TAILIEUCHUNG - Rubber Compounding - Chemistry and Applications Part 6

Tham khảo tài liệu 'rubber compounding - chemistry and applications part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 5 Thermoplastic Elastomers Fundamentals and Applications Tonson Abraham and Colleen McMahan Advanced Elastomer Systems . Akron Ohio . I. INTRODUCTION In the fifteenth century Christopher Columbus witnessed South Americans playing a game centered around a bounceable solid mass that was produced from the exudate of a tree they called weeping wood 1 . This material was first scientifically described by . de la Condamine and Francois Fressneau of France following an expedition to South America in 1736 2 . The English chemist Joseph Priestley gave the name rubber to the material obtained by processing the sap from Hevea brasiliensis a tall hardwood tree angiosperm originating in Brazil when he found that it could be used to rub out pencil marks 2 . A rubber is a solid material that can readily be deformed at room temperature and that upon release of the deforming force will rapidly revert to its original dimensions. Rubber products were plagued by the tendency to soften in the summer and turn sticky when exposed to solvents. This problem associated with natural rubber was overcome by Charles Goodyear in the 1840s by subjecting the rubber to a vulcanization after Vulcanus the Roman god of fire process. Natural rubber was vulcanized by heating it with sulfur and white lead lead monoxide 2 . In May 1920 the German chemist Hermann Staudinger published a paper that demonstrated that natural rubber was composed of a chain of isoprene units that is a polymer from the Greek poly many and mer part of isoprene 3 . In vulcanization the rubber macromolecules are chemically bonded to one another cross-linked in a thermosetting process to form a three-dimensional network composing a giant molecule of infinite Copyright 2004 by Taylor Francis molecular weight. At present the word rubber is associated with macromolecules that exhibit glass transition below room temperature and have long-chain organic carbon-based backbones or inorganic backbones typified by polysiloxanes .

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