Monday, May 7, 2012

How roofing manufacturers classify roof coatings

Roof coating systems are available for a variety of roofing systems. Manufacturers like Conklin are introducing new formulas to keep up with changing needs and roofing materials with water-based urethanes, bio-based materials, 100% solids silicones, and low volatile-organic-compound asphalt cutbacks currently in the pipeline. Also on the horizon are self-cross-linking water-based coatings, faster-setting water-based coatings, and a basecoat primers suitable for literally every roofing membrane on the market.

Manufacturers classify roof coatings according to the specific binder and carrier type, which also determine application methods and compatibility with existing roof surfaces.

A coating’s binder (or resin) is the basic matrix material - the part that actually adheres to an existing roof surface. Manufacturers use different binder chemistries to meet price and performance criteria, as well as to match specific roof substrates. The binder type dictates most of a coating’s primary physical properties including elongation, tensile strength, adhesion to a substrate material, permeance, water swelling, and low-temperature flexibility. They typically range from asphalts to a variety of elastomers (acrylics, urethanes, silicones, thermoset rubbers and various block polymers), as well as blends of these materials.

A coating’s carrier is the liquid that combines with the binder to reduce viscosity to a workable level. The carrier generally evaporates during curing. It also generally dictates a coating’s installation process and cure time. Manufacturers now more often use water as a carrier, in which case the binder is suspended in water as an emulsion though traditionally coating binders used a solvent as the carrier. Solvent-based coatings cure in a broader range of weather conditions and might be the best (or only) choice in freezing or wet conditions.

A coating’s cure rate varies greatly because it reacts to ambient humidity, temperature and sunlight. This reaction is especially true of water-based coatings. Coating installers must allow coatings to cure sufficiently to ensure they are waterproof.

Manufacturers can add pigments and fibers to binders to control physical properties and increase reflectivity. Because reflectivity and emittance are defining properties of cool roofs, organizations such as the Energy Star program and the Cool Roof Rating Council in California monitor and measure these coatings.

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1 comment:

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