Polyimide (PI) - Available both as thermoplastic and thermoset resins, polyimides (PI) are a family of some of the most heat and fire resistant polymers known. Polyimide is said to possess a greater resistance to heat than any other unfilled organic material. Unlike most plastics, polyimides are available in laminates and shapes, molded parts and stock shapes. Polyimide parts are fabricated by techniques ranging from powder-metallurgy methods to conventional injection, transfer, and compression molding and extrusion. In general, moldings and laminates are based on thermoset resins although some are made from thermoplastic grades. Laminates are based on continuous reinforcements where molding resins contain chopped (short) fiber reinforcements.

The first commercial polyimides (PIs) were introduced by DuPont in the early 1960s. Because of the processing difficulties the availability of modified polyimides was established in the 1970s.