Thermoplastic polymers are the linear or slightly long chain molecules capable of repeatedly softening and hardening on cooling and can be reused.

Thermosetting polymers are cross-linked or heavily branched molecules, which on heating undergo extensive cross-linking in moulds and again become infusible.

The thermosetting polymer, often called a thermoset, is obtained by irreversibly hardening a soft solid or viscous liquid prepolymer. These cannot be reused.

Elastomers have polymer chains held together by weak intermolecular forces and high elasticity. Fibres have high tensile strength.

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