POM , let us learn more about it .
1. Performance of POM
POM is a crystalline plastic with good rigidity, commonly known as “Saigang”. POM is a tough and elastic material that has good creep resistance, geometric stability and impact resistance even at low temperatures. It has excellent properties such as fatigue resistance, creep resistance, wear resistance and heat resistance.
POM is not easy to absorb moisture, with a specific gravity of 1.42g/cm3 and a shrinkage rate of 2.1% (POM’s high degree of crystallization leads to a relatively high shrinkage rate, which can be as high as 2%~3.5%, which is relatively large, and has different shrinkage rates for various reinforced materials), and the size is difficult to control. The heat deformation temperature is 172℃. POM has both homopolymer and copolymer materials.
Homopolymer materials have good ductility and fatigue strength, but are not easy to process. Copolymer materials have good thermal stability, chemical stability and are easy to process. Both homopolymer materials and copolymer materials are crystalline materials and are not easy to absorb moisture.
2. Process characteristics of POM
POM does not need to be dried before processing. It is best to preheat it during processing (about 100℃), which is good for the stability of product size. The processing temperature range of POM is very narrow (195-215℃), and it will decompose if it stays in the barrel for a long time or the temperature exceeds 220℃ (homopolymer materials are 190~230℃; copolymer materials are 190~210℃). The screw speed should not be too high, and the residual volume should be small.
POM products shrink greatly (in order to reduce the shrinkage rate after molding, a higher mold temperature can be selected), and they are prone to shrinkage or deformation. POM has a large specific heat and a high mold temperature (80-105℃). The product is very hot after demolding, and it is necessary to prevent scalding of fingers. The injection pressure is 700~1200bar, and POM is suitable for molding under medium pressure, medium speed, and high mold temperature conditions.
Any type of gate can be used for runners and gates. If a tunnel-shaped gate is used, it is best to use a shorter type. For homopolymer materials, it is recommended to use a hot nozzle runner. For copolymer materials, both internal and external hot runners can be used.
3. Typical application range:
POM has a very low friction coefficient and good geometric stability, and is particularly suitable for making gears and bearings. Because it also has high temperature resistance, it is also used for pipeline devices (pipeline valves, pump housings), lawn equipment, etc.
