Thermoplastic
Polystyrene (HIPS)
The cheapest molding plastic. Rigid, clear in GPPS, tough in HIPS.
Published values for unfilled grades at 23 °C unless stated. Confirm against the supplier datasheet for the grade you specify.
What it is
General purpose polystyrene is glass clear, very rigid, and brittle. High impact polystyrene adds a rubber phase, which makes it opaque and tough at the cost of stiffness and clarity. Both are the cheapest molding materials available.
They are the right answer when the part is a low-cost, low-stress, indoor component: packaging, disposable housings, and thermoformed trays.
Where it is used
- Disposable packaging and containers
- Thermoformed trays and inserts
- Low-cost appliance and toy components
- Refrigerator liners (HIPS)
- Point-of-sale display parts
Processing notes
Drying rarely needed. Melt 180–240 °C, mold 20–70 °C.
Very easy to mold, with low shrinkage and excellent detail reproduction. It is often used for tool trials before switching to the production resin.
Thermoforms at low temperature and holds fine detail.
Available through
Design notes
Do not use GPPS for anything that will be dropped or flexed. It cracks with no warning.
It is attacked by many solvents, oils, and citrus terpenes. Not suitable for food contact with fats.
Service ceiling is around 60 °C. It will distort in a hot car or a dishwasher.
Grades and variants
- GPPS, clear, rigid, brittle
- HIPS, opaque, tough, the general purpose grade
- Flame retardant grades
- Food contact certified grades
- Expanded polystyrene for packaging rather than molding
Alternatives
If Polystyrene (HIPS) is not the right answer
Specifying this material?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.