How are polymers classified into different categories on the basis of intermolecular forces? Give one example of a polymer of each of these categories.

(1) Elastomers: They have weakest intermolecular forces of attraction. They are elastic in nature. For example natural rubber, vulcanised rubber.
(2) Fibres: They are polymers having stronger forces having hydrogen-bonds. They have high tensile strength. For example: nylon, terylene.
(3) Thermoplastics: They can be easily moulded into desired shape by heating and then cooling. The force of attraction is intermediate between elastomers and fibres. For example: polythene, polypropone.
(4) Thermosetting plastics: They have the maximum force of attraction because they are cross-linked. They do not become soft on heating. For example Bakelite.