Here is an essay on ‘Fiber’ for class 7, 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Fiber’ especially written for school and college students.
Essay on Fiber
Essay Contents:
- Essay on the Meaning of Fiber
- Essay on the Classification of Fibers
- Essay on Cotton
- Essay on Silk
- Essay on Wool
1. Essay on the Meaning of Fiber:
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‘Fiber’ is the basic unit for all textile products.
According to their length the fibers are divided into two classes:
1. Filament Fibers:
These are long, continuous strands. The length normally runs into thousand of meters. Silk, Nylon and polyester are some of the examples of filament fibers.
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2. Staple Fibers:
These are short fibers and the length ranges from 1-40 centimeters. Cotton and wool are staple fibers. Sometimes the filament fibers are also cut into smaller length to make staple fibers. All kinds of fibers cannot be used for the preparation of fabrics. Only a few are suitable. The fibers that can be made into fabrics, intended for clothing or household use, must necessarily have the following properties.
There are five primary properties like staple, strength, elasticity, uniformity and spinning quality:
1. The word staple is associated with the dimension of the fiber, such as the length and diameter. It is an essential requirement because a fiber has to be long and fine enough for satisfactory use.
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2. The fiber should also be strong enough to be spun into yarn which can ultimately be converted into durable fabrics. The strength of the textile fibers is very much influenced by the moisture in the atmosphere.
3. The fiber must be elastic enough for easy production of yarn, so that it helps in weaving of the fabric. This elasticity property of the fiber makes the fabric become wrinkle resistant and helps to maintain their shape and size.
4. Uniformity is another property of fibers. Fibers of uniform dimensions spin better and make a smoother and uniform yarn.
5. The fibers must have good spinning quality. In order to have this quality, fibers must have cohesiveness as this prevents fiber slippage. Besides these essential properties, there are some other desirable properties like density or specific gravity, lustre, moisture regain, flammability, felting, resistance to heat, alkalis, acids and bleaches etc.
2. Essay on the Classification of Fibers:
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Fibers are classified on the basis of sources as:
1. Natural Fibers
2. Synthetic or Manmade Fibers.
1. Natural Fibers:
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Natural fibers are obtained from natural sources.
These are classified into:
(1) Vegetable
(2) Animal,
(3) Mineral fibers.
(1) Vegetable Fibers:
Vegetable fibers are found in the cell walls of the plants and are cellulosic in composition.
They are classified into:
(1) Seed,
(2) Bast,
(3) Leaf,
(4) Fruit Fiber.
Vegetable fibers are obtained from the various parts of the plant. Cotton and Kapok are seed fibers, Linen and Jute are bast or stem fibers. Sisal and Hemp are obtained from the leaf of the plant. So they are under the Leaf fiber group and coir is the example of fruit fiber as it is obtained from coconut fruit.
Cellulose fibers are low in resiliency, so the fabrics wrinkles easily. Because of its high absorbency nature, these fibers are comfortable for summer wear. Of the several vegetable fibers, each derived from a different plant. Cotton and Linen are recognized as major textile fibers from the vegetable sources.
(a) Cotton:
Cotton fiber grows in the seedpod or ball of the cotton plant. As it is attached to the seed of the plant it is known as ‘seed fiber’. Each fiber is a single elongated cell, that is flat, twisted and ribbon like with a wide inner hollow or lumen. Cotton fiber is composed of about 90% cellulose and about 6% moisture and the remainder consists of natural impurities. The outer surface of the fiber is covered with a protective wax like coating, which gives the fiber adhesive quality. This characteristic combined with its natural twist, helps the fiber for spinning into yarn. Cotton yarn is used to make all types of fabrics.
(b) Linen:
Linen is a vegetable fiber composed chiefly of cellulose. This is obtained from the stem of flax plant. It is composed of about 70% cellulose and 30% pectin, ash, woody tissue and moisture. This fiber is cylindrical in shape, have a thick cell wall and is characterized by the presence of “nodes”. Linen fiber is relatively smooth, straight and lustrous. It is not elastic. It absorbs water readily and gives it up quickly. It is more difficult to prepare and spin into yarn.
