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POM acetal, we sometimes call it "Saigang", sometimes we call it "Trane", so why is it called like this? Because, it is often its parents who take the name, that is, its inventor.
We know that there are two major categories of polyoxymethylene, one is called copolymer acetaldehyde, and the other is called homopolymer acetal. The company that invented acetal copolymer (Celanese, USA) registered its trade name as "celcon", which is transliterated as "Saigang", and the company that invented acetaldehyde (DuPont, USA) also registered its trade name as "delrin", which is transliterated as "Trane".
Polyoxymethylene is a linear polymer with no side chains, high density, and high crystallinity. According to the different chemical structures in its molecular chain, it can be divided into two types: acetal homopolymer and acetaldehyde copolymer.
The important differences between the two are:
Homopolymer formaldehyde has high density, crystallinity and melting point[Learn more about 'plastics', 'engineering plastics', 'modified plastics' and other industry knowledge, massive material super physical property tables, super material selection cases, cost reduction and efficiency improvement solutions, welcome to "plastic library network" to understand! ] 】However, the thermal stability is poor, the processing temperature range is narrow, and the acid-base stability is slightly low, and DuPont invented the homopolymer acetaldehyde.
The density, crystallinity, melting point and strength of acetaldehyde copolymer are low, but it has good thermal stability, is not easy to decompose, has a wide range of processing temperatures, and has good stability to acid and alkali. It is an engineering plastic with excellent comprehensive properties. It has good physical, mechanical and chemical properties, especially excellent friction resistance. Commonly known as Saigang, it is the third largest general engineering plastic. It is suitable for the production of wear-reducing and wear-resistant parts, transmission parts, as well as chemical, instrument and other parts. Celanese of the United States invented acetal copolymer.
Features of POM engineering plastics
1.POM does not need to be dried before processing, and it is best to preheat it during processing (about 80), which is good for the stability of product size;
2.The processing temperature of POM is very narrow[Learn more about 'plastics', 'engineering plastics', 'modified plastics' and other industry knowledge, massive material super physical property tables, super material selection cases, cost reduction and efficiency improvement solutions, welcome to "plastic library network" to understand! ] 】It will decompose when it stays in the barrel for a long time or the temperature exceeds 220, producing irritating formaldehyde gas;
3.The holding pressure of POM material should be large (similar to the injection pressure) during injection molding to reduce the pressure drop, the screw speed should not be too high, and the melt allowance should be small;
4.POM product shrinkage is large, easy to shrink or deform, POM specific heat is large, mold temperature is high (80 100), the product is very hot when demolding, need to be careful.
5.POM should be formed and processed under the conditions of "medium pressure, medium speed, low material temperature, and high mold temperature", and the mold temperature needs to be controlled when molding precision products;
6.It has high mechanical strength and rigidity;
7.relatively high fatigue strength ;
8.Good 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.
Typical applications for POM plastics:
It can replace most non-ferrous metals, automobiles, machine tools, instrument internals, bearings, fasteners, gears, springs, pipes, transportation belt accessories, electric kettles, pump casings, drainers, faucets, etc.
Performance of POM plastic:
Polyoxymethylene is a hard and dense material with a smooth, shiny surface, white color, and the thin-walled part is translucent. The combustion characteristics are easy to burn, continue to burn after leaving the fire, the upper end of the flame is yellow, the lower end is blue, the molten dripping occurs, there is a strong pungent formaldehyde smell, fishy odor. Polyoxymethylene is opaque, has good colorability, and has a specific gravity of 141-1.43 grams of cubic centimeters, molding shrinkage of about 2%, molding temperature 170-200, drying conditions 80-90 time 2 hours. The long-term heat resistance of POM is not high, and 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 about 10 higher than that of homopolymer POM. It can be used for a long time in the temperature range of -40 to 90 degrees[Learn more about 'plastics', 'engineering plastics', 'modified plastics' and other industry knowledge, massive material super physical property tables, super material selection cases, cost reduction and efficiency improvement solutions, welcome to "plastic library network" to understand! ] 】。POM is very easy to decompose, and the decomposition temperature is 240 degrees. There are irritating and corrosive gases during decomposition, so the mold steel should be made of corrosion-resistant materials.
1) POM is a semi-crystalline plastic with a density of 142g cm3, its rigidity is very good, commonly known as "Saigang".
2) It has excellent properties such as fatigue resistance, creep resistance, wear resistance, heat resistance, impact resistance, etc., and the friction coefficient is small and the self-lubrication is good.
3) POM is not easy to absorb moisture, and the water absorption rate is 022～0.25%, good dimensional stability in a humid environment, its shrinkage rate is about 2%, the size is difficult to accurately control during injection molding, and the heat deflection temperature is 172.
Mechanical properties of POM plastics:
POM has high strength, stiffness, good elasticity, good wear reduction and wear resistance. Its mechanical properties are excellent, and the specific strength can reach 505MPa, the specific stiffness can reach 2650MPa, which is very close to metal. The mechanical properties of POM vary with temperature, and the copolymer POM changes slightly more than the homopolymer POM. The impact strength of POM is higher, but the conventional impact is not as good as that of ABS and PC. POM is sensitive to notching, which can reduce impact strength by as much as 90%. The fatigue strength of POM is outstanding, with a fatigue strength of up to 35MPa, while PA and PC are only 28MPa. The creep of POM is similar to that of PA, which is only 2 at MPA, 3000h3%, and it is very little affected by temperature. POM has a small friction factor, good wear resistance, a large limit PV value, and good self-lubrication. When POM products are grinding, they are prone to produce scream-like noise when they are subjected to high loads.
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