B.Sc. CDF – Fibre to Fabric

B.Sc. Costume Design and Fashion

Second Year Paper No.3 FIBRE TO FABRIC

BHARATHIAR UNIVERSITY SCHOOL OF DISTANCE EDUCATION COIMBATORE – 641 046. B.Sc. CDF – Fibre to Fabric

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CONTENT

UNIT LESSON PAGE TITLE OF THE LESSON NO. NO. NO. UNIT I Textiles 1 7

Fibres 2 13

UNIT II Natural Fibres 3 27

Other Natural Fibres 4 35

Animal Fibres 5 47

Rayon 6 64

Synthtic Fibres 7 76

UNIT III 8 Introduction to spinning 93

Opening And Cleaning 9 103

Yarn Formation 10 114

Yarn MAINTENANCE 11 128

UNIT IV Weaving Preparatory Process 12 143

Drawing –In & Weft Preparation 13 155

Looming 14 163

Woven Fabric Basic Design 15 174

16 Woven Fabric Fancy Design 182 UNIT V Knitting 17 193

Non Woven 18 207

Other Fabrics 19 222

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(Syllabus) PAPER 3 FIBER TO FABRIC

UNIT - I

Introduction to the field of Textiles – major goals – classification of fibers – natural & chemical – primary and secondary characteristics of textile fibers

UNIT - II

Manufacturing process, properties and uses of natural fibers – cotton,linen,jute,pineapple, hemp, silk, wool, hair fibers, Man-made fibers – viscose rayon, acetate rayon, nylon, polyester, acrylic

UNIT - III

Spinning – definition, classification – chemical and mechanical spinning – ,opening, cleaning, doubling, carding, combing, drawing, roving, spinning Yarn classification – definition, classification – simple and fancy yarns, sewing threads and its properties

UNIT - IV

Woven – basic weaves – plain, twill, satin. Fancy weaves – pile, double cloth, leno, swivel, lappet, dobby and Jacquard Weaving technology – process sequence – machinery details

UNIT - V

Knitting type of knitting passage of material Knitting structure .Non-woven – felting, fusing, bonding, lamination, netting, braiding & calico, tatting and crocheting

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UNIT - I

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LESSON-1 TEXTILES

CONTENT 1.0 AIM AND OBJECTIVES 1.1 INTRODUCTION 1.2 THE FIELD OF TEXTILE 1.3 MAJOR GOALS 1.4 PRODUCTION METHODS 1.4.1 Spinning 1.4.2 Weaving 1.4.3 Knitting 1.4.4 Braiding 1.4.5 Lace 1.4.6 Felting 1.5 LET US SUM UP 1.6 LESSON END ACTIVITIES 1.7 POINT OF DISCUSSION 1.8 CHECK YOUR PROGRESS 1.9 REFERENCES

1.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following

• The history of clothing and textiles • Origin of Indian textiles • Textile industry and significant changes • Scope of textile

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1.1 INTRODUCTION

A textile is a flexible material comprised of a network of natural or artificial fibers often referred to as thread or yarn. Textiles are formed by weaving, knitting, crocheting, knotting, or pressing fibers together (felt).

Textiles are classified according to their component and structure or weave. Value or quality in textiles depends on several factors, such as the quality of the raw material used and the character of the yarn spun from the fibers, whether clean, smooth, fine, or coarse and whether hard, soft, or medium twisted.

Yarn, fabrics, and tools for spinning and weaving have been found among the earliest relics of human habitations. The Textile industry is a term used for industries primarily concerned with the design or manufacture of clothing as well as the distribution and use of textiles.

1.2 THE FIELD OF TEXTILE

Food, shelter and clothing are the basic needs of everyone. All clothing is made from textile and shelters are made more comfortable and attractive by the use of textiles. Everyone is surrounded by textiles from birth to death. We walk on and wear textile products; we sit on fabric covered chairs and sofas; we sleep on and under fabrics; textiles dry us or keep us; they keep us warm and product from sun, tire, and infection. Clothing and household textiles are aesthetically pleasing and vary in colour, design and texture. They are available in a variety of price ranges. . The history of clothing and textiles attempts an objective survey of clothing and textiles throughout human history, identifying materials, tools, techniques, and influences, and the cultural significance of these items to the people who used them. Textiles, defined as felt or spun fibers made into yarn and subsequently netted, looped, knit or woven to make fabrics, appeared in the Middle East during the late stone age.[1] From ancient times to the present day, methods of textile production have continually evolved, and the choices of textiles available have influenced how people carried their possessions, clothed themselves, and decorated their surroundings. Yarn, fabrics, and tools for spinning and weaving have been found among the earliest relics of human habitations. Linen fabrics dating from 5000 B.C. have been discovered in Egypt. Woolen textiles from the early Bronze Age in Scandinavia and Switzerland have also been found. Cotton has been spun and woven in India since 3000 B.C., and silk has been woven in China since at least 1000 B.C. about the 4th cent. A.D., Constantinople began to weave the raw silk imported from China. India has a diverse and rich textile tradition. The origin of Indian textiles can be traced to the Indus valley civilization. The people of this civilization used

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homespun cotton for weaving their garments. Excavations at Harappa and Mohen -jo-Daro, have unearthed household items like needles made of bone and spindles made of wood, amply suggesting that homespun cotton was used to make garments. 1500 A.D. spinning was done entirely by hand. Spinning by hand was cumbersome, tedious and a very slow process indeed. Men and women too began to look around for a more satisfactory method of weaving threads together into cloth. At the beginning of the sixteenth century, a one-thread machine was invented which was a tremendous stride ahead of the old by-hand methods. It enabled the spinner to produce about seven times more yarn than by the distaff and spindle. New improvements and new inventions were gradually made, until the making of cloth was taken entirely out of the hands of the women in the homes and spinning was relegated into the realms of the "old-fashioned." During the industrial revolution, production was mechanized with machines powered by waterwheels and engines. Sewing machines emerged in the nineteenth century. Synthetic fibers such as nylon were invented during the twentieth century. Alongside these developments were changes in the types and style of clothing worn by humans. During the 1960s, had a major influence on subsequent developments in the industry. The textile industry has undergone significant changes in business practices in several key areas. Labor relations, trade practices, product labeling, product safety, and environmental and antipollution measures have been subjects of public scrutiny and federal legislation. The words fabric and cloth are commonly used in textile assembly trades (such as tailoring and dressmaking) as synonyms for textile. However, there are subtle differences in these terms. Textile refers to any material made of interlacing fibres. Fabric refers to any material made through weaving, knitting, crocheting, or bonding. Cloth refers to a finished piece of fabric that can be used for a purpose such as covering a bed.

