Question

Define the thermoplastic and thermosetting polymers. Give one example of each.

Answer 1

Thermoplastics are defined as polymers that can be melted and recast almost indefinitely. They are molten when heated and harden upon cooling. When frozen, however, a thermoplastic becomes glass-like and subject to fracture. These characteristics, which lend the material its name, are reversible, so the material can be reheated, reshaped, and frozen repeatedly. As a result, thermoplastics are mechanically recyclable. Some of the most common types of thermoplastic are polypropylene, polyethylene, polyvinylchloride, polystyrene, polyethylenetheraphthalate and polycarbonate.


 A thermosetting plastic is a polymer that irreversibly becomes rigid when heated.

Vulcanized rubber and fiberglass are thermosetting plastics

Answer 2

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■ Thermoplastics :

Thermoplastics are the polymers which can be easily softened repeatedly on heating and hardened on cooling. Therefore, it can be used again and again. For example,

Polythene

Polyvinyl chloride

■ Thermosetting polymers :

Thermosetting polymers are those which undergo permanent change on heating. They become hard and infusible on heating and cannot be softened again. For example,

Bakelite

Melamine-formaldehyde