---
title: "Rigid polyurethane foam — density, melting point and propertie"
description: "Rigid polyurethane foam has a density of 40 kg/m³ (30–60). Melting point, strength, conductivity, what it is used for, and whether it floats, rusts or is magnetic."
url: https://atoneplace.net/material/polyurethane-foam/
site: "At One Place"
---

# Rigid polyurethane foam

**Density of rigid polyurethane foam: 40 kg/m³ (30–60)**

0.04 g/cm³ · 2.5 lb/ft³

The best-performing common insulator, at about 0.023 W/(m·K) — roughly a third better than the same thickness of expanded polystyrene, which is why a fridge wall can be thin. That figure depends on the blowing gas trapped in the closed cells and worsens over decades as the gas is replaced by air. Being a thermoset it has no melting point; heated far enough it chars and gives off isocyanates, which is why cutting it hot is a ventilation problem.

## Properties

- **Density:** 40 kg/m³ (30–60) — 0.04 g/cm³
- **Tensile strength:** 0.2–0.6 MPa
- **Young's modulus:** 0.01 GPa
- **Thermal conductivity:** 0.023 W/(m·K)
- **Floats in water:** Yes
- **Magnetic:** No

## What it is used for

- Refrigerator and freezer wall insulation
- Insulated roof and wall panels
- Expanding gap-filling foam
- Model making and tooling board

## 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
- rigid polyurethane foam: 40 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

*Water is 1,000 kg/m³. Anything below that floats.*

| Material | Density | Relative to water |
| --- | --- | --- |
| expanded polystyrene foam | 20 kg/m³ | 0.02× |
| air | 1.2 kg/m³ | 0.00× |
| rigid polyurethane foam ← | 40 kg/m³ | 0.04× |
| platinum | 21,450 kg/m³ | 21.45× |
| gold | 19,300 kg/m³ | 19.30× |
| tungsten | 19,250 kg/m³ | 19.25× |

## Does it rust?

Rigid polyurethane foam contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

## Is it magnetic?

Rigid polyurethane foam is not a metal and has no ferromagnetic response.

## Common questions

### What is the density of rigid polyurethane foam?

40 kg/m³ (30–60), or 0.04 g/cm³.

### Does rigid polyurethane foam float?

Yes. At 40 kg/m³ it is less dense than water's 1,000.

### Is rigid polyurethane foam magnetic?

Rigid polyurethane foam is not a metal and has no ferromagnetic response.

## Related pages

- [Does rigid polyurethane foam float?](https://atoneplace.net/does-it-float/polyurethane-foam/)
- [PLA](https://atoneplace.net/material/pla/)
- [ABS](https://atoneplace.net/material/abs/)
- [Acrylic (PMMA)](https://atoneplace.net/material/acrylic/)
- [Polycarbonate](https://atoneplace.net/material/polycarbonate/)
- [Polypropylene](https://atoneplace.net/material/polypropylene/)
- [PTFE](https://atoneplace.net/material/ptfe/)
- [Rigid PVC](https://atoneplace.net/material/pvc-rigid/)
- [HDPE](https://atoneplace.net/material/hdpe/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)