Properties of rubber are improved by compounding it with some chemicals like sulphur, hydrogen sulphide, etc.
Vulcanization is a chemical process for converting natural rubber or related polymers into more durable materials via the addition of sulphur or other equivalent curatives or accelerators. These additives modify the polymer by forming cross-links (bridges) between individual polymer chains. Extent of stiffness of vulcanized rubber depends on the amount of sulphur added. E.g. Tyre rubber has 3 to 5% sulphur.
Advantages of Vulcanization:
It has good tensile strength and extensibility.
It has excellent resilience i.e.it returns to the original shape, when the deforming load is removed.
It possesses low water absorption tendency.
It has higher resistance to oxidation, wear and tear abrasion.
It is better electrical insulator.
It is resistant to organic solvents (petro, benzene), fats and oils.
It has slight tackiness.
It has useful temperature range of -40.C to 100.C