Poly isobutylene Grades

All grades of regular butyl rubber are tacky, rubbery, light amber colored solids, manufactured by copolymerizing isobutylene with less than 3% isoprene. Double bonds introduced into the macromolecule by isoprene permit the polymer to be crosslinked or vulcanized. Though butyl rubber is unsaturated relative to poly isobutylene, its 0.8-2.1 mole % unsaturation (number of isoprene units per hundred monomer units in the polymer chain) is still far less than the 100% unsaturation of natural rubber or the 60-80% unsaturation of SBR. This... 

All above grades manufactured by Exxon Chemical Company butyl and halobutyl polymers are also available from Polysar Limited and poly isobutylene polymers from BASF. 

The inherent properties of polymers of the poly isobutylene family, particularly the chemical inertness, age and heat resistance, long-lasting tack, flexibility at low temperatures, and the favorable FDA position on selected grades, make these products commercially attractive in a variety of pressure-sensitive and other adhesives, in automotive and architectural sealants, and in coatings. An added dimension is achieved in the blendability of the polyisobutylene polymers with each other and with other adhesive polymers such as natural rubber, styrene-butadiene rubber, EVA, low molecular weight polyethylene, and amorphous polypropylene to achieve specific properties. They can, for example, be blended with the highly unsaturated elastomers to enhance age and chemical resistance. A description of poly isobutylene polymer family use in adhesive and sealant applications follows. 

Poly isobutylene, PIB, is a homopolymer of high molecular weight. The butyl elastomers are copolymers of isobutylene with sufficient isoprene (0.5-2.5%) to permit crosslinking. Most butyl compositions are one-component, e.g., tapes or liquid gun-grade caulks. They may be modified with plasticizers such as polybutene, or tackifiers and fillers such as calcium carbonate and fibrous talc. Two-component, curing butyl sealants are also available. 

---