(c) Jute:
Jute is a natural vegetable fiber obtained from a tall plant known as ‘Nalita’. It is grown throughout tropical Asia, chiefly in India and Bangladesh. The fiber is obtained by retting, similar to flax. The fine silk like fiber is easy to spin but is not durable. It is the cheapest textile fiber and is used in great quantities. Jute is used as a substitute for hemp, as binding threads for carpets and rugs. It is also made into coarse, cheap fibers.
(d) Kapok:
Kapok is a vegetable fiber. It is a fine, white hair like fiber obtained from the seed capsules of plants and trees grown in Java, Sumatra and central America. It is sometimes called “silk cotton” because its lustre is almost equal to that of silk. The smooth texture and weakness of kapok prevents its being spun into yarn, but it is used in mattresses, cushions, upholstered furniture. It is also used for sound proofing and for insulating.
(e) Hemp:
This is a tall plant with a natural woody fiber. They are grown in nearly all the temperate and tropical countries of the world. All these varieties resemble one another in general appearance and properties. It resembles flax closely and its fiber is just like linen. Hemp is harsh and stiff. It cannot be bleached as bleaching agents have harmful effect on the fiber.
As hemp is not pliable and elastic, it cannot be woven into fine fabrics. Hemp is durable and is used for the preparation of rugs and carpets, Manila. Hemp is a fiber from the leaves of the abaca plant, which is very strong, fine, white and lustrous. Though brittle, it is adoptable for the weaving of coarse fabrics.
(f) Sisal:
Sisal is a vegetable fiber obtained from the leaves of the plant that resembles cactus grown in Africa, Central America, West Indies and Florida. This is a smooth, straight fiber which is light yellow in colour. Sisal is used for the better grades of rope, for the bristles of inexpensive brushes and as a substitute for horse hair in upholstered furniture.
(g) Coir:
Coir is the fruit fiber under vegetable group. It is obtained from the husk of the coconut which is a coarse brown fiber. Because of its resemblance to horsehair, it is used for stuffing upholstered furniture.
(2) Animal Fibers:
There are several animal fibers. Animal fibers are produced from animals or insects which are composed of protein. They are very resilient. Wrinkles are generally removed at the time of wearing’s. They are bad conductor of heat and build up static electricity in cold and dry weather.
The animal fibers are becoming weak by concentrated acids. These fibers have great affinity to dyes but bleaching has harmful effect on animal fibers. Silk and wool fibers are the most important animal fibers which are used for textile.
(a) Silk:
Silk fiber is an animal fiber which is obtained from the Cocoons of moth caterpillar known as silk worm. Silk fiber is relatively lustrous, smooth, light weight, strong and elastic. It is composed of the protein substance fibron and a gum known as sericin. This is a filament fiber.
(b) Wool:
Wool is the hair of sheep, camel and goats which have long hair. It is composed of a protein known as ‘Keratin’. It is relatively coarse fiber. It has horny scales on the surface. Wool fiber is the only fiber which has felting property. This fiber is elastic and a bad conductor of heat. So woolen garments keep the body warm.
(3) Mineral Fibers:
These fibers are obtained from mines. Asbestos is the best example of mineral fiber. It is a fibrous form of Silicate of magnesium and Calcium, containing iron, aluminum and other minerals. The soft, long, glossy white fibers are pressed into sheets and the best quality can be spun into yarn.
Asbestos yarns always made as ply yarns to increase their tensile strength. Asbestos will not burn but it will melt at sufficiently high temperature. It is acid proof and rust proof. Asbestos is used in making firefighting suits and fire-resistant fabrics. Glass, silver, gold, ceramic and graphite are also some of the mineral fibers.
2. Manmade or Synthetic Fibers:
Man made fibers are not available directly from natural source. It is made or prepared by man by breaking down from their original form and reassembled into different structure. These are also known as synthetic fibers.
