Caoutchouc latex

Rubber is obtained from the juice of various tropical trees, mainly the tree Hevea brasiliensis. The juice is a latex consisting of a dispersion of polymer phase at a concentration of about 35% by mass, together with traces of proteins, sterols, fats, and salts. The rubber is obtained either by coagulation of the latex with acid, either ethanoic or methanoic, or by evaporation in air or over a flame. The material that results from this process is a crumbly, cheeselike substance, sometimes called raw rubber or caoutchouc. In order to... 

Rubber or caoutchouc is obtained by coagulation of the latex of numerous plants belonging to different families, principally to the Euphorbiaceae, Artocarpeae and Apocyneae. Whatever its origin and method of preparation, its value depends essentially on the content in hydrocarbons pure rubber) and on the substances accompanying it (resinous matters, various impurities). 

The selection of factors from the work [16] was done hy the significance of their effects on caoutchouc drying and after processing the opinions of eighteen researchers. The analysis included these eleven factors Xi inlet and outlet moisture ratio X2 pH value in the sixth apparatus X3 pH value in the seventh apparatus X+ NaCl consumption X5 serum consumption in the sixth apparatus X6 serum consumption in the seventh apparatus X serum temperature X8 latex type X9 fat content in caoutchouc X10 latex fat consumption on machine and Xu quantity of latex on the surface. Outcomes of the ranking of the factors are shown in Table 2.16. Determine the concordance coefficient and check its significance. 

Source.—The common substance which is known as rubber is the product obtained by the coagulation of the juice or latex which is present, usually in the bark, but sometimes in the woody tissue, of certain tropical or sub-tropical trees, shrubs and vines. Gutta-percha is a variety of rubber differing in physical properties. The chemical individual present in rubber is a terpene hydrocarbon known as caoutchouc. 

Coagulation of the Latex.—Pure rubber or caoutchouc is an emulsion colloid and in most cases is held in emulsion by the protective action of other colloids, principally proteins. The breaking up of the emulsion with the coagulation of the caoutchouc depends thus upon the removal or destruction of the protective colloids. This is accomplished by different means. The latex of the para rubber from the Amazon is coagulated by heat and smoke, while the latex from the same species of tree on the plantations of the Malay States is usually coagulated by treatment with acid. Boiling of the latex, the addition of formaldehyde, and simple dilution with water are other methods in use. Enzymes are also present associated with the protective colloid proteins but their function seems not to be connected with the coagulation of the caoutchouc. 

Latex.—This is an emulsion of xfirying composition and color found in special passages, as latex cells and laticiferous vessels of many plants. It may contain starch, sugar, proteid, oil, enzymes, tannins, alkaloids, gum, resins, caoutchouc and mineral salts. The color may be absent as in Oleander-, whitish as in Asclepias, Papaver, Hevea, and Apocynum yellowish to orange as in Celandine, or red as in Sanguinaria. 

Genin, G., Chimie et Technologie du Latex de Caoutchouc, Paris, Rev. gin. caoutchouc,... 

The modem elastomer industry was founded on the naturally occurring product isolated from the latex of the tree Hevea brasiliensis. It was first used by indigenous South Americans and was called caoutchouc, but, later, simply rubber, when it was discovered by Priestley that the material robbed out pencil marks. 

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. 

Phytochemistry The plant contains a large amount of latex, which contains 1.5 % caoutchouc, resins, and euphorbin (Pavlov 1947). The plant contains triterpenes and polyphenols (quercetin-3-galactoside, kaempferol, gallic acid, etc. Azimov and Nazirov 1969,1970 Abdulladzhanova et al. 2003). 

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. 

Amyrin a pentacyclic triterpene alcohol with one double bond. a-A. (a formal derivative of the hydrocarbon, 5-a-ursane) is found free, esterified and as the aglycon of triterpene saponins of many plants, and has been isolated from many latexes, e.g. latex of the dandelion. Taraxacum officinale. P-A. (P-amyrenol, a-viscol) (a formal derivative of the hydrocarbon, 5-a-oleane) is present in mistletoe leaves, grapeseed oil, latex of Taraxacum officinale it is found free, esterified and as the aglycon of triterpene saponins in many other plants, especially in species which yield caoutchouc and gutta percha. 

Caoutchouc elastic, high molecular mass polyter-penes, which can be converted into rubber by vulcanization. Natural C. is a mixture of polyisoprenoids with varying molecular masses, ranging from 300,000 to 700,000. According to X-ray and IR data, the double bonds are cis oriented, whereas in the C.-like polyterpenes, gutta and balata, they are trans. Hundreds of species of plants contain C in their latex, but it can only be obtained on a large scale from a... 

Natural Rubber Natural rubber, also called India rubber or caoutchouc, is an elastomer that is derived from latex, a milky colloid mainly extracted from rubber trees (Figure 5.1.35). The purified form of natural rubber is polyisoprene, which can also be produced synthetically. Natural rubber is used extensively in many applications and products, as is synthetic rubber. Today, the global annual production of natural rubber is 10 Mio. tonnes, which is about 40% of the total rubber production (natural and synthetic). The three largest producing countries of natural rubber are Thailand, Indonesia, and Malaysia. 

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. 

The latex from which caoutchouc is obtained is a milk-like fluid differing somewhat in its properties according to its origin. Biologically it is the sap of certain trees or shrubs chemically it is a disperse system consisting of globules of caoutchouc suspended in a watery liquid. 

Size of the Particles. — The suspended globules of caoutchouc found in the latex vary in rize within comparatively wide limits. Those of Hevea have been found by Fickendey to have a diameter of 0.5-2.5iu. On the other hand, few particles in the latex of Funtumia have a diameter as great as O.Im, and the milk appears almost homogeneous under the most powerful microscope. 

The objections to be raised against the first and third methods, viz, heating and smoking, and evaporation, are that many of the undesirable constituents such as dirt, bark, resin, protective colloids, etc., are left in the coagulant, caoutchouc. Some of these substances can be removed, of course, by subsequent treatment such as grinding and washing, drying in air or vacuo, but mineral matter, resins, and proteins still remain and cannot be eliminated except by expensive processes. It must be confessed, however, that Para rubber obtained by the natives of Brazil is superior to that made by the most scientific methods yet devised on plantations. It is a matter not yet decided whether the superiority of Para rubber is due to the method, or to the inherent qualities of the latex. 

G. Stafford Whitby was a towering figure in rubber science from the earliest days of the 20 century to his death in 1972. He was very precocious and entered The Royal College of Science in London at 16. Upon graduation he continued in the laboratory of Sir William Tilden. In 1910 he was sent to Sumatra to study the production of natural rubber with the Societe Financiere des Caoutchoucs. He learned the rubber business from the ground up and made major contributions to the understanding of the chemical behavior of the raw latex (Fig. 5.4). 

The term used by Mesoamericans to describe rubber latex was cahuchu, meaning the milk of the tree. French explorer, Charles MariedeLacondamine, who brought a sample of rubber back to France from Peru, translated the term to caoutchouc in French. 

---