rubber
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A rubber plantation in Kerala, India. The automotive industry of the early 20th century remained entirely dependent on natural rubber for its tyres and other components, until World War II. After Japan entered the war in 1941, most Asian rubber sources were cut off from the Allies. In response, the USA and the USSR cultivated alternative sources of natural rubber and then developed synthetic rubber. Although the natural rubber industry revived when the war ended, production of natural rubber was surpassed in the early 1960s by the improved synthetic alternatives, which now represent some 60% of all rubber production.
Coagulated latex of a variety of plants, mainly from the New World. Most important is Para rubber, which comes from the tree Hevea brasiliensis, belonging to the spurge family. It was introduced from Brazil to Southeast Asia, where most of the world supply is now produced, the chief exporters being Peninsular Malaysia, Indonesia, Sri Lanka, Cambodia, Thailand, Sarawak, and Brunei. At about seven years the tree, which may grow to 20 m/60 ft, is ready for tapping. Small cuts are made in the trunk and the latex drips into collecting cups. In pure form, rubber is white and has the formula (C5H8)n.
Plant rubber
Other sources of rubber are the Russian dandelion Taraxacum koksagyz, which grows in temperate climates and can yield about 45 kg/100 lb of rubber per tonne of roots, and guayule Parthenium argentatum, a small shrub which grows in the southwestern USA and Mexico.Treatment
Early uses of rubber were limited by its tendency to soften on hot days and harden on colder ones, a tendency that was eliminated by Charles Goodyear's invention of vulcanization in 1839.Synthetic rubber
In the 20th century, world production of rubber increased a hundredfold, and World War II stimulated the production of synthetic rubber to replace the supplies from Malaysian sources overrun by the Japanese. There are a variety of synthetic rubbers adapted to special purposes, but economically foremost is SBR (styrene-butadiene rubber). Cheaper than natural rubber, it is preferable for some purposes, for example in car tyres, where its higher abrasion resistance is useful, and it is either blended with natural rubber or used alone for industrial moulding and extrusions, shoe soles, hoses, and latex foam.rubber
Slang term for a condom.
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