Plastics is a synthetic polymer. They can be designed in any shape by applying heat or pressure.
The plastics that does not become soft on heating and cannot be remolded into desired shapes is called thermosetting plastic. It is hard and strong. It becomes harder when heated but it does not melt. It is generally resistant to heat. That is why they are used as heat bearing insulator. It is used in electric switches, plugs, handles of pressure cooker and tea kettle, radio and TV cabinets, etc Bakelite, Melamine, etc are some examples of it.
The plastic which becomes soft on heating and can be remolded into desired shape is called thermoplastic. It is usually elastic and soft. It can be given any shape when they are heated again and again.It means they can be remolded second time for different purpose. They are used in making ropes, bucket, pipe, etc. The main types if thermoplastics are polythene, Polyvinyl Chloride(PVC) and polystyrene.
The major two causes of chemical pollution due to plastic are:
a. Plastics are non-degradable.
b. Many plastics often produce poisonous gases and smoke on burning.
Two reasons that plastics are useful are:
a. It is cheaper and is easily available.
b. It can be recycled and reused.
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