Polystyrene (PS) is one of the oldest and most commonly used types of plastic. The material is relatively inexpensive and is available in numerous variants including transparent and impact resistant types. PS has a shiny surface and is non-toxic, which explains its frequent use as packaging in the food industry. It is also seen in countless colours as a casing of electrical devices, such as office machines. PS possesses an amorphous structure and has high impact resistance and hardness. A temperature of 85°C is permissible for short periods of time, but PS is not suitable for prolonged use at temperatures above 70°C. Higher temperatures cause yellowing and mechanical weakening.
PS flows excellently and has low shrinkage during injection moulding, making it suitable for precision parts with tight tolerances. The absorption of moisture is extremely low, i.e. 0.1% at 23°C/50% RH, and when saturated in water. Moisture has hardly any effect on the dimensions and mechanical properties.
Resistance to chemicals like diluted acids and bases is good. Most oils, greases and benzenes cause stress cracks. Aromatic and halogenated hydrocarbons, esters, ketones and concentrated acids damage the material and cause swelling.
UV radiation degrades the mechanical properties and makes the surface matt and yellow. UV-stabilising types are available, but the choice of black PS guarantees the best UV protection. PS is an excellent electrical insulator, but a side-effect is that it easily attracts dust due to the static charge.