Q. Explain: Vulcanization of rubber is necessary.
Ans. Importance of vulcanization of rubber:
1. Vulcanization makes cross-links between the long unsaturated hydrocarbon chains. This cross links presents intermolecular moments by anchoring, as a result of which, vulcanized rubber regains the original shape on removing stress.
2. The cross links may be directly from carbon to carbon or through an oxygen atom or through sulphur atom, or through all the three, therefore, percentage elongation at break decreases.
3. Water absorption tendency of rubber decreases.
4. Useful temperature range increases from 10-60 degree centigrade to -40-100 degree centigrade.
5. Chemical resistance of vulcanized rubber increases.