Polyphenylene Sulphide (PPS) is an aromatic, semi-crystalline thermoplastic with excellent shape stability, chemical resistance and flame retarding capability. In its pure form the mechanical properties are weak – the material is very brittle – but an enormous improvement is achievable by adding fibres. Therefore, fibre-reinforced PPS is used as standard. PPS is resistant to high temperatures and chemically resistant to all hydrocarbons and petrol. This explains why it is frequently used in the automotive industry, for example in headlight reflectors and in fuel pumps, bearings and other parts under the bonnet.
Compared with most other engineering thermoplastics, PPS is superior when it comes to thermal ageing. The material is stable at continuous temperatures up to 220°C, and reinforced types remain stable even at temperatures up to 260°C for short periods. This sets PPS apart from amorphous high-temperature polymers, which begin to deteriorate just below their glass transition temperature of 210°C.
PPS’s moisture absorption is extremely low, i.e. 0.05% at 23°C/50% RH, and 0.07% when saturated in water at 23°C. This makes the material ideally suited to use underwater. When glass fibre reinforced PPS is used in hot water, the degradation of its mechanical properties will be measurable after a few months, mainly due to the chemical reaction with the glass fibres. PPS is exceptionally resistant to chemicals like aliphatic, aromatic and halogenated hydrocarbons, most concentrated acids, strong bases, aldehydes, phenols, esters and ketones. Exceptions are concentrated oxidising acids and certain esters and amines at higher temperatures. Resistance to UV radiation is good, so PPS is also usable outdoors.
At temperatures up to approximately 80°C, reinforced PPS is one of the most rigid thermoplastics. Rigidity and creep resistance decrease significantly above the glass transition temperature of approximately 90°C, but the values remain impressive compared with other thermoplastics. Use in electronic circuits with operating voltages up to approximately 150 V is possible.