There are two types of man made fibers:
(1) Thermoplastic
(2) Non-thermoplastic.
(1) Thermoplastic Fiber:
Thermoplastic fibers are those that soften with heat and thus become pliable. If the heat is sufficiently high it will melt. These fibers are resistant to friction and wrinkling. The moisture content is low. These fibers are difficult to dye.
Thermoplastic fibers are again classified into:
(a) Cellulosic
(b) Non cellulosic.
(a) Cellulosic Thermoplastic Fiber:
The example is cellulose Acetate fiber. Cellulose Acetate fiber consists of a cellulose which is a cellulose salt. As a result acetate possesses different qualities from the rayons. Acetate fiber is thermoplastic fiber. It can be formed into a desired shape by the application of heat and pressure. Cotton pieces or wood chips are converted into sheets of pure cellulose.
The cellulose is steeped in glacial acetic acid for sometimes under a controlled temperature. Then it is mixed with acetic anhydride. A small amount of sulfuric acid is then added which produces a thick clear liquid solution of cellulose acetate. Then filaments and yarns are prepared.
(b) Non-Cellulosic Thermoplastic Fiber:
These fibers are produced from linear polymers. These fibers are Nylon, Acrylic, Olefin, Polyester, Dacron, Vinyon etc.
Nylon:
This fiber is related to a group of chemical compounds known as polyamides. It is a chemical combination of nitrogen, oxygen, hydrogen, and carbon in controlled proportions, a mixture of two coaltar products, a dibasic acid, adipic acid, and hexamethylene diamine containing nitrogen is heated and nylon polymer is formed. Nylon is thermoplastic, elastic, resilient and very strong fiber.
Acrylic:
The basic elements of this fiber are carbon, hydrogen and nitrogen. This fiber is soft and warm like wool. They are resilient and used for Household furnishings. Orion, Zeforn are under Acrylic group of fibers.
Dacron or Terrylene:
This fiber is prepared from terapholic Acid and ethylene glycol. They are polymerized in vacuum at a high temperature and polymer is separated in the form of a ribbon. The ribbons are then cut into small pieces and are passed through spinnerets. This fiber has wrinkle resistance property but melts when exposed to fire.
Polyester:
The basic substances for the production of this fiber are carbon, oxygen, and hydrogen. After polymerization, the fiber is produced. These fibers have good strength and they do not absorb water. Polyester fabrics are used for fabrics and household furnishings.
(2) Non Thermoplastic Fibers:
These fibers do not soften or melt when heat and temperature are applied. In high temperature they will only scorch. These fibers are soft, absorbent, pliable and comfortable to wear.
The fibers are classified into:
(a) Regenerated Cellulase
(b) Regenerated Protein.
(a) Regenerated Cellulase Fiber:
This fiber is Rayon fiber which has vegetable origin. Its chief source is wood pulp and cotton linters. Rayon fiber is also called as ‘Artificial Silk’ due to its lustrous effect. Two kinds of rayons are produced. They are viscose and cuprammonium. Viscose fibers are produced from wood chips and cup ammonium from cotton linters. They are treated with certain chemicals and turned into regenerated cellulose filaments which are stretched to form fine threads. Rayan fibers are good conductor of heat, but they become weak in acids and alkalies.
(b) Regenerated Protein Fibers:
The examples of these fibers are casein and ardil. Casein fiber is prepared from milk after treating it with some chemicals. The filaments which are produced are cut into short lengths like wool and spun into threads. This fiber is soft and is used as a substitute for wool.
Ardil is manufactured from groundnut proteins, treated with certain chemicals. Soybean is also used for the production of Ardil fiber. It is a cream coloured fiber with lustre. This fiber also resembles wool. It is soft and silky in appearance.
A number of fabrics are available in the modern world. So one should have some knowledge of the origin, manufacturing processes, properties or characteristic and the laundering processes of different types of fabrics.
3. Essay on Cotton:
India is the ancient home for the production of cotton fiber. After 19th century, the cultivation of cotton gradually spread throughout Asia, Africa and America. During the time of Buddha, Banaras and Dacca were famous for the manufacturing of finest cotton fabrics.
