Rubber, halobutyl

The major reason that butyl rubber is used in the tire industry is its superior resistance to air permeability, as weii as other gases. Butyi has approximately 13 times greater resistance to air permeability than natural rubber. This makes it ideal for use in making tire innerliners and inner tubes. While some polar specialty elastomers can also provide good air permeability resistance, they are far more expensive and generally do not possess the right combination of other needed properties. 

Butyl rubber, because of its chemical structure, imparts high damping properties in dynamic applications where energy absorption is needed in automotive and other applications. In addition, certain grades of butyl are used in medical applications. 

Butyl is also used in the manufacture of sealants and caulking materials. Special FDA-approved grades of butyl rubber are used in chewing gum. 

Because of butyl rubber s unique resistance to air permeability, its use is very important. It is very difficult to substitute with another elastomer, especially when those elastomers cost more. 

Tight Supply Situations in the Past and Future Supply Outlook 

4 - spreader 5 - packing 6 - static mixer and 7 - output connection for the 

The processes of washing, neutralisation, and stabilisation of the halogenated elastomer also occur in turbulent flow motion by the introduction of an appropriate agent. 

6 - neutraliser 8 - additional washing reactor 10 - stabilisation reactor 2, 5, 7, 

9 - separation chambers and 3 - pump. Flows I - halogen II and IV - water  

The process may easily be transformed for the synthesis of other elastomers and copolymers with a double bond in the backbone of the monomer unit. Therefore, the range of elastomers is extensive isoprene, butadiene, butadiene-styrene rubbers, ethylene-propylene terpolymer, and so on. 

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Butyl and Halobutyl Rubber. Butyl mbber is made by the polymerization of isobutylene a small amount of isoprene is added to provide sites for curing. It is designated HR because of these monomers. Halogenation of butyl mbber with bromine or chlorine increases the reaction rate for vulcanization and laminates or blends of halobutyl are feasible for production of mbber goods. It is estimated that of the - 100 million kg of butyl (UR) and halobutyl (HIIR) mbber in North America, over 90% is used in tire apphcations. The halogenated polymer is used in the innerliner of tubeless tires. Butyl mbber is used to make innertubes and curing bladders. The two major suppHers of butyl and halobutyl polymers in North America are Exxon and Bayer (see ELASTOLffiRS,SYNTHETIC-BUTYLrubber). 

FIGURE 14.10 Reaction of Perkalink 900 with halobutyl rubber (XIIR) in the presence of zinc oxide. 

Polyisobutylene rubber Butyl rubber Halobutyl rubber Polyepichlorohydrin Polypropylene Polypropylene oxide... 

See also Tire compounding antidegradants in, 21 785—790 antioxidants in, 21 789 butyl and halobutyl rubber in, 21 766 elastomers used in, 21 759—772 ethylene-propylene rubber in, 21 765-766... 

In summaiy, theie aie a lange of vulcanizing systems which can be used for natural rubber, and the choice is dependent on the combination of properties required. No single one offers ideal, all-around properties combined with good heat resistance. The end user has to be selective, according to the properties required foi the final application. Certain properties such as oil resistance and gas permeability have been omitted from Table 3, because in legaid to these properties natural mbbei is substantially inferior to synthetic mbbers such as acrylonitrile rubber and halobutyl rubber (see Elastomers,... 

Elastomer Natural rubber Halobutyl rubber Dimethylpolysiloxane polymer EPDM... 

Typical halogenation processes for making halobutyl rubbers involves the injection of chlorine or bromine into a solution of butyl rubber. The reactants are mixed vigorously in the halogenation reactor with a rather short resident time, typically less than 1 min, followed by the neutralization of the HC1 or HBr and removal of the unreacted halogen (13). The procedures of halogenation have been described in detail elsewhere (41,42). 

Table 1 Approximate structural composition (%) of halogenated isoprenyl units in halobutyl rubbers...

