Define thermoplastics and thermosetting polymers with two examples of each.

A thermoplastic polymers are the linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. These polymers posses intermolecular forces of attraction intermediate between elastomers and fibres. For example polythene, polystyrene, polyvinyls, etc.
A thermosetting polymer are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible. These cannont be reused. For example are bakelite, urea- formaldehyde resin etc.