polyoxymethyleen

Polyoxymethylene, abbreviated POM and also known as polyacetal or acetal resin, is a thermoplastic engineering polymer. Its repeating unit is -CH2-O-, which gives a highly regular, dense chain suited for precise mechanical parts. It is typically produced from formaldehyde derivatives such as trioxane.

Commercial POM is available mainly in two forms: the homopolymer (POM-H) and the copolymer (POM-C). POM-C contains small amounts of comonomers to improve hydrolytic stability and processing, enabling broader chemical resistance and easier fabrication. Both forms are semi-crystalline and can be colored.

POM combines high stiffness and strength with excellent dimensional stability and very low friction, yielding good wear resistance. It shows relatively low moisture uptake and good chemical resistance to fuels and many solvents. Limitations include sensitivity to strong acids and bases, and degradation at elevated temperatures or in hot water. Long-term service temperatures are modest compared with some other engineering plastics.

Production and processing involve polymerizing formaldehyde-derived monomers, typically via trioxane, using acid catalysts. POM is processed mainly by injection molding and extrusion. POM-C often offers easier processing and improved stability under certain conditions. Proper drying and mold-release practices, along with controls on crystallization, are important to minimize hydrolytic degradation during processing and in use.

Common applications include gears, bearings, cams, bushings, fittings, valves, and electrical components where low friction, high precision, and dimensional stability are required. It is widely used in automotive, consumer electronics, plumbing, and other mechanical devices.

Environmentally, POM is not biodegradable but can be recycled where facilities exist. Processing requires attention to potential formaldehyde exposure, and waste should be managed with appropriate controls; incineration should follow relevant regulations.