. Define thermoplastics and thermosetting polymers with two examples of each.
Thermoplastic polymers Those polymers (linear or slightly branched long chain molecules), which are capable of softening on heating and hardening on cooling are called thermoplastics. These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres. Examples are polythene, polyvinyl chloride, polystyrene etc.
Thermosetting polymers Those polymers (cross-linked or heavily branched molecules), which on heating do not soften and cannot be remoulded are called thermosetting polymers. On heating they undergo extensive cross-linking in moulds and becomes infusible. Examples are Bakelite, urea-formaldehyde resins etc.