Rubber That Doesn't Lose Its Elasticity.

Do you know what is the sole of your shoe made of? Or even your car tires? Yes, they are both made from rubber but not your ordinary natural rubber. They are made from vulcanised rubber.

The PCK boots. Or at least it looks like PCK's.

Why not natural rubber you asked? Well, that is because natural rubber is elastic in nature. When the natural rubber is streched, compressed or even bent, the entangled molecules will slide over one another. When the force is removed, the rubber molecules will then return to their original position. However, if the natural rubber is over-stretched, the molecules will not move back to their original position. This piece of natural rubber has lost its elasticity.

What is vulcanised rubber then? Vulcanised rubber consists of rubber molecules that are covalently bonded to their neighbouring molecules through sulphur atoms and thus, forming a huge structure. Vulcanised rubber is around 10 times stronger and more rigid than natural rubber. Besides that, vulcanised rubber is also more elastic and more durable compared to unvulcanised rubber. It is also heat and abrasion resistant.


How is natural rubber vulcanised? Natural rubber undergoes a process called the vulcanisation of rubber to form vulcanised rubber. Vulcanisation is the process where by rubber molecules known as isoprenes are cross-linked with each other by heating the rubber (in liquid form) with sulphur.

(Click to enlarge)

In the vulcanisation process, the sulphur that is added in allows some of the C-H bonds to be broken down and replaces the C-H bonds with C-S bonds. Vulcanisation cross-links the polyisoprene to one another. Every cross-link is a chain with about 8 sulphur atoms between 2 long chains of polyisoprene. These cross-linked molecules will then create a 3-dimensional network of rubber. The cross-linked molecules also makes sliding more difficult for the rubber molecules. Thus, the elasticity of the vulcanised rubber will maintain even after it is being stretched strongly and released.


We indeed have to thank Mr Charles Goodyear for discovering the vulcanised rubber. If there weren't vulcanised rubber, a lot of our rubber goods will wear off and lose their elasticity in no time. And we got to spend more money buying the same thing again and again. With the money saved, more money for shopping? :P It's still Mega Sales!!!