Polyester film is a high-performance film made from polyethylene terephthalate (PET) resin. The Polyethylene Terephthalate (PET) resin is made from Ethylene Glycol and dimethyl terephthalate (DMT). The PET resin used is of a similar intrinsic viscosity (IV) to fiber grade resin, used to produce polyester fibers, but has a higher purity. PET resin is made in special grades for specific film types and often contains slip modifiers.

In comparison with other common plastic films, polyester film is characterized by high tensile strength, excellent dimensional stability, low moisture absorption, good retention of physical properties over a fairly wide temperature range (-70° to 150°C), excellent electrical properties, and good optical clarity. Because of its higher price relative to PVC, polyethylene, and polypropylene film, polyester film is generally considered a specialty film among all plastic films; however, markets of considerable volume have developed that require this strong, dimensionally stable film. Prices are higher than most commercial plastic films primarily because the manufacturing process is much more costly due to the need for an orientation step. (Most polypropylene film is also oriented.)

The strength of polyester film requires rugged machinery for orientation. In order to assure strict gauge control, the buildings containing the film lines are carefully engineered and have very strong foundations and special reinforced flooring to prevent vibrations. Many end uses for polyester film have stringent specifications (e.g., photographic film and magnetic media) and require clean room conditions. Thus, capital costs are much higher than for other oriented films. Polyester Films have a unique combination of physical, chemical, thermal, and optical properties which result in the following: Strong, tough, brilliant and clear and ease of converting, laminating, extrusion coating, embossing, metallizing, printing, punching, corrugating, dyeing, stamping and forming. Polyester film is sold in various types, thicknesses, widths, and properties designed in many cases to satisfy the requirements of particular end applications.