Twenty Kinds of Plastics and Their Properties—(15) POM

15.POM Polyoxymethylene

Typical application range:

POM has very low friction coefficient and good geometric stability. It is especially suitable for making gear and bearing. Because of its high temperature resistance, it is also used for pipeline devices (pipe valves, pump shells), lawn equipment, and so on.

Injection molding process conditions:

Drying process: if the material is stored in a dry environment, it is usually not required to dry.
Melting temperature: the homopolymer material is 190~230 °C, and the copolymer is 190~210 °C.
Mold temperature: 80~105 °C. In order to reduce the shrinkage after molding, a higher mold temperature can be used.
Injection pressure: 700~1200bar
Injection speed: medium or high injection speed.
Runner and gate: you can use any type of gate. If a tunnel gate is used, it is best to use a shorter type. For homopolymer materials, it is recommended to use hot nozzle flow channel. For the copolymer, external heat flow can be used as well as internal heat flow.

Chemical and physical properties:

POM is a tough and elastic material, even at low temperature, it has good creep resistance, geometric stability and impact resistance. POM has both homopolymer and copolymer materials. The homopolymer material has good ductility and fatigue strength, but it is not easy to process. The copolymer has good thermal stability, chemical stability and easy processing. Both homopolymer material or copolymer material is crystalline material and is not easy to absorb water. The high degree of crystallization of POM leads to a fairly high shrinkage rate to up to 2%~3.5%. There are different shrinkage rates for various reinforced materials.