Vulcanized rubber is a natural elastomer that has been made more durable by a biochemical process that cures the rubber. During vulcanization, the milky latex from a rubber tree is combined with a curing ingredient — usually sulfur — and heated under pressure. This process, which was discovered by an American inventor named Charles Goodyear in 1839, made the rubber more stable, tougher and more resistant to heat, which made it more useful for industrial purposes and ideal for certain products. Its name comes from Vulcan, the Roman god of smiths.

Making Rubber Stronger

Before vulcanization was discovered, natural rubber could be coagulated with acid and made malleable so that it could be shaped and formed. At high temperatures, though, the rubber would become sticky or melt. At low temperatures, the rubber would become brittle. These qualities made this type of rubber impractical to use in industrial settings.

Vulcanization chemically combines the rubber and sulfur. At high pressure and high temperatures, the sulfur atoms form links or bridges between long chains of the rubber molecules. This increases the rubber's strength and durability and reduces its stickiness. It also makes the rubber retain its elasticity at a much wider range of temperatures, making vulcanized rubber more useful for many purposes.

Discovery

Goodyear had experimented with rubber for several years before discovering vulcanization. A former hardware store owner who had no scientific training or knowledge of chemicals, Goodyear suffered financially and went into debt while looking for a way to make rubber more stable and durable. It is often said that his discovery was by accident after a mixture of sulfur and rubber gum splattered onto a hot stove and formed a hardened material. Goodyear, however, claimed that it was not accidental but rather the result of a series of experiments and observations.

He sent samples of his cured rubber to British rubber plants. An Englishman named Thomas Hancock, who had been trying to make weatherproof rubber for 20 years, saw one of the samples and he noticed a telltale yellowish powdery residue — sulfur — on the surface of the sample. Hancock reinvented the process in 1843, four years after Goodyear. Goodyear obtained the United States patent for this process in 1944, but when he applied for the British patent, he found that Hancock had beaten him to it. The term "vulcanized rubber" did not come from Goodyear, but was coined by a friend of Hancock's.

Applications

Vulcanized rubber has come to be used to make a wide variety of products. Among the most common of these are automobile tires, rubber seals and gaskets, transmission belts, shoe soles and hockey pucks. The Goodyear Tire and Rubber Company, a well-known manufacturer of automobile tires and other rubber products, was named in honor of Charles Goodyear, although there are no family connections.