1.3 MAJOR GOALS

Textile production played a crucial part in the industrial revolution, the establishment of organized labor, and the technological development of the country. Once, textile production was simple enough that the entire process could and did take place in the home. Now, textiles represent a complex network of interrelated industries that produce fiber, spin yarns, fabricate cloth, and dye, finish, print, and manufacture goods.A material made mainly of natural or synthetic fibers. They are found in apparel, household and commercial furnishings, vehicles, and industrial products. Textiles have an assortment of uses, the most common of which are for clothing and containers such as bags and baskets. In the household, they are used in carpeting, upholstered furnishings, window shades, towels, covering for tables,

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beds, and other flat surfaces, and in art. In the workplace, they are used in industrial and scientific processes such as filtering. Miscellaneous uses include flags, tents, nets, cleaning devices, such as handkerchiefs; transportation devices such as balloons, kites, sails, and parachutes; strengthening in composite materials such as fibre glass and industrial geotextiles, and smaller cloths are used in washing by "soaping up" the cloth and washing with it rather than using just soap. Textiles used for industrial purposes, and chosen for characteristics other than their appearance, are commonly referred to as technical textiles. Technical textiles include textile structures for automotive applications, medical textiles (e.g. implants), geotextiles (reinforcement of embankments), agrotextiles (textiles for crop protection), protective clothing (e.g. against heat and radiation for fire fighter clothing, against molten metals for welders, stab protection, and bullet proof vests. In all these applications stringent performance requirements must be met.

1.4 PRODUCTION METHODS

There is a logical development of raw material into finished consumers' goods. Studying textile materials in the interesting sequence of "fibre to yarn to fabric" will help understand the construction and ultimate qualities of the fabrics with which will become familiar. Here are the steps in the manufacture of fabrics from raw material to finished goods:

1.4.1 Spinning

The fabrication of yarn (thread) from either discontinuous natural fibers or bulk synthetic polymeric material. In a textile context the term spinning is applied to two different processes leading to the yarns used to make threads, cords, ropes, or woven or knitted textile products.

1.4.2 Weaving

Weaving is a textile production method which involves interlacing a set of vertical threads (called the warp) with a set of horizontal threads (called the weft). This is done on a machine known as a loom, of which there are a number of types. Some weaving is still done by hand, but the vast majority is mechanized.

1.4.3 Knitting

Knitting and crocheting involve interlacing loops of yarn, which are formed either on a knitting needle or on a crochet hook, together in a line. The two processes are different in that knitting has several active loops at one time, on the knitting needle waiting to interlock with another loop, while crocheting never has more than one active loop on the needle.

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1.4.4 Braiding

Braiding or plaiting involves twisting threads together into cloth. Knotting involves tying threads together and is used in making macrame.

1.4.5 Lace

Lace is made by interlocking threads together independently, using a backing and any of the methods described above, to create a fine fabric with open holes in the work. Lace can be made by either hand or machine.

1.4.6 Felting

Felting involves pressing a mat of fibers together, and working them together until they become tangled. A liquid, such as soapy water, is usually added to lubricate the fibers, and to open up the microscopic scales on strands of wool.

• Carpets, rugs, velvet, velour, and velveteen, are made by interlacing a secondary yarn through woven cloth, creating a tufted layer known as a nap or pile.

1.5 LET US SUM UP

A material made mainly of natural or synthetic fibers. Modern textile products may be prepared from a number of combinations of fibers, yards, films, sheets, foams, furs, or leather. They are found in apparel, household and commercial furnishings, vehicles, and industrial products. Yarn, fabrics, and tools for spinning and weaving have been found among the earliest relics of human habitations.

The natural progression from raw material to finished product requires: the cultivation or manufacture of fibers; the twisting of fibers into yarns (spinning); the interlacing (weaving) or interlooping (knitting) of yarns into cloth; and the finishing of cloth prior to sale.

1.6 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Interact with textile industries owners and technicians • Go through the textile magazine journals and Analyze the field of Indian textile and its developments.

1.7 POINT OF DISCUSSION

In this lesson we will endeavor to familiarize you with the names of different textiles, their comparative values and their uses in the making of clothes.

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1.8 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). The basic unit of a textile structure is fabric.

2. Explain current trends and technology in the textile industry.

• Equipment and machinery continues to change the industry. Machinery continues to be more productive, processes are constantly monitored by computer systems, and product quality is expected to improve. • Microfibers. New microfibers will enhance the characteristics of high performance fabrics for wicking (a fiber’s ability to draw moisture away from the body), coolness, warmth, and protection resulting in the production of intelligent garments. • Development of new recycling processes. Plastic soda bottles are converted into a polyester fiber that is used to make fabric for t-shirts and filling for pillows. The fiber can be recycled numerous times without losing its performance attributes. • Nonwoven fabrics are finding increasing usage in reusable apparel and other products, thus replacing the traditional knits and wovens. • Individuality - Consumers have more and more choices when they go to shop for clothing. Individuality in clothing choices continues to advance the demand for mass-customization in clothing. • Demand for new technologies for developing new, improved textile products

3. Discuss about the sequence of fabric construction. • Fibre, which is either spun or twisted into yarn or else directly compressed into fabric • Yarn, which is woven, knitted, or otherwise made into fabric • Fabric, which by various finishing processes becomes finished consumers' goods. A fibre is defined as any product capable of being woven or otherwise made into a fabric. It may be thought of as the smallest visible unit of textile production.

