Properties of Butyl Rubber (IIR)
Butyl rubber (IIR), a synthetic elastomer made from isobutylene with a small amount of isoprene, is valued for its outstanding impermeability to gases and liquids. Its high resistance to moisture, chemicals, and environmental exposure makes it ideal for applications requiring airtight seals, such as inner tubes, protective clothing, and pharmaceutical stoppers.
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The following table provides a comprehensive list of butyl rubber (IIR) properties in both SI and US customary/Imperial units at normal temperature and pressure (NTP).
Click on the icon to switch between Metric and Imperial units.
| Physical Properties | Metric |
|---|---|
| Category | Elastomer |
| Density | 917 kg/m3 |
| Mechanical Properties | Metric |
| Ultimate Tensile Strength | 17 MPa |
| Young’s Modulus (E) | 0.3 - 3.4 GPa |
| Elongation at Break | 700 - 950% |
| Shore Hardness (A) | 30 - 100 |
| Thermal Properties | Metric |
| Thermal Conductivity | 0.13 - 0.23 W/m·K |
| Specific Heat Capacity (Cp) | 1950 J/kg·K |
| Glass Transition Temperature (Tg) | -65 °C |
| Optical Properties | Metric |
| Refractive Index (589 nm) | 1.5081 |
Unless stated otherwise, all values are taken at room temperature (approximately 20°C or 68°F) and 1 atm pressure. (1 atm = 101,325 Pa)