Halobutyl-based compounds

Critical to a tire s life cycle performance is the ability to maintain air pressure. Tire innerliners composed of halobutyl-based compounds exhibit very low air and moisture permeability. Therefore, tires built with the proper selection of compounds can reduce the rate of premature failure, again delaying entry into the scrap tire and solid waste streams. 

Alkyl phenol disulfide accelerator is commonly used in combination with other accelerators to cure halobutyl-based compounds. This accelerator also imparts some tackiness to the compound as well, which helps in the construction of a tire or other rubber products. 

Halobutyl rubber-based compounds are attractive for use in conveyor belts, particularly for conveying hot materials or passing through high temperature zones, because they exhibit good heat, flex, tear, and... 

ISO 9924-2 2000 Rubber and rubber products — Determination of the composition of vulcanizates and uncured compounds by thermogravimetry — Part 2 Acrylonitrile-butadiene and halobutyl rubbers ISO 10356 1996 Cinematography — Storage and handling of nitrate-base motion-picture films ISO 10993-17 2002 Biological evaluation of medical devices — Part 17 Establishment of allowable limils for leachable substances... 

Halobutyl rubber (HIIR) is used primarily in tire innerliner and white sidewalls. These elastomers are best for tire air retention owing to lower air permeability as well as aging and fatigue resistance. The chlorinated (CIIR) and brominated (BUR) versions of isobutylene isoprene rubber (HR) can be blended with other elastomers to improve adhesion between HIIR compounds and those based on general purpose elastomers, and improve vulcanization kinetics [16]. 

Sandstrom and co-workers utilized the cyclized polyisoprene polymers incorporated into tyre tread compounds to improve traction, tread wear and tear resistance. Cyclized polyisoprene is further based upon the discovery that blends of cyclized polyisoprene polymers with halobutyl rubber and/or NR can be employed as tyre inner liner formulations. 

The demand for white and coloured mbber articles for various applications is steadily growing. Rubbers are, depending on their content of olefinic double bonds, very sensitive to ozone, and hence effective antiozonants are necessary. Due to their discolouring and staining effect, para-phenylenediamine antiozonants cannot be used in compounds for white or coloured articles. A survey of the effectiveness of Vulkazon AFS, a cyclic acetal providing excellent ozone protection in coloured compounds based on various elastomers, is presented. The effectiveness of the cyclic acetal is compared with paraphenylenediamine antiozonants in chloroprene, butyl and halobutyl compounds. The effect in diene rubbers, where the cyclic acetal has to be used in combination with waxes, is investigated. Cyclic acetals do not affect the peroxide cure like other antiozonants and hence the material has also been tested in peroxide-cured cable jacket compounds based on a saturated elastomer. 2 refs. 

An example of an inner liner compound based on BUR and NR is presented in Table 20. In practice, blends of halobutyl rubbers with NR or BUR + CIIR are used. A medium reinforcing carbon black such as GPF (providing adequate green strength and flow properties)... 

The technical alternatives to halobutyl rubber in tire innerliner applications are very poor, in the short term. However, with the development of new innerliner compounds based on DIMS (see below), a substitution could be achieved long term with much development work. 

If not available, a user could revert back to the thermoset innerliner compound based on halobutyl rubber, which might increase the cost of production and hurt tire performance. 

It is used as an accelerator usually in compounds based on halobutyl rubber to give better adhesion to other compounds based on general-purpose elastomers. 

Halobutyl rubbers can be blended successfully with virtually any elastomer that cures at approximately the same rate when sharing a common curing system. This capability is put to good use when there is a need to impart some measure of butyl-like properties to non-butyl compounds, to modify halobutyl compounds with other elastomers, or to reduce the cost of compounds based on more expensive elastomers. 

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