1.9 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile Fibres. Gordon Cook, J.,

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LESSON-2 FIBRES

CONTENT 2.0 AIM AND OBJECTIVES 2.1 INTRODUCTION 2.2 FIBRES 2.3 CLASSIFICATION OF FIBRES 2.3.1 Natural fiber and 2.3.1.1 Vegetable fibers 2.3.1.2 Animal fibers 2.3.1.3 Mineral fibers 2.3.2 Man made or synthetic fiber. 2.3.2.1 Properties of synthetic fibres. 2.4 CHECK YOUR PROGRESS 2.5 FIBRE PROPERTIES 2.5.1 Primary Characteristics of Textile Fibre 2.5.2 Secondary Characteristics of Textile Fibre 2.5.3 Other Characteristics of Textile Fibre 2.6 LETS SUMUP 2.7 LESSON END ACTIVITIES 2.8 POINT OF DISCUSSION 2.9 CHECK YOUR PROGRESS 2.10 REFERENCES

2.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following • Textile fibres and its definition • Fibre classification • Sub classification of natural and man made fibres • Essential and Desirable properties of textile fibres

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2.1 INTRODUCTION

Fibre, fine hair-like structure of animal, vegetable, mineral, or synthetic origin. Fibres average less than 0.05 cm (0.02 in) in diameter. Used for textiles and for many other products, fibres are classified according to their origin, their chemical structure, or both. The first essential of a fibre is that it must be hundreds of tines longer than it is wide to enable it to be spun into a thread for weaving. It must also be strong and flexible and elastic enough to withstand the strain of the processes required to produce a cloth that wears well. If the fibre is a very coarse one, it produces a cloth resembling sacking. For comfort in weaving, all fibres need to be able to absorb moisture. Luster may be desirable for appearance, and weight and flexibility can affect draping.

2.2 FIBRES

The basic unit of a textile structure is fibre. The textile industry uses many different kinds of fibres as its raw materials. Some of these fibres were known and used in the earlier years of civilization, as well as in modem times.

Fibre is a class of hair-like materials that are continuous filaments or are in discrete elongated pieces, similar to pieces of thread. They can be spun into filaments, thread, or rope. They can be used as a component of composite materials. They can also be matted into sheets to make products such as paper or felt.

2.3 CLASSIFICATION OF FIBRES

In order to simplify the study of textile fibres, materials with similar properties must be grouped in some logical order. Each country has developed its own system for naming fibres. The two major groups, or families, of fibres specified by the act are: 2.3.1 Natural fiber and 2.3.2 Man made or synthetic fiber.

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2.3.1 Natural Fibers

The term “natural fibers” covers a broad range of vegetable, animal, and mineral fibers.

2.3.1.1 Vegetable fibers

Vegetable fibers are generally comprised mainly of cellulose: examples include cotton, linen, jute, flax, ramie, sisal, and hemp. Cellulose fibers serve in the manufacture of paper and cloth. This fiber can be further categorized into the following: • Seed fiber: Fibers collected from seeds or seed cases. E.g. cotton and kapok. • Leaf fiber: Fibers collected from leaves. E.g. sisal and agaves. • Bast fiber or skin fiber: Fibers are collected from the skin or bast surrounding the stem of their respective plant. These fibers have higher tensile strength than other fibers. Therefore, these fibers are used for durable yarn, fabric, packaging, and paper. Some examples are flax, jute, kenaf, industrial hemp, ramie, rattan, soybean fiber, and even vine fibers and banana fibers. • Fruit fiber: Fibers are collected from the fruit of the plant, e.g. coconut (coir) fiber. • Stalk fiber: Fibers are actually the stalks of the plant. E.g. straws of wheat, rice, barley, and other crops including bamboo and grass. Tree wood is also such a fiber.

The most used natural fibers are cotton, flax and hemp, although sisal, jute, kenaf, and coconut are also widely used. Hemp fibers are mainly used for ropes and aerofoil because of their high suppleness and resistance within an aggressive environment. Hemp fibers are, for example, currently used as a seal within the heating and sanitary industries.

2.3.1.2 Animal fibers

Animal fibers generally comprise proteins and are commonly made from hair or fur.

• Wool refers to the hair of the domestic goat or sheep, which is distinguished from other types of animal hair in that the individual strands are coated with scales and tightly crimped, and the wool as a whole is coated with an oil known as lanolin, which is waterproof and dirt proof. Woolen refers to a bulkier yarn produced from carded, non-parallel fibre, while worsted refers to a finer yarn which is spun from longer fibres which have been combed to be parallel. Wool is commonly used for warm clothing.

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Cashmere, the hair of the Indian Cashmere goat, and mohair, the hair of the North African Angora goat, are types of wool known for their softness. Other animal textiles which are made from hair or fur are alpaca wool, llama wool, and camel hair, generally used in the production of coats, jackets, ponchos, blankets, and other warm coverings. Angora refers to the long, thick, soft hair of the Angora rabbit.

• Silk is an animal textile made from the fibers of the cocoon of the Chinese silkworm. This is spun into a smooth, shiny fabric prized for its sleek texture.

2.3.1.3 Mineral fibers

Mineral fibers are naturally occurring fiber or slightly modified fiber procured from minerals. These can be categorized into the following categories: • Asbestos and basalt fiber are used for vinyl tiles, sheeting, and adhesives, "transit" panels and siding, acoustical ceilings, stage curtains, and fire blankets. • Glass Fiber is used in the production of spacesuits, ironing board and mattress covers, ropes and cables, reinforcement fiber for composite materials, insect netting, flame-retardant and protective fabric, soundproof, fireproof, and insulating fibers. • Metal fiber, metal foil, and metal wire have a variety of uses, including the production of cloth-of-gold and jewelry. Hardware cloth is a coarse weave of steel wire, used in construction.

2.3.2 Man Made fibres

Synthetic fibers are the result of extensive research by scientists to improve upon naturally occurring animal and In general, synthetic (manmade) fibers are created by forcing, usually through extrusion, fiber forming materials through holes (called spinnerets) into the air, forming a thread. Before synthetic fibrers were developed, artificial (manufactured) fibers were made from cellulose, which comes from plants.

