May 5 2001
Polyoxymethylene is made in homopolymer as well as in copolymer forms which are not very different from each other. Both forms are tough, hard, stiff polymers with good appearance (can offer high surface gloss) and excellent abrasion resistance.
They are normally opaque, highly crystalline, and white in color, but they are often used colored. They have poor resistance to UV and generally to alkalis and acids.
When compared with the copolymer, the mechanical properties of the homopolymer are slightly better but its thermo-oxidative stability is somewhat worse. Only the copolymer is suited for continuous use with hot water.
Polymer Type
Thermoplastic
Advantages
Superior rigidity, hardness, and tensile strength compared with unmodified copolymer are some of the advantages.
Improved mould shrinkage and lower coefficient of expansion. Excellent creep resistance. Also excellent solvent resistance associated with the copolymer.
Disadvantages
Reduced impact strength compared to unmodified grades. Properties of glass reinforced grades are strongly influenced by the dimensions of the glass fibres and the efficiency of distribution in components can be highly anisotropic.
Applications
Applications include toys, ski boot bindings, models, sports equipment, for example, snap fit components, mast supports on wind surfing boards, and handles for tennis racquets.
The material is also used in frame connectors, sprockets and gears, slide guides for drawers, bearing bushes, water filter bodies, snap fittings, bearings, and many other engineering components.
Typical Properties
| Property |
Value |
| Density (g/cm3) |
1.63 |
| Surface Hardness |
RM86 |
| Tensile Strength (MPa) |
134 |
| Flexural Modulus (GPa) |
9.6 |
| Notched Izod (kJ/m) |
0.1 |
| Linear Expansion (/°C x 10-5) |
4 |
| Elongation at Break (%) |
3.5 |
| Strain at Yield (%) |
N/A |
| Max. Operating Temp. (°C) |
100 |
| Water Absorption (%) |
0.3 |
| Oxygen Index (%) |
15 |
| Flammability UL94 |
HB |
| Volume Resistivity (log ohm.cm) |
14 |
| Dielectric Strength (MV/m) |
20.7 |
| Dissipation Factor 1 kHz |
0.0025 |
| Dielectric Constant 1 kHz |
3.95 |
| HDT @ 0.45 MPa (°C) |
168 |
| HDT @ 1.80 MPa (°C) |
160 |
| Material. Drying hrs @ (°C) |
2 @ 90 |
| Melting Temp. Range (°C) |
200 - 210 |
| Mould Shrinkage (%) |
0.5 |
| Mould Temp. Range (°C) |
60 - 120 |
Source : Abstracted from Plascams
For more information on Plascams please visit RAPRA Technology Ltd.