Cotton fiber is a vegetable fiber under natural group. The fiber is white in colour which is attached to the seed of the cotton plants. Cotton fiber is the shortest of all the textile fibers. Its length varies from 1/8 or 1/10 of an inch to 2 inches.
Manufacturing Process of Cotton Fiber:
The production process of cotton fiber passes through certain stages.
i. Growing and Harvesting:
Cotton plants are grown in hot climates. It requires about 200 days of continuous warm weather with adequate moisture and sunlight. The cotton seeds are sown in rows. When the plants are 3 to 4 inches height, unnecessary plants are chopped out. When cotton plants grow up to 3 to 5 feet height, pods are blossomed on the plant and begin to ripe.
ii. Gathering of Cotton pods:
When the cotton pods are ripen and burst open, they are collected immediately. If left on the plant, white coloured cotton may get discolored by sun and weather and may be destroyed by strong currents of wind. There are a large number of seeds in one pod and to each seed fibers are attached.
iii. Ginning:
This is a process by which cotton fibers are separated from seeds. This process can be easily done by a machine known as ‘Gin’ machine where certain combs or wire hook are attached. These machines separate the fibers from the seeds.
iv. Baling:
The cotton fibers are then packed in bundles called Bales. These bales are covered with jute bags and bound with steel bands. They may be circular, square, and rectangular in shape. These bales are then sent to mills by vehicles for further processing.
v. Beating:
In the mills, the bales are opened. Cotton fibers are removed from the bales and they are beaten with the machine in order to remove dust, dirt, dried leaves and other foreign particles from the ‘fiber’. This process is given to cotton fiber before spinning process.
vi. Carding:
Then the loose fibers are passed through another machine called as ‘card’. In this machine all the dirty materials are removed from the fiber. The fibers are cleaned and made parallel by carding process.
vii. Combing:
This is an improved method of carding process. All the short fibers are separated from long ones and the long fibers are laid more parallel. A film like sheet of fiber is formed after the combing process.
viii. Slivering:
This is the last manufacturing process of cotton fiber. The film like sheet of fiber is passed through a number of strands or silvers of varying diameter. Then the fine thread is collected through coilers and is ready for spinning or weaving of cloth.
Physical and Chemical Properties of Cotton Fiber:
i. Composition:
As cotton fiber is a vegetable fiber cellulose is the main constituent of this fiber. It is composed of 88 to 90% cellulose, 5 to 8% water and other natural impurities.
ii. Structure:
Cotton fiber is the shortest of all the fibers. It has a tube like structure containing sap when it is raw. But when the fiber ripens, the sap dries up, the two side collapses and the fiber becomes a twisted ribbon like structure. These twists are called convolutions. They help to keep the yarn firm and strong. Spinning is becoming easier due to many convolutions.
iii. Microscopic Appearance:
Cotton fiber is seen to be a narrow flattened twisted ribbon like structure with thick irregular edges. Mercerized cotton appears smooth and cylindrical.
iv. Strength:
Cotton fiber is relatively strong due to the intrinsic structure. Strength can be improved by mercerization process given to cotton fiber.
v. Shrinking:
The fiber itself does not shrink but the fabric may shrink which are treated with certain finishing processes.
vi. Elasticity:
It refers to the extent to which the fiber can be stretched and then returning to the former condition. Cotton fiber has less natural elasticity. Mercerized cotton has some amount of elasticity.
vii. Absorbency:
Cotton fiber is very absorbent because of the hydroxyl group. As it is composed of cellulose it is very absorbent. Low twisted yarns are more absorbent than high twisted yarns.
viii. Effect of Moisture and Friction:
Cotton fiber is not affected by moisture. It becomes stronger when moisture content is increased. Friction has no harmful effect on cotton fiber. So cotton fabrics can be washed with soap and water with friction without any damage.
