POM Plastic - Name
Chinese name: (Polyoxymethylene) (Saigang - Trane)
English name: Polyoxymethylene (Polyformaldehyde)
Properties of POM plastics
Density: 1.41-1.43 grams/cubic centimeter
Molding shrinkage rate: 1.2-3.0%
Forming temperature: 170-200 ℃
Drying conditions: 80-90 ℃ for 2 hours
POM Plastics - Overview
POM (Polyoxymethylene resin) definition: Polyoxymethylene is obtained by polymerization of formaldehyde. 
POM plastic is a high-density, high crystallinity thermoplastic engineering plastic. It has good physical, mechanical, and chemical properties, especially excellent friction resistance. It is precisely because these excellent chemical and physical properties can be comparable to steel, and their weight is lighter than steel, that they are called "Saigang"! 
Physicochemical properties
General performance
Polyoxymethylene is a kind of hard and dense material with smooth and shiny surface, light yellow or white, and the thin-walled part is translucent. The combustion characteristic is easy to burn, and it continues to burn after leaving the fire. The upper end of the flame is yellow, and the lower end is blue, causing molten droplets and a strong irritating formaldehyde odor and fishy odor. Polyoxymethylene is white powder, generally opaque, with good colourability, specific gravity of 1.41-1.43g/cm3, molding shrinkage of 1.2-3.0%, molding temperature of 170-200 ℃, and drying condition of 80-90 ℃ for 2 hours. The long-term heat resistance of POM is not high, but it can reach 160 ℃ in the short term. Among them, the short-term heat resistance of homopolymer POM is more than 10 ℃ higher than that of copolymer POM, but the long-term heat resistance of copolymer POM is actually about 10 ℃ higher than that of homopolymer POM. It can be used for a long time within the temperature range of -40 ℃ to 100 ℃. POM is highly prone to decomposition, with a decomposition temperature of 240 degrees. During decomposition, irritating and corrosive gases occur. Therefore, the mold steel should be made of corrosion-resistant materials.
Chemical properties
POM has high strength, stiffness, good elasticity, and good wear resistance. Its mechanical properties are excellent, with a specific strength of up to 50.5MPa and a specific stiffness of up to 2650MPa, which is very close to metals. The mechanical properties of POM vary little with temperature, while the variation of co polymer POM is slightly greater than that of homopolymer POM. POM has a higher impact strength, but its conventional impact is not as good as ABS and PC; POM is sensitive to notches, and having notches can reduce impact strength by up to 90%. The fatigue strength of POM is very prominent. After 10 alternating loads, the fatigue strength can reach 35MPa, while PA and PC are only 28MPa. The creep behavior of POM 100P is similar to that of PA, with only 2.3% at 20 ℃, 21MPa, and 3000h, and is little affected by temperature. POM has a small friction coefficient, good wear resistance (POM>PA66>PA6>ABS>HPVC>PS>PC), a large limit PV value, and good self-lubrication. When POM products are ground, they are prone to producing noise similar to screaming under high loads.
The electrical performance of POM has good electrical insulation, almost unaffected by temperature and humidity; The dielectric constant and dielectric loss vary very little over a wide range of temperature, humidity, and frequency; Excellent arc resistance and can be maintained at high temperatures. The Dielectric strength of POM is related to the thickness. It is 82.7kV/mm when the thickness is 0.127mm, and 23.6kV/mm when the thickness is 1.88mm.
Environmental performance
POM is not resistant to strong alkalis and oxidants, and has certain stability towards enoic and weak acids. POM has good solvent resistance, can withstand hydrocarbons, alcohols, aldehydes, ethers, gasoline, lubricants, and weak alkalis, and can maintain considerable chemical stability at high temperatures. Low water absorption and good dimensional stability. The weather resistance of POM is poor, and under long-term ultraviolet radiation, its mechanical properties decrease, resulting in surface powdering and cracking.
