Page 34 - Curriculum Visions Dynamic Book

Rubber, a natural addition polymer
Rubber is the name of an elastic material that can be stretched to several times its own length before breaking. The word rubber originally referred to the material, known as latex, that is the sap of the rubber tree. However, a wide variety of synthetic rubbers are now also produced.
The rubber molecule is an example of a polymer, a giant molecule made of tens of thousands to millions of simple units arranged in a chain.
The individual units (called monomers) are each about the size of a sugar molecule.
The rubber polymer is elastic because the long chains are linked together (called cross-linking). Each chain can be pulled
slightly past each other chain. The cross-linking, however,
pulls the chains back into their original place when the force
is removed.
Rubbers can be more strongly cross-linked using sulphur through a process called vulcanisation. Vulcanisation produces the very strong form of rubber used for vehicle tyres.
 Latex is tapped from rubber trees and then collected for processing. It is still a very labour-intensive operation.
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