What is polyoxymethylene (POM)?
Polyoxymethylene (POM) is a linear polymer with no side chains, high density, and high crystallinity. Based on the differences in the chemical structure of its molecular chains, it can be divided into two types: homopolymer POM and copolymer POM (POM-C).
The key differences between the two are as follows: homopolymer POM has higher density, crystallinity, and melting point, but poorer thermal stability, a narrower processing temperature range (approximately 10°C), and slightly lower resistance to acids and alkalis; copolymer POM has lower density, crystallinity, melting point, and strength, but better thermal stability, is less prone to decomposition, has a wider processing temperature range (approximately 50°C), and exhibits better resistance to acids and alkalis.
Both are engineering plastics with excellent comprehensive properties, featuring good physical, mechanical, and chemical properties, particularly outstanding wear resistance. Commonly known as "Sai Gang" or "Duo Gang," they are the third most widely used engineering plastic.
Applications of PolyacetalProducts Description
Good for making parts that resist wear and tear, parts for transmissions, and parts for chemical and instrumentation applications. It is quite stiff and resistant to wear. Mainly utilized in structural frameworks for things like gears, bearings, car parts, machine tools, and instrumentation parts.
Due to its high rigidity, low friction, dimensional stability, and resistance to chemical corrosion, it is often paired with CNC machining's high precision and complex shape processing capabilities. It is involved in mechanical transmission, fluid and chemical, electronic and electrical, precision equipment, high-end manufacturing, and prototype and small-batch customization fields. Therefore, POM in CNC machining covers both mass-produced wear-resistant/ transmission components in mass production, as well as supporting high-end precision customization. Its core advantage lies in the combination of "material performance + processing flexibility," making it particularly suitable for applications with stringent requirements for friction, precision, and chemical resistance.
Features of pom plastic products
| Serial Number | Product Features |
|---|---|
| 1 | Before processing POM, drying is not necessary. It is best to preheat it during processing (around 80°C), which is beneficial for the dimensional stability of the product. |
| 2 | The processing temperature range of POM is narrow (0～215°C). If it stays in the barrel for a slightly long time or the temperature exceeds 220°C, it will decompose and produce highly irritating formaldehyde gas. |
| 3 | When injecting POM material, the holding pressure should be relatively high (similar to the injection pressure) to reduce the pressure drop; the screw speed should not be too high, and the residual amount should be small. |
| 4 | POM products have a relatively high shrinkage rate and are prone to shrinkage or deformation; they have a high specific heat and a high mold temperature (80～100°C). The product is very hot when demolded, so it is necessary to prevent finger burns. |
| 5 | POM is suitable for molding and processing under conditions of medium pressure, medium speed, low material temperature, and relatively high mold temperature. For precision products, the mold temperature needs to be controlled during molding. |
| 6 | It has high mechanical strength and rigidity. |
| 7 | The highest fatigue strength. |
| 8 | Excellent environmental resistance and resistance to organic solvents. |
| 9 | It has strong resistance to repeated impacts, good electrical properties, good resilience, self - lubricating property, good abrasion resistance, and excellent dimensional stability. |
