Rubber. Natural rubber is a substance obtained from the milky juice, called latex, produced by a number of different kinds of plants. Synthetic rubber, made by various chemical manufacturing processes, is similar to natural rubber. The rubber used in most commercial products is vulcanized rubber— natural or synthetic rubber that has been altered chemically by a process called vulcanization. Scientists and engineers often use the term "elastomer" to refer to any elastic material such as rubber.
Rubber is composed of very large molecules weighing some 50,000 to 3,000,000 times as much as the hydrogen atom. Molecules of natural rubber are essentially long chains of isoprene, a simple compound of carbon and hydrogen with the chemical formula C5H8. A molecule formed by a chain of simple molecules is called a polymer; large polymers, such as those that make up rubber, are often called high polymers.