ix. Cleanliness and Wash-Ability:
Cotton fibers attract dust and dirt particles because of its roughness. But these fabrics can be easily washed. Hot water can also be used for washing purposes. These fabrics launder well and withstand rough handling. Due to its easy wash-ability, it is considered as a “hygienic fiber”.
x. Resilience:
Low resiliency is common to cotton fabrics. They wrinkle easily and may beset by different finishing processes.
xi. Heat Conductivity:
Cotton fiber is a good conductor of heat. So it can be used as clothing during summer season.
xii. Affinity to Dyes:
As cotton fibers are cellulose fibers they have less affinity to dyes. If a mordent is used cotton can take in dye easily.
xiii. Effects of Acids and Alkalies:
Cotton fibers are totally destroyed by the action of strong acids. Dilute acids make the fibers weak. But they are less affected by organic acids as acetic acid (vinegar). Alkalies have no harmful effect. Sodium hydroxide is used to mercerized cotton.
xiv. Effect of Bleaching:
All types of bleaches can be safely used on white cotton. Bleach should be put into the rinse water after washing, so that it is thoroughly mixed and diluted to avoid the oxidizing or yellowing the fabric.
xv. Effect of Heat and Light:
Cotton fibers can withstand moderate heat. Very hot iron is allowed to remain at a particular place for longer period of time during pressing, it will scorch. So while ironing the cotton fabrics they will be first dampened. Cotton fiber oxidizes, and turns yellow while exposed to sunlight for a longer period of time. It also losses strength in sunlight.
xvi. Effect of Mildew and Moth:
Cotton fibers are easily attacked by mildew and silverfish if kept in a damp condition. Greenish black or rust coloured sports are caused by mildew fungus. So cotton fabrics should be kept in dry atmosphere. The fabrics are not effected by moths like silk and wool.
Cotton fibers ignite easily and burn with an odour of burning wood or paper. Many new finishes have improved some of the characteristics of cotton fiber. It can have lustrous and shining appearance when mercerization finishing is given. Now it can be dyed easily with fast colours. Different wrinkle resistant and flame resistant finishing processes are also given to cotton fibers.
4. Essay on Silk:
Silk is an animal fiber under natural group. This fiber is often referred to as the queen of the fibers. It is always attracted by its strength lustre, softness and gracefulness. The production of silk-fiber was first started in China thousands of years ago. According to the legend of China, The Empress Si-ling-chi discovered the process of reeling of silk from the cocoons of silk worms. She made a robe of the silk thread and presented to her husband.
The Empress was called the Goddess of silk by the Chinese. The Chinese kept the art of manufacturing silk a secret, for more than 2000 years. Then the countries like Japan, India, Persia, Central Asia could know the art of production of silk. The western countries took to the silk industry much later than the Asian countries. In India, silk is produced more in Kashmir, Bengal, Mysore and Chennai.
Silk is obtained from the secretion of the silk worm. The cultivation of the silkworm requires much care and constant supervision. The collection, spinning and weaving of silk can only be done by skilled persons. Cultivated silk is obtained by a carefully controlled process, but wild silk production is not a controlled manufacturing process.
Manufacturing Process of Silk Fiber:
The manufacturing process of silk fiber includes three important processes:
1. Sericulture
2. Reeling
3. Degumming
1. Sericulture:
The preparation of silk fiber is produced by a process known as “sericulture” which includes the breeding and rearing of silk worm. Silk fibers are obtained from the cocoons of the silkworm. So breeding and rearing of silkworm is an essential step for getting cocoons. In many places this becomes a cottage industries and done by many agriculturists.
The silk worms have a life span of two months during which they pass through four stages like:
(a) Egg,
(b) Worm or Larvae
(c) Pupa,
(d) Moth.
In sericulture all these four stages are important to get good cocoons. Under scientific breeding, silk worms may be hatched three times a year. But under natural conditions breeding occurs only once a year.
(a) Egg:
The female silk worms are made to lay eggs on sheet of paper. One worm lays up to 500/ 600 eggs at a time in a circular manner on the paper and then dies. The eggs are then stored in cold storage for six weeks. Then these sheets with the eggs on them are washed in hot water and left to dry indoors. The eggs take ten days to hatch. Even temperature, hot sunlight, and good ventilation help in satisfactory hatching.
