Polymer bromobutyl/butyl rubber

Synonyms BIIR Brominated butyl rubber Brominated isobutylene/isoprene copolymer Bromobutyl rubber 1,3-Butadiene, 2-methyl-, polymer with 2-methyl-1-propene, brominated Butyl rubber, brominated Isobutylene, isoprene polymer, brominated Definition Elastomer vulcanized by sulfur systems vulcanizate offers low gas permeability, good weather/ozone resist., better chem./heat resist, than butyl rubber... 

Chlorobutyl Rubber and Bromobutyl Rubbers (CIIR and BUR). The addition of chlorine or bromine to HR in an inert solvent (e.g., hexane) gives the facile attachment of one halogen atom per isoprene unit in the allylic position. Compared with HR, the halogenated butyl rubbers have certain advantages. The cure reactivity is increased to give faster vulcanization rates, greater extents of vulcanization, and reduced reversion. Also, the halo-genation improves the compatibility of the isoprene polymer with other types of rubber (e.g., NR) to make useful rubber-blend compositions possible. 

In bromobutyl/chlorobutyl rubber blends, both elastomers have the polyisobutylene backbone and halogen reactive functionality. These polymers, being molecularly miscible, constitute an ideal system for co-vulcanization. Bromobutyl and chloro-butyl can be used interchangeably without significant effect on state of cure as measured by extension modulus, tensile strength, and cure rheometer torque development. Bromobutyl will increase the cure rate of a blend with chlorobutyl. However, where bromobutyl is the major part of the blends, chlorobutyl does not reduce scorch tendencies because the more reactive halogen unit can dominate. 

Manufacturers AkzoNobel Recommended for polymer bromobutyl and butyl rubber, EPDM, EVA, HDPE, LDPE, LLDPE, PA, PP, SBR, natural rubber ... 

Saturated polymers such as butyl and ethylene-propylene-diene terpolymer are more difficult to bond and generally exhibit lower bond strengths compared to those found with the general purpose polymers. Once a degree of functionality is introduced into the polymer such as with chloro or preferably bromobutyl rubber and chlorosulfonated polyethylene (Hypalon ) then the ability to bond is enhanced. 

The manufacture of halobutyl rubbers such as Bromobutyl, Chlorobutyl, and Exxpro [bromopoly(isobutylene-co-/j-methylstyrene)] requires a second chemical reaction the halogenation of the polymer backbone. This can be achieved in two ways, the finished polymer produced in the butyl plant can be dissolved in a hydrocarbon solvent such as hexane or pentane, or a solvent replacement process can be used to dissolve the polymer from the slurry leaving the reactor. A schematic flow diagram of the halogenation process is shown by Figure 2. 

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