As we found out previously the process of vulcanisation and the addition of carbon
black not only make the rubber strong and less brittle, but they also prevent it
from streaching. Thisunwanted quality is removed by the addition of short chained
polymers(oils). Just like we use oil in a car engine to lubricate it these oils
added to the rubber lubricate the large polyisoprene chains which have been sulphur
bonded to each other. This allows the molecules to slide over one and other and uncoil
resulting in the material streaching. When the force streaching the rubber is released
then all the molecules re-coil and move over each other to their origional positions.
To find out more about rubber please take a look at
any of the listed topics below or any of the links.