308 – Butyl Rubber (IIR)

ASTM D-2000 classification: AA, BA


Temperature Range:

-55°C to +105°C (-65°F to +225°F)



Butyl rubber is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for Isobutylene Isoprene Rubber. Polyisobutylene, also known as "PIB" or Polyisobutene, (C4H8)n, is the homopolymer of isobutylene, or 2-methyl-1-propene, on which butyl rubber is based
Butyl compounds have very high impermeability to gases, as well as good resistance to ozone, ultra violet light and weathering.

With high chemical and acid resistance, it is particularly good when applications involving high and low temperatures exist. A unique combination of high damping, barrier properties, resistance to ozone and heat aging make butyl products an ideal choice for many automotive non-tire applications.



One of the largest applications of butyl rubber parts includes vibration control applications and dynamic parts including body mounts. Butyl rubber is widely used in these applications because of its high damping, fast reversion-resistant cures and its excellent aging properties, especially in respect to hot flex fatigue.


EMI ReferenceSpecificationHardness IRHDSGTensile Strength (MPa)Elongation at Break %Colour

Full data sheets for all grades are available on request.

* The information above is supplied in good faith and believed to be correct. This information is supplied upon the condition that persons receiving this will make their own determination as to its suitability for their purposes prior to use. EMI makes no representations or warranties, either expressed or implied with respect to the information or the product to which this information refers.