Rubber is a white elastic solid with properties like good elasticity, water repellency etc. Also it's a good electrical insulator. Rubber showed different characteristics at different temperature for example- at high temperature it become sticky and at low temperature it become brittle. It was Charles Goodyear who discovered the usefulness of sulphur in improving the properties of rubber, in 1839. According to this new discovery, rubber when mixed with sulphur and cooked at 120°C to 160°C, converted into a substance which functioned as elastic over wide range of temperature. It didn't become sticky or brittle and also its mechanical durability increased.
Organic formula of rubber is C5H8 including C=C bonds to each unit. These double bonds enable sulphur to prepare cross linking between the polymer chains. Rubber with 0.915 g/cc density is a (1,4) polymer of isoprene. However, it has not been possible to reproduce the natural rubber. Natural rubber will be in the demand till it's cost-effective, as there are many types of artificial rubber have been produced into different countries. Production of artificial rubber was highly encouraged by the break-down of plantation rubber during 2nd world war.
Different quantity of sulphur mixed with rubber, results in different applications. For instance 32% sulphur mixed with rubber gives the hard rubber which is highly durable plastic. Also called as ebonite, this hard rubber was once used in many electrical apparatus as structural material and later replaced with other cheaper plastics.
5% sulphur mixed with rubber makes it flexible and soft.