Q.Why do elastomers possess elastic properties?

Elastomers are polymers that can be stretched to several times their original length and then return (retract) to nearly their original shape and size when the deforming force is released. This elastic behaviour arises from their molecular structure:

1. In the relaxed (unstretched) state, the polymer chains are held together by only weak intermolecular forces (van der Waals forces), and the chains themselves are coiled/curled in a random, irregular arrangement (not closely packed as in a fibre).
2. On applying a stretching force, these weak forces allow the coiled chains to uncoil and align/straighten along the direction of the applied force.
3. A few 'crosslinks' are introduced between the chains (either naturally present or, more effectively, introduced by processes such as vulcanisation with sulfur). These crosslinks act like tiny anchors that prevent the chains from slipping past one another permanently. …

Describe the resting coiled state (weak intermolecular forces), what happens on stretching (uncoiling/alignment), and the role of the sp …

• Saying elastomers have 'strong' intermolecular forces — it is actually the opposite; weak forces allow the stretching.
• Omitting the role of crosslinks, which is essential to explain the 'return to original shape' part of elasticity. …