Cell- Structure and Function6
Synthetic Fibers an Plastics3
Coal and Petroleum4
Stars and The Solar System6
Pollution of Air and Water5
Force and Pressure4
Materials: Metals and Non-Metals4
Chapter Notes – Synthetic Fibers an Plastics
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:
(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.
(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.
(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.
(iv) Terrycot is made by mixing of two types of fibres terylene and cotton. Polycot, polywool, etc. are other fabrics are made by the mixing of polyester with other natural fibres.
(v) PET is a very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.
(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.
(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.Plastic is easily mouldable in all types of possible shapes. Plastic can be recycled, coloured, reused, rolled into sheets or made into wires.
(i) Plastic is used in making toys, suitcase, bags, cabinets, brush, chairs, tables, and many other countless items.
(ii) Polythene (Poly + ethene) is one of the most famous examples of plastic, which is used in manufacturing of carry bags.
Types of Plastic:
Plastic can be divided into two main types – Thermoplastics and Thermosetting.
(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.
(ii) These plastics are used in making hard board, electric switch, handles of electrical appliances, handles of kitchen utensils, floor tiles, etc.
(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.
Plastic as a material of choice:
Plastic has light weight, lower price, good strength and easy handling. Being lighter as compared to metals, plastics are used in cars, aircrafts and spacecrafts, too.
Characteristic properties of plastics:
1. Plastic is non-reactive:
(i) Plastics do not react with water and air that’s whyit does not get rusted like iron. They are not corroded easily. That is why they are used to store various kinds of material, including many chemicals.
(ii) Due to this property of plastic, it is suitable for making of container, water tank, water bottle, plastic pipes, taps, chair, table and other many types of furniture.
2. Plastic is light, strong and durable:
(i) Plastics are light weight, durable, cheap, very strong and can be moulded into different shapes and sizes.
(ii) Due to this property of plastic, it is very much in need today. It is used for various purposes like polythene bags or pencil box, water bottle or umbrella, furniture or air craft, the use of plastic can be seen everywhere.
3. Plastics are poor conductors:
(i) Plastics are poor conductor of heat and electricity.
(ii) Due to this property of plastics, it is suitable to make the insulating covering of electric wires, handles of electrical appliances, handles of utensils, handles of screw drivers, kitchenware, floor tiles, etc.
Some Uses of Plastic in Various Fields:
(i) Plastics find extensive use in the health-care industry. Plastics are used for the packaging of tablets, threads used for stitching wounds, syringes, doctors’ gloves and a number of medical instruments.
(ii) Special plastic cookware is used in microwave ovens for cooking food without affecting the plastic vessel.
(iii) Teflon is a special plastic on which oil and water do not stick. It is used for making non-stick coating on cook wares.
(iv) Fire-proof plastics: Synthetic fibre catches fire easily. The uniforms of firemen have coating of melamine plastic to make them flame resistant.
Biodegradable and Non-biodegradable:
A substance which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. Examples: peels of vegetables, food stuffs, fruit, paper, cotton cloths, wood, etc.
A substance which is not easily decomposed or takes many years to get decomposed by natural processes is termed as non-biodegradable. Examples: tin, aluminium, plastics, etc.
Plastics and the Environment:
(i) Plastic is a non-biodegradable material. It takes many years to get decomposed or either does not get decomposed.
(ii) Due to non-biodegradable property of plastic, it is a very major problem for environment.
(i) Now days, plastic is very popular and used it for many purposes. As a result, we generate a large amount of plastic waste. Since plastic has non-biodegradable property, so plastic waste is getting accumulated in the environment. It causes environmental pollution.
(ii) Accumulated plastic waste is a major concern as it does not get completely burnt easily. In the process it releases lots of poisonous fumes into the atmosphere causing air pollution.
(i) We should avoid the use of plastics things as far as possible.
(ii) Do not throw plastic bags in the water bodies or on the road.
(iii) The biodegradable and non biodegradable wastes should be collected separately and disposed off separately.
For dealing with plastic waste, we should follow the three Rs, i.e. Reduce, Reuse and Recycle.
We should reduce the use of plastic. Examples: We should use cloth or jute bag for purchasing any things instead of using plastic bags.
We should reuse some plastic things and containers in our homes and offices, For example: Empty plastic bottles and container should be used for keeping other items in the home and kitchen.
Thermoplastic can be recycled. So, items made of thermoplastic should be sent to the recycling industry. Examples: Toys, buckets, mugs etc.