Expanded polystyrene foam
Density of expanded polystyrene foam
20 kg/m³ (11–35)
0.02 g/cm³ · 1.2 lb/ft³
About 98% air by volume, which is why 20 kg/m³ is typical and why a large block can be carried in one hand — it is the lightest solid material in everyday use. A crash helmet liner works by crushing permanently, absorbing energy once, which is exactly why a dropped or crashed helmet is replaced even when it looks fine. It has no melting point worth quoting: the foam collapses and shrinks back towards solid polystyrene from around 100 °C.
Properties
- Density
- 20 kg/m³ (11–35) — 0.02 g/cm³
- Tensile strength
- 0.2–0.5 MPa
- Young's modulus
- 0.005 GPa
- Thermal conductivity
- 0.033 W/(m·K)
- Floats in water
- Yes
- Magnetic
- No
What it is used for
- Packaging inserts and cool boxes
- Cavity wall and floor insulation board
- Cycle and motorcycle helmet liners
- Concrete formwork voids
How it compares
Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.
air 1.2 kg/m³
expanded polystyrene foam 20 kg/m³
Water — the float line 1,000 kg/m³
tungsten 19,250 kg/m³
gold 19,300 kg/m³
platinum 21,450 kg/m³
| Material | Density | Relative to water |
|---|---|---|
| air | 1.2 kg/m³ | 0.00× |
| expanded polystyrene foam ← | 20 kg/m³ | 0.02× |
| platinum | 21,450 kg/m³ | 21.45× |
| gold | 19,300 kg/m³ | 19.30× |
| tungsten | 19,250 kg/m³ | 19.25× |
Does it rust?
Expanded polystyrene foam contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.
Is it magnetic?
Expanded polystyrene foam is not a metal and has no ferromagnetic response.
Common questions
- What is the density of expanded polystyrene foam?
- 20 kg/m³ (11–35), or 0.02 g/cm³.
- Does expanded polystyrene foam float?
- Yes. At 20 kg/m³ it is less dense than water's 1,000.
- Is expanded polystyrene foam magnetic?
- Expanded polystyrene foam is not a metal and has no ferromagnetic response.
Related pages
- Does expanded polystyrene foam float? Yes
- PLA 1,240 kg/m³
- ABS 1,050 kg/m³
- Acrylic (PMMA) 1,180 kg/m³
- Polycarbonate 1,200 kg/m³
- Polypropylene 905 kg/m³
- PTFE 2,170 kg/m³
- Rigid PVC 1,400 kg/m³
- HDPE 955 kg/m³
Sources
- Typical range compiled from manufacturer specifications — At One Place