Rubber, Caoutchouc

Vulcanization.—The most important treatment of rubber, in the process of converting it into a technically valuable product, is that known as vulcanization. This consists in the addition of sulphur which produces a very definite change in properties. The sticky or adhesive character of pure caoutchouc is entirely lost and it becomes very elastic and does not set when stretched. Even with wide range in temperature it neither hardens nor softens and it becomes insoluble in caoutchouc solvents. The presence of sulphur, usually in small 

As to whether the addition of sulphur is a chemical or physical change we shall say little. Evidence appears on both sides and all we need say here is that, in whichever manner the sulphur really acts, it affects the caoutcHouc in a very definite way, is absorbed by it, remains there in some kind of union and is unable to be removed by sulphur solvents. The amount of sulphur thus definitely held by the caoutchouc is about 3 per cent, in the case of soft rubber, while in hard rubber it may be as much as 32 per cent. In both cases more than this amount of sulpher is usually present but the excess is as free sulphur which may be removed by solvents. 

Constitution. Synthesis.—The constitution and synthesis of caoutchouc is connected with two of the terpene hydrocarbons previously mentioned. It has been stated that caoutchouc is a hydrocarbon of the composition (CsHg). As this is the formula for certain of the terpenes we should naturally expect to find that caoutchouc is itself a member of this group. 

Isoprene.— As early as i860 it was found that caoutchouc on distillation yielded a terpene hydrocarbon to which the name isoprene (p. 162) was given by its discoverer Williams, an Englishman. With the isoprene another hydrocarbon was also obtained which was given 

The synthesis of caoutchouc from other compounds than the ter-penes themselves was made possible by two syntheses of isoprene which established its constitution. These syntheses were by Ipatiew and Euler in 1897-98. The synthesis of Ipatiew was from di-methyl tri-methylene di-bromide or di-brom iso-pentane which is 2-methyl 2-4-di-brom butane. The reactions are as follows two products being obtained one of which is isoprene  

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Gummi, n. gum (India) rubber, caoutchouc. (For compounds see also under Kautschuk-.) -abf e, m.pl. scrap rubber, -arabicum, gum arable, -art, /. variety of gum, gum kind of rubber. 

Tire industry copolymer of styrene and butadiene in 1 3 ratio SBR Rubber caoutchouc (isopr. polymer)... 

Rubber [Indian rubber, caoutchouc, from (South American) Indianic language caa=tears and ochu= tree or cahuchu=crying tree]. R. is the name (according to DIN 53501, 11/1980) for non-cross-linked but cross-linkable (vulcanizable) polymers with rubber-elastic properties at room temperature. At higher temperatures or under the action of deforming forces R. show viscous flow. Thus, under suitable conditions, R. can be processed into specific shapes. They are the starting materials for the manufacture of elastomers and other rubber products. 

Isoprenoids with more than eight isoprene units are classified as polyterpenes Natural rubber (caoutchouc), formerly an important raw material for the rubber industry, is primarily obtained by coagulating the milk juice (latex) of Hevea bra-siliensis (Euphorbiaceae) growing in the Amazonian area of Brazil and southeastern Asia. It consists essentially of c -polyisoprene. The milky juice is an emulsion of this polyterpene in water stabilized by proteins as protecting colloids. 

Resin, Acrylic (Series Of Additives) a 631-2897 Rubber, Caoutchouc ... 

Rubber, natural (India rubber, Caoutchouc) n. An amorphous polymer consisting essentially of ds-1,4-polyisoprene, obtained from the sap (latex) of certain trees and plants, mainly the Hevea brasiliensis tree. The material is shipped from tropical plantations in one of two primary forms latex, usually stabilized and preserved with ammonia and centrifuged to remove part of the water or sheets made by milling the coagulum from the latex. Natural rubber has very high molecular weight and is usually masticated to reduce the molecular weight and improve processability. A major use is sidewalls of automotive tires. 

In 1802, almost four decades before the discovery of the process of curing (vulcanization) natural rubber by Charles Goodyear, a blind scientist used his other senses such as his lips, to detect the increase in temperature when a band of india rubber (caoutchouc) was stretched. Tbis increase in temperature could not be detected by the crude thermometers that were available in the early 19th century but was readily detected by Gough s sensitive lips. 

The study of the physical and chemical properties of rubber has received a decided impetus as a result of recent developments in colloidal chemistry, for it cannot be denied that in caoutchouc, the fundamental substance from which commercial rubber is ma de, we have a typical colloidal body. Many of the processes in the manufacture of both the crude rubber, caoutchouc, and the finished product, rubber, such as the coagulation of the latex, find no explanation from the purely crystalloidal chemical standpoint. Unfortunately in the discussions on the subject it has not always been recognized that in most instances both the colloidal and crystalloidal processes take place simultaneously. Consequently important facts are often ignored by the extreme advocates of the colloidal and the purely chemical schools. Only by a proper perspective involving both views, can we arrive at the true explanation of many of the phenomena connected with the chemistry of rubber. 

Indian rubber/caoutchouc Naturkautschuk, natttrliches Gummi... 

Indian rubber/ caoutchouc Naturkautschuk, natiirliches Gummi... 

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