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 colored. 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
Superior UV resistance compared with unmodified grades. Titanium dioxide used for non-black UV resistant mouldings. Excellent mechanical properties and solvent resistance as expected with Acetal copolymer.
Disadvantages
In the case of carbon black modification best results are obtained with 1.5% of well-dispersed fine particles. However the finer the particle, the poorer the heat stability. Also prone to high mould shrinkage and attack by acids and bases as with unmodified copolymers.
Applications
Applications are wide-ranging including sporting equipment, for example ski boot bindings tennis racquet handles, most supports and frame connectors for windsurfing boards, toys, and also snap fittings, gears, bearings, and many other engineering components.
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Acetal Polyoxymethylene Copolymer is used in sporting equipment such as windsurfing boards. Image Credit: ShutterStock/COLOMBONICOLA
Typical Properties
| Property |
Value |
| Density (g/cm3) |
1.41 |
| Surface Hardness |
RR117 |
| Tensile Strength (MPa) |
68 |
| Flexural Modulus (GPa) |
2.5 |
| Notched Izod (kJ/m) |
0.069 |
| Linear Expansion (/°C x 10-5) |
11 |
| Elongation at Break (%) |
60 |
| Strain at Yield (%) |
8 |
| Max. Operating Temp. (°C) |
90 |
| Water Absorption (%) |
0.22 |
| Oxygen Index (%) |
15 |
| Flammability UL94 |
HB |
| Volume Resistivity (log ohm.cm) |
14 |
| Dielectric Strength (MV/m) |
19 |
| Dissipation Factor 1 kHz |
0.0018 |
| Dielectric Constant 1 kHz |
3.8 |
| HDT @ 0.45 MPa (°C) |
155 |
| HDT @ 1.80 MPa (°C) |
105 |
| Material. Drying hrs @ (°C) |
2 @ 90 |
| Melting Temp. Range (°C) |
190 - 210 |
| Mould Shrinkage (%) |
1.8 |
| Mould Temp. Range (°C) |
60 - 120 |
Source : Abstracted from Plascams
For more information on Plascams please visit RAPRA Technology Ltd.