Question

If rubber is mixed with sulphur in less propartion

Answer 1

it is known as vulcanisation of rubber

Answer 2

In most instances, raw rubber for general use (natural rubber, butadiene, or butadiene-styrene) is vulcanized by heating it with elemental sulfur to 140°-160° C (sulfur vulcanization). The intermolecular cross-links that form are made up of one or several sulfur atoms. If 0.5 to 5 percent sulfur is added to the raw rubber, a soft vulcanizate (for automotive inner tubes and tire casings, balls, tubes, and so on) is formed. The addition of 30 to 50 percent sulfur leads to the formation of a hard, inelastic substance, ebonite. Sulfur vulcanization can be accelerated by the addition of small quantities of organic compounds—so-called vulcanization accelerators such as kaptaks or thiuram