When rubber is heated with sulphur_ its tensile strength, elasticity and resistance to swelling are increased tremendously. This process is named as Vulcanization. Vulcanization brings about a stiffness of the rubber by anchoring and restricting the intermolecular movement of the rubber springs. The vulcanization can be carried out in several ways:-
1. The article to be vulcanised is heated with a steam under pressure.
2. The article is immersed in hot water under pressure.
3. By heating the article in air or in carbon dioxide.
4. By vulcanizing the article in the mould in which it is shaped.
PROPERTIES OF VULCANIZED RUBBER.
• High tensile strength.
• Elastic to lesser extent.
• Water absorption is small.
• Do not swell much in organic solvents.
• Better abrasion resistance.