Butyl rubber (IIR)

AL-Gummi Butyl-Kautschuk (IIR) (auch Isobuten-Isopren-Kautschuk)

Registered trade name: Polysar

Butyl rubber is a copolymer of isobutylene and isoprene. The characteristic property of butyl is its low gas permeability, which is why one of its main applications is air hoses for tyres. Compared to NR and other synthetic rubbers, IIR has a very low permeability to air, water vapour and gases. Other advantages include good resistance to heat, oxygen, ozone and chemicals.

IIR cannot be blended with other elastomers due to its chemical structure and behaviour during the vulcanisation process.

Property spectrum of IIR

Hardness 40 to 85 Shore A
Elongation at break normally between 400 to 800%, also above 1000
Maximum temperature +90° C
Minimum temperature -30°C
Electrical properties very good insulating properties
Gas permeability very low, about 10 times lower than NR
Ageing and ozone resistance good to very good
Chemical resistance good chemical resistance with the exception of mineral oil and grease

Areas of application for IIR

Butyl rubber is used wherever low gas permeability and good heat and ageing resistance are required. The main areas of application are tyre tubes and the air-tight inner liners of tubeless tyres. The low gas permeability is also used for special protective clothing (e.g. gloves).
Due to its good chemical resistance, butyl is used for chemical hoses, seals and tank liners.

Other areas of application: Bicycle hoses, inner layers of tubeless tyres, acid protection linings, boiler seals and membranes.