Acetal Polyoxymethylene Copolymer - POM

Made in both copolymer and homopolymer forms which do not greatly differ. Both are tough, hard, stiff polymers with exceptional abrasion resistance and good appearance (can provide high surface gloss).

Usually highly crystalline and opaque, their natural color is white but they are frequently colored. They have poor resistance to U.V. and normally to alkalis and acids.

The homopolymer has better mechanical properties to a certain extent but somewhat worse thermo-oxidative stability than the copolymer. Only the copolymer is ideal for nonstop use with hot water.

Polymer Type

Thermoplastic

Advantages

Excellent rigidity, impact toughness, abrasion resistance, creep resistance and solvent resistance. Good appearance, hydrolytic stability fatigue endurance and low coefficient of friction. Better creep resistance, thermal stability, resistance to bases and processability than homopolymer. Higher continuous use temperature than homopolymer, about 100 °C ( 212 °F ) in air compared to 80 °C ( 175 °F ).

Disadvantages

High mould shrinkage (approximately 2%). Post moulding shrinkage of about 0.1% normally complete within 48 hrs. Attacked by acids and bases, very rapid attack by nitric acid. Very poor resistance to UV radiation. Homopolymers have higher tensile strength, flexural strength, fatigue resistance and hardness. Cannot be fire retarded   Explosive decomposition if processed with halogens.

Applications

Due to low coefficient of friction, commonly used as bearings, gears and conveyor belt limits. Electric kettles and water jugs. Components with snap fits. Chemical pumps. Bathroom scales. Telephone keypads, pulley wheels, and housings for domestic appliances, showerheads, and fuel expansion tanks.

Typical Properties

Property Value
Density (g/cm3) 1.41
Surface Hardness RR117
Tensile Strength (MPa) 73
Flexural Modulus (GPa) 2.58
Notched Izod (kJ/m) 0.069
Linear Expansion (/°C x 10-5) 11
Elongation at Break (%) 65
Strain at Yield (%) 8
Max. Operating Temp. (°C) 90
Water Absorption (%) 0.22
Oxygen Index (%) 15
Flammability UL94 HB
Volume Resistivity (log ohm.cm) 15
Dielectric Strength (MV/m) 20
Dissipation Factor 1 kHz 0.0015
Dielectric Constant 1 kHz 3.7
HDT @ 0.45 MPa (°C) 160
HDT @ 1.80 MPa (°C) 110
Material. Drying hrs @ (°C) 3 @ 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.

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