Halogenated butyl rubbers applications

Bis-alkylating systems, such as those which may be used to crosslink polychloroprenes, may be used to vulcanize halogenated butyl rubbers but are not known to be used commercially. Similarly quinone dioximes will also cross-link but are not known to have any practical application. 

Application of the silver halide precipitation method to halogenated butyl rubbers in cyclic ether and comparison with results of graft co-polymerlzatlon studies from the same backbones. 

As mentioned in Section 8.1.1, ethylene-propylene elastomers are currently used in compounds for tyre sidewalls. In this application also ternary blends have been used, including halogenated butyl rubber.With regard to EPDM and butyl rubber blends, there are no covulcanisation problems because both have a similar level of unsaturation. 

Modified butyl rubbers—the crosslinked butyl and halogenated butyl rubbers—all possess the shock absorbency, stability and gas barrier properties that are characteristic of standard butyl rubbers. However, they differ from each other, and from standard butyl rubbers, in terms of the variables that distinguish standard butyl rubbers from each other, and in respects related to the types, amounts and functions of their modifiers. The crosslinked butyl rubbers resist flow, which is an important requirement in uncured sealant tape, their primary application. The halogenated butyl rubbers cure much faster than standard or crosslinked butyl rubbers, use less complicated curing systems and can be covulcanised with highly unsaturated elastomers. 

Where there is a need for very rapid cures coupled with optimum resistance to heat, weather and ozone, or for maximum adhesion to highly unsaturated elastomers, the halogenated butyl rubbers should be considered. Table 3 lists examples of appropriate selections of elastomers by unsaturation level, for a variety of applications. 

Chemical reactions are used to modify existing polymers, often for specialty applications. Although of considerable importance for plastics, very few polymer reactions (aside from crosslinking) are important for elastomers. Chlorination and bromination of Butyl rubber to the extent of about one halogen atom per isoprene unit yields elastomers which are more easily crosslinked than Butyl rubber. Substitution occurs with rearrangement to yield an allylic halide structure... 

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 (HR) and halobutyl (HIIR) mbber in North America, over 90% is used in tire applications. The halogenated polymer is used in the innerliner of tubeless tires. Butyl mbber is used to make innertubes and curing bladders. The two major suppliers of butyl and halobutyl polymers in North America are Exxon and Bayer (see ELASTOLffiRS, synthetic-butyl rubber). 

---