Vulcanization

Chemical process, discovered by Charles Goodyear (1839), by which the physical properties of natural or synthetic rubber are improved.

It consists principally of heating rubber with sulfur; other substances (accelerators, carbon black, antioxidants, etc.) are also added. The sulfur does not simply dissolve or disperse in the rubber, but rather combines chemically, mostly in the form of cross-links (bridges) between the long-chain molecules; however, the reactions are not fully understood. Vulcanized rubber has higher tensile strength and resistance to swelling and abrasion, and is elastic over a greater range of temperatures.