Several conclusions have to be drawn. The first is related to the obvious gap between the empiricism and even archaism of most of industrial cationic polymerization processes and the level of fundamental science devoted for decades to these reactions. Previous chapters in this volume clearly illustrate the situation. This feature was pointed out in the early book of Kennedy and Marechal [1], and the explanation based on the very favorable price/performances characteristics of the products is still realistic. Nevertheless it is noteworthy that recent improvements or new processes based on more scientific approaches led to a better control of the polymerization, of polymer structure, and to high-performance commercial products which will increasingly occupy the market. This is the case for the recently marketed reactive BF3-based polybutenes with high content of exomethylenic chain ends, for the strongly developing pure monomer hydrocarbon resins ( + 8% in 1994), or for the new benzyl halide-based halobutyl rubber, and it is revealing that these products represent the three families of cationically prepared industrial polymers... 

J. Duffy and G. J. Wilson, Synthesis of butyl rubber by cationic polymerization, Vol. A23, pp. 288-294 Halobutyl rubber, Vol. A23, 314-318, Ull-mann s Encyclopedia of Industrial Chemistry, 5th Ed., VCH Publishers, Weinheim, 1993. 

J. V. Fusco and P. Hous, Butyl and halobutyl rubbers, Rubber Technology... 

Figure 5-16. Physical stress relaxation at 25 °C in a crosslinked network made by a zinc oxide cure of a halobutyl rubber. The elastomer has been soaked in oil to speed the relaxation. The line is the fit to the data using the Chasset-Thirion equation with E =0.018 MPa, t= 1.04 s and m = 0.31. The nature of the polymer and the cure makes for a chemically stable structure otherwise, the plot would begin to curve downward at long time.

A variety of synthetic rubbers are commercially used styrene-butadiene rubber (SBR), polybutadiene, ethylene-propylene rubber, butyl and halobutyl rubber, etc. The most important is SBR, which is mainly used as a major component of all passenger tyres and in significant amounts in most tyre products. 

Butyl rubber consists mostly of isobutylene (95-98%) and about 2-5% isoprene units. 1 The isoprene unit is halogenated by either chlorine or bromine to obtain the corresponding halobutyl rubbers. Despite the superior elastomeric properties of halobutyl, the elastomer can easily undergo dehydrohalogenation leading to crosslinfang, and the isoprene unsaturation is subject to ozone cracking. To remedy these problems and to improve the halobutyl properties, a new class of elastomer poly(isobutylene-co-p-methylstyrene) [poly (IB-PMS)] was developed. Unlike butyl rubber, it contains no double bonds and therefore cannot be crosslinked unless otherwise functionalized. The chemical structures of butyl rubber and poly (IB-PMS) copolymers are shown below. 

The accelerated-sulfur vulcanization of these rubbers along with the vulcanization of other rubbers, which are vulcanized by closely related technology, comprises more than 90% of all vulcanization. These rubbers include ethylene-propylene-diene-monomer rubber (EPDM), butyl rubber (HR), halobutyl rubbers, and nitrile rubber (NBR). Nevertheless, we give some consideration to vulcanization by the action of other vulcanization agents such as organic peroxides, phenolic curatives, and quinoid curatives. 

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)... 

Isobutylene and isoprene are in a ratio of approximately 50 1. Chlorobutyl rubber and bromobutyl rubber are produced by the halogenation of butyl rubber. Butyl rubber and halobutyl rubber are highly impermeable to air and show very low water absorption, and good heat, oxygen and ozone resistance. As noted earlier, they therefore find extensive use in liners of radial tires, covers and insulation of high-voltage electric cables, and automobile engine and radiator hoses. 

Halobutyl rubber is one of the butyl rubber (BR) modifications (chlorinated (CBR) and bromated (BBR) rubbers) the main advantage of which is its ability to vulcanize with any types of... 

Poly(isobutylene), butyl rubber, halobutyl rubber... 

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