(b) Worms:
These worms are also called as larvas. At the first stage, one larvae is about 1/8 inch (3mm) in length. The larvas require careful nurturing in a controlled atmosphere for about 20 to 30 days. They are fed on finely cut mulberry leaves for ten days. The larvas pass through five progressive periods during their life time and cast off their skin at the end of each period. At the end of fourth period the larvas reach full growth.
They are in the form of smooth grayish white caterpillars about 3 1/2 inches long. During this period each larvae moves round its own body forming a figure of eight and spins its cocoon from its secretion. It secretes a viscous fluid from two glands situated in the head which comes outside through a single opening. This fluid becomes hard when it comes in contact with air. The larvae covers its own body by this fluid and builds its cocoon. One cocoon contains 2000 to 4000 yards of silk.
(c) Pupa:
It is the third stage of the silk worm. Inside the cocoon the larva’s are going on with their physical changes and are converted to full grown moth after two weeks. At the pupa stage the cocoons are collected and are put in boiling water so that the worms are being suffocated and killed. Then the cocoons are dried and stored.
(d) Moth:
Moth is the final stage of silk worm in which we can find a full grown silk worm. It can easily break the wall of the cocoons and come outside with the small wings.
2. Reeling:
Cocoons are collected at the pupa stage and placed in warm water. This helps in killing the worm inside and making the cocoons soft so that the threads can be easily separated. The cocoons are sorted according to colour size, shape and texture as they affect the quality of silk.
The process of unwinding the filament from the cocoon is called Reeling. Fibers are pulled out from several cocoons and are grouped together in order to get strong thread. These are then passed through a small hole in the reeling frame. After giving a twist this thread is again passed through another hole and again twisted on. The process of twisting continues until a strong thread or yarn is obtained. This is then wound or reeled round spools or in skeins and sent for weaving.
3. Degumming:
The silk yarns contain sericin, the silk gum which must be removed to bring out the natural luster and the soft feel of the silk fiber. Degumming is necessary for this. After the cloth is woven, it is boiled in soapy alkaline solution to remove the gum. As much as 25% of the weight is lost by degumming process. When the gum is removed, the silk fiber or fabric becomes creamy white colour beautifully lustrous and soft feel.
The short fibers which cannot be reeled are collected, boiled to remove gum and then dried. These are then combed and drawn in film like sheet as cotton fibers. This film like sheets are passed through rollers and then through a spinning frame. This process is called rowing.
After several twist yarns are formed from which silk fabrics are made. These fabrics are known as spun silk. These are less expensive and are used for the preparation of velvet, satin, pile fabrics and insulative materials.
Physical and Chemical Properties:
Silk is the only natural filament which are 300 – 1800 yards long.
i. Composition:
As it is an animal fiber it is composed of n protein substance known as ‘fibrion’. Silk gum ‘sericin’ is also present which helps in holding the filaments together.
ii. Structure:
Silk fiber has a double rod like structure which is covered with lumps of gum. Cross sectional study of silk finds that the fibers are like triangles with rounded corners.
iii. Strength:
Silk is the strongest natural fiber. The strength of silk fiber is affected by its construction as well as its finish.
iv. Elasticity:
Silk is an elastic fiber. It may be stretched from 1/7 to 1/5 its original length. It returns to its original size gradually, and losses little of its elasticity.
v. Resilience:
Silk fiber has high resiliency. Fabrics that contain a large percentage of weighting or are made from short staple have less resilience.
vi. Heat Conductivity:
Silk is a poor conductor of heat. As it prevents body heat from radiating outward, it is desirable for winter wear. It is warmer than cotton, linen or rayon.
