NCERT Gist: Synthetic Fibres and Plastics | Additional Study Material for UPSC PDF Download

- Natural fibres like cotton, wool, silk, etc., are obtained from plants or animals.
- The synthetic fibres, on the other hand, are made by human beings.
- That is why these are called synthetic or man-made fibres.
- A synthetic fibre is also a chain of small units joined together.
- Each small unit is actually a chemical substance.
- Many such small units combine to form a large single unit called a polymer.
- The word ‘polymer’ comes from two Greek words; poly meaning many and mer meaning part/unit.
- So, a polymer is made of many repeating units.
- Cotton, for example, is a polymer called cellulose. Cellulose is made up of a large number of glucose units.

Types of Synthetic Fibres

- Fibre was obtained by chemical treatment of wood pulp. This fibre was called rayon or artificial silk.
- Although rayon is obtained from a natural source, wood pulp, yet it is a manmade fibre.
- It is cheaper than silk and can be woven like silk fibres.
- It can also be dyed in a wide variety of colours.
- Rayon is mixed with cotton to make bed sheets or mixed with wool to make carpets.
- Nylon is another man-made fibre.
- In 1931, it was made without using any natural raw material (from plant or animal).
- It was prepared from coal, water and air.
- It was the first fully synthetic fibre.
- Nylon fibre was strong, elastic and light. It was lustrous and easy to wash.
- So, it became very popular for making clothes.
- Nylon is also used for making parachutes and ropes for rock climbing.
- A nylon thread is actually stronger than a steel wire. Polyester is another synthetic fibre.
- Terylene is a popular polyester.
- PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.
- We wear sweaters and use shawls or blankets in the winter. Many of these are actually not made from natural wool, though they appear to resemble wool.
- These are prepared from another type of synthetic fibre called acrylic.
- The wool obtained from natural sources is quite expensive, whereas clothes made from acrylic are relatively cheap.
- All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.
- Plastic is also a polymer like the synthetic fibre.
- All plastics do not have the same type of arrangement of units.
- In some it is linear, whereas in others it is cross-linked.
- Polythene (Poly+ethene) is an example of a plastic. Plastic which gets deformed easily on heating and can be bent easily are known as thermoplastics.
- Polythene and PVC are some of the examples of thermoplastics.
- These are used for manufacturing toys, combs and various types of containers.
- Some plastics which when moulded once cannot be softened by heating.
- These are called thermo setting plastics. Two examples are bakelite and melamine.
- Bakelite is a poor conductor of heat and electricity.
- It is used for making electrical switches, handles of various utensils, etc.
- Melamine is a versatile material.
- It resists fire and can tolerate heat better than other plastics.
- It is used for making floor tiles, kitchenware and fabrics which resist fire.
- Plastics are poor conductors of heat and electricity.
- Teflon is a special plastic on which oil and water do not stick. It is used for nonstick coating on cookwares.
- A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable.
- A material which is not easily decomposed by natural processes is termed as non-biodegradable.
- Plastic takes several years to decompose, it is not environment friendly.