How is Rubber made?

Harvesting Natural Rubber

Rubber production begins with the harvesting of latex, a milky sap-like substance found in the bark of certain trees, most notably the Hevea brasiliensis tree, also known as the rubber tree. These trees are typically grown in large plantations in tropical regions such as Southeast Asia, Africa, and South America, where the climate is ideal for their growth.

To obtain latex, a skilled worker, called a rubber tapper, makes a precise incision in the bark of the tree using a specialised tool. This incision allows the latex to flow out of the tree into a collection cup. The tapper repeats this process on multiple trees until enough latex is collected.

Coagulation

Once the latex is gathered, it undergoes a series of processing steps to transform it into the rubber we are familiar with. Firstly, the raw latex is sieved to remove any impurities like leaves, twigs, or insects. It is then mixed with various compounds such as acid, ammonia, and other chemicals to stabilise and preserve it during transportation.

Next, the latex is coagulated. In the past, the most common method was to add acetic acid or vinegar to the latex, causing it to curdle and form large lumps. However, nowadays, more efficient methods involving synthetic coagulants are used. These coagulants cause the latex to solidify into a thick mass resembling coagulated milk, which is then cut into smaller pieces called coagulum.

The coagulum is then washed to remove any remaining impurities. This process is repeated several times until the rubber is considered clean. The resulting material is often referred to as wet rubber since it still contains a considerable amount of water.

Sheet Formation, Smoking & Curing:

To eliminate the excess water content and improve the quality of the rubber, it is sent to a drying process. This can be achieved through various methods such as air drying, smoke drying, or mechanical dewatering. Often, the rubber is rolled into thin sheets or made into thick blocks for ease of handling and transportation. This can be done manually or through automated processes. The sheets are then hung to dry, allowing excess water to evaporate and leaving behind a rubbery material.

Once the rubber is dried, it undergoes a curing process, also known as vulcanisation. This step involves subjecting the rubber to heat and adding sulphur or other chemicals to improve its elasticity, strength, and resistance to ageing. The curing process usually occurs in large industrial presses.