Where Does Natural Rubber Come From?

hevea rubber plant

Rubber is an elastomer made from the tapped latex of certain tropical plants (natural rubber) or petroleum and natural gas (synthetic rubber). Rubber is the primary component of tires used in automobiles, planes, and bicycles because of its flexibility, durability, and hardness. More than half of all rubber produced is used in automotive tires, with the remainder going into mechanical parts like mountings, gaskets, belts, and hoses, as well as consumer goods like shoes, furniture, and toys.

Elastomers, or “elastic polymers”, are the main chemical ingredients of rubber. Elastomers are long chainlike molecules that can be stretched to vast distances and still return to their original shape. Polyisoprene, from which natural rubber is derived, was the first common elastomer. Natural rubber is made up of particles suspended in a milky fluid called latex that flows in the inner sections of the bark of a variety of tropical and subtropical trees and shrubs, but mostly Hevea brasiliensis, a tall softwood tree native to Brazil.

Natural rubber is still in demand today, thanks to its resistance to heat accumulation, which makes it ideal for all types of vehicle tires. However, it only accounts for less than half of all rubber generated commercially; the rest is synthetic rubber created by chemical procedures that were partially understood in the nineteenth century but not practically utilized until the second half of the twentieth century. Styrene-butadiene rubber (SBR), neoprene, butyl rubber, and silicones are some of the most important synthetic rubbers. Both synthetic and natural rubber can be vulcanized to toughen them up and reinforced with additional materials to improve and modify them for specific applications.

The Rubber Tree

Hevea brasiliensis, the natural rubber tree, being tapped for latex.
Hevea brasiliensis, the natural rubber tree, being tapped for latex.

Natural rubber is almost solely obtained from Hevea brasiliensis, a South American tree that grows wild to a height of 120 feet!  However, when grown in plantations, the tree only reaches a height of around 80 feet since carbon, which is required for growth, is also a component of rubber. When the tree is actively producing, its carbon intake is split between both growing itself and producing latex. 

The natural contours of the terrain are followed in the cultivation of Hevea, and the trees are shielded from the wind. Cover crops are placed next to rubber trees in order to help hold rainwater on hill slopes and enrich the soil by fixing nitrogen from the air. Standard horticultural techniques are also used, such as nursery-grown hardy rootstocks with grafting on top, hand pollination, and vegetative propagation to generate a genetically homogenous product.

Hevea develops as it were inside a well-defined region of the tropics and subtropics where ice is never experienced. Overwhelming yearly precipitation of around 100 inches is fundamental, with accentuation on a wet spring. As a result of these necessities, regions of natural rubber trees are restricted. Southeast Asia is especially well arranged for this climate as well as parts of South Asia and West Africa. Development of Hevea in Brazil, its local living space, was essentially devastated by scourge early within the 20th century.

Latex Processing

When the bark of the Hevea tree is tapped, a smooth fluid radiates from the wound and dries to yield a rubbery film. The purpose of the latex within the tree is still largely unknown. It may offer assistance with wound-healing by securing the internal bark, or it may serve other functions. The latex comprises of an watery suspension of small particles, approximately 0.5 microns in size, of the rubber polymer polyisoprene. After collection of the latex, it is then coagulated with formic acid, and turns into crumbs that resemble curds of milk. The crumbs are washed, dried between rolls, and compacted into blocks. These blocks are then wrapped in polyethylene sheets and pressed into one-ton cartons for shipping.

This natural crumb rubber can then be compounded with other rubber additives such as reinforcing fillers (carbon black), processing oils, and curatives. Once compounded into a specific recipe, the rubber compound is molded by a rubber molder into all types of products.

Do you need natural rubber for your application or project? Contact Wayne Rubber to see how we can supply you with a quality natural rubber product!

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