Polyoxymethylene (POM) Copolymer POM is a hard, dense material with a smooth, shiny surface, yellowish or white, and the thin-walled portion is translucent. The combustion characteristics are easy to burn, and continue to burn after the fire. The upper end of the flame is yellow, the lower end is blue, and melted and dripped, and there is a strong irritating formaldehyde smell and fish odor. POM is a white powder, generally opaque, good coloring, specific gravity 1.41-1.43 g / cm3, molding shrinkage 1.2-3.0%, molding temperature 170-200 ° C, drying conditions 80-90 ° C 2 hours. The long-term heat resistance of POM is not high, but it can reach 160 °C in the short term. The short-term heat-resistant POM of homopolymerized POM is higher than 10 °C, but the long-term heat-resistant copolymerized POM is about 10 °C higher than the homopolymerized POM. It can be used for a long time in the temperature range of -40 ° C to 100 ° C. POM is easily decomposed and has a decomposition temperature of 240 degrees. Irritating and corrosive gases occur during decomposition, so the mold steel should be made of corrosion-resistant materials. [2] Mechanical properties Wood Shell Activated Carbon,Wood Based Powder Activated Carbon,Wood Powder Activated Carbon,Wood Based Activated Carbon NINGXIA TIANFU ACTIVATED CARBON CO.,LTD , http://www.tjfyhxt.com
POM has high strength, high rigidity, good elasticity and good wear resistance. Its mechanical properties are excellent, the specific strength can reach 50.5MPa, the specific stiffness can reach 2650MPa, and it is very close to metal. The mechanical properties of POM change little with temperature, and the copolymerized POM changes slightly more than the homopolymerized POM. The impact strength of POM is higher, but the conventional impact is less than ABS and PC; POM is sensitive to the gap, and the gap can reduce the impact strength by as much as 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 of POM is similar to that of PA, which is only 2.3% at 20 °C, 21 MPa, and 3000 h, and is little affected by temperature. POM has a small friction coefficient and good wear resistance (POM>PA66>PA6>ABS>HPVC>PS>PC), the limit PV value is large, and the self-lubricating property is good. POM products are prone to scream-like noise when subjected to high loads.
Electrical performance
POM has good electrical insulation and is almost independent of temperature and humidity; dielectric constant and dielectric loss vary little over a wide range of temperatures, humidity and frequencies; excellent arc resistance and high temperature maintain. The dielectric strength of POM is related to the thickness, which is 82.7 kV/mm at a thickness of 0.127 mm and 23.6 kV/mm at a thickness of 1.88 mm.
Environmental performance
POM is not resistant to strong bases and oxidants, and has certain stability to olefinic acids and weak acids. POM has good solvent resistance and is resistant to hydrocarbons, alcohols, aldehydes, ethers, gasoline, lubricating oils and weak bases, and maintains considerable chemical stability at high temperatures. Low water absorption and good dimensional stability.
The weather resistance of POM is not good. Under the action of ultraviolet rays for a long time, the mechanical properties are degraded, and the surface is pulverized and cracked.
The formable crystal material has a narrow melting range, fast melting and solidification, and crystallization occurs when the material temperature is slightly lower than the melting temperature. Medium mobility. Low moisture absorption, no drying treatment.
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