Halobutyl

Halobutyl refers to a halogenated derivative of butyl rubber, typically produced by chlorination or bromination of polyisobutylene-based butyl rubber. By introducing chlorine or bromine into the polymer, halobutyl chains gain increased chemical resistance and a reduced level of unsaturation. The halogenated grades are usually described as chlorinated or brominated halobutyl rubber, with the extent of halogenation tailored to desired properties.

Production and composition

Halobutyl is formed from standard butyl rubber (an isobutylene–isoprene copolymer) via controlled halogenation. The process lowers the polymer’s unsaturation, enhancing barrier properties while maintaining elasticity. The resulting material can be compounded with conventional vulcanization systems, though halogenation can influence cure chemistry and accelerators.

Key properties

Halobutyl exhibits superior gas and moisture barrier performance compared with non-halogenated butyl rubber, contributing to reduced gas permeability and improved aging resistance. It retains flexibility at low temperatures and offers better chemical and ozone resistance. The halogen content affects cure behavior and processability, with highly halogenated grades requiring adjustments to vulcanization formulations.

Applications

The principal use of halobutyl is in tire innerliners and inner tubes, where low gas permeability helps minimize spoilage and loss of pressure. Additional applications include seals, gaskets, protective coatings, and certain medical and pharmaceutical components that benefit from barrier properties and chemical resistance.

Safety and handling

As with other halogenated polymers, halobutyl should be handled in accordance with standard industrial hygiene practices. Combustion of halogenated polymers can release halogen acids; appropriate controls and ventilation are advised during processing and disposal.