Polystyrene and EPS: Characteristics
What makes EPS such a good insulator
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.PS is chosen for clarity (GPPS), impact strength (HIPS) or foam density and insulation (EPS). Melt flow, Vicat softening point, rubber content and residual monomer matter for moulders; for EPS, bead size, pentane content and flame retardancy matter.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Density | solid PS about 1.04-1.05 g/cm3; EPS foam about 10-40 kg/m3 (indicative) | EPS is about 98% air, which gives insulation and light weight but makes waste bulky. | standard polymer data (indicative) |
| Thermal conductivity (EPS) | about 0.031-0.038 W/m.K; graphite EPS lower (indicative) | Sets insulation thickness needed. | industry standard (indicative) |
| Vicat softening point | about 90-105°C (indicative) | Limits hot-food and appliance uses. | industry standard (indicative) |
| Residual styrene | typically below about 500 ppm (indicative) | Food-contact and odour limits. | industry standard (indicative) |
| Carbon content | about 92% by mass | About 3.4 t CO2 per t if incinerated, the highest of the commodity plastics. | stoichiometric |
Commercial grades
- GPPS (clear packaging, cups, lab ware)
- HIPS (fridge liners, housings, dairy cups)
- EPS white (packaging)
- EPS flame-retardant (insulation)
- Graphite EPS (high-performance insulation)
- XPS-grade GPPS
- Recycled PS