The manufacturing process of regenerated fibres consists of bringing a natural high polymer substance into solution in a suitable way and extruding this solution through a nozzle (orifice), regenerating the same high polymer in the form of a solid filament. A regenerated fibre is one which has a different physical structure than the substance from which it is made, but is essentially the same chemically. Rayon is Regenerated Cellulose, i.e., cellulose that has gone through the manufacturing process, from solid to liquid to solid, without chemical change.

The first artificial fiber, known as artificial silk from 1855 onwards, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both

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artificial fibers, but not truly synthetic, being made from wood. Although these artificial fibers were discovered in the mid-nineteenth century, successful modern manufacture began much later

Nylon, the first synthetic fiber, made its debut in the United States as a replacement for silk, just in time for World War II rationing. Its novel use as a material for women's stockings overshadowed more practical uses, such as a replacement for the silk in parachutes and other military uses.

Common synthetic fibers include:

• Polyester fiber is used in all types of clothing, either alone or blended with fibres such as cotton. • Aramid fiber (e.g. Twaron) is used for flame-retardant clothing, cut- protection, and armor. • Acrylic is a fibre used to imitate wools, including cashmere, and is often used in replacement of them. • Nylon is a fibre used to imitate silk; it is used in the production of pantyhose. Thicker nylon fibers are used in rope and outdoor clothing. • Spandex (trade name Lycra) is a polyurethane fibre that stretches easily and can be made tight-fitting without impeding movement. It is used to make active wear, bras, and swimsuits. • Olefin fiber is a fiber used in active wear, linings, and warm clothing. Olefins are hydrophobic, allowing them to dry quickly. A sintered felt of olefin fibers is sold under the trade name Tyvek. • Ingeo is a polylactide fiber blended with other fibres such as cotton and used in clothing. It is more hydrophilic than most other synthetics, allowing it to wick away perspiration. • Lurex is a metallic fiber used in clothing embellishment.

2.3.2.1 Properties of synthetic fibres.

They are flexible, light and very resistant. They do not absorb humidity and maintain body heat, therefore they are not suitable for the manufacture of summer articles if not mixed with other natural fibres. They do not shrink, crease and maintain machine pleating, avoiding ironing. They dye well. Due to their elasticity they are used in the manufacture of underwear, swimming costumes and sportswear

2.4 CHECK YOUR PROGRESS

Explain natural fibers, manufactured fibers, and blends.

1. Natural fibers:

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Fibers from plants or animal sources. Lower quality, short fibers are staple fibers. Long, continuous fibers of higher quality are filament fibers. • Cellulosic fibers: Fibers derived from plants. • Protein fibers: Fibers derived from animals or insects.

2. Manufactured fibers:

Fibers that are man-made (synthetic) and are created by combining various substances with chemicals. Solid raw materials and chemicals are melted or dissolved to form a thick liquid. The liquid is forced through the tiny holes of a mechanical device known as a spinneret to form filaments. (This process is similar to pushing dough through a pasta machine to make spaghetti.) The filaments are then stretched, hardened, and crimped and/or cut into lengths.

• Cellulosic manufactured fibers are made from cellulose from plants such as soft wood pulp and are changed into usable fibers by applying chemicals. • Noncellulosic manufactured fibers are made from various petrochemical mixtures of crude oil, natural gas, air, and water.

2.5 FIBRE PROPERTIES

To be spinnable, a fibre must have sufficient length, pliability, strength, and cohesiveness to form a yarn. Fibres must also be inexpensive, available, and constant in supply to be economically suitable for production. To make such a fabric the manufacturer chooses fibres, yarns, weaves, and finishes with a combination of properties which will give the type of Serviceability the consumer wants.

2.5.1 Primary Characteristics of Textile Fibre

The primary properties of textile fibre is • Stable length • Tensile strength, • Fineness, • Spinnability, and • Uniformity

Stable length - Staple fibres are short in length, measured in inches and range from three-quartos of an inch to 18 inches in length. All the natural fibres, except silk, are staple fibrres. Any filament fibre can be cut into staple of a length determined by the end-use desired.

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Tensile strength - Strength of a fibre is the ability to resist strains and stresses. It is expressed as tensile strength which is measured in pounds per square inch (p.s.i.) or as tenacity which is measured in grams per denier. Some fibres gain strength when wet, some lose strength, and some are unaffected by water.

Fineness – In a fibre, the ratio or relationship if length to width or cross- sectional area is expressed as its fineness. In coarse fibres the length is about 700 times more than the width. The ratio may be even 5000 in case of very fine fibres. Only fine fibres can produce fine yarn. Fineness does much to determine properties and characteristics of particular fibre and it also determines the end use of fibres.

Spinnability – Spinnability inclues several physical properties each having an effect on the ability of the fibres to be spun into yarn. For Example: Staple fibres must have to be capable of taking a twist. They must have a certain degree of friction against one another to stay in place when pull is applied to the yarn. And they must be able to take on hole special finishes for lubrication during spinning or to provide additional surface resistance to abrasion.

Uniformity –This means the evenness of the individual fibres in length and diameter. A fibre possessing this property can produce reasonably even threads. This is also important in connection with the strength of the resulting yarn. The more uniform the yarn the stronger the yarn.

2.5.2 Secondary Characteristics of Textile Fibre

The secondary properties of textile fibre is

• Crimp • Elasticity • Cohesion • Density • Plasticity • Absorbency • Resilience • Capillarity or Porosity • Colour • Luster • Flexibility • Rigidity • Abrasion resistance • Static electric resistance

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Crimp - Crimp refers to the waves or bends that occur along the length of a fibre. Wool has natural crimp. Manmade fibres may be given a permanent crimp. Fibre crimp increases cohesiveness, resiliency, and resistance to abrasion. It helps fabrics maintain their thickness.

Elasticity - Elasticity means the ability of a stretched material to return immediately to its original size.

Cohesion - Cohesiveness is the ability of fibres to cling together. This is important in staple fibres, but unimportant in filament fibres.

Density - Density and specific gravity are measured of the weight of a fiber. Density is the weight in grams per cubic centimetre. Specific gravity is the ratio of the mass of the fibre to the mass of an equal volume of water at 40°C. The weight of a fabric is determined by the density or specific gravity of the fibres.

