Why Polyurethane Formliners Are the Best for Concrete Projects

Unlike traditional materials such as plastic or foam, polyurethane formliners offer a unique blend of qualities that make them the superior choice for concrete projects. One of urethane’s most remarkable characteristics is its flexibility. Due to its flexible nature, it can replicate complex patterns and intricate designs, including incuts, curves, and irregular shapes. It has unlimited design potential for replicating natural materials, pushing boundaries with abstract patterns, and even incorporating logos into architecture.

Other, more rigid materials can’t achieve the same highly realistic detail and definition on concrete surfaces. Urethane is also much more durable than any other material. With its resistance to abrasion, chemicals, and excessive wear, a single liner withstands multiple uses.

How are Urethane Formliners Made and Used?

Polyurethane formliners are made of a high quality, two-component material that combines isocyanate and polyol, which forms a liquid rubber that is poured into a mold and over a master. The liquid flows into all voids and contours every line to pick up every minor detail, including the porous nature of rocks, creating a perfect replica. Urethane cures at room temperature and comes in a range of hardnesses to fit a variety of application needs.

Before casting concrete into the new mold, it’s recommended that an acceptable release agent be used on the face, edges, and ends before each cast. Do not over-apply, as this may create pooling in the mold that will cause surface voids or bug holes. These voids prevent the concrete from copying all the details from the urethane.

The formliners are generally placed inside formwork before the concrete is poured. They must be properly aligned and secured for the best results. Large liners are usually attached to plywood backing since they weigh more and are less flexible. Plywood allows for attachment points in order to pick up the liners with machinery for precise placement and increased size. Using larger liners this way also allows for a quicker set-up and application on larger projects.

Once the concrete hardens, the formliner is removed, and all the details are transferred onto the surface. Urethane’s elasticity simplifies the stripping process, allowing it to easily release from intricate details and undercuts in the concrete for damage-free demolding. These formliners can also be inverted to generate different, less predictable patterns on the concrete. When using urethane, it’s much easier to avoid noticeable seams in the design as well, especially if you’re using large panels of the material. When plastic is used, more effort goes into making larger forms, as an adhesive must be used to glue several pieces together.

Where Are They Used?

Polyurethane form liners see the most use in large projects and areas with a lot of square footage to cover. If you need long spans or a seamless appearance in the concrete, urethane is the best option capable of fulfilling these requirements. It is a cost effective choice for any project that requires a high number of reuses.

Urethane is the best material for producing high detail and relief for projects, especially when a certain level of realism is needed. There’s almost no limit to where urethane can be used, including tilt-up, cast-in-place, and precast applications. Other instances where urethane makes a great form lining material include:

• Architectural facades. Add depth and character to flat, plain concrete surfaces on the exterior of buildings and give them a new identity.
• Landscaping. Craft inviting outdoor spaces such as charming pathways with natural rock formations in retaining walls to connect with surrounding landscapes.
• Interior design. Enhance plain walls and columns and turn them into a stunning focal point for indoor spaces such as hotels, residences, and shopping centers.
• Infrastructure. Beautify utilitarian structures such as bridges, tunnels, and public spaces with artistic, textured elements.

How to Take Care of Your Formliners

A urethane formliner’s reusability will depend on how it’s used, how it’s cared for, how detailed it is, and the job site conditions. Key steps to preserve the life and quality of the liners include:

• A release agent should be applied before each use for easier demolding and to prolong the life of the liner. Cleaning the release agent off after use is also essential, as some release agents can be reactive and degrade the material over time.
• A clean liner will last longer and produce excellent results each time. Proper cleaning after each use removes concrete dust and buildup, preventing debris from affecting the detail of subsequent pours. Clean with hot water, soap, and a natural bristle brush. Never use a wire brush or harsh chemicals that might damage the urethane.
• Be careful and gently pry the formliner from the concrete in the stripping process. Peeling it back can create additional stress, reducing its usefulness over time.
• The form should be removed within 24 hours after the concrete has cured, or stripping may be difficult. While urethane is durable, you want demolding to be easy to keep the detail intact.
• Proper storage is also required to maintain its usability. Store it flat and in a clean, temperature-controlled environment. Do not let it sit face up in the sun for long durations of time. UV rays deteriorate urethane and may cause it to expand and fall apart.

VFI Polyurethane for Concrete Projects

VFI manufactures several lines of urethane products not just for use in form lining. The type of rubber you choose for your project will depend on your production process and the detail you require. Our 2100 series 55A-70A rubbers can produce advanced detail for highly aesthetic concrete pieces. Our 2100 series 70A-90A rubbers are also great for concrete projects but offer basic detail at lower pour thickness minimums. If you’re interested in these materials or softer rubbers for cast and manufactured stone applications, contact us today.