What is polyoxymethylene
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Polyoxymethylene, also known as polyoxymethylenes, has the English name polyoxymethylene (abbreviated as POM). Its regular molecular structure and crystallinity confer excellent physical and mechanical properties, earning it the nickname of metal plastic. POM is a milky-white, opaque, crystalline linear thermoplastic resin with excellent overall properties and coloring capabilities. It features a high elastic modulus, as well as high stiffness and hardness; its specific strength and specific stiffness are comparable to those of metals ； Excellent tensile strength, bending strength, creep resistance, and fatigue resistance; resistant to repeated impacts, with good recovery after unloading ； It has a low coefficient of friction, is wear-resistant, offers good dimensional stability, has a pleasant surface finish, exhibits high viscoelasticity, superior electrical insulation properties, and is not affected by temperature ； It has good insulation resistance and is not affected by humidity ； Excellent chemical resistance: Stable against other chemicals except strong acids, phenols, and organic halides; oil-resistant ； Its mechanical properties are little affected by temperature, and it has a high heat distortion temperature. The disadvantages are poor flame retardancy, as it burns slowly when exposed to fire; its oxygen index is low, and even the addition of flame retardants does not yield satisfactory results. Additionally, its weather resistance is inadequate, requiring the use of stabilizers for outdoor applications. Homopolymerous polyoxymethylene has a high degree of crystallinity, and its mechanical strength, rigidity, and heat deformation temperature are superior to those of copolymerous polyoxymethylene. Copolymerous polyoxymethylene has a lower melting point, and its thermal stability, chemical resistance, flow properties, and processability are all better than those of homopolymerous polyoxymethylene. Newly developed grades include those with ultra-high flow properties (for rapid molding), impact resistance, and reduced mold deposition; there are also grades enhanced with inorganic fillers. The water absorption rate of POM is greater than 0.2%, so it should be pre-dried before molding. The melting temperature of POM is close to its decomposition temperature, resulting in poor formability; however, it can be processed by injection molding, extrusion, blow molding, rotational molding, welding, bonding, coating, printing, electroplating, and machining. Injection molding is the most important processing method. Due to the high shrinkage rate during molding, the mold temperature should be kept high, or annealing treatment can be applied, or reinforcing materials such as alkali-free glass fibers can be added. POM has high strength and low weight, and is often used as a substitute for non-ferrous metals such as copper, zinc, tin, and lead. It is widely applied in industries such as industrial machinery, automobiles, electronics and electrical appliances, daily necessities, pipes and fittings, precision instruments, and building materials. POM is widely used in the manufacture of various sliding and rotating mechanical parts, such as gears, levers, pulleys, and sprockets. It is particularly suitable for use in bearings, hot water valves, precision metering valves, chain links and rollers for conveyors, flow meters, interior and exterior handles for vehicles, crankshafts and other window-rotating mechanisms, oil pump bearing housings and impellers, gas control valves, electronic switch components, fastening elements, terminal cover mirrors, electric fan components, heating plates, and instrument buttons ； Bearings for audio and video tapes ； Various pipes and agricultural sprinkler systems, as well as valves, nozzles, faucets, and bath tub parts ； Power on keyboard, buttons, audio/video tape reels ； Temperature control timer ； Power tool parts, garden maintenance tool parts ； It can also be used as parts for surfboards, sailboats, and various sleds, as well as miniature gears for watches, components for the frames of sports equipment, and various buckles, fasteners for backpacks, lighters, zippers, and clasp buttons ； Cardiac pacemakers in medical devices ； Artificial heart valves, cervical vertebrae, prosthetics, etc. This post was last edited by QXZ-1966 on 2008-10-16 at 15:33.]
