Which of the following polymers soften on heating and harden on colling? What are the polyfmers with this property collectively called ? What are the structural similarites between such polymers? Bakelite urea formaldehyde resin , polythene, polyvinyls, polystyrene.

Explanation

Polythene, polyvinyls and polystyrene soften on heating and harden on coling. Such polymers are collaed thermoplastic polymers. These polymers are linear array of slightyl branched long chain molecules.
These posseess intermolecular forces whose strength lies betweeen strength of intermolecular forces of elastomers and fiber while bakelite urea formaldehyde resin are thermosetting polymers which on heating undergo extensive cross linking in moulds and again become infusible