vii. Effect of Moisture and Friction:
This fiber is not affected by moisture. It neither shrinks nor stretch when wet. Due to smooth surface of silk, it does not attract soil and dirt easily. If dirt is gathering, it is removed easily by washing or dry cleaning. Care should be taken for laundering this fabric. Friction may spoil the smooth, soft texture of the fiber. So friction must be avoided while washing the fabric.
viii. Effect of Hygroscopic Moisture:
Silk fiber absorbs 10 to 30% moisture without feeling wet to the touch but it does not allow the moisture to spread rapidly.
ix. Affinity to Dyes:
Being a protein fiber, silk fiber has a great affinity to dye stuff. All types of dyes like acid, basic and direct dyes can be used. Dyed silk is colorfast under most conditions.
x. Effects of Acids and Alkalies:
Concentrated mineral acids will dissolve silk faster than wool. Organic acids do not harm silk. Strong alkalies have a harmful effect on silk but weak alkalies like borax, ammonia, can be safely used. Mild soap or detergent in luke warm water can be used for washing of silk fabrics.
xi. Effect of Bleaches:
Strong bleaches containing sodium hypochlorite (Javelle water) will destroy silk fiber. A mild bleach of hydrogen peroxide or sodium per-borate may be used in normal condition.
xii. Shrinkage:
The normal shrinkage of silk fabric may be easily restored by ironing.
xiii. Effect of Light:
Continuous exposure to light weakens silk faster than either cotton or wool. Raw silk is more resistant to light than degummed silk.
xiv. Effect of Mildew and Moth:
Silk will not be affected by mildew unless left for sometime in a damp condition and under extreme conditions of tropical dampness. But silk fabrics may be easily attacked by the larva of clothes moth and are destroyed when blended with wool.
xv. Effect of Perspiration:
Silk fabrics are damaged by perspiration. The colour is affected causing staining. Silk fibers burn briefly and chars. It is self extinguishing. It produces black crushable ashes with odour of burning hair or feathers while burning. In spite of high cost, silk has been one of the most popular fabrics because of its unique properties.
5. Essay on Wool:
Wool fiber is an animal fiber under natural group. It is also a protein fiber made up of sulphur, carbon, hydrogen, oxygen and nitrogen. Wool is the soft hair covering of sheep, camel and goats which have long hair. Now-a-days all the animals which provide long hair either in their natural state or some sort of artificial treatment are being used as wool for spinning.
In cold countries, it was the first textile fiber to be made into fabric. The primitive men first used the skin of certain animals to protect and then decorate the body. We can know from History that Mesopotamia was the birthplace of wool. Now it is manufactured in England, America, Australia, Africa and India. Australia produces more wool and of good quality than any other countries of the world. In India 75% of the woolen handloom industry is situated in Uttar Pradesh, Kashmir, Punjab and Rajasthan.
Manufacturing Process of Wool Fiber:
Wool fibers of different qualities and lengths are prepared in a special manner to be woven into different kinds of fabrics. The manufacturing processes of wool fiber pass through certain stages.
i. Shearing:
This is the first process. Sheep are sheared once or twice a year, generally in spring season. Wool can be fleeced or pulled from the body of the animals. Fleecing is done either by hand or with machinery from the body of the living animals. Superior fleeced wool comes from the sides and shoulders of the animals where it grows longer, finer and softer.
Wool fleeced from head, chest, belly and shanks is treated as second fleece. When wool is pulled out of the body of dead animals, this is known as pulled wool. Fleeced wool are of better quality than pulled wool. The yield of pulled wool is about 1/5th as much as that of sheared wool.
ii. Sorting and Grading:
Sorting of wool is done by skilled workers who are experts in distinguishing qualities by tough and sight. They keep them in different grades as per their quality. Each grade is determined by type, length, fineness, elasticity and strength. Nearly 20 separate grades of wool may be obtained by the experts.
iii. Scouring:
The fleece is then boiled in soapy alkaline solution to remove dirt, grease and dried perspiration. It can be done easily with the help of a machine.
iv. Drying:
The fiber is then allowed to dry in a humid atmosphere to preserve the elasticity and softness. Usually about 12 to 16% of moisture is left in wool.
