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.
Glass is hard, amorphous, transparent and homogenous mixture of silicates of different metals. P.V.C. is not used to cover the handle of pressure cooker but Bakelite is used because P.V.C. becomes soft on heating while Bakelite becomes hard on heating and is bad conductor of heat.
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.
The thermosetting plastic is used to cover the handle of pressure cooker because it is bad conductor of heat and it does not become soft on heating.
Environmentalists request to avoid the use of plastic because plastic is non-degradable substance which produces poisonous gas and pollutes the environment.
Two reasons that plastics are useful are:
a. It is cheaper and is easily available.
b. It can be recycled and reused.
The process of formation of soap is ______.
All the answers are correct
Fat or Oil + calcium hydrooxide
Fat or Oil + Sodium hydroxide
Fat or Oil + benzene sulphate
Thermoplastics used for mobile phone casings is ______.