find main points of synthetic fibres and plastics class 8
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Answer:
Explanation:
Fibres and Fabrics
The clothes are made of fabrics. Fabrics are made from fibres obtained from natural or artificial sources.
Types of Fibres:
1. Natural fibres: These are obtained from natural sources, called natural resources. Examples: cotton, silk, wool, etc.
2. Synthetic fibres: These are man-made are called man-made or synthetic fibres. Examples: rayon, nylon, acrylic, etc.
(i) Synthetic fibres are made of small units of chemicals joined together in the form of large chain. The formed chain is called polymer.
(ii) Polymer is a Greek word in which ‘poly’ means many and ‘mer’ means units. So, a polymer is made of many repeating units.
(iii) Polymers occur in nature also. Example: Cotton is a polymer called cellulose. Cellulose is made up of a large number of glucose units.
Types of Synthetic Fibres:
1. Rayon:
(i) Fibre is obtained by chemical treatment of wood pulp. This fibre is called rayon or artificial silk.
(ii) Rayon fibre can be made in different colours by dyed. Rayon is very cheap compared to silk.
(iii) Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets.
2. Nylon:
(i) Nylon is man-made fibre. It was first fully synthesized fibre. The production of nylon was started without using any natural raw material (from plant or animal) almost simultaneously in New York and London, thus it got its name (NY for New York and Lon for London) as nylon. It is synthesized from coal, water and air. Cloths from nylon are very strong elastic and light lustrous and easy to wash.
(ii) Firstly nylon was used in making bristle of toothbrush commercially. After that, it was used for making fabrics.
(iii) Nylon is used for making clothes, ropes, socks, curtains, sleeping bags, parachutes, etc. The nylon fibre is stronger than a steel wire.
3. Polyester:
(i) Polyester (Poly + ester) is made up of the repeating units of a chemical called an ester.
(ii) Polyester is a man made or synthetic fibre. Fabric made from this fibre does not get wrinkled easily, remains crisp and easy to wash. Example: shirts, pants, jacket, bed sheets, curtains, sarees, mouse-pad, etc.
(iii) Polyester is used to make ropes, fabrics for conveyor belt, cushioning and insulating material in pillow, etc.
4. Acrylic:
(i) Acrylic is man-made or synthetic fibre. Acrylic resembles wool. It is also called as artificial wool or synthetic wool. Acrylic is cheaper than natural wool and can be made in various colours by dyeing.
(ii) Clothes are made from acrylic are relatively cheaper than cloths are made by wool.
(iii) Acrylic is used in making sweaters, blanket, and other many clothes.
Characteristics of Synthetic Fibres:
(i) Synthetic fibres are cheaper, stronger and durable than natural fibre.
(ii) It is easy to maintain, easy to wash, dry up in less time and readily available.
(iii) Synthetic fibres possess unique characteristics which make them popular dress materials.
Plastics:
(i) Plastic is also a polymer like the synthetic fibre. All plastics do not have the same arrangement of units. In some it is formed in linear, whereas in others it is formed cross-linked
Types of Plastic:
Plastic can be divided into two main types – Thermoplastics and Thermosetting
1. Thermoplastic:
(i) Such plastics which get easily bent or deform on heating are known as thermoplastic.Examples of thermoplastics are PVC and Polythene.
(ii) It is used in making toys, bottles, combs, containers, etc
2. Thermosetting plastic:
(i) Such plastics which when mould once, cannot be softened or deformed by heating. These are called thermosetting plastics. Examples of thermosetting plastics are Bakelite and melamine.
(iii) Melamine is versatile material and poor conductor of heat. It resists fire, thus it is used in making floor tiles, kitchen materials, fabrics which resist fire.
(iv) Bakelite is poor conductor of electricity and heat, thus it is used for making electrical switches, handles of various utensils and other electrical appliances.
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