v. Oiling:
After scouring process, wool becomes slight rough. So they are usually treated with various oils to remove the brittleness and lubricate it for the spinning.
vi. Blending:
Different grades of wool may be mixed together at this stage. Sometimes other fibers are also blended with wool.
vii. Carding:
The process of carding is similar to that of cotton. In this process, the fibers are laid parallel in a film like sheet like cotton.
viii. Roving:
The film like sheet is drawn into silver. The silvers are passed through a combing process in which short fibers are removed. Then the silvers are drawn in a fine strand and this process is called “roving”. The thread is then wound round the bobbin and is ready for spinning.
Physical and Chemical Properties of Wool Fiber:
i. Composition:
The fiber is composed of a protein substance called “Keratin”. This is only fiber which contains sulphur.
ii. Structure:
It has rod like structure with rough surface of overlapping horny scales. Its length varies from 1/2 inch to 14 inches.
The fiber is composed of two or three layers:
1. The cuticle or the horny outer layer.
2. The cortex or the inner structure made up of cortical cells.
3. The medulla is the canal which gives the colour to the fiber.
iii. Felting Property:
Wool is the only fiber which has felting property. When heat, moisture and pressure are applied, the rough surface or the scales of wool fiber become softened, gelatinous and open out and get interlocked and mat together. This property helps in the preparation of blanket.
iv. Strength:
Wool is the weakest of all natural textile fibers. But selected grades of wool may last longer. Wool fabric is strengthened by the use of ply yarn.
v. Elasticity:
Wool fabrics have been given mechanical and chemical treatment to increase their elasticity. The chemical treatments have also resulted in improved shape retention.
vi. Resilience:
Wool fiber has resiliency. It recovers from crushing and bending. Due to this high degree of resilience wool fabric wrinkles less than other fabrics. Good quality wool is very soft and resilient. Poor quality wool is rough and harsh.
vii. Heat Conductivity:
As wool fiber is an animal fiber, it is bad conductor of heat. It permits the body to retain its normal temperature. So woolen garments are excellent for winter wear.
viii. Shrinking:
Woolen fabrics shrink if pressure, heat and moisture are applied during the time of laundering. In dry cleaning shrinkage is less.
ix. Effect of Moisture and Friction:
Friction will destroy the fiber specially when wet. Dirt is easily fixed on wool fiber. Wool retains odour if not thoroughly cleaned. Extreme care is required for laundering. Wool temporarily loses about 25% of its strength when wet. Woolen fabrics should not be pulled at the time of washing. By squeezing method water should be removed.
x. Effect of Hygroscopic Moisture:
Wool is considered the most hygroscopic of all the fibers. It absorbs moisture from the atmosphere and holds as much as 30% of its weight without feeling wet to the touch.
xi. Affinity to dyes:
As it is a protein fiber, it can take in dye very easily. All types of dyes can be used in wool fiber.
xii. Effect of Acids and Alkalies:
Alkalies have a harmful effect on wool. It makes the fabric yellow, hard and causes felting. Borax and Ammonia have no harmful effect on wool. Wool is not effected by acids except sulfuric acid which can damage wool.
xiii. Effect of heat and Light:
Wool becomes harsh at 212°F (100°C). It is destroyed by high temperature. It will scorch at 400°F (204°). Wool is becoming weak when exposed to sunlight for a long time.
xiv. Resistance to Mildew, Math and Perspiration:
If woolen fabrics are left in damp condition mildew develops. Woolen fabrics are destroyed by the larvae of the moth and carpet beetles. Wool is becoming weak by alkali perspiration. Garments should be dry cleaned and washed with care. Perspiration may cause discoloration.
xv. Effect of Bleaches:
Strong bleaching agents like sodium hypochlorite have harmful effect on wool Mild bleaches may be used for stain removal. Besides these wool has certain other characteristics. Wool is easily charged with static electricity. It burns slowly with the odour of burning feather or hair. It does not catch fire easily, wool absorb odours easily. Wools are used for garments, carpets and blankets etc.