Define thermoplastics and thermosetting polymers with two examples of each

Thermoplastics polymer

The polymers that soften on heating and which can be converted into any shape on cooling are called thermoplastics. The process of heating, reshaping and retaining the shape on cooling can be repeated several times without affecting their properties much. They are either linear or slightly branched long chain molecules. Their intermolecular forces of attraction are intermediate between elastomers and fibers.

Example - polythene, polystyrene, polyvinyl chloride

Thermosetting polymers

Some cross-linked or heavily branched polymers undergo chemical changes and cross linking on heating and become permanently hard, rigid and infusible on cooling. These are called thermosetting polymers and they do not soften on reheating, instead, they undergo degradation. These are not reusable.

Example - phenol-formaldehyde (bakelite), urea-formaldehyde