NCERT Class XII Chemistry
Chapter - Polymers
Questions with Solutions

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Question : 15
Total: 26
Discuss the main purpose of vulcanisation of rubber.
Solution:  
Natural rubber becomes soft at high temperature (> 335 K) and brittle at low temperature (< 283 K) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.
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