Ch – 3 Synthetic Fibres & Plastic

Important Notes:

  • A fibre is a strong and flexible thread-like material which is used to make fabric.
  • Fibres are of two types: Natural fibres and Synthetic fibres.
  • Natural fibres are those fibres which are obtained from plants or animals. For eg: wool, silk, cotton, etc.
  • Synthetic fibres are those fibres which are obtained through different chemical processes in industries. For eg: Rayon, Nylon, Polyester, etc.
  • A monomer is a small molecule which can combine together end to end in large number to form a larger unit.
  • A polymer is a very large unit formed by the combination of a large number of smaller molecules joined end to end by chemical bonds.
  • Polymerisation is a process of joining together a large number of smaller molecules to form a very large molecule.
  • Polyvinyl chloride (PVC) is used for making water pipes, soles of shoes and sandals, handbags, raincoats, bathroom curtains, etc.
  • Nylon is prepared by the polymerisation of amide molecules.
  • The polymers is which monomers are linked in a linear arrangement are known as linear polymers.
  • The polymers in which monomers are cross-linked to each other are known as cross-linked polymers.
  • Rayon:
    • It is prepared from wood pulp.
    • wood pulp is dissolved in an alkaline solution and passed through tiny pores to convert them into fibres.
    • As it resembles silk in appearance, it is known as artificial silk.
    • It is also known as regenerated fibre because it is reformed from original cellulose fibres.
    • It is used in textile industries.
    • It is mixed with cotton to make bed sheets, dresses, etc.
    • It is mixed with wool to make carpets.
    • It is used in manufacturing tyre cords.
    • It is used in making bandages.
  • Nylon:
    • It is the first fully synthetic fibre.
    • It is a polyamide fibre prepared by polymerisation of large number of amide molecules.
    • It is strong, lustrous, easy to wash, wrinkle-free, lightweight, elastic, etc.
    • It does not absorb water.
    • It is used for making ropes, parachute fabrics, fishing nets, etc. because of its high tensile strength.
    • It is used in textile industries.
    • It is mixed with wool to make socks, carpets, etc.
    • It is used in making parts of machines.
  • Polyester:
    • It is a polymer made up of the repeating units of a chemical named ester.
    • Ester gives fruity smell.
    • Examples of polyester are terylene, terene, dacron, etc.
    • When terylene is mixed with cotton it forms terrycot and when it is mixed with wool it forms terrywool.
    • It is light, strong, absorbs little amount of water, dries quickly and is wrinkle-free.
    • It is used in making sari, dress materials, curtains, etc.
    • It is used in making water hoses.
    • It is used in making conveyor belts.
  • Acrylic:
    • It is made from a polymer named polyacrylonitrile.
    • It is lightweight, soft, and can be dyed with different colours.
    • It is used in making sweaters, shawls, blankets, jackets, etc.
  • Advantages of Synthetic Fibres:
    • High tensile strength
    • Low water absorption
    • Wrinkle-free
    • Durable
    • Moth resistant
    • Lightweight
    • Inertness
    • Less expensive
    • Good elasticity
  • Disadvantages of Synthetic Fibres:
    • Can burn easily
    • Non-biodegradable
    • Absorbs little water
    • Causes skin problems
  • Plastics:
  • It is made up of carbon compounds.
  • It can be moulded into any shape.
  • It melts easily.
  • Types of plastic:
    • Thermoplastics:
    • It deforms easily on heating and can be moulded again into any shape.
    • Eg: Polythene, Polyvinyl Chloride, Polystyrene
    • Thermosetting Plastics:
    • It doesn’t deform on heating.
    • Eg: Bakelite, Melamine, Formica.
  • Properties of Plastics:
    • It is non-reactive.
    • It is light-weight.
    • It is durable.
    • It is poor conductor of heat and electricity.
    • It is inert to chemicals.
    • It is insoluble in water.
  • Teflon is used in making non-stick cookwares.
  • Bakelite is used in making switches, plugs, and handles of utensils.
  • PVC is used as an insulation cover in electric wires.
  • Polystyrene is filled in the hollow walls of refrigerator, air coolers and thermos flasks.
  • Melamine is used in making unbreakable kitchenwares, tiles, decorative objects, etc.
  • Thermocol is used in making disposable cups and packaging materials.

Published by Priya Prakash

In the midst of winter, i found there was within me an invincible summer ~ Albert Camus

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