Charles Goodyear accidentally discovered vulcanization when he dropped a mixture of natural rubber and sulfur onto a hot stove. Before this, rubber was an impractical material that turned brittle in the cold and melted in the heat. Vulcanization creates cross-links between polymer chains, making the rubber durable, elastic, and heat-resistant. This invention made the modern tire industry possible, which in turn enabled the success of the bicycle and the automobile. Goodyear himself never profited significantly from the discovery and died in debt, but his name was later used for the Goodyear Tire and Rubber Company. Vulcanized rubber remains essential for everything from shoe soles and gaskets to waterproof clothing and conveyor belts.