caoutchouc

caoutchouc, natural rubber obtained as a latex from various tropical plants, e.g., the Pará rubber tree. It is much more elastic than balata or gutta-percha. It is the most familiar and widely used of the natural rubbers. It is usually processed by coagulating the latex and by milling or smoking the solid rubber. It is then further treated, e.g., by vulcanization, to produce useful articles.

or India rubber plant

Tropical tree (Ficus elastica) of the mulberry family. The rubber plant is large in its native Southeast Asia and other warm areas; elsewhere it is commonly grown indoors as a potted plant. The plant has large, thick, oblong leaves and pairs of figlike fruits along its branches. The milky sap, or latex, was once an important source of an inferior natural rubber. Young plants available in the florist's trade are durable and grow well under less-than-ideal indoor conditions. Some cultivated varieties have broader, darker green leaves; others are variegated. Seealso rubber tree.

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Flexible material that can recover its shape after considerable deformation.The best-known rubber is natural rubber, made from the milky latex of the rubber tree (Hevea brasiliensis). Natural rubber is still important industrially, but it now competes with synthetic alternatives (e.g., neoprene, silicone) derived from petroleum, natural gas, and other source materials. Rubber's usefulness is based on the unique elasticity of its constituent polymer molecules (built of thousands of isoprene monomers; see isoprenoid), which are capable of returning to their original coiled shape after being stretched to great extents; it is made more durable by vulcanization with sulfur or another agent that establishes chemical cross-links between the polymers. Fillers and other additives allow tailoring of properties to the desired use (e.g., by foaming, shaping, and curing). More than half of all rubber goes into making tires; the rest is used principally in belts, hoses, gaskets, shoes, clothing, furniture, and toys.

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See Natural rubber