Plasticity - Plasticity is that property of a fibre which enables the user to 'shape it semi-permanently or permanently by moisture, heat, and pressure or by heat and pressure alone.

Absorbency - Absorbency is the ability of a fibre to take up moisture and is expressed as percentage of moisture regain, which is the percentage of moisture that a bone-dry fibre will absorb from the air under standard conditions of temperature and humidity. The ability of a fibre to absorb moisture is directly related to washability, dyeing, shrinkage, absorption of aqueous finishes, comfort on humid days, and soiling. Staple fibres hold more water than filament fibres since they pack less compactly and create a sponge-like condition in the yarn and fabric. For this reason staple fibre fabrics require a longer drying time.

Resilience - Resiliency is the ability of a fibre or fabric to recover, over a period of time, from deformation such as stretching, compressing, bending or twisting. A resilient fabric has good crease recovery, hence requires a minimum of ironing. Resilient fabrics also retain high bulk.

Capillarity or Porosity - This two terms express properties with the similar influence on the ability of a textile fibre or yarn to accept and hold a dye, a finish a lubricant or even resin in order to increase the wrinkle resistance of a fabric or to give it a wash and wear finish. Liquids passed rapidly through porosity. In the case of the passage of these liquids through the hollow centre or lumen in cotton or through small voids on the surface of wool fibre. It is usually regarded as the effect of the mechanism capillarity.

Colour – Most natural fibre have some colour. The synthetic fibres too have a slight creamy or yellow colour.

For Example: Silk is yellow to tan Wool is brownish tint Cotton is a creamy white or brown

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Luster - Lustre is the shine, sheen or brightness of a fibre caused by reflection of light. Smooth fibres reflect more light than rough or serrated fibres; round fibres reflect more light than flat fibres. Filaments which are laid together with little or no twist reflect more light than short fibres which must be twisted together to forth yarns. Manmade fibres can be delustered by adding oil or pigments to the solution from which the fibre is spun.

Flexibility - Pliability or flexibility is the ease of bending or shaping. Pliable fibres are easily twisted to make yarns. They make fabrics that resist splitting when folded or creases many times in the same place.

Rigidity - Stiffness or rigidity is the opposite of flexibility. It is the resistance to bending or creasing. Rigidity and weight together make up the body of the fabric.

Abrasion resistance - Abrasion resistance is the ability of a fibre to withstand the rubbing or abrasion it gets in everyday use. Inherent toughness, natural pliability, and smooth filament surface are fibre characteristics that contribute to abrasion resistance.

Static electric resistance - Phenomenon of static electricity creates a problem in the spinning and other processing of textile fibres especially in rooms with very low relative humidity. The problem is much more severe in the case of synthetic fibres which have extremely low electrical conductivity and generally absorb too little moisture to provide a path where y the static electricity can be carried away. Static electrical properties create problems in the packaging and in the sewing

2.5.3 Other Characteristics of Textile Fibre

• Wicking or wetting • Chemical resistance • Resistance to moths, and mildew • Flammability or inflammability

Wicking or wetting - Wicking or wetting refers to the conduction of moisture along the fibre or through the fabric, although the fibre itself does not absorb much moisture. This property is related to surface wetting and is not the same as absorbency.

Chemical resistance - The chemical reactivity of each fibre depends on the arrangement of the elements in the molecule and the reactive groups it contains. Dry-cleaning solvents, perspiration, soap, synthetic detergents, bleaches, atmospheric gas, soot, and sunshine may all cause chemical degradation on some or all of the fibres.

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Resistance to moths, and mildew - Resistance to moths, and mildew is due to the chemical composition of the fibre. These properties are important to the consumer because they indicate the type of care needed during storage as well as during use. Fibres without natural resistance must have protective finishes added or have their chemical composition changed to make them resistant.

Flammability or inflammability - Flammability or inflammability refers to the ease of ignition and the speed and length of burning. Non-flammable fibres will not burn. Flammability depends not only on the chemical composition but on the air incorporated in the yarn or fabric. Combustible finishes or dyes may take a non-flammable fibre burn. Finishes can also be added to make fibres non- flammable.

2.6 LETS SUMUP

A textile is a flexible material comprised of a network of natural or artificial fibers often referred to as thread or yarn. Yarn is produced by spinning Textiles can be made from many materials. These materials come from four main sources: animal, plant, mineral, and synthetic.

The physical structure of a fibre includes length, diameter, surface contour, crimp, and shape. These properties help determine the roughness, smoothness, softness, and sail-resistance of a fabric.

2.7 LESSON END ACTIVITIES

The students may do the following activities based on this lesson.

• Search and collect various types of fibre and identify the name of each fibre and basic properties of the same.

2.8 POINT OF DISCUSSION

Here the students are asked to discuss about the following points

• The factors influencing the development and utilization of all these fibres include their ability to be spun, their ability in sufficient quantity, the cost or economy of production, and desirability of their properties to consumers

2.9 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. The tree major groups, or families of fibres specified by the act are natural fibres, man-made fibres and synthetic fibres.

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b. Natural fibres can be classified as vegetable and animal. c. Vegetable fibres are cellulosic in composition. d. Animal fibres are protein in composition. e. Nylon is a cellulosic fibre. f. The only filament fibre that occurs naturally is silk. g. Crimp refers to the waves that occur along the length of a fibre. h. Lustre is the shine, sheen, or brightness of a fibre caused by reflection of light. i. Pliable fibres are easily twisted to make yarns.

2. Briefly explain the two classes of fibres according to their length.

There are two classes of fibres according to length: (a) filament, (b) staple.

(a) Filaments

They are of a continuous length measurable in yards or metres. The only filament that occurs naturally is silk. All other filaments are manmade. Yarns made from filaments are of two types: multifilament and monofilament.

(b) Staple Fibres

They are short in length, measured in inches and range from 3/a" to 10" in length. All natural fibres except. silk are staple fibres. Any filament can be cut into staple of a length determined by the end-use desired.

