When rubber was first introduced to Europe from the New World, it was considered a marvelous novelty. Early explorers were amazed to find Caribbean natives playing games with bouncing balls made from the milky white juice (latex) of certain trees. A French explorer, Charles Marie de la Condamine, brought back samples of Indian-made rubber from the Amazon Valley in 1738 and set about promoting interest in the new substance. It was variously called caoutchouc (from the South American Indian word for it), gum elastic , and India rubber--"India" because the substance came from the West Indies, which Columbus thought were India, and "rubber" from the observation of British chemist Joseph Priestley (1733-1804) that the substance rubbed out lead pencil marks.
Europeans were fascinated with rubber's attributes: it was elastic, waterproof, strong, springy, and moldable. Since latex coagulates quickly, rubber always arrived in Europe in solid form, usually as bottles. Manufacturers like Thomas Hancock (1786-1865) in England sliced up the bottles to make rubber novelties like shoe lasts, tobacco pouches, and rings that were used as garters and wristbands--the Western world's first rubber bands. Experimenters soon found that the hardened gum could be dissolved in turpentine and then reshaped. Cloth soaked in the liquid became waterproof, but it also smelled like turpentine. Hancock and Charles Macintosh solved that problem in the early 1820s by dissolving rubber in naphtha instead. Hancock also designed commercially successful rubber manufacturing machines.
A great craze for India-rubber products ensued, both in England and the United States. Five hundred pairs of India rubber boots were imported to Boston, Massachusetts, in 1823. In England, Charles Macintosh (1766-1843) began producing rubber-lined waterproof coats. Manufacturers vied with one another to produce rubber overshoes, coats, caps, wagon covers, and suspenders. Hancock developed rubber tubing from which he cut rubber bands and hoses. But natural rubber's most serious flaw soon showed itself: it is unstable over varying temperatures. People soon discovered that their overshoes became stiff and brittle in cold weather, and that in the heat their raincoats dissolved into a stinking, gummy mess that had to be disposed of by burial.
In 1839, Charles Goodyear (1800-1860), a Yankee inventor who had devoted himself to improving the usefulness of rubber, discovered the answer. Goodyear, with absolutely no knowledge of chemistry, had spent five years mixing crude gum elastic with every possible substance, with the idea that sooner or later something would work. He had no success with salt, sugar, castor oil, ink, soap, or even cottage cheese. Magnesia, quicklime, and nitric acid all seemed promising for a time, but failed. Goodyear then experimented with Nathaniel Hayward's process of mixing rubber with sulphur. While doing so, Goodyear had a famous accident: he spilled some of his rubber-sulphur compound on a hot stove and was amazed to find that instead of melting, as natural rubber would have, it "charred like leather" and lost its stickiness. Goodyear noticed a tiny line of perfectly cured rubber on the edge of the piece. Further tests revealed that the cured rubber remained flexible even when left outdoors overnight in intense cold.
Goodyear spent the next five years perfecting his rubber-sulphur curing-by-heat process, securing a patent for it in 1844. The process became known as vulcanization--named after Vulcan, the Roman god of fire. A sample of Goodyear's vulcanized rubber found its way across the Atlantic to Hancock in England. Hancock studied and experimented with the sample and soon took out a British patent for his version of rubber-sulphur vulcanizing. Other variations of the vulcanizing process were developed, one by Alexander Parkes (1813-1890) in 1846 which used sulphur monochloride vapor and another by S. J. Peachy using sulphur dioxide gas.
Vulcanizing made rubber a practical, eminently usable product. The rubber industry flourished, spewing out hundreds of everyday items (including waterproof clothing and footwear, fire hoses, rubber bands, mattresses, combs, and balloons), and contributed greatly to the process of industrialization. Rubber provided the electrical and communications industries with the effective insulation they badly needed. Rubber seals perfected industrial machinery. Perhaps most importantly, the use of rubber for pneumatic tires helped to expand both the automotive and rubber industries.
Today, natural rubber, which is essentially cis-1,4-polyisoprene, remains the strongest of all rubbers, with its excellent dynamic properties such as resistance to fatigue. In some products the rubber of choice is determined solely by properties (e.g., aircraft tires which require 100 per cent natural rubber) but in many products the choice between between natural and synthetic rubbers hinges on price and properties. World consumption of natural rubber in 1996 was 6.13 million metric tons, corresponding to 39% of world consumption of all elastomers (i.e. natural plus synthetic rubber).
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