Rubber
. Rubber, natural or synthetic substance characterized by elasticity, water repellence, and electrical resistance. Natural rubber is obtained from the milky white fluid called latex , found in many plants; synthetic rubbers are produced from unsaturated hydrocarbons . NATURAL RUBBER In its natural state, rubber exists as a colloidal suspension in the latex of rubber-producing plants (see Colloid ). The most important of these plants are the tree Hevea brasiliensis of the spurge family, and other species in the same genus, which were the sources of the original South American rubber, the commercially important Para rubber. The term Para rubber was then also applied to the product of H. brasiliensis trees cultivated in the rubber plantations of Indonesia, the Malay Peninsula, and Sri Lanka. These trees produce about 90 percent of all the new natural rubber consumed. Crude rubber from other plant sources is generally contaminated by an admixture of resins that must be removed before the