Edit entry: Polyformaldehyde Polyformaldehyde (English: polyformaldehyde) is a thermoplastic crystalline polymer. Known as “supersteel,” it is also called polyoxymethylene. Its structure is such that the English abbreviation is POM. Typically, the polymers obtained from the polymerization of formaldehyde have a low degree of polymerization and are prone to depolymerization upon heating. Around 1955, DuPont Company produced the homopolymer of formaldehyde by polymerizing formaldehyde. Polyoxymethylene crystallizes easily, with a crystallinity of over 70%. The melting temperature of homopolymerized formaldehyde is around 180°C. The scientific name for polyoxymethylene is polyoxymethylenepolymer, abbreviated as POM. Polyoxymethylene is a linear polymer without side chains, featuring high density and high crystallinity, as well as excellent overall properties. Polyoxymethylene is a hard and dense material with a smooth, shiny surface; it is pale yellow or white in color, and can be used over extended periods at temperatures ranging from -40 to 100°C. Its wear resistance and self-lubricating properties are also superior to those of the vast majority of engineering plastics, in addition to having good oil resistance and peroxide resistance. It is very sensitive to acids, strong alkalis, and ultraviolet radiation from moonlight. Polyoxymethylene has a tensile strength of 70 MPa, low water absorption, dimensional stability, and a glossy finish – all properties that are superior to those of nylon. It is a highly crystalline resin and the toughest among thermoplastic resins. It possesses high heat resistance, high bending strength, and high fatigue resistance, as well as excellent wear resistance and electrical properties. Properties of polyoxymethylene:
Property values:
Density: 1.43
Melting point: 175°C
Tensile strength (yield): 70 MPa
Elongation at yield: 15%
(Elongation at break): 15%
Impact strength (notched): 108 KJ/m2
(Impact strength with notch): 7.6 KJ/m2
The synthesis of homopolymerized polyoxymethylene generally involves the condensation polymerization of an aqueous solution of formaldehyde in the presence of acid. a-Polyoxymethylene with a degree of polymerization of 100 or more is obtained, and then heated to decompose it into formaldehyde gas. After purification and dehydration, the monomer is usually purified using a partial pre-polymerization method, and subsequently polymerized in a dry solvent containing a small amount of initiator. The presence of water results in a significant decrease in molecular weight. Initiators can be Lewis acids or bases, etc. However, tertiary amines are mostly used for anionic addition polymerization, with the reaction proceeding as follows: The end groups of polyoxymethylene are hemiacetals (—CH2OH), and at temperatures above 100°C, these end groups tend to break apart; therefore, end-group treatment is generally required to stabilize them. After stabilization treatment, it can withstand temperatures up to 230 ℃. Polyformaldehyde can be processed at temperatures of 170–200 °C, such as by injection, extrusion, blow molding, etc. It is mainly used as an engineering plastic in automobiles, mechanical components, etc. www.seafar.cn Typical applications of POM polyoxymethylene: POM has a very low friction coefficient and excellent geometric stability, making it particularly suitable for manufacturing gears and bearings. Due to its high-temperature resistance, it is also used in piping components (pipe valves, pump housings), lawn equipment, and more. Injection molding process conditions: Drying treatment: If the material is stored in a dry environment, drying treatment is usually not required. Melting temperature: 190~230 for homopolymer materials℃ ； The copolymer material is at 190~210°C. Mold temperature: 80~105°C. A higher mold temperature can be used to reduce the shrinkage rate after molding. Injection pressure: 700~1200 bar Injection speed: moderate to high injection speed. Flow channels 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 runner. For copolymer materials, either internal hot runners or external hot runners can be used. Chemical and physical properties of POM polyoxymethylene: POM is a tough and elastic material that retains excellent creep resistance, geometric stability, and impact resistance even at low temperatures. POM includes both homopolymer and copolymer materials. Homopolymer materials possess excellent ductile strength and fatigue resistance, but are difficult to process. Copolymer materials have excellent thermal stability and chemical stability, and are easy to process. Both homopolymer materials and copolymer materials are crystalline materials and do not absorb moisture easily. The high degree of crystallinity of POM results in a fairly high shrinkage rate, which can reach as much as 2% to 3.5%. Different enhanced materials have different shrinkage rates. Polyoxymethylene (POM) is an engineering plastic with excellent properties; it is known abroad as \"steel rival\" or \"super steel\". POM possesses metal-like hardness, strength, and rigidity; it exhibits excellent self-lubricating properties over a wide range of temperatures and humidity levels, good fatigue resistance, and elasticity. In addition, it also has good chemical resistance. At a cost lower than that of many other engineering plastics, POM is replacing metals in various markets where they have traditionally been used; it is used to manufacture many components in place of zinc, brass, aluminum, and steel. Since its introduction, POM has been widely applied in fields such as electronics and electrical equipment, machinery, instrumentation, consumer goods, the automotive industry, building materials, and agriculture. In many new application areas such as medical technology and sports equipment, pom also shows good growth trends. Continuous growth in application demand POM is used in sliding and rolling mechanical