Natural rubber is a versatile material derived from latex, a milky fluid found in certain plants. This substance, capable of returning to its original shape after being stretched, forms the foundation for numerous products. A specific tree is the primary commercial source, and its liquid sap undergoes processes that transform it into solid rubber for various industries.
The Rubber Tree
The world’s natural rubber originates primarily from Hevea brasiliensis, the Pará rubber tree. Native to the Amazon basin in South America, including Brazil, Venezuela, and Peru, its cultivation spread globally. Extensive plantations are now found across Southeast Asia, accounting for over 90% of the world’s natural rubber output.
The Hevea brasiliensis tree produces latex as a milky-white fluid that oozes from its inner bark when damaged. This latex is an aqueous suspension of small particles, primarily cis-polyisoprene, with about 30% rubber content. The tree stores this latex in specialized channels called lactiferous vessels, concentrated in the soft bast layer of its bark.
Tapping for Latex
Harvesting latex from a rubber tree involves tapping, where a thin layer of bark is removed. This procedure typically begins when a tree is five to six years old, reaching a circumference of about 50 centimeters at 100 to 120 centimeters from the ground. A specialized hooked knife makes a precise incision, usually a downward half-spiral cut across roughly half the tree’s circumference.
The cut is made at an angle of about 30 degrees to the horizontal, allowing gravity to guide the flowing latex. Tappers ensure the incision is shallow, 1 to 1.5 millimeters from the cambium layer, to avoid damaging the tree’s growth tissue and promote bark regeneration. Tapping is often performed in the early morning or at night, as cooler temperatures allow the latex to flow longer before coagulating. Trees are commonly tapped every two to three days, a frequency that balances latex yield with tree health and sustainability.
Latex Collection and Initial Handling
Once the cut is made, milky latex flows from the opened lactiferous vessels. This liquid drips along the channeled cut, directed by a small spout into a collection cup. These cups, typically porcelain or plastic, are attached to the tree at the base of the tapping cut.
The latex continues to exude for several hours, filling the collection cup. Workers then gather the collected latex from each cup. To prevent premature coagulation, a preservative like ammonia is often added directly to the collected liquid. This initial stabilization allows the latex to be transported to processing facilities.
Transforming Latex into Raw Rubber
Upon arrival at a processing facility, the collected liquid latex undergoes several stages to convert it into solid raw rubber. A common method involves inducing coagulation, where the stable latex emulsion is broken down to separate the rubber particles. This is typically achieved by adding an acidic solution, such as formic acid, which causes the rubber particles to clump together.
After coagulation, the resulting wet, crumbly rubber mass is passed through rollers. This pressing process serves to squeeze out excess water and impurities from the rubber. The compressed rubber is then prepared for drying, often in the form of thin sheets. These sheets can be air-dried or, more commonly, dried in smokehouses, where the smoke imparts specific properties and helps preserve the rubber. The dried rubber is then pressed into bales for transport and further manufacturing.