Polystyrene is one of the oldest thermoplastic polymers dating back to the 1930’s when BASF in Europe and DOW in the US pioneered the developments of PS. After some mergers and takeovers, the most important polystyrene producers are Trinseo, Styrolution and Total.
Polystyrene chemical formula.
Polystyrene grades can be divided into two main groups:
- GPPS – general purpose polystyrene
- HIPS – high impact polystyrene
GPPS, general purpose polystyrene or crystal clear polystyrene, is fully transparent, yet brittle, and is widely used in food packaging applications or jewel cases.
HIPS, high impact polystyrene, is polystyrene which has butadiene rubber as impact modifier, giving the material good impact performance, but losing the transparency.
Polystyrene is easy to process, has a nice gloss and it is still the most preferred material for thermoforming. The most well known polystyrene application is yoghurt cups.
Another big thermoforming application of polystyrene is the inner liners of refrigerators and freezers, for which special high ESCR (environmental stress crack resistance) grades have been designed.
Typical polystyrene applications are:
- Petri dishes
- Coat hangers
- Office equipment
- Disposable cutlery
- Coffee cups