polycarbonates, group of clear, thermoplastic polymers used mainly as molding compounds (see plastic). Polycarbonates are prepared by the reaction of an aromatic difunctional phenol with either phosgene or an aromatic or aliphatic carbonate. The commercially important polycarbonates use 2,2-bis (4-hydroxyphenol)-propane (bisphenol A) and diphenyl carbonate. This polymer is a clear plastic with a slight yellow discoloration. It has excellent electrical properties and a high impact strength.