Halobutylrubber

Halobutylrubber is a synthetic elastomer derived from a halogenated butyl polymer. The polymer backbone is a linear saturated hydrocarbon chain, in which one or more hydrogen atoms on the butyl side groups are replaced with halogen atoms such as chlorine or bromine. The presence of these halogen atoms increases the thermal stability, resistance to ozone and aging, and improves the oil and fuel resistance of the material. The halogen content is usually in the range of 5 % to 30 % by weight, depending on the intended application.

Manufacture of halobutylrubber commences with the production of a halogenated butyl monomer, typically via chlorination or bromination of butyl rubber. The monomer is then polymerised in a bulk or solution process, often with a chain transfer agent to control the molecular weight. After polymerisation the material is processed by extrusion, molding or compounding with additives such as carbon black, plasticizers and antioxidants. Dilution by conventional rubber oils can reduce viscosity and tailor the mechanical properties.

The elastomer exhibits excellent abrasion resistance and impermeability to gases and vapors. Its low permeability to fuels and oils makes it useful in fuel hoses, seals, and gaskets for automotive, aerospace and industrial equipment. The halogenation also imparts a degree of flame retardancy, limiting ignition rates in certain applications. However, the addition of halogens can lower weatherability and render the material more susceptible to mechanical failure in abrasive environments if not properly reinforced.

Halobutylrubber is typically compared with conventional neoprene, EPDM and standard butyl rubber. Compared to butyl rubber, it offers higher solvent resistance but at a higher cost. Compared to neoprene, it has lower flexibility and higher flammability. Regulations on halogenated polymers in some regions have limited its usage or necessitated post‑processing treatments to reduce halogen release. Nonetheless, it remains a relevant material for specialized seals and gaskets where its unique blend of chemical resistance, thermal stability and low permeability is indispensable.