IIR O-rings

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Butyl rubber, sometimes referred to simply as butyl, is a synthetic rubber, a copolymer of isobutylene and isoprene. The abbreviation IIR stands for isobutylene isoprene rubber.

Polyisobutene, also known as PIB or polyisobutene, is the homopolymer of isobutylene, or 2-methyl-1-propene, on which butyl rubber is based.

Butyl rubber is produced by polymerization of approximately 98% isobutylene with approximately 2% isoprene. Polyisobutylene is structurally similar to polypropylene, but it has two methyl groups that are substituted on each other carbon atom instead of one. Polyisobutylene is a colorless to slightly yellow visco-elastic material. It is generally odorless and tasteless, although it may have a slight characteristic odor.

After isobutylene and polyisobutylene were already discovered, it was later developed into butyl rubber in 1937 by researchers William J Sparks and Robert M Thomas in the Standard Oil of New Jersey laboratory in Linden, NJ. Today, most of the worldwide supply of butyl rubber is produced by two companies. Exxonmobil and Polymer Corporation.

In the 1950s and 1960s, halogenated butyl rubber (halobutyl) was developed, in the chlorinated (chlorobutyl) and brominated (bromobutyl) variants, with considerably higher curing speeds and covulcanization with other rubbers such as natural rubber and styrene-butadiene rubber. Halobutyl is today the most important material for the inner linings of tubeless tires.

Benefits IIR:
• Excellent low gas permeability
• Good flexibility
• Good electrical properties
• Good chemical resistance
• Good moisture resistance
• Good wear resistance
• It can function for a longer time at -50 degrees to +120 degrees
• It has good ozone and aging resistance
• Excellent air impermeability
• Good flex properties
• Is known for its high degree of gas tightness
• Good weather resistance
• Resistant to acids and alkalis oxidation sunlight

Downsides of IIR:
 - Cannot be used with mineral oils