General Description: The most common thermoplastic polyester, this polymer is often called just "polyester". This often causes confusion - not only is the chemically similar PBT also a (thermoplastic) polyester, the most common resin system used in GRP is also a polyester system - and also often called just "polyester". (In this latter case, however, the polyesters are chemically unsaturated and are "free-radical polymerized" into a thermoset).

PET is a hard, stiff, strong dimensionally stable material that absorbs very little water. It has good gas barrier properties and good chemical resistance except to alkalis (which hydrolyse it). Its crystallinity varies from amorphous to fairly high crystalline; it can be highly transparent and colorless but thicker sections are usually opaque and off-white.

Applications include bottles and electrical components but it is probably most widely known as the biaxially oriented and thermally stabilized films used for capacitators, graphics, film base and recording tapes etc.