rubber

rubber¹

—rubberless, adj. —rubberlike, adj.

/rub"euhr/, n.

1. Also called India rubber, natural rubber, gum elastic, caoutchouc. a highly elastic solid substance, light cream or dark amber in color, polymerized by the drying and coagulation of the latex or milky juice of rubber trees and plants, esp. Hevea and Ficus species.

2. a material made by chemically treating and toughening this substance, valued for its elasticity, nonconduction of electricity, shock absorption, and resistance to moisture, used in the manufacture of erasers, electrical insulation, elastic bands, crepe soles, toys, water hoses, tires, and many other products.

3. any of various similar substances and materials made synthetically. Cf. synthetic rubber.

4. See rubber band.

5. an eraser of this material, for erasing pencil marks, ink marks, etc.

6. Informal. a rubber tire or a set of rubber tires.

7. a low overshoe of this material.

8. an instrument or tool used for rubbing, polishing, scraping, etc.

9. a person who rubs something, as to smooth or polish it.

10. cutter (def. 7).

11. Brit. a dishcloth.

12. a person who gives massages; masseur or masseuse.

13. swipe (def. 6).

14. Baseball. an oblong piece of white rubber or other material embedded in the mound at the point from which the pitcher delivers the ball.

15. a coarse file.

16. Slang. a condom.

v.i.

17. Informal. to rubberneck.

adj.

18. made of, containing, or coated with rubber: a rubber bath mat.

19. pertaining to or producing rubber: a rubber plantation.

[1530-40; RUB + -ER¹]

rubber²

/rub"euhr/, n.

1. (in certain card games, as bridge and whist)

2. a series or round played until one sidereaches a specific score or wins a specific number of hands.

3. a series consisting of an odd number of games won by the side winning the majority, usually two out of three.

4. the deciding game in such a series.

adj.

5. Also called rubber match. Sports. noting a deciding contest between two opponents who have previously won the same number of contests from each other.

[1585-95; orig. uncert.]

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I

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.

II

(as used in expressions)

rubber plant

India rubber plant

rubber tree

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▪ chemical compound

 elastic substance obtained from the exudations of certain tropical plants (natural rubber) or derived from petroleum and natural gas (synthetic rubber). See also elastomer.

      Because of its elasticity, resilience, and toughness, rubber is the basic constituent of the tires used in automotive vehicles, aircraft, and bicycles. The same properties make it useful for machine belting and hoses of all kinds. Rubber is also used in electrical insulation, and because it is waterproof, it is a favoured material for shoe soles.

      Natural rubber was first scientifically described by C.-M. de la Condamine and François Fresneau of France following an expedition to South America in 1735. The English chemist Joseph Priestley (Priestley, Joseph) gave it the name rubber in 1770 when he found it could be used to rub out pencil marks. Its major commercial success came only after the vulcanization process was invented by Charles Goodyear (Goodyear, Charles) in 1839.

      Natural rubber is produced from a wide variety of plants, but predominantly from Hevea brasiliensis (family Euphorbiaceae), a tall softwood tree originating in Brazil. Hevea trees descended from seedlings transplanted to South and Southeast Asia now produce most of the modern world's natural rubber. The largest producing countries are Indonesia, Malaysia, Thailand, India, Sri Lanka, and China.

      The latex found in the inner bark of H. brasiliensis is obtained by tapping—cutting or shaving the bark with a sharp knife—and collecting the latex in cups. Solid rubber is coagulated from the fluid by the addition of chemicals, such as formic acid, that cause the rubber to form curds on the surface of the liquid. The curds can then be pressed between rollers to remove excess moisture and to form sheets. The sheets are commonly packed in bales for shipping. Rubber is also commonly transported in the form of a concentrated latex.

      Despite the competition of synthetic rubber, natural rubber continues to hold an important place; its resistance to heat buildup makes it valuable for tires used on racing cars, trucks, buses, and airplanes.

      Research on the chemistry of natural rubber led in the 19th century to the isolation of isoprene, the chemical compound from which natural rubber is polymerized. Polymerization, the process by which long chainlike molecules are built up from smaller molecules, attracted continued research in the early 20th century. During World War I, German scientists produced a crude synthetic rubber, and during the 1920s and '30s several polymerizing processes were developed in Germany, the Soviet Union, Britain, and the United States. During World War II huge quantities of synthetic rubber, mostly based on polymers of butadiene, were produced. By the early 1960s synthetic rubbers had overtaken natural rubber in quantity produced.

      Among the most important synthetics are polybutadiene; styrene-butadiene copolymer; polychloroprene (neoprene); the polysulfides (Thiokol); the isobutylene-isoprene copolymers (butyl rubbers); and the polysiloxanes (silicone rubbers). Synthetic rubbers, like natural rubbers, can be toughened by vulcanization and improved and modified for special purposes by reinforcement with other materials.

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