Isobutene-isoprene rubber (IIR), synthetic rubber, soft rubber, chlorobutyl and bromobutyl rubber as variants containing halogens with modified properties, high chemical resistance and high resistance to permeation, resistant to ozone and weathering
A general purpose synthetic elastomer (rubber) produced by copolymerizing isobutylene with small amounts of isoprene. Butyl rubber has a high resistance to chemicals and low permeability to gases. Its permeability to air is 70% better than that of natural rubber and for this reason is superior for tire tubes and tubeless tire inner liners.
A copolymer of about 98% isobutylene and 2% isoprene. It has the poorest resistance to petroleum oils and gasoline's of any rubber. Excellent resistance to vegetable and mineral oils: to solvents such as acetone, alcohol, phenol and ethylene glycol; and to water and gas absorption. Heat resistance is above average. Sunlight resistance is excellent. It's abrasion resistance is not as good as natural rubber. Usually low permeability to gases.
Butyl rubber—also known as polyisobutylene (C4H8) is a synthetic rubber, a homopolymer of 2-methyl-1-propene. Polyisobutylene is produced by polymerization of about 98% of isobutylene with about 2% of isoprene. Structurally, polyisobutylene resembles polypropylene, having two methyl groups substituted on every other carbon atom.