Synthetic Fibres and Plastics

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Synthetic Fibres and Plastics

Plastics and fibres are the most widely used material around us. From packaging to clothing, we need it for almost every essential purpose. One of the important parts of the Class 8 course is the chapter on Synthetic Fibres and Plastics. In this blog, we shall discuss synthetic fibres and plastics class 8. Let’s now check out the best notes for this chapter:

Synthetic Fibres and Plastics: Types of Fibres

Here are two types of fibres – natural fibres: obtained from natural sources e.g. Cotton, silk, wool and synthetic fibres which are man-made for example – rayon, nylon, acrylic etc.

Synthetic Fibres

They are made by joining small units of chemical substances known as monomers together. Polymers are formed by the combination of monomers

Types of Synthetic Fibre

  • Rayon- A man-made fibre obtained from wood pulp and can be dyed in a wide variety of colours. Rayon is mixed with cotton to make bedsheets or mixed with wool to make carpets
  • Nylon- Nylon was the first commercially synthesized fibre. Nylon is synthesized from coal, water and air. Nylon is very strong and its fabric is like silk.
  • Polyester- Polyester, one of the most popular man-made fibres, is made of a repeating unit of a chemical called ester and widely used to make clothes.
  • Acrylic- Acrylic is a man-made fibre. Acrylic is known as artificial wool or synthetic wool because it resembles wool. Acrylic is cheaper than natural wool and can be dyed in various colour. This makes acrylic is very popular among other fabrics.

Characteristics of Synthetic Fibres

  •   Synthetic fibres are not very expensive
  •    They are stronger
  •     Synthetic fibres are more durable
  •     Can be dried up in less time
  •    Easy to maintain 

Plastics

Plastic is a polymer in which units can have linear arrangement whereas some plastics are formed by the cross-linked arrangement of their units. Plastics can be easily recycled, coloured, reused, mould or drawn into wires or various other shapes. Plastic is popularly used in making toys, suitcase, bags, cabinets, brush, chairs, tables, and many other countless items. Polythene is one of the most famous types of plastic, which is used in manufacturing of carry bags.

Types of Plastics

There are two types of plastics :

  • Thermoplastic- Can be easily bent or deform on heating. PVC and Polythene are examples of thermoplastics.
  • Thermosetting plastic-  Do not get deformed or softened on heating when mould once. Bakelite and melamine are examples of thermosetting plastics.

Characteristics of Plastics

  • Poor conductor of heat and electricity.
  • Does not react with air and water and with many of the chemicals.
  • Lightweight, durable, cheap and very strong.
  • Non- biodegradable substances and takes years to get decomposed and sometimes does not get decomposed at all. 

Synthetic Fibres and Plastics: NCERT Selected Answers

Explain why some fibres are called synthetic.

Some fibres are called synthetic fibres because they are man made. 

2.Mark (✓) the correct answer.
Rayon is different from synthetic fibres because
(a) it has a silk-like appearance.
(b) it is obtained from wood pulp.
(c) its fibres can also be woven like those of natural fibres.

(b) it is obtained from wood pulp.

Fill in the blanks with appropriate words.
(a) Synthetic fibres are also called ____ or ____ fibres.
(b) Synthetic fibres are synthesised from a raw material called _____
(c) Like synthetic fibres, plastic is also a _____

Answer:
(a) man-made, artificial fibres
(b) petrochemicals
(c) polymer

Give examples which indicate that nylon fibres are very strong.

(i) They are used for making parachutes and ropes for rock climbing.
(ii) They are used in making seat-belts, fishing nets, tyre cord, a string for sports rackets and musical instruments.

Explain why plastic containers are favoured for storing food.

Plastic containers are favoured for storing food because they do not react with the food stored in them, are lightweight and are strong and easy to handle.

Explain the difference between thermoplastic and thermosetting plastics.

Thermoplastic: Can be easily bent or deform on heating. PVC and Polythene are the examples of thermoplastics. Thermosetting plastic:  Do not get deformed or softened on heating when mold once. Bakelite and melamine are the examples of thermosetting plastics.

Explain why the following are made of thermosetting plastics.
(a) Saucepan handles
(b) Electric plugs/switches/plugboards

(a) Since, thermosetting plastics are a bad conductor of heat and do not get heated up while cooking, they are used for making saucepan handles.
(b) Since thermosetting plastics are a bad conductor of electricity and the electric current does not pass through such plastics, they are used for making electric plugs/switches/plugboards.

8. Categorise the materials of the following products into ‘can be recycled’ and ‘can not be recycled’.
Telephone instruments, plastic toys, cooker handles, carry bags, ballpoint pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Can be recycled: Plastic toys carry bags, plastic bowls, plastic covering on electrical wires, plastic chairs.
Cannot be recycled: Telephone instruments, cooker handles, ballpoint pens, electrical switches.

Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

He should buy cotton shirts as cotton has more capacity to hold moisture than synthetic clothes. In summers the sweating is easily soaked by cotton shirts.

Give examples to show that plastics are non-corrosive in nature.

Plastic containers do not react with items stored in it.
They do not get rusted when exposed to moisture and air.
They do not decompose when left in open for a long period.

This was all about synthetic fibres and plastics class 8. For more such content, stay connected to Leverage Edu!

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