Synthetic Fibres And Plastics || NCERT Notes || CTET / TET / Other Exam Preparation Notes

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FIBRE TO FABRICS || Complete Notes || NCERT Based

INTRODUCTION: SYNTHETIC FIBRES AND PLASTICS

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.

Polymers occur in nature also!

Cotton, for example, is a polymer called cellulose. Cellulose is made up of a large number of glucose units.

TYPES OF SYNTHETIC FIBRE:

RAYON:

Fabric obtained from silk fibre was very costly. But its beautiful texture fascinated everybody. Attempts were made to make silk artificially. Towards the end of the nineteenth century, scientists were successful in obtaining a fibre having properties similar to that of silk. Such a 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 man-made 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:

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.
• We use many articles made from nylon, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains etc.
• Nylon is also used for making parachutes and ropes for rock climbing.
• A nylon thread is actually stronger than a steel wire.

POLYESTER AND ACRYLICS:

Polyester is another synthetic fibre. Fabric made from this fibre does not get wrinkled easily. It remains crisp and is easy to wash. So, it is quite suitable for making dress material. Terylene is a popular polyester. It can be drawn into very fine fibres that can be woven like any other yarn.

PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Polyester (Poly+ester) is actually made up of the repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Fabrics are sold by names like polycot, polywool, terrycot etc. As the name suggests, these are made by mixing two types of fibres. Polycot is a mixture of polyester and cotton. Polywool is a mixture of polyester and wool.

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. They are available in a variety of colours. Synthetic fibres are more durable and affordable which makes them more popular than natural fibres.

Disadvantage of Synthetic Fibre: synthetic fibres melt on heating. If the clothes catch fire, it can be disastrous. The fabric melts and sticks to the body of the person wearing it. We should, therefore, not wear synthetic clothes while working in in the kitchen or in a laboratory.

All the synthetic fibres are prepared by a number of processes using raw materials of petroleum origin, called petrochemicals.

Characteristics of synthetic fibre: Synthetic fibres possess unique characteristics which make them popular dress materials. They dry up quickly, are durable, less expensive, readily available and easy to maintain.

PLASTICS:

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.

Plastic articles are available in all possible shapes and sizes. The fact is that plastic is easily mouldable i.e. can be shaped in any form. Plastic can be recycled, reused, coloured, melted, rolled into sheets or made into wires. That is why it finds such a variety of uses.

POLYTHENE

(Poly+ethene) is an example of a plastic. It is used for making commonly used polythene bags.

THERMOPLASTICS Such 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.

THERMOSETTING PLASTICS On the other hand, there are some plastics which when moulded once, can not be softened by heating. These are called thermosetting 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.

Characteristic Properties Of Plastics:

• Plastic is non-reactive. Plastics do not react with water and air. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.
• Plastic is light, strong and durable.
• Plastics are poor conductors of heat and electricity. That is why electrical wires have plastic covering, and handles of screw drivers are made of plastic

Did You Know?

• Plastics find extensive use in the health-care industry. Some examples of their use are the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.
• Special plastic cookware is used in microwave ovens for cooking food. In microwave ovens, the heat cooks the food but does not affect the plastic vessel.
• Teflon is a special plastic on which oil and water do not stick. It is used for nonstick coating on cookwares.
• Fire-proof plastics: Although synthetic fibre catches fire easily, it is interesting to know that the uniforms of firemen have coating of melamine plastic to make them flame resistant.

PLASTICS AND THE ENVIRONMENT:

A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. Paper, cotton clothes, wood and woolen clothes are some example of biodegradable material. A material which is not easily decomposed by natural processes is termed as non-biodegradable . Plastic bags, tin / aluminium and other metal cans are an example of non-biodegradable material.

Since plastic takes several years to decompose, it is not environment friendly. It causes environmental pollution. Besides, the burning process in the synthetic material is quite slow and it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution. How can this problem be solved?

• Avoid the use of plastics as far as possible.
• Make use of bags made of cotton or jute when you go for shopping.
• The biodegradable and non biodegradable wastes should be collected separately and disposed off separately.

It is better to recycle the plastic waste. Most of the thermoplastics can be recycled. However, during recycling certain colouring agents are added. This limits its usage especially for storage of food. As a responsible citizen remember the 4 R principle. Reduce, Reuse, Recycle and Recover. Develop habits which are environment friendly.

Interesting fact about Nylon

Nylon appears like silk. It is strong and flexible. These endearing qualities of nylon created a public sensation, or nylon mania, when it was introduced in 1939. Women’s stockings made from this new fibre were in great demand. But, unfortunately, most of the nylon production had to be diverted to making parachutes during the Second World War (1939-1945). After the war, when production of stockings resumed, supply did not match the demand. There was a huge black market for this product. Women had to wait for hours in queues to get a pair. Often there were nylon riots.