How Does Rubber Get Made?

Tree Tapping

Natural rubber is made from the latex that flows from the rubber tree, or the Hevea brasilienesis. Synthetic rubber, which now makes up about 65 percent of the market, is made by emulsifying two chemicals, butadiene, and styrene, both made from oil. For centuries the native people of the regions around the Equator have collected the sap by cutting a slanted slice into the bark of the tree about one third of the way around. The cut cannot be too deep or it will kill the tree but deep enough to reach the latex that flows under the surface of the bark.

Collection of Latex

At the bottom of the slice, a container is attached to collect the drippings. A coconut shell was and still is used by many plantations as a suitable container for the amount of latex that will flow before it coagulates and stops dripping. Roughly, a cup will flow about every three hours after which another cut will have to be made, just under the previous one.

Latex Treatment

If left alone, the latex will solidify in contact with air, so many times, a substance such as ammonia is added to keep the latex a liquid. A liquid is easier to pour into larger containers for transport. Otherwise, the latex is allowed to harden into a cup shape and it is collected along with the strip of latex that hardened along the cut on the tree and sent to processing plants.

Vulcanization

The natural latex can be used in many applications that require elasticity and the ability to melt easily, but most rubber is vulcanized. Vulcanization is a process that takes the unstable latex and under the presence of heat adds sulfur to form a harder and more stable product. Before vulcanization, rubber would get sticky if it was hot and brittle if it was cold.

Product Formation

The liquid rubber, vulcanized or not, is now poured into heated molds designed for their specific use. Sometimes other materials are added such as steel reinforcement or carbon black for tires. Latex gloves are formed by dipping a preformed cast into the liquid and allowing it to dry.