POM performance and use

POM (Polyoxymethylene) Polyoxymethylene Polyoxymethylene (POM) Polyoxymethylene scientific name Polyoxymethylene (abbreviated as POM), also known as Saigang, special steel. It is obtained by polymerizing formaldehyde as raw materials. POM-H (polyoxymethylene homopolymer) and POM-K (polyoxymethylene copolymer) are thermoplastic engineering plastics with high density and high crystallinity. Has good physical, mechanical and chemical properties, especially excellent friction resistance. POM is a linear polymer with no side chains, high density and high crystallinity, with excellent comprehensive properties. POM is a hard and dense material with a smooth, shiny surface, light yellow or white, and can be used for a long time in the temperature range of -40-100°C. Its wear resistance and self-lubricity are also superior to most engineering plastics, and it has good oil resistance and peroxide resistance. Very intolerant to acids, strong alkalis and ultraviolet radiation.
Physical properties
Polyoxymethylene has a tensile strength of 70MPa, low water absorption, dimensional stability, and gloss. These properties are better than nylon. Polyoxymethylene is a highly crystalline resin, which is the toughest among thermoplastic resins. It has high thermal strength, bending strength, fatigue resistance strength, and excellent wear resistance and electrical properties. POM performance: performance number value specific gravity 1.43 melting point 175°C tensile strength (yield) 70MPa elongation (yield) 15% (uncut) 15% J/m2 (notch) 7.6 KJ/m2
Application range
POM is a crystalline plastic with obvious melting point. Once it reaches the melting point, the melt viscosity drops rapidly. When the temperature exceeds a certain limit or the melt is heated for too long, it will cause decomposition. POM has good comprehensive properties. It is the hardest among thermoplastics. It is one of the plastic materials whose mechanical properties are closest to metal. Its tensile strength, bending strength, fatigue strength, wear resistance and electrical properties are all Very good, can be used for a long time between -40 degrees and 100 degrees.
chemical properties
According to the different molecular chain structure, polyoxymethylene can be divided into homopolyoxymethylene and copolyoxymethylene. The former has high density, crystallinity, and melting point, but has poor thermal stability, narrow processing temperature (10 degrees), and slightly lower stability to acid; The latter has low density, crystallinity, and melting point, but has good thermal stability, is not easy to decompose, and has a wide processing temperature (50 degrees). The shortcomings are: corrosion by strong acid, poor weather resistance, poor adhesion, thermal decomposition and softening temperature close to , The oxygen limiting index is small. They are widely used in the automobile industry, electronic appliances, mechanical equipment, etc. It can also be used as a faucet, frame window, and wash basin. POM physical property table: density g /cm3 1.39
Water absorption % 0.2
Continuous use temperature ℃ -50--110
Yield tensile strength MPa 63
Tensile strain at yield% 10
Ultimate tensile strength MPa
Ultimate tensile strain% 31
Impact toughness Kj/㎡
Notch impact toughness Kj/㎡ 6
Rockwell hardness MPa 135
Shore hardness MPa 85
bending strength MPa
Elastic modulus MPa 2600
softening temperature ℃ 150
Heat distortion temperature HDT ℃ 155
coefficient of thermal expansion
1.1
Thermal conductivity W/(m×K) 031
Friction coefficient
0.35
POM has a very low coefficient of friction and good geometric stability, especially suitable for making gears and bearings. Because it also has high temperature resistance, it is also used in pipeline devices (pipe valves, pump housings), lawn equipment, etc. POM products
Process conditions
Drying treatment: If the material is stored in a dry environment, it usually does not need to be dried. Melting temperature: 190~230℃ for homopolymer materials; 190~210℃ for copolymer materials. Mold temperature: 80~105℃. 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: any type of gate can be used. If a tunnel-shaped gate is used, it is best to use a shorter type. For homopolymer materials, hot nozzle runners are recommended. For copolymer materials, both internal hot runners and external hot runners can be used. POM Chemical and physical properties of polyoxymethylene: POM is a tough and elastic material that has good creep resistance, geometric stability and impact resistance even at low temperatures. POM has both homopolymer materials and copolymer materials. Homopolymer materials have good ductility and fatigue strength, but they are not easy to process. Copolymer materials have good thermal and chemical stability and are easy to process. Both homopolymer and copolymer materials are crystalline materials and are not easy to absorb moisture. The high degree of crystallinity of POM leads to a very high shrinkage rate, which can be as high as 2% to 3.5%. There are different shrinkage rates for a variety of different reinforced materials.

The difference of POM is that its toughness and hardness are relatively close to metal, and its high temperature and wear resistance is also excellent. It can be used as wear parts such as gears.

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