Reinforcement, combined with resins or coatings, makes high-strength composites possible.
Photos: Courtesy of Acrymax
Would you go out in rough seas in a sportfishing boat made of resin with no fiberglass reinforcement? Or would you rather be in a boat with a composite hull comprised of resins and high-strength reinforcement? Not a very difficult choice.
Combining reinforcement with resins or coatings creates a composite. A composite is a material made from two or more constituent materials that, when combined, produce a material with characteristics different from the individual components. The individual components of the composite act in concert with each other, yet they remain separate and distinct because they don't fully merge or dissolve into one another. Reinforcement in a composite material is, fundamentally, intended to enhance the mechanical properties of the overall system.
Since the 1950s, elastomeric roofing materials — both in sheet and liquid-applied forms — have gained widespread use. There have been problems, however, when reinforcement has not been used. In some cases, catastrophic shattering occurred with unreinforced PVC membranes. Shrinkage in some early-generation EPDM membranes caused pulling at the curbs, penetrations, perimeters and flashings.
Combining high-strength reinforcement with elastomeric coatings creates durable composite roof membranes.
While elastomeric roof coatings are highly versatile materials that can often be used as standalone products, there are distinct advantages to using reinforcement to create a composite roof membrane system. Incorporatingreinforcement creates high-strength, seamless, monolithic membranes that are fully adhered and have no seams. They have a proven track record of success in many different types of applications. Reinforced systems are used to recover single-ply, existing asphalt, and other existing roof substrates. They can also be used in new construction over insulation board or other suitable materials.
In the case of a reinforced, fluid-applied roofing system, the coating provides weather resistance and waterproofing capabilities, and the fabric reinforcement provides increased strength and dimensional stability. Reinforced roof coating systems distribute stress and prevent defects in the underlying substrate from “telegraphing” through the membrane.
Polyester fabrics are the most common reinforcements used with elastomeric coatings in fluid-applied roof membranes. Stitch-bonded and spunlaid fabrics are available. Manufactured with different processes, they both offer high strength; however, there are some differences. Stitch-bonded fabrics are made by stitching fibers together to create a coherent fabric. These fabrics offer excellent conformability to irregular surfaces and are especially useful for flashings, seams and wall transitions. Spunlaid fabrics provide equal multidirectional elongation and easy saturation. They are more rigid and useful on smooth surfaces.
Reinforcing fabrics are easily and quickly incorporated into fluid applied roof membranes.
FEATURES OF REINFORCED COATING SYSTEMS
Reinforced coating systems exhibit improved mechanical properties and are designed to be far stronger than coatings alone.
Reinforced systems retain their shape and size when they are heated or cooled and when they go through wet-dry cycles. In a ponded water situation, a reinforced system will provide improved performance because the reinforcement will limit the swelling of the membrane caused by any water absorption of the coating.
Good physical properties are obtained in reinforced systems with relatively thin membranes. A fully reinforced 45-mil acrylic roof membrane weighs approximately 0.4 pounds per square foot.
These systems provide excellent resistance to hail impact and foot traffic.
Reinforced membranes are durable and require little maintenance. There are Acrymax composite membrane roof systems in place that are still providing superior protection after more than 30 years of service. Simple recoats are being used to extend the life of these systems indefinitely.
Stitch-bonded reinforcement fabrics provide excellent conformability to irregular surfaces and shapes.
If specifying a system only to provide architectural color or reflectivity, coatings alone will provide acceptable performance. They can also provide protection from UV degradation; however, using reinforcement with an elastomeric coating will achieve maximum performance.
So to specify a winning roofing solution, bring in the reinforcements!