Polyoxymethylene (POM), in the USA also commonly known under DuPont's brand name Delrin, is an engineering plastic, a polymer with the chemical formula -(-O-CH2-)n-. It is often marketed and used as a metal substitute. Delrin is a lightweight, low-friction, and wear-resistant thermoplastic with good physical and processing properties and capable of operating in temperatures in excess of 90 degrees celsius (approximately 200 degrees fahrenheit). According to the material safety data sheet from DuPont, the material has a slight odor of formaldehyde.
It is also known as polyacetal, acetal resin, polytrioxane, polyformaldehyde, and paraformaldehyde (the latter term is usually restricted to the short-chained polymer). Polyacetals are sold under the trade names Delrin, Kepital, Celcon, Hostaform, Iupital and Ultraform, the last five being copolymers.
Delrin was first synthesized by DuPont's research chemists around 1952. The company filed for patent protection of the material in 1956 and completed construction of a plant to produce the material at Parkersburg, West Virginia in 1960. Another form of the polymer was developed in Europe.
The polymer shares common characteristics with other synthetic polymers such as low density (1.4 - 1.5 g/cm3), and ease of moulding when the molecular weight is low enough. It is a semi-crystalline polymer (75-85% crystalline) with a melting point of 175 °C as a homopolymer. A copolymer version has slightly lower melting point of 163 °C. It is a tough material with a very low coefficient of friction. However, it is susceptible to polymer degradation catalysed by acids, which is why both polymer types are stabilised. In the case of the homopolymer, it has chain end groups which resist depolymerization. With the copolymer, the second unit is a cyclic ether which resist chain cleavage. It is also sensitive to oxidation, and an anti-oxidant is normally added to moulding grades of the material.