Polyamides are a group of thermoplastic polymers containing amide groups in the main chain. They are popularly known as Nylons, which is the tradename of E.I.Du Pont. The work carried out by Carothers at E.I.Du pont led to the commercialization of PA-6 in 1938.Another important figure P.Schlack at I.G.Farbenindustrie polymerised carpotactam to PA-6 in 1938. In the following two decades works were carried out to synthesize many other polymides and developed in to injection mouldable and extrudable materials. Some of the other commercially important polymides are PA-11, PA-12, PA-6/10, PA-6/12 and their copolymers. Polyamides are manufactured either by polymerising diamines and dicarboxylic acid or polymerising amino carboxylic acids. PA-66 is manufactured by polymerising hexamethylene diamine with adipic acid and PA-6 is manufactured by ring opening polymerisation of caprolactam.

Hard and tough thermoplastic Good abrasion resistance Low coefficient of friction High tensile strength Good dimensional stability Low tendency to warp Smooth appearance of surface Average to high surface gloss Resistant to lubricant, engine fuels, grease etc. Good resistance to coolants, refrigerants, paint solvent cleaners Resistant to aqueous solution of many inorganic chemicals Possess high HDT Attacked by strong acids, phenols, cresols at elevated temperature Poor UV resistance High temperature resistance Low thermal co-efficient of expansion High Water absorption