May 5 2001
Polyoxymethylene is made in both homopolymer and copolymer forms which are not very different from each other. Both are tough, hard, stiff polymers with good appearance (can give high surface gloss) and excellent abrasion resistance.
Usually highly crystalline and opaque, their natural colour is white but they are typically used coloured. They have poor resistance to UV and generally to alkalis and acids.
When compared to the copolymer, the homopolymer has slightly better mechanical properties but somewhat worse thermo-oxidative stability. Only the copolymer is suited for continuous use with hot water.
Polymer Type
Thermoplastic
Advantages
Significantly increased flexural modulus, moderate increase in tensile strength and HDT compared with unmodified Acetal.
Disadvantages
Significant reduction in elongation at break and moderate reduction in notched izod impact strength compared with unmodified Acetal. Incorporation of carbon fibres can cause anisotropic mechanical properties in moulded components and reduced electrical resistance.
Applications
Applications are wide-ranging such as bearings, cams, gears, snap fittings, and many other engineering components. Polyoxymethylene is also used in jug kettles, appliance casings, and plumbing fittings.
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Polyoxymethylene has excellent abrasion resistance which is why it is used in plumbing fittings. Image Credit: ShutterStock/ DmitryNaumov
Typical Properties
| Property |
Value |
| Density (g/cm3) |
1.48 |
| Surface Hardness |
RM94 |
| Tensile Strength (MPa) |
85 |
| Flexural Modulus (GPa) |
17.2 |
| Notched Izod (kJ/m) |
0.038 |
| Linear Expansion (/°C x 10-5) |
4 |
| Elongation at Break (%) |
1 |
| Strain at Yield (%) |
N/A |
| Max. Operating Temp. (°C) |
105 |
| Water Absorption (%) |
0.2 |
| Oxygen Index (%) |
18 |
| Flammability UL94 |
HB |
| Volume Resistivity (log ohm.cm) |
2.95 |
| Dielectric Strength (MV/m) |
3.3 |
| Dissipation Factor 1 kHz |
NA |
| Dielectric Constant 1 kHz |
NA |
| HDT @ 0.45 MPa (°C) |
168 |
| HDT @ 1.80 MPa (°C) |
162 |
| Material. Drying hrs @ (°C) |
2 @ 90 |
| Melting Temp. Range (°C) |
170 - 210 |
| Mould Shrinkage (%) |
0.2 |
| Mould Temp. Range (°C) |
100 - 120 |
Source : Abstracted from Plascams
For more information on Plascams please visit RAPRA Technology Ltd.