Polyphenylene Sulphide PPS
Introduction to Polyphenylene Sulphide (PPS)
Exceptional heat, chemical and flame resistance have contributed to widespread use of the rigid opaque thermoplastic Polyphenylene Sulphide (PPS) in a wide variety of applications. These include cooking appliances, sterilisable laboratory equipment, hairdryer grills, automotive components including exhaust gas return valves, carburettor components, ignition plates.
Its heat resistance combined with good electrical insulation properties means PPS has found use in electrical components in place of metals and some thermosets. Lamp reflectors need to withstand up to 250 degC, which is why they are still made mainly in thermosets or diecast metal. On the other hand, Tedur (PPS) is able to produce a surface finish that can accept vapour metallisation without the need for intermediate painting, as is normally the case with filled thermoplastics.
PPS can be prepared in a number of ways. For commercial purposes, PPS would be produced by the reaction of p-dichlorobenzene with sodium sulphide in a polar solvent. It can also be formed by polymerisation of p-halothiophenoxide metal compounds both in the solid state and in solution, or by condensation of p-dichlorobenzene with elemental sulphur in the presence of sodium bicarbonate.
Rigid, opaque non-burning continuous use at 250'C, good chemical resistance, good electrical insulator, moisture resistant, rarely used unfilled.
Good tensile strength and flexural modulus together with good electrical properties. Glass fibre filled PPS gives good heat distortion whereas carbon fibre filled PPS does this even better with dimensional stability and rigidity. PPS, when PTFE lubricated, will give good wear and low coefficient of friction.
PPS is generally found as filled grades:
- Glass-reinforced grades (30 and 40% glass content loading)
- Glass-fibre/particulate-mineral-filled grades (for cost-effective solution with high tracking resistance and high temperature ratings)
- Glass-fibre/mineral-filled colour compounds
- Carbon-fibre-reinforced grades (high tensile strength and more effective than glass fibre in reducing the coefficient of friction against steel)
- Lubricated fibre-filled grades (usually contain 15% PTFE, 2% silicone)
Tensile Strength 0.50 N/mm²
Notched Impact Strength 1.50 Kj/m²
Thermal Coefficient of expansion 70 x 10-6
Max Cont Use Temp 200 oC
Density 1.34 g/cm3
RESISTANCE TO CHEMICALS
Dilute Acid ****
Dilute Alkalis ****
Oils and Greases ****
Aliphatic Hydrocarbons ****
Aromatic Hydrocarbons ****
Halogenated Hydrocarbons ****
KEY * poor ** moderate *** good **** very good
Note that these ratings are generalised. The resistance against specific substances can deviate and are dependent on temperature, applied stresses, exposure time etc.
Over the years, PPS has seen increased use:
Electrical & Electronics (E&E)
Uses include electronic components including connectors, coil formers, bobbins, terminal blocks, relay components, moulded bulb sockets for electrical power station control panels, brush holders, motor housings, thermostat parts and switch components.
PPS boasts effective resistance to corrosive engine exhaust gases, ethylene glycol and petrol, making it the ideal material for exhaust gas return valves, carburettor parts, ignition plates and flow control valves for heating systems.
PPS finds use in cooking appliances, sterilisable medical, dental and laboratory equipment, hair dryer grills and components.