What Is Polyurea?

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. We also offer a joint filler (VFI-5075) to seal joints and concrete pads in industrial applications with light traffic. Contact VFI for assistance in finding the right material for you.