In 1839, Charles Goodyear was experimenting with a mixture of rubber and sulfur. He accidentally dropped some of the mixtures on to a hot stove. The result was an incredibly tough piece of rubber. After a little experimentation, Goodyear was able to perfect his ‘vulcanisation’ technique, which he used to make his tyre company successful.
Goodyear had accidentally made the discovery that heating rubber molecules in the presence of sulfur made them much tougher. Vulcanised rubber is ten times tougher than natural rubber, and it’s also about ten times more rigid. These different characteristics make vulcanized rubber useful for different applications to natural rubber
While you may think that Vulcan is a planet in the Star Trek series, the word actually has Roman roots. Vulcan was the god of fire, and that was the inspiration for Goodyear to call his new process vulcanization. It now has its own place in the dictionary, meaning, ‘to throw into the fire’.
When rubber is heated with the sulfur present, it changes the chemical structure. Natural rubber is found in rubber trees which grow in East Asia. They are tapped for latex, which is rubber molecules suspended in water. Natural rubber is made up from long-chains of isoprene. When the chains are heated with sulfur, the sulfur bonds to the compound and create cross-links. This is what gives vulcanized rubber its strength.
If you are interested in learning more about the vulcanization process, then you can learn more from this BBC Bitesize article: https://www.bbc.co.uk/education/clips/z38yr82.
Not Just Natural
Vulcanisation can also be carried out on other forms of rubber – for example, the silicone rubber used to make Silicone Hose such as these from https://www.goodflexrubber.com/pages/silicone-hose-manufacture becomes much stronger. This has enabled products such as internal hoses, gaskets and the like to become much harder-wearing.
Although silicone rubber doesn’t have the isoprene molecules, it is still a long-chain polymer. The sulfur allows those chains to cross-link in the same way as it does for natural rubber.
Goodyear’s happy accident has left us with the ability to create tough and hard-wearing rubbers from a range of materials. We now use those in products throughout the world and across many industries. Tyres are still made from vulcanized rubber, and they are so tough that they can get a second life as cushioning in children’s play areas.