Question

What is the utility of vulcanisation of rubber? How is vulcanisation carried out?

Answer 1

Natural rubber has the following drawbacks:

$1)$ It is soft and sticky at room temperature. At high temperatures, $(>335K)$, softness increases.

At low temperatures, $(<283K)$, it is brittle.

Hence, to maintain elasticity, natural rubber can be used in the temperature range of $283K-335K$.

$2)$ It can absorb large amounts of water.

$3)$ It's tensile strength is low and it has low resistance to abrasion.

$4)$ It is soluble in non-polar solvents.

$5)$ It is easily attacked by oxidizing agents.

Vulcanization is carried out to improve this property. This process involves heating a mixture of raw rubber with sulphur and other additives at a temperature range between ${100}^{\circ }C$ to ${145}^{\circ }C$.

After vulcanization sulphur forms cross-links at the reactive sites of double bonds and thus the rubber gets stiffened.