A molecular spring, sort of. However, despite this elastic quality of the individual chains, a mass of natural rubber will deform and come apart if stretched. This is because the chains slide past one another rather than sticking together. Vulcanization is the process of applying cross-links to the chains in natural rubber in order to make it stronger and more elastic. He was surprised to see that the mixture had become strong and elastic.
Vulcanized rubber has many properties that make it useful.
Since rubber is puttylike before being vulcanized, it can be cast into complex shapes. It is first mixed with sulfur and forced into a mold. The mold is then heated and the rubber cross-linked. By controlling the amount of sulfur used in the vulcanization, rubber can be prepared with a wide range of properties. It is good for rubber bands and inner tubes.