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How do elastomers return to their original shape after being stretched?

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Diagram illustrating a homopolymer arrangement using polyvinyl chloride as an example, showing a chain of identical repeating vinyl chloride units with the chemical structure highlighted. — polymer Industrial polymers are synthesized from simple compounds joined together to form long chains. For example, polyvinyl chloride is an industrial homopolymer synthesized from repeating units of vinyl chloride.

Elastomers are able to return to their original shape after being stretched due to the unique behavior of their long, chainlike polymer molecules.1

Under normal conditions, these molecules exist in an irregularly coiled, compact, and random arrangement. When an external force is applied, the molecules straighten out in the direction of the pull. Once that force is released, the molecules spontaneously return to their disordered, coiled state through the random motion of their repeating units, which is facilitated by rotations around carbon-carbon bonds.12

For an elastomer to exhibit this high elasticity, it must not be in a glassy state—meaning its glass transition temperature must be well below room temperature—and it must not spontaneously crystallize. Additionally, many elastomers undergo vulcanization, a process of cross-linking that ties the molecules together into a loose network. This prevents the molecules from flowing past one another, ensuring the material maintains its structural integrity and recovers its shape even when warm.23