What Is Vulcanized Rubber?

Vulcanized rubber is an elastomer that has been made more durable through vulcanization, a biochemical process. The milky latex from a rubber tree is combined with a curing ingredient, usually sulfur, and heated under pressure.

The vulcanization process was discovered by American inventor Charles Goodyear in 1839. Vulcanization makes the rubber more stable, tougher and more heat resistant, so that it becomes more useful for industrial purposes and certain products. The term "vulcanized" is derived from Vulcan, the Roman god of fire and metalworking.

Before the discovery of vulcanization, natural rubber would 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, while at low temperatures, the rubber would become brittle. These qualities made 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 between long chains of the rubber molecules. This increases the rubber's strength and durability and reduces its stickiness. It also allows the rubber to retain its elasticity at a much wider range of temperatures, making vulcanized rubber far more useful for various applications.

Charles Goodyear had experimented with rubber for several years before discovering vulcanization. A former hardware store owner with no scientific training or knowledge of chemicals, Goodyear went into debt while looking for a way to make rubber more stable and durable. It is often said that his discovery occurred 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.

Goodyear sent samples of his cured rubber to British rubber manufacturers. An Englishman named Thomas Hancock, who had been trying to make weatherproof rubber for 20 years, saw one of the samples and noticed the telltale yellowish powdery residue of 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 1844, 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 actually coined by a friend of Hancock's.

Vulcanized rubber is currently used in a wide variety of products. Among the most common are: