Physical properties of rubber

Molecular deformation of raw rubber

Here is a diagram of the deformation of rubber molecules in raw and cross-linked rubber.
Raw rubber is rubber that has not been cross-linked. (see above)
In its raw rubber state, it expands and contracts when force is applied, but does not fully return to its original shape after the force is removed.
This is because the entanglement of rubber molecules, which are formed by the intertwining of rubber molecular chains, unravels during deformation and the rubber molecules are cut and broken apart.
The state of raw rubber does not fully achieve the property of elastic deformation.

Molecular deformation of cross-linked rubber: the property of elastic deformation.

Cross-linked rubber is raw rubber that has been cross-linked.
Cross-linking is the process of linking polymers together and changing their physical and scientific substance. (The red dot in the diagram of cross-linked rubber is the cross-linking point).
Cross-linking generates cross-linking points.
This cross-linking point allows the rubber to scientifically bond the molecular chains together so as to prevent their entanglement from unravelling.
By cross-linking raw rubber, the property of elastic deformation can be achieved.