Pom compared to polycarbonate (pC)
| Performance Indicators | Unit | Homopolymer POM | Copolymer POM | 25%GF POM | General - Purpose PC (PC - 2805) | 20%GF PC (PC - GF20) |
|---|---|---|---|---|---|---|
| Physical Properties | ||||||
| Relative Density | - | 1.43 | 1.41 | 1.61 | 1.20 | 1.45 |
| Water Absorption (24h, 23°C, in water) | % | 0.25 | 0.21 | - | 0.35 | 0.25 |
| Molding Shrinkage | % | 1.5~3.0 | 1.5~3.5 | 0.5~1.0 | 0.5~0.8 | 0.2~0.5 |
| Mechanical Properties | ||||||
| Tensile Strength | MPa | 70 | 62 | 130 | 65 | 120 |
| Elongation at Break | % | 40 | 60 | 3~5 | ＞100 | 3~5 |
| Flexural Strength | MPa | 90 | 98 | 182 | 90 | 160 |
| Tensile Modulus of Elasticity | MPa | 3160 | 2830 | 8300 | 2400 | 6000 |
| Flexural Modulus of Elasticity | MPa | 2880 | 2600 | 7600 | 2200 | 5500 |
| Compressive Strength | MPa | 127 | 110 | 155 | 80 | 110 |
| Shear Strength | MPa | 67 | 54 | 75 | 45 | 60 |
| Izod Notched Impact Strength (23°C) | J/M | 76 | 65 | 86 | 600 | 200 |
| Rockwell Hardness (noted scale) | - | M94 (M scale) | M81 (M scale) | M100+ (M scale) | R120 (R scale) | R125 (R scale) |
| Coefficient of Friction (vs steel, dry) | - | 0.15 | 0.15 | 0.18 | 0.3 | 0.25 |
| Bending Cycle Fatigue Limit | MPa | 35 | 31 | 42 | 25 | 35 |
| Thermal Properties | ||||||
| Heat Deflection Temperature (1.82MPa) | °C | 110 | 124 | 163 | 130 | 160 |
| Long - Term Service Temperature | °C | 80 | 100 | 110 | 120 | 130 |
| Coefficient of Linear Expansion | ×10⁻⁵ °C⁻¹ | 7.5 | 8.5 | 2.6 | 6.5 | 3.0 |
| Thermal Conductivity | W/(M·K) | 0.23 | 0.23 | 0.32 | 0.20 | 0.30 |
| Electrical Properties | ||||||
| Volume Resistivity | Ω·cm | 10¹⁴ | 10¹⁴ | 3.8×10¹³ | 10¹⁶ | 10¹⁶ |
| Dielectric Constant (10Hz) | - | 3.8 | 2.7 | 3.6 | 3.0 | 3.2 |
| Dielectric Loss Tangent (10Hz) | - | 0.005 | 0.007 | 0.009 | 0.0009 | 0.0015 |
| Dielectric Strength (power frequency) | KV/mm | 20 | 20 | 16 | 18 | 15 |
| Arc Resistance | S | 220 | 240 | 180 | 120 | 100 |
FAQ
Q: What is polyoxymethylene (POM) material?
A: Polyoxymethylene (abbreviated as POM, also known as polyacetal) is a high-performance engineering plastic. It features:
Exceptional stiffness, low friction, and self-lubrication.
High wear resistance and dimensional stability.
Good chemical resistance to oils, solvents, and weak acids.
Commonly used in precision parts like gears, bearings, and connectors.
Q: What are the applications of POM plastic material?
A: POM material excels in scenarios requiring durability and precision:
Automotive: Gears, bushings, fuel system components (resists fuel corrosion).
Electronics: Connector housings, sensor brackets (high rigidity + low creep).
Industrial: Pump valves, conveyor parts, and CNC-machined precision tools (wear resistance).
Consumer Goods: Zippers, toy gears, and knife handles (low friction + toughness).
Q: How to machine polyacetal (POM) in CNC machining?
A: For CNC machining of POM:
Tooling: Use sharp carbide tools (prevents melting/sticking).
Speeds/F feeds: Moderate speeds (avoid overheating, as POM degrades above 220℃).
Cooling: Air cooling (avoids moisture absorption, as POM has low water uptake).
Shrinkage: Compensate for shrinkage (1.5~3.5%) in mold design or post-processing.
Q:How does POM compare to nylon (PA) or PC?
A:
|
Property |
POM (Polyacetal) |
Nylon (PA) |
PC (Polycarbonate) |
|
Stiffness |
Higher |
Lower (more flexible) |
Lower |
|
Wear Resistance |
Superior |
Weaker (needs lubricant) |
Weaker |
|
Dimensional Stability |
Better (low creep) |
Poorer (absorbs moisture) |
Good |
|
Impact Toughness |
Lower |
Higher |
Far higher |
|
Temperature Limit |
Up to 100℃ (long-term) |
Up to 120℃ |
Up to 130℃ |