Polyoxymethylene (POM) is one of the most frequently used semi-crystalline engineering thermoplastics on account of its unique combination of rigidity, strength and dimensional stability. Thanks to the regular molecular structure, this material reaches a crystallinity of 80%, more than most other thermoplastics. POM is obtainable as a homopolymer and as a copolymer. The homopolymer has higher crystallinity, giving it better impact resistance and slightly higher rigidity and hardness, while the copolymer provides greater formability and is easier to process.
POM exhibits the lowest wear of almost all thermoplastics at room temperature. In cooperation with its remarkable dimensional stability, this makes POM excellently suited to gear wheels and bearings. POM is usable for prolonged periods of time at temperatures of up to 90°C to 100°C. Temperatures up to 150°C are permissible briefly; prolonged exposure to temperatures above 100°C causes a rapid oxidising degradation of the polymer.
POM absorbs significantly less moisture than polyamide, i.e. approximately 0.2% at 23°C/50% RH and 0.8% when saturated. Consequently, humidity has virtually no influence on the size of a part.
POM is chemically resistant to alkalis, aliphatic and aromatic hydrocarbons, oils, greases, petrol and most cleaning agents. It is not resistant to strong acids or oxidising materials.
POM is not UV-resistant and outdoor applications are possible only with qualities stabilised with active carbon. These qualities are used for most parts of a conveyor system. Flame-retarding types are unavailable.