Products · POM
Polyoxymethylene (POM, also called acetal) is a high-crystallinity engineering polymer produced by polymerization of formaldehyde (homopolymer) or trioxane with a comonomer (copolymer). The highly crystalline structure gives POM exceptional stiffness, low friction, and excellent fatigue resistance — making it the workhorse material for precision gears, bearings, snap-fit assemblies, and fuel system components. POM is also one of the most dimensionally stable engineering polymers due to its low water absorption and high crystallinity. Reference grades from DuPont (Delrin), Celanese (Hostaform), and domestic Chinese suppliers (Yunda POM) cover the full property range.
Section 1
A reference overview of the molecular architecture and the design variables that govern the performance of this polymer family.
POM is a polymer of formaldehyde (–CH2–O– repeating unit). The homopolymer (Delrin) is produced by anionic polymerization of formaldehyde and has the highest crystallinity and mechanical performance. The copolymer (Hostaform, Celcon) is produced by copolymerization of trioxane with a small amount of a comonomer (typically ethylene oxide or 1,3-dioxolane) to introduce occasional C–C bonds that interrupt the long –CH2–O– sequences, giving better thermal stability and chemical resistance at the cost of slightly lower crystallinity and stiffness. The homopolymer has higher mechanical strength and slightly better fatigue resistance; the copolymer has better hydrolytic stability and resistance to oxidative degradation.
Section 2
Typical property ranges across commercial grades. Test methods are listed in the rightmost column for traceability to public manufacturer data sheets.
POM's defining properties are high crystallinity (up to 80%), high stiffness, low coefficient of friction, excellent fatigue resistance, and low moisture absorption. The combination of low friction and fatigue resistance is unique among engineering polymers and is the reason POM is specified for precision gears and bearings.
| Property · 性能 | POM Homopolymer | POM Copolymer | Test Method · 测试方法 |
|---|---|---|---|
| Density · 密度 | 1.42 – 1.45 g/cm³ | 1.40 – 1.43 g/cm³ | ASTM D792 |
| Melt Point · 熔点 | 175 – 181 °C | 165 – 175 °C | ISO 3146 |
| Tensile Strength · 拉伸强度 | 65 – 80 MPa | 60 – 75 MPa | ASTM D638 |
| Flexural Modulus · 弯曲模量 | 2.8 – 3.2 GPa | 2.5 – 2.9 GPa | ASTM D790 |
| Elongation at Break · 断裂伸长 | 20 – 40 % | 30 – 60 % | ASTM D638 |
| HDT (1.82 MPa) · 热变形 | 100 – 125 °C | 95 – 115 °C | ASTM D648 |
| Water Absorption (24h) · 吸水率 | 0.20 – 0.30 % | 0.20 – 0.30 % | ASTM D570 |
| Coefficient of Friction · 摩擦系数 | 0.2 – 0.3 | 0.2 – 0.3 | ASTM D1894 |
Section 3
The major application areas for this polymer family, each illustrated with a brief description of how the material is specified and used.
POM is the dominant material for precision gears, gear racks, bearings, and gear trains in consumer and industrial applications. The combination of high stiffness, low friction, and excellent fatigue resistance (under cyclic loading) makes POM uniquely suited to precision motion components. Common in automotive window regulators, seat adjusters, printer gears, and small appliance mechanisms.
POM is widely used in snap-fit assemblies — clips, fasteners, latches, and connectors — where the combination of high fatigue resistance (snap-fit can be assembled and disassembled many times without failure) and low moisture absorption (consistent dimensions in humid environments) is required.
POM copolymer is used in fuel system components — fuel pump housings, fuel rail components, fuel sender units, and filler neck components — where the combination of broad chemical resistance to gasoline, diesel, ethanol blends, and methanol fuels is required. POM copolymer is preferred over homopolymer for fuel applications due to better hydrolytic and oxidative stability.
POM is used in conveyor components, chain links, idler rollers, and material handling parts where low friction, high wear resistance, and dimensional stability are required. Common in food processing conveyors, packaging machinery, and warehouse automation.
Section 4
Key processing parameters and equipment considerations. Contact our business manager for grade-specific processing recommendations.
| Melt Temperature | 190 – 210 °C; mold temperature 80 – 110 °C |
| Drying | 80 – 100 °C for 2 – 4 hours (POM is less moisture-sensitive but drying improves surface) |
POM releases formaldehyde gas at processing temperatures above 220°C — adequate ventilation is mandatory. Avoid copper, brass, and bronze tooling (catalyzes oxidation); chrome-plated or tool-steel tooling is recommended. POM is highly flammable; do not process at temperatures above 230°C. Annealing at 140-160°C for 1-2 hours can improve dimensional stability in tight-tolerance parts.
Section 5
A summary of when this polymer family is the right choice and what to consider as alternatives. For project-specific grade selection, contact our business manager.
Choose POM for precision gears, bearings, snap-fit, and fuel system components where low friction and high fatigue resistance are required. Choose POM homopolymer for highest mechanical performance; POM copolymer for better hydrolytic and oxidative stability. For higher temperature (above 120°C continuous) or better chemical resistance, PA66 GF or PPA is preferred. For lower cost with similar stiffness, PA6 GF may suffice.
Section 6
Reference grades from publicly available manufacturer catalogs. Complete catalog available on request.
| Grade | Manufacturer | Key Properties | Typical Use |
|---|---|---|---|
| Delrin® 100Original document · reference copy | DuPont | Homopolymer · High viscosity · High toughness | Extrusion · Stock shapes · Heavy section |
| Delrin® 100PInternal snapshot · original TDS on request | DuPont | Homopolymer · Lubricated · Wear grade | Gears · Bearings · High-cycle parts |
| Hostaform® C9021 | Celanese | Copolymer · Standard · High flow | General purpose · Snap-fit · Consumer |
| Yunda POM M90 | Yunda (云达) | Copolymer · Standard · 国产 | 国产替代 · 通用 · 工业件 |
Section 7
Cross-references to industry-specific applications and case studies.