Epoxies are used by the plastics industry in several ways. One is in combination with glass fibers (i.e., impregnating fibers with liquid epoxy resins) to produce high-strength composites or reinforced plastics that provide heightened strength, electrical and chemical properties, and heat resistance. Typical uses for epoxy-glass reinforced plastics are in aircraft components, filament wound rocket motor casings for missiles, pipes, tanks, pressure vessels and tooling jigs and fixtures. Epoxies are also used in the encapsulation or casting of various electrical and electronic components and in the powder coating of metal substrates. Major outlets for epoxies also include adhesives, protective coatings in appliances, industrial equipment, gymnasium floors, etc., and sealants. Epoxies are thermosetting resins that, in the uncured form, contain one or more reactive epoxide or oxirane groups. These epoxide groups serve as cross-linking points in the subsequent curing step, in which the uncured epoxy is reacted with a curing agent or hardener. Cross-linking is accomplished through the epoxide groups as well as through hydroxyl groups that may be present. Most conventional unmodified epoxy resins are produced from epichlorohydrin (chloropropylene oxide) [CH2OCHCH2Cl] and bisphenol A [(CH3)2C(C6H4OH)2]. The other types of epoxy resins are phenoxy resins, novolac resins, and cycloaliphatic resins.