Gel coat
Gel coat means a thermosetting resin surface coating containing styrene (Chemical Abstract Service or CAS No. 100-42-5) or methyl methacrylate (CAS No. 80-62-6), either pigmented or clear, that provides a cosmetic enhancement or improves resistance to degradation from exposure to the elements. Gel coat layers do not contain any reinforcing fibers and gel coats are applied directly to mold surfaces or to a finished laminate.
Source
40 CFR § 63.5779
Scoping language
Terms used in this subpart are defined in the Clean Air Act, in 63.2, and in this section as follows: