Plastics | Synthetic Fibres and Plastics | CBSE Class 8 Science | Chapter 3

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Plastics | Synthetic Fibres and Plastics | CBSE Class 8 Science | Chapter 3
What is fibres/fibers? what is plastic, types of fibers, types of plastics, natural fibres and artificail fibres etc. topics are described in this video.

First of all, check out the other part here,
Part 1 :

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Now the first thing is to know is,

What is Fiber?

Fibers are very thin, a thread-like strands from which clothes are made.

Types of Fibres:

1) Natural Fibres
2) Artificial Fibres or Synthetic Fibres

What is the Plastics?

Plastic is a polymer that can be recycled, colored, reused, mould or drawn into wires or various other shapes.

Types of plastics:

There are mainly 2 types of plastics.
1) Thermoplastics
2) Thermosetting


A plastic which can be softened repeatedly by heating and can be moulded into different shapes, again and again, is called thermoplastic.

Thermoplastics are also known as ‘thermosoftening’ plastics.

Examples: Polythene and Polyvinyl chloride (PVC)

These are used for manufacturing toys, combs and various types of containers.

In thermoplastics, the long polymer chains are not cross-linked with one another. Due to this, on heating, the individual polymer chains can slide over one another. This makes thermoplastic soft and capable of melting.


A plastic which once set, does not become soft on heating and cannot be moulded a second time, is called a thermosetting plastic.

Thermosetting plastics are also known as ‘thermosets’.

In thermosetting, the long polymer chains cross-linked with one another. This cross-linking prevents the displacement or sliding of individual polymer chains on heating.
Due to this, thermosetting plastics do not become soft on heating once they have been set into a particular shape.

Examples: Bakelite and melamine.

Bakelite is a poor conductor of heat and electricity. It is used for making electrical switches, handles of various utensils etc.
Melamine resists fire and can tolerate heat better than other plastics.
It is used for making floor tiles, kitchenware, and fabrics which are fire-resistant.

Properties of plastics:

1) They are chemically inactive. Examples are Iron, Plastic.

Metals like iron get rusted when exposed to air and water for a long time. This is because metals are chemically reactive. Plastics do not react with air and water. Due to this, plastics are resistant to corrosion. In other words, plastics are not affected by the weather. Plastics are also often unaffected by various chemicals like acids and bases.

2) It is a poor conductor of heat.
3) Plastics are a bad conductor of electricity.
4) Plastic is light and cheap, at the same time it is strong and durable. An example is Metal Pipe, Plastics Pipe
5) Plastics can be moulded into different shapes. Like Bucket, Mugs, Furniture Items, Bags, Slippers, Toys, Comb, Toothbrush.

All the above-mentioned topics are described in an interactive and efficient manner so that the students could easily understand them.

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