Butyl rubber halogenated form

The standard polymers used for rubber linings consist of materials that are cross-linkable macromolecules which, on mixing with suitable reactants that form strong chemical bonds, change from a soft deformable substance into an elastic material. These polymers include natural rubber and its corresponding synthetic, c/s-polyisoprene, styrene-butadiene rubber, polychloroprene, butyl rubber, halogenated butyl rubbers, acrylonitrile-... 

Forms of BR and polyisobutylene. The properties of butyl rubber and polyisobutylene depend on their moleeular weight, degree of unsaturation, nature of the stabilizer incorporated during manufacture and, in some cases, chemical modification. It is common to produce halogenated forms of butyl rubber to increase polarity and to provide a reactive site for alternate cure mechanisms [6],... 

Butyl rubber is produced at very low temperature (below — 90°C) to control the rapid exotherm, and to provide high molecular weight. The process consists of charging isobutylene along with isoprene (2-4%) with an inert diluent such as methyl chloride to a reactor to which a Friedel-Crafts catalyst is added. The polymerization is very rapid, and the polymer forms in a crumb or slurry in the diluent. Heat is removed via the reactor jacket. The slurry is steam-stripped to remove all volatiles. The catalyst is neutralized, and antioxidants are added to the slurry prior to drying.53 The halogenated derivatives are produced by the direct addition of the halogen to a solution of the isobutylene-isoprene polymer. 

Butyl rubber (HR) is an isobutylene-based rubber which includes copolymers of isobutylene and isoprene, halogenated butyl rubbers, and isobutylene/p-methylstyrene/bromo-p-methylstyrene terpoly-mers. HR can be slurry polymerized from isobutylene copolymerized with small amounts of isoprene in methyl chloride diluent at -130 to - 148°F (-90 to - 100°C). Halogenated butyl is produced by dissolving butyl rubber in a hydrocarbon solvent and introducing elemental halogen in gas or liquid state.Cross-linked terpolymers are formed with isobutylene + isoprene + divinylbenzene. 

The reagent, for example a diamine, forms covalent bonds with the polymer chains. Usually the use of catalysts is not necessary. This vulcanisation method is mainly used for the production of halogen butyl rubbers and results in materials with good chemical characteristics (few incompatibihties). 

Butyl rubbers are also available in halogen-ated form, as a low molecular weight semi-liquid, as a latex, and in various modified and... 

Butyl rubber is also available in a halogenated form with either bromine or chlorine and this often increases its thermal performance while retaining the low gas permeability to gas and moisture. 

The most prevalent approach to achieve long-lasting and nonstaining ozone protection of rubber compounds is to use an inherently ozone-resistant, saturated backbone polymer in blends with a diene rubber. The ozone-resistant polymer must be used in sufficient concentration (minimum 25 phr) and must also be sufficiently dispersed to form domains that effectively block the continuous propagation of an ozone-initiated crack through the diene rubber phase within the compound. Elastomers such as ethylene-propylene-diene terpolymers, halogenated butyl mbbers, or brominated isobutylene-co-para-methylstyrene elastomers have been proposed in combination with NR and/or butadiene rubber. 

Halogenation is the second major chemical reaction in the production of halobutyl pol5uners. It is usually carried out by adding bromine liquid or chlorine vapor to a solution of rubber in hydrocarbon solvent (hexane or pentane), which is often referred to as cement. The cement must be essentially free of monomers, or low molecular weight toxic species will be formed dining the chlorine or bromine reactions. The halogenation of the butyl backbone is an ionic-substitution reaction in which the halogen is added to the cement stream in a well-mixed reactor (eq. 1). This reaction is unusual for polymers where it s more typical for the bromine to add across the double bond. 

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