The word rubber comes from the Indian word cau-uchu, which means "tree with tears". Natural rubber is made by coagulating and drying the latex that flows out when the rubber tree is tapped. In 1770, the British chemist J. Priestley discovered that rubber can be used to erase pencil writing. At that time, the material for this purpose was called rubber, and this term is still used today. The molecular chain of rubber can be cross-linked. When the cross-linked rubber is deformed by external force, it has the ability to recover quickly, and has good physical and mechanical properties and chemical stability. Rubber is the basic raw material of the rubber industry and is widely used in the manufacture of tires, hoses, tapes, cables and various other rubber products. Hevea trees provide the most commercially available rubber. It will secrete a lot of sap containing rubber emulsion when it is injured (such as the bark of the stem is cut).
In addition, fig trees and some plants of the Euphorbia family can also provide rubber. Germany tried to obtain rubber from these plants because its rubber supply was cut off during World War II, but later switched to producing synthetic rubber.
The first rubber trees were grown in South America, but after artificial transplantation, a large number of rubber trees are also planted in Southeast Asia. In fact, Asia has become the most important source of rubber.
Rubber made of guayule gum can reduce sensitivity.
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