2.10 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile Fibres. Gordon Cook, J.,

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UNIT - II

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LESSON-3 NATURAL FIBRES

CONTENT 3.0 AIM AND OBJECTIVES 3.1 INTRODUCTION 3.2 COTTON 3.2.1 Types of Cotton 3.2.2 The Cotton Plant 3.2.3 The Production Process 3.2.4 Properties of cotton fibre 3.2.5 End Uses 3.3 LET US SUM UP 3.4 LESSON END ACTIVITIES 3.5 POINTS FOR DISCUSSION 3.6 CHECK YOUR PROGRESS 3.7 REFERENCES

3.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following • Meaning of natural fibres. • The manufacturing method of cotton fibres. • Properties and Uses of cotton fibres. • Different types of cotton fibre based on its length.

3.1 INTRODUCTION

Fibers are the raw materials for all fabrics. Some fibers occur in nature as fine strands that can be twisted into yarns. These natural fibers come from plants, animals, and minerals. For most of history, people had only natural fibers to use in making cloth.

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The use of natural fibers extends back beyond recorded history with archaeological evidence indicating that wool and flax were being woven into fabrics by the sixth century BC.

3.2 COTTON

The seed of plant is often attached to hairs which are constructed in the main from cellulose. Many of these fibres are used in the textile industry, on of them- cotton-has become the most important textile fibre in the world.

Cotton is a fibre that grows from the surface of seeds in the pods, or bolls, of a bushy mallow plant. Each fibre is a single elongated cell that is flat, twisted, and ribbonlike with a wide inner hollow (lumen). It is composed of about 90% cellulose and about 6% moisture; the remainder consists of natural impurities. The outer surface of the fibre is covered with a protective waxlike coating, which gives the fibre a somewhat adhesive quality. This characteristic combined with its natural twist contributes to making cotton an excellent fibre for spinning into yarn. Cotton yam is used to make fabrics that are universally used for all types of apparel, home furnishings, and industrial applications.

In common with other natural fibres, cotton is available in a great variety of fibre qualities, which are determined particularly according to fibre length and fibre fineness. The West Indies produces a small quantity of cotton compared with world production, but its supreme excellence is well known and it is commonly known as Sea Island. Its length of about 6cm. (which is very long for cotton), lustre, fineness, and accompanying softness make it suitable for fine, best quality yarns and fabrics. A very short, coarse cotton which is only suitable for coarse yarns and fabrics could be, for instance, an Indian cotton known as Bengals.

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3.2.1 Types of Cotton

Raw cotton is creamy white in colour.The cotton of commerce can be classified into three general groups on basic of fibre length, fibre fineness, and geographical region (country) of growth as follows:

Type 1 Long, fine cotton Long staple, fine strong fibre of good lustre, which form the top quality cotton. The fibres are generally of 115 microns diameter, staple length from 1 to 2W. It includes Sea Island, American and Egyptian cotton. They are not easy to grow, they are expensive and are used only for high quality, fine cloths, and hosiery yarns.

Type 2 Standard cotton .. Intermediate staple, coarser texture and charter length. Thefibres are generally of 12-17 microns diameter, from 1 to 1 5/16". The principal member of this group is American Upland . They are used far standard fabrics.

Type 3 Coarse, shorter cotton ...Short staple, waiter fibres of no lustre and low in strength that range in staple length from 3/8 to 1". The fibres are generally of 13-22 microns diameter. These are the Indian or Asiatic cottons. It is used for lower quality fabrics (sometimes blended with wool, far cotton blankets and carpets).

3.2.2 The Cotton Plant

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The cotton plant belongs to the genus Gossypium of the family Malvaceae (mallow family). It is generally a shrubby plant having broad three-lobed leaves and seeds in capsules, or bolls; each seed is surrounded with downy fiber, white or creamy in color and easily spun. The fibers flatten and twist naturally as they dry.

Cotton is of tropical origin but is most successfully cultivated in temperate climates with well-distributed rainfall. The requisites on the basis of which to judge the quality of the cotton are the grade, the colour, and the length of the fibres and the character.

3.2.3 The Production Process

1. In spring, the acreage is cleared for planting. Mechanical cultivators rip out weeds and grass that may compete with the cotton for soil nutrients, sunlight, and water, and may attract pests that harm cotton. The land is plowed under and soil is broken up and formed into rows. 2. Cottonseed is mechanically planted by machines that plant up to 12 rows at a time. The planter opens a small furrow in each row, drops in seed, covers them, and then packs more dirt on top. Seed may be deposited in either small clumps (referred to as hill-dropped) or singularly (called drilled). The seed is placed 0.75 to 1.25 in (1.9 to 3.2 cm) deep, depending on the climate. The seed must be placed more shallowly in dusty, cool areas of the Cotton Belt, and more deeply in warmer areas. 3. With good soil moisture and warm temperature at planting, seedlings usually emerge five to seven days after planting, with a full stand of cotton appearing after about 11 days. Occasionally disease sets in, delaying the seedlings' appearance. Also, a soil crust may prevent seedlings from surfacing. Thus, the crust must be carefully broken by machines or irrigation to permit the plants to emerge. 4. Approximately six weeks after seedlings appear, "squares," or flower buds, begin to form. The buds mature for three weeks and then blossom into creamy yellow flowers, which turn pink, then red, and then fall off just three days after blossoming. After the flower falls away, a tiny ovary is left on the cotton plant. This ovary ripens and enlarges into a green pod called a cotton boll. 5. The boll matures in a period that ranges from 55 to 80 days. During this time, the football-shaped boll grows and moist fibers push the newly formed seeds outward. As the boll ripens, it remains green. Fibers continue to expand under the warm sun, with each fiber growing to its full lengthabout 2.5 in (6.4 cm)during three weeks. For nearly six weeks, the fibers get thicker and layers of cellulose build up the cell walls. Ten weeks after flowers first appeared, fibers split the boll apart, and cream- colored cotton pushes forth. The moist fibers dry in the sun and the fibers collapse and twist together, looking like ribbon. Each boll contains three to five "cells," each having about seven seeds embedded in the fiber.

