Rubber is an elastic material made up of long chain molecules known as polymers. Such polymers occur naturally in the sap of Hevea and Ficus trees, but for industrial purposes are now more often synthesised from a variety of other chemical compounds having short chain molecules, or monomers.

In their raw form polymers generally lack most of the properties required in finished rubber products. It is not until these polymers are mixed together with other materials, or compounded, that these properties are achieved.