components where high requirements are placed on lubricity, wear resistance, stiffness, and dimensional stability; its excellent performance makes it particularly suitable for use in industrial machinery, automobiles, electronics and electrical equipment, piping fittings, and irrigation products. In recent years, China’s POM market has experienced rapid growth. In 2002, the apparent consumption volume of POM in China was 136,570 tons, and the average annual growth rate of apparent consumption in this market from 1990 to 2002 was 11.7%. It is estimated that China’s apparent consumption of Pom in 2005 will be 168,000 tons, with an average annual growth rate for apparent consumption in the Pom market from 2000 to 2005 reaching 10.3%. By 2010, the apparent consumption volume of Pom in our country is expected to rise to 197,000 tons, with an average annual growth rate for the Pom market’s apparent consumption volume between 2005 and 2010 reaching 3.2%. The main factors contributing to the rapid development of China’s Pom market include: the overall growth of the national economy, which leads to an expanding application market for Pom, one of the five major engineering plastics, with increasing demand for it ； In our country, the raw materials used for Pom production are inexpensive and readily available, resulting in substantial profits from Pom production and trading ； New breakthroughs are continuously emerging in the application fields of PM, such as the research and development of modified materials. Given the steady growth in market demand in our country, the price of Pom is expected to continue rising at a steady pace in the near future. The technological gap cannot be ignored. Although the market demand for Pom in our country is on the rise, due to the relatively late start of research and development related to Pom in our country, the domestic production scale, output, as well as the variety and quality of Pom fail to meet market demands. Compared with the advanced levels abroad, China’s pom production still faces issues such as high raw material consumption per unit, small plant scale, unstable quality, and a limited range of product grades. For example, DuPont’s consumption of formaldehyde per ton of homopolymerized PMMA is 2.56 tons, with some reports indicating 3.08 tons; in contrast, the formaldehyde consumption per ton of PMMA produced in China is 5–6 tons. Although this figure has decreased due to improvements, the gap remains significant. For many years, the production capacity and output of the Pom industry in our country have remained low, and these figures still fail to meet market demand. In 2002, there were only 3 PMM manufacturers in China, and among them, only Yuntianhua Group’s PMM production facility had a capacity of 10,000 tons per year (which has since been expanded to 20,000 tons per year). In 2002, China’s Pom production capacity was 12,800 tons per year, with a production volume of around 10,000 tons. From 1966 to 2002, the average annual growth rate of China’s Pom production capacity was 16.7%, while the average annual growth rate of output was 18.8%. It is evident that it is necessary to expand the production capacity of domestic Pom manufacturers. It is estimated that by 2005, there will be 6 POM manufacturers in China, with a total production capacity of 130,000 tons per year ； It is estimated that China’s Pom production capacity will be 190,000 tons per year in 2010, with an average annual growth rate of 7.9% for the period from 2005 to 2010. The reason why the increase in China’s Pom production capacity is not sufficient to meet market demand is that the domestic Pom market is growing rapidly, while China’s foundation for Pom production is relatively weak ； In addition, Pom is a capital- and technology-intensive chemical product in the materials sector. China’s large market has attracted the attention of foreign companies, which have been trying to gain a foothold in this market with their own products. They are unwilling to transfer technology, which has resulted in slow progress in improving the technical level of domestically produced Pom, failing to meet the needs of consumers ； Furthermore, for a long time, China’s economic system and corporate management mechanisms have not conformed to the laws of a market economy; as a result, enterprises have been unable to obtain sufficient funding in a timely manner, which has hindered the development of Pom production. Imbalance in imports and exports Although China’s Pom production has increased, it still cannot meet the demands of the domestic market, resulting in the need to import large amounts of Pom each year. The main countries and regions from which China imports Pom are Japan, the United States, South Korea, and Taiwan Province of China, among others. In 2002, China’s import volume of Pom was 135,570 tons, and the average annual growth rate of Pom imports from 1995 to 2002 was 26.3%. Our country also engages in small-scale export trade of Pom on an annual basis; in 2002, 9,000 tons of Pom were exported. The development of high-tech industries and emerging sectors in our country has led to a significant increase in the demand for engineering plastics. As an engineering plastic suitable for various industries, pom has promising prospects for development. It is understood that there are several ongoing Pom projects in China at present; for example, the Pom project of DuPont-Kasuga (Zhangjiagang) has already begun construction, while the planned Pom project at Shanghai Lanxing Chemical New Materials Factory is also in active development. Given the situation of planned Pom projects in our country, it will be the trend for the development of the Pom industry there to introduce funds and advanced technical equipment to build Pom plants on a scale that is economically viable, in locations that possess the necessary raw material and technical foundations.
