Polyoxymethylene

Polyoxymethylene (POM), also known as acetal, polyacetal and polyformaldehyde is an engineering thermoplastic used in precision parts that require high stiffness, low friction and excellent dimensional stability. As with many other synthetic polymers, it is produced by different chemical firms with slightly different formulas and is therefore sold under various commercial names like Delrin, Celcon and Hostaform.

It was discovered by Hermann Staudinger, a German chemist who received the 1953 Nobel Prize in Chemistry. He had studied the polymerization and structure of POM in the 1920s while researching macromolecules, which he characterized as polymers. Due to problems with thermal stability, POM was not commercialized at that time.

Around 1952 research chemists at DuPont successfully synthesized a version of POM, and in 1956 the company filed for patent protection of the homopolymer. DuPont credits R N MacDonald as the inventor of high molecular weight POM. Patents by MacDonald and coworkers describe the preparation of high molecular weight hemiacetal (~CH₂OH) terminated POM, but these lack sufficient thermal stability to be commercially viable. The inventor of a heat-stable (and therefore useful) POM homopolymer was Dal Nagore, who discovered that reacting the hemiacetal ends with acetic anhydride converts the readily depolymerizable hemiacetal into a thermally stable, melt processable plastic. DuPont completed construction of a plant to produce its own version of acetal resin, named Delrin at Parkersburg, West Virginia, in 1960. Also in 1960, Celanese completed its own research. Shortly thereafter, in a limited partnership with the Frankfurt firm Hoechst AG, a factory was built in Kelsterbach, Hessen; from there, Celcon was produced starting in 1962, with Hostaform joining it a year later. Both remain in production under the auspices of Ticona (a subsidiary of Celanese), and are sold as parts of a product group now called Hostaform/Celcon POM.