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Synthetic Fibres- Chemistry Guide for Class 8

Synthetic Fibres- Class 8 Science Guide

Information about Synthetic Fibres

Title

Synthetic Fibres

Class

Class 8

Subject

Class 8 Chemistry

Topics Covered

  • Synthetic Fibres
  • Different Synthetic Fibres
  • Rayon or Artificial Silk
  • Nylon
  • Terylene
  • Poly Ethene Tetraphthalate (PET)
  • Acrvlic Fibres (Acrvlon)
  • Advantages of Synthetic Fibre
  • Disadvantages of Synthetic Fibres


There are plant fibres or animal fibres depending upon the source from which they are obtained. We can say that fibres, like cotton, jute, wool and silk, are obtained from 'natural sources'; they can, therefore, be called as natural fibres.

All natural fibres are used for making fabrics, which are then used for making clothes. These fibres are also used for making a large variety of household articles, like ropes, carpets, and a variety of other articles of daily use.

The demand for fibres and fabrics is so large that natural fibres are unable to fulfill it. To meet this 'ever-increasing demand' scientists have developed artificial fibres. These fibres are also called synthetic fibres or man-made fibres

Synthetic Fibres

  • It has now been found that natural fibres are made from simple molecules called monomers.
  • These monomers join in a large number to form a long chain molecule called a polymer.
  • A synthetic fibre is also a chain of small units (monomers) joined together.
  • The process, by which a polymer is made by joining a large number of small molecules, is called polymerisation.
  • Man-made polymers have been developed to meet the ever increasing demands of present day civilisation. 
In addition to natural and synthetic polymers, there is yet another class of polymers called semi-synthetic polymers. These are obtained from natural polymers by subjecting them to specific chemical processes. For example, vulcanised rubber is an example of a semi-synthetic polymer, formed by mixing molten rubber and molten sulphur, under specific conditions. 

Different Synthetic Fibres

Let us now study about the different types of synthetic fibres and their uses in some detail. 

1. Rayon or Artificial Silk

Silk fibre, obtained from silkworm, was discovered in China. Fabric, obtained from silk fibre, is quite costly; its texture is very beautiful.
Later on, attempts were made to make silk artificially. By the end of the nineteenth century, scientists were successful in their attempts.
  • A fibre, having properties similar to that of silk, was obtained by chemical treatment of wood pulp. This fibre was called Rayon or Artificial silk.
  • The raw material, used in the preparation of rayon, is wood cellulose which is a natural fibre. This natural fibre is processed to obtain a silk-like fibre. Therefore, rayon is sometimes also called regenerated fibre.
Rayon is thus, not completely an artificial fibre; its raw material is a natural fibre. 
Uses of Rayon
  1. Rayon can imitate the feel and texture of silk, wool, cotton and linen. Hence, it is often mixed with cotton (to make bed sheets) or mixed with wool (to make carpets).
  2. Rayon fabrics are smooth, cool and comfortable. Rayon can be easily dyed in a wide range of colours.
  3. It is suitable for wear in summer because its fabric can absorb sweat.
  4. It is used in making apparels (like dresses, jackets, linings, suits, hats, etc.)
  5. It is widely used in industries; in surgical products and in tyre cords. 

2. Nylon

It is a truly artificial (man-made) fibre. It does not use any natural fibre as its raw material. It is the first fully synthetic fibre. Nylon is also called the wonder polymer

Uses of Nylon
  1. It is highly elastic, tensile and has silk-like appearance. It is used in making carpets, socks and other hosiery items.
  2. Nylon is used in many military applications like making of ropes, parachutes, etc.
  3. It is highly durable. Hence, its fibres are used for making seat belts, tyre cords, clothes, etc.
  4. It is used for making common household articles, such as toothbrushes, combs, hooks, etc.
  5. It is used for making ropes for rock climbing; also used for making fishing nets.

3. Terylene

Terylene is another synthetic fibre which is used for making clothes. Like nylon, terylene is also elastic, highly durable, wrinkle resistant and moth resistant. 

Uses of Terylene
  1. It is largely used for making fabrics.
  2. It does not absorb water and is very strong. It is, therefore, used for making sails for boats, and for making raincoats.
  3. It is used for making conveyor belts.
  4. It is used in home furnishings.

4. Poly Ethene Tetraphthalate (PET)

It is a synthetic polymer commonly used to make bottles, boxes, etc.

Uses of PET
  1. It is used for making containers for packaging food and soft drinks. PET bottles are commonly used in industry for selling all kinds of soft drinks, oils and other food articles.
  2. It is used for making magnetic tapes used in audio and video cassette recordets. 

5. Acrvlic Fibres (Acrvlon)

These are synthetic fibres which appear to resemble wool. We wear sweaters and shawls in winter. Many of these are actually not made from natural wool; still they appear to resemble wool made articles. 

Uses of Acrylic fibres
  1. These are used for making blankets, which are very light and have quite the same warmth as woollen blankets. 
  2. Articles, made from acrylic fibres, are relatively less expensive and are available in a wide variety of colours. 


Advantages of Synthetic Fibre

  1. They have a long lasting lustre.
  2. They last longer as compared to natural fibres.
  3. They are easy to clean.
  4. They dry quickly.
  5. They do not wrinkle and, therefore, need very little or no ironing.
  6. They do not shrink on washing.
  7. They ate less expensive than natural fibres.

Disadvantages of Synthetic Fibres

  1. They have very low melting point (melt at very low temperature); they burn to form small sticking beads at high temperature. It is, therefore, not advisable to wear synthetic clothes while working in the kitchen.
  2. Unlike natural fibres, they do not absorb sweat. Clothes made from synthetic fibres are, therefore, very uncomfortable in summer and rainy season.
  3. Synthetic fibres are not biodegradable; hence they cause a lot of pollution. 

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