Tubeless tire innerliner

Halogenation of the isoprenyl unit provides enhanced cure reactivity to the rubber molecule, increases the covulcanizability and adhesion to unsaturated tire elastomers, and opens the field of tubeless tire innerliners. 

Halobutyl rubber is used mostly to make the innerliner compound for today s modern tubeless tires. This is because halobutyl rubber is compatible with general-purpose rubbers, can be covulcanized with them, and can impart good adhesion to them. Virtually all tubeless tire innerliners use halobutyl rubber. 

Butyl and Halobutyl Rubber. Butyl mbber is made by the polymerization of isobutylene a small amount of isoprene is added to provide sites for curing. It is designated HR because of these monomers. Halogenation of butyl mbber with bromine or chlorine increases the reaction rate for vulcanization and laminates or blends of halobutyl are feasible for production of mbber goods. It is estimated that of the - 100 million kg of butyl (UR) and halobutyl (HIIR) mbber in North America, over 90% is used in tire apphcations. The halogenated polymer is used in the innerliner of tubeless tires. Butyl mbber is used to make innertubes and curing bladders. The two major suppHers of butyl and halobutyl polymers in North America are Exxon and Bayer (see ELASTOLffiRS,SYNTHETIC-BUTYLrubber). 

Halobutyls, which can easily covulcanize with high-unsaturation rubbers, are used in innerliners for tubeless tires as component for sidewalls of passenger-car tires and for heat-resistant truck inner tubes. Other applications involve a variety of sealant tapes, caulks, and pharmaceutical closures. 

Halogenated butyl rubber greatly extended the usefulness of butyl rubber by providing much higher vulcanization rates and improving the compatibility with highly unsaturated elastomers, such as natural rubber and styrene-butadiene rubber (SBR). These properties permitted the production of tubeless tires with chlorinated or brominated butyl innerliners. The retention of air pressure (5) and low intercarcass pressure (6) extended tire durability. 

Kaolin is primarily used in the rubber industry as a filler and is frequently used in the calcined form. It is being widely used in innerliner compound in the tubeless tire industry. Use of kaolin in glass fiber reinforced thermosets improves surface quality, reduces warpage, and lowers crack formation. Kaolin is used in polyvinyl chloride (PVC) wire coating because of its good electrical insulating properties. Surface-treated calcined kaolines are used for tire wheel cap made from polyamides (PA) and greenhouse films from LDPE [7[. 

The primary application for halobutyl rubber is in tires. The combination of low gas and moisture permeability, high heat and flex resistance, and ability to covulcanize with highly chemically unsaturated rubber has secured the use of these rubbers in the innerliners of tubeless tires. Passenger tires use chlorobutyl alone or in a blend with 20 to 40% natural rubber. High-service steel-belted truck tires use 100% bromobutyl innerliner compoimds. Chlorobutyl is also used for truck inner tubes for its superior heat resistance compared to butyl rubber. Halobutyl rubbers are added to sidewall compounds for improved ozone and flex resistance, and to certain tread compounds for improved wet skid resistance and traction. 

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