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rubber
An elastic substance, i.e., one that returns to its original size after it has been stretched or compressed. Natural rubber is obtained from many plants, and commercially from Hevea brasiliensis, a tree native to South America and cultivated in Southeast Asia and West Africa. A slanting cut is made in the bark, and the milky fluid latex, occurring in the inner bark, is tapped off. The latex – an aqueous colloid of rubber and other particles – is coagulated with dilute acid, and the rubber creped or sheeted and smoked. Natural rubber is a chain polymer of isoprene, known as caoutchouc when pure; its elasticity is due to the chains being randomly coiled, but tending to straighten out when the rubber is stretched. Known to have been used by the Aztecs since the 6th century AD, and first known in Europe in the 6th century AD, it was a mere curiosity until the pioneer work of Thomas Hancock (1786-1865) and Charles Macintosh (1766-1843).
Synthetic rubbers have been produced since World War I, and the industry has developed greatly during and since World War II. They are long chain polymers known as elastomers; the main types are: copolymers of butadiene/styrene, butadiene/nitriles and ethene/propylene; polymers of chloroprene (neoprene rubber), butadiene, isobutylese, and silicones; polyurethanes, polysulfide rubbers and chlorosulfonated polyethenes. Some latex (natural or synthetic) is used as an adhesive and for making rubber coatings, rubber thread, and foam rubber. Most, however, is coagulated, and the rubber is treated by vulcanization and the addition of reinforcing and inert fillers and antioxidants, before being used in tires, shoes, rainwear, belts, hoses, insulation, and many other applications.
Related categories
• INDUSTRIAL CHEMISTRY
• ORGANIC CHEMISTRY
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