tailieunhanh - Rubber Compounding - Chemistry and Applications Part 5

Tham khảo tài liệu 'rubber compounding - chemistry and applications part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 4 Butyl Rubbers Walter H. Waddell and Andy H. Tsou ExxonMobil Chemical Company Baytown Texas . I. INTRODUCTION Isobutylene-based elastomers include butyl rubber halogenated butyl rubbers star-branched versions of these polymers and the terpolymer bromin-ated isobutylene-co-para-methylstyrene. A number of recent reviews on the manufacture physical and chemical properties and applications of isobutylene-based elastomers are available 1-7 . Butyl rubber IIR is the copolymer of isobutylene and a small amount of isoprene see Fig. 1 . Patented in 1937 and first commercialized in 1943 the primary attributes of butyl rubber are excellent impermeability for use as an air barrier and good flex fatigue properties. These properties result from low levels of unsaturation in between the long polyisobutylene chain segments. Tire innertubes were the first major use of butyl rubber and this continues to be a significant market today. The development of halogenated butyl rubbers started in the 1950s. These polymers greatly extended the usefulness of butyl rubbers by having faster curing rates and increased polarity. This enabled covulcanization with general-purpose elastomers such as natural rubber NR butadiene rubber BR and styrene butadiene rubber SBR that are used in tire compounds. The enhanced cure properties do not affect the desirable impermeability and fatigue properties thus permitting development of more durable tubeless tires in which the air barrier is an innerliner compound chemically bonded to the carcass ply. Today tire innerliners are the largest application for halobutyl rubber. Both chlorobutyl CIIR and bromobutyl BIIR rubbers are used commercially. Copyright 2004 by Taylor Francis Figure 1 Butyl rubber poly isobutylene-co-isoprene . In addition to tire applications isobutylene-based elastomers good impermeability resistance to ultraviolet light degradation oxidation and ozone viscoelastic dampening characteristics and thermal stability make butyl rubbers the