Rubber, rubber is described in the Encyclopaedia Britannica, Volume 19, 1965 edition: Rubber the substance caoutchouc (q.v.), a milklike fluid that is obtained from certain tropical shrubs or tyres and then subjected to various processes of manufacture; or it may be a product of chemical synthesis. The uniqueness of rubber lies in its physical properties of extensibility and toughness. In its natural state, it is greatly affected by temperature, becoming harder when cooled (at 0 x-10 x C it is opaque) and softer when heated (above 50x C it becomes tackier and less elastic, decomposing into liquid form at 190 x-200x C). When vulcanized (i.e. heated with sulfur at 120 x-160 x C) it loses its thermoplasticity and becomes stronger and more elastic..... Chemically, rubber is a polymer of isoprene..... The term synthetic rubber is used to describe an evergrowing number of elastic materials, some of which closely resemble natural rubber while others have completely different physical properties. According to the American Standard for Testing Material, (A.S.T.M.) raw rubber is defined as crude or uncompounded rubber, either natural or synthetic. Indian Standards Institution (I.S.I) de-fines rubber as follows: Rubber in its modified state free of all diluents, retracts within one minute to less than 1.5 times its original length after being stretched at normal room temperature to twice its length and held for one minute before release. It also defines raw rubber as 'vulcanised rubber'. According to H. J. Stern in his book 'Rubber - Natural and Synthetic', V. P. Latex is composed of butadiene, styrene and vinyl pyridine in the ratio of 70: 15: 15 respectively. A synthetic latex is produced as the first stage in the manufacture of most synthetic rubbers. V. P. Latex is one such synthetic rubber latex. The Condensed Chemical Dictionary, 8th Edition, 1971, defines latex as a white free-flowing liquid obtained from some species of shrubs or trees in which microscopically small particles or globules of natural rubber are suspended in a water serum. Natural rubber latex obtained from the tree Hevea Braziliensis, contains about 60% water, 35% rubber hydrocarbon, and 5% proteins and other substances. Coagulation is prevented by protective colloids, but can be induced by addition of acetic or formic acid. Synthetic latices include polystyrene, SBR rubber, neoprene, polyvinyl chloride, etc. Both natural and synthetic latices are available in vulcanized form. It describes their uses for thin rubber products (surgeons' gloves, drug sundries); girdles, pillows, etc.; emulsion paints; adhesives; tire cord coating; rubber, natural, Dunlop India Ltd. v. Union of India, AIR 1977 SC 597: (1976) 2 SCC 241.
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