Important Notes for CBSE Class 8 Science Chapter 3 – Synthetic Fibres and Plastics. Synthetic Fibres and Plastics Class 8 Notes and Study Material Download in PDF form.
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Synthetic Fibres and Plastics Class 8 Notes
- Fibers: Fibers are thin, long strands which can be spun into yans and woven into fabrics
Classification: They are of two Types
Natural fibers:
Fibers obtained from plant or animal source e.g.: cotton, silk, wool etc.
Examples of natural fibers
Silk
- Silk is a natural fiber obtained from silkworms.
- The process was first obtained in China.
- It is very expensive and has good texture and used to make sarees etc.
Synthetic fibers:
Manmade fibers or fibers synthesized by humans in industries are called synthetic fibers. E.g., rayon, nylon etc.
Synthetic fibers are obtained bychemical processing of petrochemicals
- Polymers: A synthetic fiber made up of many small repeating subunits. It is derived from Greek word ‘poly’ meaning many and ‘Mer’ meaning unit
Examples of synthetic fibers
Rayon
- It is obtained by chemical treatment of wood pulp.
- It is known as Artificial silk.
- It is cheaper than silk
- It can also be mixed with cotton and wool
Nylon
- Nylon is strong, elastic, light, lustrous, easy to wash.
- It is the first completely synthetic fiber composed from coal, air and water
- It has number of applications in synthesis of ropes, tents, parachutes ropes, belts, bags, curtains etc.
Polyester
- Polyester is a wrinkle free fibric, easy to wash fibric. E.g., Terylene
- It is a polymer made out of repeating unit of esters.
- It can be mixed with wool to make polywool, with cotton to make polycot etc.
- PET also known as polyethylene terephthalate has a number of applications in making bottles, films, wires etc.
Acrylic
- It is an alternative fiber to wool which is quite expensive.
- Acrylic is cheaper, can be easily dyed and sturdy than natural wool.
Advantages of synthetic fibers
- They are less expensive
- They are readily available, durable, dries up quickly etc.
Plastics:
- It is a synthetic fiber composed of large chains of carbon. The carbon chain can hane two possible arrangement:
- Linear or
- Cross-linked arrangement.
- Plastics are available in different colors, sizes, can be easily remolded and reused
- One common example is polythene used to make bags.
Two types of plastics
- Thermoplastics:
These plastics get easily bent or deformed when heated. E.g., PVC, Polythene used for making toys, combs and containers
- Thermosetting plastics:
Once molded these plastics, cannot be reused again by heating. E.g., Bakelite and Melamine
Advantages of using plastic
- It is non-reactive
- It is light,strong and durable
- Plastics are poor conductors of heat and electricity.
Plastic and the environment:
- Plastic is non-biodegradable and takes a number of years for degradation.
- It causes environmental problems as burning process is quite slow and releasees fumes in the atmosphere
- It is very important to use plastics responsibly
- One should keep the 5 Rs in mind when using plastic- Reduce, Reuse,Recycle, Recover and Refuse