Natural rubber is very soft and in summer it becomes brittle. Moreover, it cannot withstand wear and tear. The cross linking in natural rubber is done by the prcoess of vulcanisation as a result of which sulphur atoms are introduced in the linear chains and they becomes cross linked. The vulcanised rubber is more stiff as compared to natural rubber. Moreover, it is also hard and non-sticky. its elasticity can be maintained over a wide range of temperature.