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How is Rubber Made?

Rubber is an incredibly common and versatile material, used for making many items such as elastic bands, footwear, swimming caps and hoses. Indeed, half of all rubber produced goes towards making vehicle tyres. As such a vital material, how is rubber made and where does it come from?

Natural Rubber

© Panya Studio / Adobe Stock

 

Origins of rubber

Humans have been exploiting the durable and elastic nature of rubber for making products for over 1,000 years. Although early forms of rubber were made from natural sources, as demand increased for this material, scientists developed artificial or synthetic rubber in laboratories that mimicked the natural material. These days, most rubber produced is of the synthetic kind.

 

Natural rubber

Natural rubber is made by extracting a liquid sap, called latex, from certain types of tree. There are over 2,500 types of tree that produce this sap (including plants like dandelions), but the overwhelming majority of latex for rubber production stems from the Hevea brasiliensis tree, or the aptly named rubber tree. These trees are native to South America but are today commonly found in Southeast Asia.

Latex is gathered from the trees by making a cut in the bark and collecting the runny sap in cups. This process is called tapping.

In order to prevent the sap from solidifying, ammonia is added. Acid is then added to the mix to extract the rubber, in a process called coagulation. This can take about 12 hours.

The mixture is then passed through rollers to remove excess water. Once this is complete, the layers of rubber are hung over racks in smokehouses or are left to air dry. Several days later they will then be folded into bales ready for processing.

 

Synthetic rubber

It was when natural rubber sources became scarce during World War I that German scientists developed artificial rubber. Although these early forms of rubber were inferior in quality to natural rubber, as research developed, synthetic rubber improved. Today, synthetic rubber is as strong and reliable as natural rubber.

Synthetic rubber differs from natural rubber in that it is made by linking polymer molecules together in a laboratory.

 

Processing rubber

Both natural and synthetic rubber need to undergo a series of processes to turn it into a usable product. These stages can be adapted slightly according to the intended use of the final product.

Firstly, chemicals are added to the rubber to make it stable. Without this, the rubber would get brittle if it got cold or become sticky during high temperatures. Commonly, a carbon black filler is added to the rubber mix, to improve its strength and durability.

The rubber is then carefully mixed together and allowed to cool, before being shaped. It can be shaped by pushing it into rollers, called calendering, or by squeezing it through holes to make hollow tubes, known as extrusion.

 

Vulcanisation

In order to make rubber strong and durable, it finally goes through a heat-treatment phase known as vulcanisation. This is where the rubber is cooked (often with sulphur) to create extra bonds or cross-links between the molecules of the rubber, so they don't easily fall apart.

Charles Goodyear accidentally discovered this process, when he dropped some rubber onto a hot stove and noticed how the heat made the rubber harder and more durable.

After vulcanisation, any imperfections are removed from the rubber and it is then shaped or moulded into the final product.

As one of the most important inventions ever, rubber continues to enjoy versatile use today.

If you require a wide variety of high-quality rubber products, ranging from matting to seals and extrusions, look no further than Coruba.



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