Where Does Rubber Come From?

Rubber coming from a tree

Natural rubber is extracted from latex, a white milky liquid that can be found in about 10 percent of all plants including dandelions and lettuces. Most rubber latex is cultivated from Hevea Brasiliensis trees, which produce a high volume of excellent quality latex. Hevea Brasiliensis is a species native to Brazil. These trees were not found in any other place around the world until 1876, when a British explorer, Henry Wickham smuggled 70,000 seeds out of Brazil. These seeds were used to grow rubber plantations in the British Colonies including Indonesia, Sri Lanka, and Malaysia. These countries are now the world’s leading producers of natural rubber and over 90% of natural rubber is produced in Asia. 

The latex is collected from the trees by “tapping”, a method whereby a thin strip of bark is pulled back from the tree, revealing the latex. The strip is cut in a spiral fashion causing the latex which seeps out from the wound to flow down the spiral where it can then be collected in a container. Preservatives such as ammonia are added to the collection cups to stop the latex from solidifying.

Rubber Tree Tapping

Figure 1: Latex "tapping"

Tapped latex consists of rubber particles suspended in a serum, containing mainly water. Originally, the South American Indians obtained solid rubber by simply drying out the latex over fires. Nowadays, more sophisticated methods of extracting rubber have been developed depending on the intended use of the final product. Natural rubber can be sold as a liquid concentrate or processed into dry solid rubber. 

The latex collected from the tree contains only around 30% by weight of rubber. Latex concentrate is processed by removing some of the water, increasing the rubber content to around 60% solid. The water is removed either by evaporation, adding chemical agents to the latex or using a centrifugal force to spin the water out of the latex. 

Processing of the latex into a solid rubber involves the addition of an acid such as formic acid (systematically called methanoic acid). Adding acid to the latex will cause it to coagulate (solidify) and the rubber particles will join to form lumps. Once the rubber has solidified the water can be removed, leaving behind the coagulated rubber. The coagulated rubber can be formed into thin ribbed smoked sheets by passing the rubber through a series of rollers, which help to get rid of any excess water. Finally, the sheets are dried in smokehouses for up to a week.

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