(1)The clothes which we wear made up of different fabric and fabric is made up of different fibers. Fibres are the thread which we obtained from different sources and need them in weaving or manufacturing of clothes.
Types of fibres–
There are two types of fibre:-
(i) Natural fibre- Natural fibres are those fibres which we obtained from the nature such as animals, trees etc.
Eg:- Wool from animals(sheep, rabbit, yak etc), Cotton from plant.
(ii) Synthetic fibre –Synthetic fibres are those fibres which are made by humans. All the synthetic fibres are prepared by using raw material of petroleum origin(Petrochemical).
Eg:- Rayon, polyster etc.
(2)Types of natural fibre
(i) Wool comes from hair of sheep, goat, yak, camel and some other animals.
(i) Wool comes from hair(fleece) of sheep, goat, yak, camel and some other animals.
(ii)Sheep has two types of fibres that form its fleece(hair).
(a) The coarse beard hair and
(b)The fine soft under hair close to the skin.
(iii)The process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep, is termed selective breeding.
(iv)From fibre to wool
(a)Rearing and breeding of sheep
- Food-Grass, pulses, corn, jowar, oil cakes.
- The process in which sheep or other animals are helped to grow ,is called rearing.
(b) Processing fibers into wool
- Rearing is a processes in which thin layer of skin of sheep with its hair is removed.
- Machines which are used to remove hair are similar to barber’s machines.
- Hair of sheep are removed in hot weather to protect sheep from cold weather.
- Shearing does not hurt sheep because the uppermost layer of the skin is dead. The hair of sheep grow again.
- Scouring is a process in which skin of sheep with hair(sheared skin) is washed thoroughly to remove dirt and grease on it.
- In modern time, it is done by machines.
- Sorting is a process done after scouring. In this process, hair of sheep is separated according to their different textures in factories.
- The small fluffy fibers which are picked out from the hair are called burrs.
- The fibers are scoured again and dried.
- The fibers can be dyed in various colours.
- Natural fleece of sheep and goat is black, brown or white.
- The fibers are straightened, combed and rolled into yarn.
- The longer fibers are made into wool for sweaters and the shorter fibers are spun and woven in to woolen cloth.
(i)The rearing of silkworms for obtaining silk is called sericulture.
(ii)Life history of silk moth
(a)The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworm.
(b) The next stage of caterpillar’s life is called pupa.
(c) The pupa first weaves a net for itself. Then it swings its head from side to side in the form of the figure of 8. During these movements it secretes fibre made of a protein which hardens on exposure to air and becomes silk fiber.
(d)The covering in which caterpillar completely cover itself by silk fibers and turns in to pupa is known as cocoon.
(e)The pupa developed in to moth inside the cocoon.
(iii) Silk fibre is used in weaving silk. It is as strong as steel thread.
(iv)Different moths yield different silk yarn in texture as coarse, smooth, shiny etc.
(v)Tassar silk, mooga silk, kosa silk etc are different variety of silk which are obtained from cocoons spun by different types of moths.
(vi)The most common silk moth is the mulberry silk moth.
(vii)The silk fiber from the cocoon of mulberry silk moth is soft, lustrous and elastic and can be dyed in beautiful colours.
Different pieces of silk are collected and shown below:-
(viii)From cocoon to silk
For obtaining silk, moths are reared and their cocoons are collected to get silk threads.
- A female silk moth lays hundreds of egg sat a time.
- These eggs stored carefully on strips of cloth or paper and sold to farmers.
- The farmers keep eggs under hygienic conditions and under suitable conditions of temperature and humidity for the larvae to hatch from eggs.
- The eggs are hatched when mulberry trees bear a fresh crop of leaves.
- The larvae or caterpillars kept in clean bamboo trays along with freshly chopped mulberry leaves.
- After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in the tray to spin cocoons which develop the silk moth.
- Small racks or twigs may be provided in the trays to which cocoon get attached.
- A pile of cocoons is kept under the sun or boiled or exposed to steam to get silk fibers which is separated out form cocoons.
- The process of taking out threads from the cocoon for use as silk is called reeling the silk. It is done in special machines.
