Monday 7 September 2020

LECTURE -3 : CLASS VIII : SCIENCE : CHAPTER 3 : SYNTHETIC FIBRES & PLASTICS

CLASS VIII   |    SCIENCE    |    CHAPTER 3
      notes prepared by subhankar Karmakar
                                                                         

ADVANTAGES OF SYNTHETIC FIBRES

Important properties and advantages of synthetic fibres as follows:

1. Synthetic fibres are very strong whereas natural fibres like cotton, wool and silk have low strength. 

2. Synthetic fibres are more durable. Synthetic fibres have high resistance to abrasion and hence, the clothes made of synthetic fibres are very durable whereas natural fibres like cotton, wool and silk have low abrasion resistance due to which the clothes made of natural fibres are not much durable. They do not last long.

3. Synthetic fibres absorb very little water and hence, the clothes made of synthetic fibres dry up quickly. On the other hand, natural fibres like cotton, wool and silk absorb a lot of water. So, the clothes made a natural fibres do not dry up quickly.

4. Synthetic fibres are wrinkle resistant and hence, class made of synthetic fibres do not get crumpled easily during washing or wear. They keep permanent creases. But, natural fibres like cotton, wool and silk are not wrinkle resistant. So, the clothes made of natural fibres get crumpled easily during washing and wear.

5. Synthetic fibres are quiet lightweight. Whereas natural fibres are comparatively heavy.

6. Synthetic fibres are extremely fine. So the fabrics made from synthetic fibres have a very smooth texture. But, natural fibres are not so fine. Therefore, the fabrics made from natural fibres do not have a very smooth texture. 

7. Synthetic fibres are not attacked by moths. But natural fibres are damaged by moths.

8. Synthetic fibres do not shrink. So, the clothes made of synthetic fibre retain their original size even after washing. On the other hand, natural fibres shrink after washing.

9. Synthetic fibres are less expensive and readily available as compared to natural fibres.

10. Clothes made from synthetic fibres are easier to maintain as compared to those made from natural fibres.

11. The manufacturing of fully synthetic fibres is helping in the conservation of forests. As the synthetic fibres are made from petrochemical products, so no trees have to be cut down for making them. On the other hand, semi synthetic fibres like Rayon are made from wood pulp request cutting down of forest trees.


DISADVANTAGES OF SYNTHETIC FIBRES:

There are several disadvantages of synthetic fibres. They are as follows:

1. Synthetic fibres always melt on heating. Therefore, if a person is wearing clothes made of synthetic fibres and his clothes catch fire accidentally, then the synthetic fibres of clothes melt and stick to the body of the person causing severe burns. So, it is quite safe to wear clothes made of natural fibres while working in the kitchen or in a science laboratory.

2. The clothes made of synthetic fibres are not suitable for wearing during hot summer weather. As the synthetic fibres are extremely fine so the clothes made of synthetic fibres do not have sufficient pores for the sweat to come out, evaporate and coo our body. Due to this, clothes made of synthetic fibres make us feel hot and uncomfortable during summer. 

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