Selecting correct coatings—part 1

Because there are more roof coatings available to roofing contractors than ever before, it can be difficult to choose a proper coating. And choosing a coating becomes even more complicated given the myriad of roof systems currently on the market. However, before you can determine what coating to use, it is important you understand some basic information about coating technology.

Coating technology

Roof coatings commonly are classified according to binder type and carrier type. Application methods and compatibility with existing roof surfaces stem from the binder type and carrier type.

A coating's binder is its basic matrix material that adheres to a roof surface. Different binder chemistries are used to meet price and performance criteria, as well as to match specific roof substrates. The binder type generally dictates most of a coating's primary physical properties, including elongation, tensile strength, adhesion to a particular substrate material, permeance, water swelling, low-temperature flexibility, and resistance to fungi and dirt. Binders commonly used in roof coatings range from asphalts to a wide variety of elastomers (acrylics, urethanes, silicones, thermoset rubbers and various block polymers), as well as blends of these. Binder chemistries constantly are evolving, and new coating formulas are being developed for special applications.

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