Property values:
Density: 1.43
Melting point: 175°C
Tensile strength (yield): 70 MPa
Elongation at yield: 15%
(Elongation at break): 15%
Impact strength (notched): 108 KJ/m2
(Impact strength with notch): 7.6 KJ/m2
The synthesis of homopolymerized polyoxymethylene generally involves the condensation polymerization of an aqueous solution of formaldehyde in the presence of acid. a-Polyoxymethylene with a degree of polymerization of 100 or more is obtained, and then heated to decompose it into formaldehyde gas. After purification and dehydration, the monomer is usually purified using a partial pre-polymerization method, and subsequently polymerized in a dry solvent containing a small amount of initiator. The presence of water results in a significant decrease in molecular weight. Initiators can be Lewis acids or bases, etc. However, tertiary amines are mostly used for anionic addition polymerization, with the reaction proceeding as follows: The end groups of polyoxymethylene are hemiacetals (—CH2OH), and at temperatures above 100°C, these end groups tend to break apart; therefore, end-group treatment is generally required to stabilize them. After stabilization treatment, it can withstand temperatures up to 230 ℃. Polyformaldehyde can be processed at temperatures of 170–200 °C, such as by injection, extrusion, blow molding, etc. It is mainly used as an engineering plastic in automobiles, mechanical components, etc. www.seafar.cn Typical applications of POM polyoxymethylene: POM has a very low friction coefficient and excellent geometric stability, making it particularly suitable for manufacturing gears and bearings. Due to its high-temperature resistance, it is also used in piping components (pipe valves, pump housings), lawn equipment, and more. Injection molding process conditions: Drying treatment: If the material is stored in a dry environment, drying treatment is usually not required. Melting temperature: 190~230 for homopolymer materials℃ ； The copolymer material is at 190~210°C. Mold temperature: 80~105°C. A higher mold temperature can be used to reduce the shrinkage rate after molding. Injection pressure: 700~1200 bar Injection speed: moderate to high injection speed. Flow channels 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 runner. For copolymer materials, either internal hot runners or external hot runners can be used. Chemical and physical properties of POM polyoxymethylene: POM is a tough and elastic material that retains excellent creep resistance, geometric stability, and impact resistance even at low temperatures. POM includes both homopolymer and copolymer materials. Homopolymer materials possess excellent ductile strength and fatigue resistance, but are difficult to process. Copolymer materials have excellent thermal stability and chemical stability, and are easy to process. Both homopolymer materials and copolymer materials are crystalline materials and do not absorb moisture easily. The high degree of crystallinity of POM results in a fairly high shrinkage rate, which can reach as much as 2% to 3.5%. Different enhanced materials have different shrinkage rates. Polyoxymethylene (POM) is an engineering plastic with excellent properties; it is known abroad as \"steel rival\" or \"super steel\". POM possesses metal-like hardness, strength, and rigidity; it exhibits excellent self-lubricating properties over a wide range of temperatures and humidity levels, good fatigue resistance, and elasticity. In addition, it also has good chemical resistance. At a cost lower than that of many other engineering plastics, POM is replacing metals in various markets where they have traditionally been used; it is used to manufacture many components in place of zinc, brass, aluminum, and steel. Since its introduction, POM has been widely applied in fields such as electronics and electrical equipment, machinery, instrumentation, consumer goods, the automotive industry, building materials, and agriculture. In many new application areas such as medical technology and sports equipment, pom also shows good growth trends. Continuous growth in application demand POM is used in sliding and rolling mechanical components where high requirements are placed on lubricity, wear resistance, stiffness, and dimensional stability; its excellent performance makes it particularly suitable for use in industrial machinery, automobiles, electronics and electrical equipment, piping fittings, and irrigation products. In recent years, China’s POM market has experienced rapid growth. In 2002, the apparent consumption volume of POM in China was 136,570 tons, and the average annual growth rate of apparent consumption in this market from 1990 to 2002 was 11.7%. It is estimated that China’s apparent consumption of Pom in 2005 will be 168,000 tons, with an average annual growth rate for apparent consumption in the Pom market from 2000 to 2005 reaching 10.3%. By 2010, the apparent consumption volume of Pom in our country is expected to rise to 197,000 tons, with an average annual growth rate for the Pom market’s apparent consumption volume between 2005 and 2010 reaching 3.2%. The main factors contributing to the rapid development of China’s Pom market include: the overall growth of the national economy, which leads to an expanding application market for Pom, one of the five major engineering plastics, with