Polystyrene comes in two main forms. They start from the same polymer but behave very differently in a part.
The short version
GPPS (general-purpose, or “crystal” polystyrene) is clear, rigid, glossy and brittle. HIPS (high-impact polystyrene) has rubber particles blended in, which makes it opaque and much tougher.
| Property | GPPS | HIPS |
|---|---|---|
| Clarity | Transparent | Opaque |
| Impact strength | Low (brittle) | Medium to high |
| Stiffness | Higher | Lower |
| Elongation at break | Very low (a few %) | Much higher |
| Heat resistance | Similar | Similar |
| Gloss | High | Lower (high-gloss grades exist) |
| Chemical resistance | Limited | Limited |
| Relative cost | Lowest | Slightly higher |
Where each one is used
- GPPS: clear food containers and lids, display and point-of-purchase parts, lab ware, and as a modifier in compounding and some adhesive and coating formulas.
- HIPS: refrigerator liners, appliance and electronics housings, toys, thermoformed cups and trays, and signs.
- Blends: many processors mix GPPS and HIPS to tune stiffness against toughness.
What to match when you need an equivalent
- Melt flow at 200°C / 5 kg. GPPS grades vary in mineral oil content, which raises flow.
- Heat resistance (Vicat or HDT).
- For HIPS: rubber content and impact strength.
- Food contact: FDA status, if it applies.
- For adhesive and compounding use: molecular weight and melt flow matter most, because they drive solution and melt viscosity.
See our GPPS & HIPS page and resin for adhesives & sealants.