating and/or can be retrofitted once they are in the field. They can also be sprayed through a plural component machine or injected while in the field. With easy molding characteristics, you can create large shapes, complex parts, or multipart components.
• Cost-effective. Setup and tooling costs tend to be lower. They can be molded at different tolerances, allowing for flexible product designs. Surface finishing is not required, which makes the process even more cost and time efficient.
• Versatile. There are a wide range of industries that use thermosets due to their chemical and thermal stability, as well as their various hardnesses. They have the unique advantage of being used as plastic, rubber, or foam. For example, you can make a thermoset elastomeric, but thermoplastics are incapable of achieving the same flexibility, so you would have to use a material like natural rubber. They have excellent flowability as a liquid, which allows them to fill all voids in a mold to copy small details that can’t be made with metal or thermoplastics.

Weaknesses: They might not be used over thermoplastics in instances where a recyclable or remoldable material is desired since they cannot be melted down to their original liquid state. Even though they have high strength, their rigidity can lead to reduced hardness at high temperatures. If they are overheated, they may begin to degrade but will not melt. This makes picking the correct thermoset product and the relevant HDT or heat cycling numbers important for your application.

Where Are They Used?

With good chemical resistance and thermal stability, they meet a variety of conditions for a range of applications. Their properties make them an excellent choice for high-heat applications or situations where heat is a factor. They are widely used in the aerospace, defense, electrical, automotive, and construction industries. They are a great alternative to metals and other plastics when complex, detailed parts and components are needed. Easy molding characteristics and on-site use get around many issues that you would encounter with thermoplastic materials.

What Is a Thermoplastic?

A thermoplastic is a solid polymer at room temperature (commonly stored as pellets) but becomes soft and pliable once heat is applied. There is no chemical bonding that occurs during the curing process, which means that it is reversible and only a physical change. Parts and products are made from this material by the processes of extrusion, thermoforming, or injection molding. Since they have a low melting point, they soften and deform when exposed to heat after curing, but their properties remain unaffected once the heat is removed.

Common materials: ABS, acrylic, nylon, polystyrene

Advantages & Weaknesses

Advantages: 

• Reusable. They are best known for their recyclability, as they can be melted down and molded into a new shape for reuse. Even after the material has been reshaped, its physical properties will not be negatively affected.
• Durable. They have great impact resistance and high strength while also being lightweight. They also resist shrinking as they offer good elasticity and flexibility. Since they are known for being versatile, they work well in both high and low-stress applications.
• Chemically resistant. They are desirable for their resistance to chemicals, detergents, and corrosion. They are the perfect material for applications that need protection from highly corrosive environments. While thermosets also have decent chemical resistance, it doesn’t compare to thermoplastics.

Weaknesses: Thermoplastics are not always the best or most cost-effective option, especially for low-volume or custom part production. The production process usually requires high heat and pressure, which can be more costly.

When exposed to heat and sunlight for extended periods, they experience UV degradation and soften or deform. They can’t handle heavy loads because they will stretch and weaken, which makes them more susceptible to creep and fractures.

They also struggle with application or retrofitting in the field. Primarily all work is done in the manufacturing setting and the original part may not be able to be modified in the field.

Where Are They Used?

Thermoplastics are ideal for applications that require recyclable and reusable materials. They are a good substitute for metal, as they can withstand corrosive conditions, though they are limited in high-temperature environments. They’ve also found use in the construction, electronics, medical, food and beverage, chemical, and automotive industries. They can be used to encapsulate rigid objects in electrical equipment or rope and belt production.

VFI Thermosetting Polymers

VFI has been manufacturing thermosetting polymers for almost 30 years. Our products have been used in a vast number of markets and industries. Most of our materials are two component liquids that become solid from a chemical reaction once combined and allowed to cure. They are strong, long-lasting, and third-party tested for quality assurance. If you have specifications for a needed material or questions on if you should be using a thermosetting polymer, contact VFI today.