Rubber has been used since ancient times. The Aztecs and M ayas o f South America
used rubber for shoe soles, coated fabrics, and playballs well over 2,000 years ago.
Rubber was used successfully on a commercial scale since the 18th century. Real
progress occurred with the development o f the vulcanization process in the mid 19th
century. This process gave increased strength, elasticity, and resistance properties to the
rubber compound. Rubber offers some unique properties including high extensibility,
softness and flexibility, impermeability to gases and high friction. Conventional rubber
compounds are therm oset materials as a result o f the vulcanization (crosslinking) process.
M ost rubber compounds are composed o f many additives to give the desired properties to
the finished product. The m odem process o f rubber manufacturing involves mastication,
mixing, shaping, m olding and vulcanization.