increasing demand for it ； In our country, the raw materials used for Pom production are inexpensive and readily available, resulting in substantial profits from Pom production and trading ； New breakthroughs are continuously emerging in the application fields of PM, such as the research and development of modified materials. Given the steady growth in market demand in our country, the price of Pom is expected to continue rising at a steady pace in the near future. The technological gap cannot be ignored. Although the market demand for Pom in our country is on the rise, due to the relatively late start of research and development related to Pom in our country, the domestic production scale, output, as well as the variety and quality of Pom fail to meet market demands. Compared with the advanced levels abroad, China’s pom production still faces issues such as high raw material consumption per unit, small plant scale, unstable quality, and a limited range of product grades. For example, DuPont’s consumption of formaldehyde per ton of homopolymerized PMMA is 2.56 tons, with some reports indicating 3.08 tons; in contrast, the formaldehyde consumption per ton of PMMA produced in China is 5–6 tons. Although this figure has decreased due to improvements, the gap remains significant. For many years, the production capacity and output of the Pom industry in our country have remained low, and these figures still fail to meet market demand. In 2002, there were only 3 PMM manufacturers in China, and among them, only Yuntianhua Group’s PMM production facility had a capacity of 10,000 tons per year (which has since been expanded to 20,000 tons per year). In 2002, China’s Pom production capacity was 12,800 tons per year, with a production volume of around 10,000 tons. From 1966 to 2002, the average annual growth rate of China’s Pom production capacity was 16.7%, while the average annual growth rate of output was 18.8%. It is evident that it is necessary to expand the production capacity of domestic Pom manufacturers. It is estimated that by 2005, there will be 6 POM manufacturers in China, with a total production capacity of 130,000 tons per year ； It is estimated that China’s Pom production capacity will be 190,000 tons per year in 2010, with an average annual growth rate of 7.9% for the period from 2005 to 2010. The reason why the increase in China’s Pom production capacity is not sufficient to meet market demand is that the domestic Pom market is growing rapidly, while China’s foundation for Pom production is relatively weak ； In addition, Pom is a capital- and technology-intensive chemical product in the materials sector. China’s large market has attracted the attention of foreign companies, which have been trying to gain a foothold in this market with their own products. They are unwilling to transfer technology, which has resulted in slow progress in improving the technical level of domestically produced Pom, failing to meet the needs of consumers ； Furthermore, for a long time, China’s economic system and corporate management mechanisms have not conformed to the laws of a market economy; as a result, enterprises have been unable to obtain sufficient funding in a timely manner, which has hindered the development of Pom production. Imbalance in imports and exports Although China’s Pom production has increased, it still cannot meet the demands of the domestic market, resulting in the need to import large amounts of Pom each year. The main countries and regions from which China imports Pom are Japan, the United States, South Korea, and Taiwan Province of China, among others. In 2002, China’s import volume of Pom was 135,570 tons, and the average annual growth rate of Pom imports from 1995 to 2002 was 26.3%. Our country also engages in small-scale export trade of Pom on an annual basis; in 2002, 9,000 tons of Pom were exported. The development of high-tech industries and emerging sectors in our country has led to a significant increase in the demand for engineering plastics. As an engineering plastic suitable for various industries, pom has promising prospects for development. It is understood that there are several ongoing Pom projects in China at present; for example, the Pom project of DuPont-Kasuga (Zhangjiagang) has already begun construction, while the planned Pom project at Shanghai Lanxing Chemical New Materials Factory is also in active development. Given the situation of planned Pom projects in our country, it will be the trend for the development of the Pom industry there to introduce funds and advanced technical equipment to build Pom plants on a scale that is economically viable, in locations that possess the necessary raw material and technical foundations.
Our country uses other people’s technology as its foundation
Our country is quite strong in the field of polymer science
In the mid-to-low-end market, domestic products are sufficient; for high-end products, imports are still necessary
The experts are all out competing for fame and profit; how can they have time for genuine research?
What is polyoxymethylene? Polyoxymethylene is something that many companies want to adopt these days, but they don’t know which technology to use; they can’t find good technologies, and they’re too hesitant to use ordinary ones, as a result more companies choose to wait rather than proceed