Polyoxymethylene (POM) Modification Techniques and Applications
Polyoxymethylene (POM) is a high-performance engineering plastic, also known as "steel beater," "super steel," or "steel match," and is widely used to replace metals like steel, copper, zinc, and aluminum in various components. It is one of the world's five major engineering plastics (polyamide, polycarbonate, POM, polyester, and polyphenylene ether).
The Significance of POM Modification
POM is prone to crystallization during the molding process, forming larger spherulites. When subjected to impact, these larger spherulites can easily become stress concentration points, leading to material failure. Thus, POM has a high notch sensitivity, low impact strength, high shrinkage rate during molding, and is prone to internal stress, making it difficult to achieve a tight fit. This limits the scope of POM's application and fails to meet certain industrial requirements. Therefore, to better adapt to stringent working conditions such as high speed, high pressure, high temperature, and high load, it is necessary to further enhance the impact toughness, heat resistance, and wear resistance of polyoxymethylene.
Key Research on POM Modification
The key to POM's physical modification lies in the compatibility between phases in the composite system, which requires increased development and research of multifunctional compatibilizers. The newly developed gel system and in-situ polymerized toughening agents create a stable interpenetrating network within the composite system, representing a new research direction for addressing phase compatibility.
The chemical modification of POM is crucial in the synthesis process, where the introduction of multifunctional groups into the molecular chain through the selection of copolymer monomers provides conditions for further modification. By adjusting the amount of copolymer monomers and optimizing the design of molecular structure, a series of POMs with functionalization and high performance are synthesized.
Technical Route for POM Modification Research
1. Filling and Enhanced Modification
Inorganic materials such as Al2O3, magnesium oxide, glass fiber, carbon fiber, glass microspheres, mica, talcum powder, calcium carbonate,二氧化硅, and potassium titanate are blended into polyformaldehyde through melting, thereby enhancing its strength, stiffness, hardness, heat deflection temperature, and dimensional stability. Filled and reinforced polyformaldehyde is primarily used in the production of complex mechanical structures, thin-walled precision parts, and engineering products.
2. Toughening Blending Modification
Utilizing thermoplastic polyurethane (TPU), nitrile rubber (NBR), modified polyolefins, polyamides, and lignocellulosic materials as elastic toughening agents, ultra-tough POM alloys are produced through mechanical blending and graft copolymerization methods.
3. Functionalized Modified
Enhance Friction and Wear Resistance Properties
Adding organic oil or silicone oil, and molybdenum disulfide to polyoxymethylene resins can reduce the surface friction coefficient and wear rate of the products. Lubricated polyoxymethylene is suitable for transmission materials in mechanical and electronic electrical components, such as gears, roller, cam, and linkage products.
Added crystalline high molecular materials with low friction coefficients, such as PTFE, PE, and UHMWPE.
② Added fiber materials such as glass fiber and carbon fiber.
③ Add silicone oil, mineral oil, grease, and other lubricating oils and greases.
④ Added MoS2, graphite, and other inorganic powder lubricants.
⑤ Introduced lubricating chain segments into the POM molecular chains by means of grafting and block copolymerization.
Enhance the weather resistance of polyoxymethylene
Adding antioxidants and light stabilizers to polyoxymethylene can enhance its weather resistance. In response to the drawbacks of POM, such as whitening and cracking upon exposure to ultraviolet radiation, various research institutions have developed weather-resistant varieties to meet the demands of automotive interior and exterior decorative materials.
Conductive and antistatic polyformaldehyde
By incorporating conductive fillers such as carbon black, carbon fiber, and stainless steel fiber, the electrical conductivity of polyoxymethylene (POM) can be enhanced. Adding a special antistatic agent to POM enables it to exhibit antistatic properties, reducing interference caused by dust and debris accumulation and static charge in its applications in the electronics field.
POM's primary applications
1. Machinery Industry
Polyoxymethylene is extensively used in the mechanical industry for manufacturing gears, rollers, cams, bearings, springs, bolts, nuts, as well as various pump bodies, casings, impellers, and more.
2. Automotive Parts
POM is primarily used in automobiles for manufacturing components such as radiator caps, fuel tank lids, filler ports, exhaust control valves, water valve bodies, heater fans, air compressor valves, heater control rods, combination switches, washing pumps, door locks, sunshade brackets, speedometer cases, window adjustment handles, mirror support plates, wiper pivot bearings, and wiper gears.
3. Electronics & Appliances
Parts for manufacturing various electric tools, such as socket wrench casings and switch handles, as well as components for household appliances.
