Synthetic Fibres and Plastic NCERT CBSE Class 8 Science Chapter 3 Summary Note

 Synthetic Fibres and Plastic- 
                 Summary
        NCERT CBSE CLASS 8 SCIENCE


* Fibres-
       -Very thin thread
       - Thread is prepared from it.

* Fibres ----> Thread/Yarn---->Fabric/Cloth---->             ---->Dress

* Types of Fibres-
     (a) Natural fibres -
      -Fibres that are obtained from plants or 
       animals, is called natural fibres.
      -Examples- Cotton, Jute, Silk, Wool
     (b) Artificial/Synthetic fibres-
       -Fibres that are not obtained from plants
        or animals, is called synthetic fibres.
      -Examples- Rayon, Nylon, Acrylic,
                           tericot etc.,

* Monomer- (Mono- Single, Mere- Part/Unit)
     -Small Single unit whose repeatation make
      a large single unit.
     -Example- Paper is the monomer of book.

* Polymer- (Poly- Many, Mere- Part/Unit)
     -Large single unit which is formed from
      small single units.
     -Example- Book is the polymer of paper.

* Types of synthetic fibres-
      (a)Rayon (b) Nylon (c) Polyester (d) Acrylic

* Rayon-
   - Rayon is Also called artificial silk(because it
     is similar to silk)
   - Rayon  is obtained from wood pulp. (Yet it is
     a man-made fibre)
   - Rayon is cheaper than silk.
   - It can be woven like silk fibres.
   - Rayon can be dyed in wide variety of 
     colours.
   - Uses- Rayon is mixed with cotton to make 
                bedsheets.
             - Rayon is mixed with wool to make
               carpets.

* Nylon-
    - Nylon is First fully synthetic fibre.
    - Nylon is Prepared from coal, water and air.
    - Nylon is strong, elastic and light.
    - Nylon is lustrous and easy to wash.
    - Uses of Nylon-
       - Nylon is used to make - socks, ropes, tents,
         toothbrush, car seatbelt, sleeping bags,                 curtain etc.,
       -Nylon is used for making parachute.
       -Nylon is used for rock climbing ropes.

* Polyester-
    - Polyester is made from esters.
    - Polyester fabric do not wrinkle easily.
    - Polyester fabric remains crisp.
    - Polyester fabric is easy to wash.
    - Terylene and PET are a popular polyester.
    - Uses of PET polyester-
         Used for making bottles, utensils, films,
         wire etc.,

* Acrylic-
    - Acrylic is also called artificial wool.
      (Because it resembles wool)
    - Acrylic is cheaper than wool.
    - Acrylic is used to make sweater, shawl and
      blankets.

* Difference between natural fibre and synthetic/artificial fibres-
    - Natural fibres are obtained from plants or
      animals.
      Synthetic fibres are obtained from
      petrochemicals.
    - Natural fibres donot melt on heating.
      Synthetic fibres melt on heating.
    - Natural fibres are expensive.
      Synthetic fibres are cheaper.
    - Natural fibres are not readily available.
      Synthetic fibres are readily available.
    - Natural fibres are not easy to maintain.
      Synthetic fibres are easy to maintain.
    - Both Natural fibres and synthetic fibres are
      durable.
    - Synthetic fibres dry up quickly.
      Natural fibres dry up slowly.

* Plastic-
    - Plastic is a polymer like synthetic fibres.
    - Example- Polythene (Polymer of ethene)

* Types of plastic- (a) Thermoplastic 
                                   (b) Thermosetting plastic

* Thermoplastic-
   -Plastic which get deformed easily on heating.
   -Examples - polythene, PVC

* Thermosetting plastic-
    -Plastic which moulded once cannot be
     softened by heating.
    -Examples- Bakelite, Melamine etc.,

* PVC- Polyvinyl Chloride
           -PVC is used for making toys, combs,
            container etc.,

* Bakelite is poor conductor of heat and
   electricity.
   Bakelite is used for making electrical
   switches, handles of utensils.

* Melamine can tolerate heat better.
   Melamine is used for making floor tiles,
   kitchenware etc.,

* Characters of plastic-
    - Plastic is non-reactive.
    - Plastic is light, strong and durable.
    - Plastic is poor conductor  of heat and
      electricity.
    - Plastic is non-biodegrable substance.

* Biodegradable substance-
   -Substance which gets decomposed by action
    of microorganisms, is called biodegradable
    substance.
   -Example- Paper

* Non-biodegrable substance-
    -Substance which do not gets decomposed
     by action of microorganisms, is called non-
     biodegrable substance.

* We should avoid plastic. Reasons-
    - Plastic is non-biodegrable.
    - Plastic causes soil pollution.
    - On burning, plastic causes air pollution.
    - Plastic decrease soil fertility.

* 4R Principles-
    Reduce, Reuse, Recycle, Refuse.

* Teflon is used for nonstick coating on
    cookware.

* Melamine is used to make fire proof   
   uniform.