Natural rubber becomes soft at high temperatures and brittle at low temperatures. It has a high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidizing agents.
To improve upon these physical properties, the process of vulcanization is carried out. It consists of heating a mixture of raw rubber with sulphur with a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at reactive sites of double bonds and thus the rubber gets stiffened.
