Vulcanisation Explained: Why Tyres Stay Strong

As tyres have developed over the years, they have not only become stronger but also more flexible and better suited to the complexity of mixed terrains and changing conditions. With modern tyres typically bridging performance with safety attributes and durability, it’s crucial that the materials used are accustomed to that balance of endurance and performance; safety and comfort.

Which is where processes like vulcanisation come in.

What is Vulcanisation?

Vulcanisation is the process through which raw and natural rubber is transformed into a material that’s suitable and stable enough for use in modern tyres. Without vulcanisation, completely natural rubber is formed of molecules which slide past each other and feel tacky to the touch. Vulcanisation bonds these molecule chains and gives them lasting structure.

As such, it is responsible for adding the resilience that tyres need in order to navigate changing terrain and varying conditions and makes tyres both stronger and more pliable. Vulcanisation is also responsible for ensuring that tyres are able to handle and withstand changing temperatures both inside and outside of the tyre and helps support the integrity of the tyre tread.

But how does it work and what does it involve?

Understanding the Process of Vulcanisation

The simplest way to understand vulcanisation, is that it’s a heated process through which the polymer chains within the natural rubber are locked together into a three-dimensional framework – using sulphur and other curing materials. This process is conducted at a high temperature of between 140 and 180° C, because the higher temperature speeds up the process and gives the manufacturer more control over the end result.

Today, vulcanisation occurs in tyre moulds which are made from metal and exposed to a hydraulic press – applying the right level of force at the allotted temperature, so that the rubber absorbs the strength from the sulphur while also setting into the correct shape and structure.

This end-to-end process is important because, without vulcanisation, the rubber would quickly become deformed under the stress of driving at speed or under the weight of a vehicle.

So, how are different tyre types formed under this single process?

How Different Tyre Types Are Achieved With Vulcanisation

The fewer links are created within the rubber, the more pliable the resulting tyre will be. As such, for softer tyres and more flexible rubbers, the process needs to create fewer cross-links between the molecules. The more cross-links there are, the strong the rubber is and the stiffer it will feel.

This is what facilitates the creation of performance tyres, off-road tyres, rigid tyres for commercial use, and much softer tyres for off-road terrain and adventuring.

Fun Fact About Vulcanisation

You’d be forgiven for thinking that this process all feels and sounds very modern – but in fact it was Charles Goodyear who first discovered the process and its impact on natural rubber, back in 1839.

Goodyear dropped a pot of raw rubber and sulphur onto a hot stove by accident and noticed how the resulting rubber was actually much firmer and stronger than it had been before being exposed to the sulphur. This created a breakthrough in the design of tyres that could last much longer on the road under the pressure of the right manufacturing process, with Goodyear spending the rest of his life developing and improving the formula for vulcanisation.

The Future of Vulcanisation

There are studies and processes that are currently being explored, which seek to carry out vulcanisation at lower temperatures – typically around 100° C or below.

The aim of this is to improve the efficiency of the process and reduce the reliance of manufacturing plants on high energy outputs. It could contribute towards the tyre industry being considered as more sustainable and eco-friendlier in the long run.

One final thing worth considering and noting is the impact that vulcanisation has on the ability to recycle tyres. By adding the sulphur or similar chemical to the rubber, tyres and other products made using vulcanisation cannot be effectively melted down – and so there need to be other avenues for tyre recycling. This is why so many used tyres are shredded to create playground surfaces, race tracks, and other products.

Is vulcanisation something that you had already heard of, or did you think that your car tyres were manufactured using natural rubber? You can learn more interesting facts like this by browsing our Tyres.co.uk Knowledge Hub – or head straight to our brand pages to compare and uncover the top tyre models on the market right now.