- Silk fibers are than spun in to silk threads, which are woven in to silk cloth by weavers.
(3) Polymer is a combination of many small units. The word polymer is made up of two greeks words `poly’ means many and `mer’ means units.
Eg:- Rayon, nylon etc.
Polymer found in nature also.
Cotton is a polymer called cellulose which is made up of a large number of glucose units.
(4)Types of synthetic fibre
(i) Rayon is made by scientists.
(ii)It is obtained by chemical treatment of wood pulp.
(iii) It looks like silk but it is artificial fabric. It is cheaper than silk.
(iv) It is obtained from natural resource (wood pulp)but it is made by humans. Therefore it is also known as artificial silk.
(v)It can be dyed in many colours.
(vi)It can be used in making carpet when mixed with wool.
(vii) It can be used in making bed sheets when mixed with cotton.
(i) Nylon is discovered in 1931 without using any natural raw material, ie, animals or plants.
(ii) It was prepared from coal, water and air.
(iii) It was the first fully synthetic fibre.
(iv)It is very strong, elastic, light, lustrous and easy to wash. Hence, it became popular. Its thread is stronger than steel wires.
(v) It is used to make socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains, parachutes and ropes for rock climbing.
Polyester and Acrylic
(i)Polyester(Poly + ester) is made up of the repeating units of chemical called ester.
(ii)Polyester fabric is sold by name like polycot(poly + cotton), polywool (poly + wool), terrycot etc.
(iii) It is a synthetic fibre that does not get wrinkle easily.
(iv)Terelyene is popular polyester and is used in making dresses.
(v)PET is also a known polyester. It is used in making bottles, containers, films, utensils and many more products.
(vi)Nowadays, sweaters, shawls, blankets are prepared by the synthetic fibre which is known as acrylic. These are very cheap in comparison of fabric made up of natural resources.
(vii) All synthetic fibres melt on heating. So cloth made by them can not be wear by people while working near fire such as cooking, working on furnaces in factories etc.
(i) Plastics are also polymer. They have different arrangements of units.
(a)Linear Polymer – When all the monomers is exit in a single line is called linear polymer.
Diagrammatically presentation of linear polymer is showing below:-
(b) Cross linked polymer – When one polymer chain is linked with another polymer chain is called cross linked polymer.
Diagrammatically presentation of cross linked polymer is showing below:-
(ii)Plastics can be recycle, reuse, coloured, rolled into sheets, moulds and made into wires.Therefore, it is widely used in making different useful items.
(iii)Polythene (Poly + thene) is also a plastic and used in making plastics bags.
(iv) The plastics which can be deformed and bent easily on heating are known as thermoplastics.
Eg:- Polythene and PVC
Thermoplastics are used in making toys, bottles, containers, combs etc.
(v) The plastics which can not be deformed and bent easily by heating are known as thermosetting plastics.
Eg:-Bakelite and melamine
Bakelite is a poor conductor of heat and electricity. So it is used in handles of pans and electric switches etc.
Melamine can bear heat better than other plastics. So it is used in making floor tiles, kitchenware etc.
(vi) Different uses of the plastics-
(a) It is widely used in health care industry in packaging tablets, threads, syringes, stitching wounds, gloves and in many more medical equipments.
(b)Plastic cookware is used in microwave to cook the food.
(c) The non stick coating on cookwares is known as teflon which is made up of plastics.
(d)Though plastic catches fire easily but clothes of firemen have coating of melamine which protects them from fire.
(vii)Harmful effect of plastics:-
(a)It is non bio degradable. Hence , it is not good for environment.
(b)It can not be burnt completely. It fumes releases polluted air in the environment.
(c) The street animals swallowed polythene bags while trying to eat food from garbage dumps. These bags choked their respiratory system.
(d) Plastics bags are also responsible for clogging the drains.
(viii)Steps to protect environment from the plastics:-
(a)Do not throw plastics bottles or bags on road or in the water bodies.
(b) Use cotton bags for shopping.
(c) Try to minimum use of plastics.
(d) Try to reuse plastic containers.