A thermoplastic alkyd type resin. Polyester is made by the reaction of an ester of dihydric alcohol and terephthalic acid. There are two major types of polyester. One type, polyethylene terephthalate (PET) was first developed by English chemists, J. R. Whinfield and J.T. Dickson, in 1941. PET is used to make Mylar® and other strong moisture-resistant films. The second type, polybutylene terephthalate (PBT), is mainly used as a moulding compound. When catalysed, polyesters can harden at room temperature and pressure with very little shrinkage to produce a clear, colourless fibre, block or film. Synonyms: Dacron® [DuPont]; Mylar® [DuPont]; Bio-Plastic; Caroplastic; Castolite; Vestopal; Terylene [ICI]; Tergal; Tetlon; Palatal; Leguval [Bayer]; Kodel® [Eastman Chemical]; Paraplex [Resinous Products and Chemicals]. Museum of Fine Arts, Boston (2000). [J. Cassar, R. de Angelis]