Formative crystalline materials have a narrow melting range, fast melting and solidification, and crystallization occurs when the material temperature is slightly lower than the melting temperature. Moderate liquidity. Low moisture absorption, can be treated without drying. 
POM plastic properties
1. Crystalline materials have a narrow melting range and fast melting and solidification. Crystallization occurs when the material temperature is slightly lower than the melting temperature. Moderate liquidity. Low moisture absorption, can be treated without drying. 
2. Low friction coefficient, good elasticity, and surface defects prone to wrinkles and patterns on the surface of plastic parts. 
3. Extremely easy to decompose, with a decomposition temperature of 240 degrees. During decomposition, irritating and corrosive gases occur. Therefore, the mold steel should be made of corrosion-resistant materials.
Injection molding process POM 500P
(1) Before POM processing, drying is not necessary. It is best to preheat (around 800 ℃) during the processing, which is beneficial for the stability of product size
(2) The processing temperature of POM is very narrow (0-215 ℃), and it will decompose when it stays in the barrel for a slightly longer time or when the temperature exceeds 220 ℃, producing highly irritating formaldehyde gas
(3) When injecting POM material, the pressure maintaining pressure should be relatively high (similar to the injection pressure) to reduce pressure drop. The screw speed should not be too high and the residual amount should be less;
(4) POM products have a high shrinkage rate and are prone to shrinkage or deformation. POM has a high specific heat and high mold temperature (800-100 ℃), making it very hot during demolding. It is necessary to prevent fingers from being burned
(5) POM should be formed and processed under the conditions of "medium pressure, medium speed, low material temperature, and high mold temperature". When forming precision products, it is necessary to control the mold temperature
(6) High mechanical strength and rigidity
(7) Maximum fatigue strength
(8) Excellent environmental resistance and organic solvent resistance
(9) Strong resistance to repeated impacts, good electrical properties, good resilience, self lubrication, good wear resistance, and excellent dimensional stability
Drying treatment:
If the material is stored in a dry environment, it usually does not require drying treatment.
Melting temperature:
The homopolymer material is 190~230 ℃; The copolymer material is 190~210 ℃.
Mold temperature:
80-105 ℃. To reduce the shrinkage rate after molding, a higher mold temperature can be selected.
Injection pressure:
700-1200bar
Injection speed:
Moderate or slightly higher injection speed.
Runners and Gates
Any type of gate can be used. If a tunnel gate is used, it is best to use a shorter type. For homopolymer materials, it is recommended to use a hot nozzle flow channel. For copolymer materials, either internal Hot runner or external Hot runner can be used.
POM plastic usage
POM has a low coefficient of friction and good geometric stability, making it particularly suitable for making gears and bearings. Due to its high temperature resistance, it is also used in pipeline components (pipeline valves, pump housings), lawn equipment, etc. It can replace most non-ferrous metals, automobiles, machine tools, instrument internals, bearings, fasteners, gears, spring pieces, pipes, transport belt accessories, electric water cookers, pump shells, water emitters, faucets, etc. POM has very low friction coefficient and good geometric stability, especially suitable for making gears and bearings. Due to its high temperature resistance, it is also used in pipeline components (pipeline valves, pump housings), lawn equipment, etc.
The current development status of China
Polyoxymethylene (pom) is a kind of engineering plastics with excellent performance. POM has similar hardness, strength, and steel properties to metals, and has good self-lubrication, fatigue resistance, and elasticity over a wide range of temperature and humidity. In addition, it also has good chemical resistance. POM is replacing some traditionally occupied markets with metals at a lower cost than many other engineering plastics, such as replacing zinc, brass, aluminum, and steel to make many components. Since its inception, POM has been widely used in fields such as electronics and electrical, machinery, instruments, daily light industry, automobiles, building materials, agriculture, etc. In many new fields such as medical technology and sports equipment, POM has also shown good growth momentum.
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