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6. At this point the cotton plant is defoliated if it is to be machine harvested. Defoliation (removing the leaves) is often accomplished by spraying the plant with a chemical. It is important that leaves not be harvested with the fiber because they are considered "trash" and must be removed at some point. In addition, removing the leaves minimizes staining the fiber and eliminates a source of excess moisture. Some American crops are naturally defoliated by frost, but at least half of the crops must be defoliated with chemicals. Without defoliation, the cotton must be picked by hand, with laborers clearing out the leaves as they work. 7. Harvesting can be done by machine, with a single machine replacing 50 hand-pickers. Two mechanical systems are used to harvest cotton. The picker system uses wind and guides to pull the cotton from the plant, often leaving behind the leaves and rest of the plant. The stripper system chops the plant and uses air to separate the trash from the cotton. Most cotton is harvested using pickers. Pickers must be used after the dew dries in the morning and must conclude when dew begins to form again at the end of the day. Moisture detectors are used to ensure that the moisture content is no higher than 12%, or the cotton may not be harvested and stored successfully. Not all cotton reaches maturity at the same time, and harvesting may occur in waves, with a second and third picking. 8. Next, most cotton is stored in "modules," which hold 13-15 bales in water-resistant containers in the fields until they are ready to be ginned. 9. The cotton module is cleaned, compressed, tagged, and stored at the gin. The cotton is cleaned to separate dirt, seeds, and short lint from the cotton. At the gin, the cotton enters module feeders that fluff up the cotton before cleaning. Some gins use vacuum pipes to send fibers to cleaning equipment where trash is removed. After cleaning, cotton is sent to gin stands where revolving circular saws pull the fiber through wire ribs, thus separating seeds from the fiber. High-capacity gins can process 60, 500-lb (227-kg) bales of cotton per hour. 10. Cleaned and de-seeded cotton is then compressed into bales, which permits economical storage and transportation of cotton. The compressed bales are banded and wrapped. The wrapping may be either cotton or polypropylene, which maintains the proper moisture content of the cotton and keeps bales clean during storage and transportation. 11. Every bale of cotton produced must be given a gin ticket and a warehouse ticket. The gin ticket identifies the bale until it is woven. The ticket is a bar-coded tag that is torn off during inspection. It is assessed for color, leaf content, strength, fineness, reflectance, fiber length, and trash content. The results of the evaluation determine the bale's value. Inspection results are available to potential buyers. 12. After inspection, bales are stored in a carefully controlled warehouse. The bales remain there until they are sold to a mill for further processing.

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3.2.4 Properties of cotton fibre

Property Evaluation Fairly uniform in width, 12-20 micrometers; length Shape varies from 1 cm to 6 cm (½ to 2½ inches); typical length is 2.2 cm to 3.2 cm (8 ⅞ to 1¼ inches). Luster low Tenacity (strength) Dry 3.0-5.0 g/d Wet 3.3-6.0 g/d Resiliency low Density 1.54-1.56 g/cm³

Moisture absorption raw:conditioned 8.5% saturation 15-25% mercerized: conditioned 8.5-10.3% saturation 15-27%+

Dimensional stability good

Resistance to acids damage, weaken fibers alkali resistant; no harmful effects organic solvents high resistance to most sunlight Prolonged exposure weakens fibers. microorganisms Mildew and rot-producing bacteria damage fibers. insects Silverfish damage fibers.

Thermal reactions Decomposes after prolonged exposure to to heat temperatures of 150˚C or over. to flame Burns readily.

3.2.5 End Uses

Cotton is used in apparel, home furnishing, and industrial fabrics. Its comfort and hand are usually given as reasons for its preference by consumers of apparel and household fabrics. The fact that it is a "natural" product is a factor cited by many who select cotton products.

Apparel fabrics of all styles and weights are being used. Knit cotton T-shirts and cotton underwear are preferred for their absorbency and ease of care. Men's shirts and summer suits contain cotton, and the fibre is predominant in women's and children's wear.

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The domestics market -sheets and towels- is dominated by cotton. Most sheets and pillowcases are blends of cotton and polyester, but 100% cotton sheets are available once again. Polyester is occasionally blended with cotton in towels to provide strength and durability to the base fabric, but the surface pile remains cotton for absorbency.

3.3 LET US SUM UP

Plants provide more textile fibers than do animals or minerals. Cotton fibers produce soft, absorbent fabrics that are widely used for clothing, sheets, and towels. Fibers of the flax plant are made into linen. The strength and beauty of linen have made it a popular fabric for fine tablecloths, napkins, and handkerchiefs.

95% composed of cellulose, cotton is the cloth with which more than 90% of men's shirts are manufactured. It, in fact, has properties that render it particularly indicated to be worn in contact with the skin.

Soft and light, cotton allows the skin to breath and good absorption capabilities; differently from wool it does not felt in washing, but, on the contrary, tends to become more soft. It is a very resistant fibre that does not wear, but rips; is dyed easily and the colour holds in washings that it tolerates even at high temperatures.

3.4 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Find the availability of Indian cotton and grade the quality of each variety. • Prepare a chart for different varieties of cotton based on its fibre properties.

3.5 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Why cotton is a right choice to mix with synthetic fibres? • The reason for cotton is called as “King of fibres”. • Apart from apparel industry, the uses of cotton.

3.6 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. All cellulose fibres are prepared by retting process.

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b. All the natural fibres are staple fibres. c. Cotton makes very comfortable skin contact fabrics because of its absorbency. d. The cotton of commerce can be classified into three general groups. 2. Identify basic natural fibers, their characteristics, care, and uses of cotton The soft, white, downy fiber (boll) attached to the seed of a cotton plant. Cotton, grown in the southern United States and other warm climates, is the most widely used of all natural fibers. a. Characteristics: (1) Strong and durable (2) Absorbent (3) Cool to wear (4) Shrinks in hot water (5) Wrinkles easily b. Proper care: (1) Machine wash (2) Tumble dry at moderate temperatures (3) Press with warm to hot iron (depending on fabric weight) c. Some common uses: (1) Underwear (2) Socks (3) Shirts, blouses (4) Jeans (5) Sheets, towels (6) Slip covers

3.7 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile fibers, II Manmade Fibers, J. Gordon Cook. • Handbook of Fiber Science and Technology: Fiber Chemistry, Vol. IV

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LESSON-4 OTHER NATURAL FIBRES

CONTENT 4.0 AIM AND OBJECTIVES 4.1 INTRODUCTION 4.2 LINEN 4.2.1 Raw Materials 4.2.2 The Manufacturing Process 4.2.3 Physical and Chemical Properties of Flax 4.2.4 Uses 4.3 CHECK YOUR PROGRESS 4.4 JUTE 4.4.1 Cultivation 4.4.2 Retting 4.4.3 Properties of Jute 4.4.4 Uses 4.5 PINEAPPLE 4.5.1 Properties and Uses of Pina 4.6 HEMP 4.6.1 Flow chart 4.6.2 Harvesting 4.6.3 Properties 4.6.4 Uses 4.7 LESSON END ACTIVITIES 4.8 POINTS FOR DISCUSSION 4.9 CHECK YOUR PROGRESS 4.10 REFERENCES

4.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following

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• Meaning of vegetable fibres. • The sequences of operation involved to manufacturing linen, jute, pineapple and hemp • Properties and Uses of vegetable fibres.

4.1 INTRODUCTION

Vegetable fibers are generally comprised mainly of cellulose: examples include cotton, linen, jute, flax, ramie, sisal, and hemp. Cellulose fibers serve in the manufacture of paper and cloth.

The numerous varieties of bast fibres are used for purposes ranging from weaving fine textiles to manufacturing cordage. Linen cloth is made from flax, and coarser cloths and rope and twine are produced from hemp, jute, and ramie. Vascular fibres are used almost entirely for cordage making. They include agave (sisal), henequen, manila hemp, yucca, and a number of others. The vascular fibres of the pineapple have been used in the production of textiles.

4.2 LINEN

Linen yarn is spun from the long fibers found just behind the bark in the multi- layer stem of the flax plant (Linum usitatissimum). In order to retrieve the fibers from the plant, the woody stem and the inner pith (called pectin), which holds the fibers together in a clump, must be rotted away. The cellulose fiber from the stem is spinnable and is used in the production of linen thread, cordage, and twine. From linen thread or yarn, fine toweling and dress fabrics may be woven. Linen fabric is a popular choice for warm-weather clothing. It feels cool in the summer but appears crisp and fresh even in hot weather. Household linens truly made of linen become more supple and soft to the touch with use; thus, linen was once the bed sheet of choice.

4.2.1 Raw Materials

All that is needed to turn flax fiber into linen, and then spin and weave the linen fibers into linen fabric is the cellulose flax fiber from the stem of the flax plant. The process for separating the fibers from the woody stalk can use either water or chemicals, but these are ultimately washed away and are not part of the finished material.

4.2.2 The Manufacturing Process

1. Cultivating • It takes about 100 days from seed planting to harvesting of the flax plant. Flax cannot endure very hot weather; thus, in many countries, the planting of seed is figured from the date or time of year in which the flax must be

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harvested due to heat and the growers count back 100 days to determine a date for planting. In some areas of the world, flax is sown in winter because of heat in early spring. In commercial production, the land is plowed in the spring then worked into a good seedbed by dicing, harrowing, and rolling. Flax seeds must be shallowly planted. Seeds may be broadcast by hand, but the seed must be covered over with soil. Machines may also plant the seed in rows. • Flax plants are poor competitors with weeds. Weeds reduce fiber yields and increase the difficulty in harvesting the plant. Tillage of the soil reduces weeds as do herbicides. When the flax plants are just a few inches high, the area must be carefully weeded so as not to disturb the delicate sprouts. In three months, the plants are straight, slender stalks that may be 2-4 ft (61- 122 cm) in height with small blue or white fibers. (Flax plants with blue flowers yield the finest linen fibers.)

2. Harvesting

• After about 90 days, the leaves wither, the stem turns yellow and the seeds turn brown, indicating it is time to harvest the plant. The plant must be pulled as soon as it appears brown as any delay results in linen without the prized luster. It is imperative that the stalk not be cut in the harvesting process but removed from the ground intact; if the stalk is cut the sap is lost, and this affects the quality of the linen. These plants are often pulled out of the ground by hand, grasped just under the seed heads and gently tugged. The tapered ends of the stalk must be preserved so that a smooth yarn may be spun. These stalks are tied in bundles called beets and are ready for extraction of the flax fiber in the stalk. However, fairly efficient machines can pull the plants from the ground as well.

3. Releasing the Fiber from the stalk

• The plant is passed through coarse combs, which removes the seeds and leaves from the plant. This process, called rippling, is mechanized in many of the flax-producing countries.

• The woody bark surrounding the flax fiber is decomposed by water or chemical retting, which loosens the pectin or gum that attaches the fiber to the stem. If flax is not fully retted, the stalk of the plant cannot be separated from the fiber without injuring the delicate fiber. Thus, retting has to be carefully executed. Too little retting may not permit the fiber to be separated from the stalk with ease. Too much retting or rotting will weaken fibers.

• Retting may be accomplished in a variety of ways. In some parts of the world, linen is still retted by hand, using moisture to rot away the bark. The stalks are spread on dewy slopes, submerged in stagnant pools of water, or placed in running streams. Workers must wait for the water to begin rotting

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or fermenting the stem sometimes more than a week or two. However, most manufacturers use chemicals for retting. The plants are placed in a solution either of alkali or oxalic acid, then pressurized and boiled. This method is easy to monitor and rather quick, although some believe that chemical retting adversely affects the color and strength of the fiber and hand retting produces the finest linen. Vat or mechanical retting requires that the stalks be submerged in vats of warm water, hastening the decomposition of the stem. The flax is then removed from the vats and passed between rollers to crush the bark as clean water flushes away the pectin and other impurities.

• After the retting process, the flax plants are squeezed and allowed to dry out before they undergo the process called breaking. In order to crush the decomposed stalks, they are sent through fluted rollers which break up the stem and separate the exterior fibers from the bast that will be used to make linen. This process breaks the stalk into small pieces of bark called shives. Then, the shives are scutched. The scutching machine removes the broken shives with rotating paddles, finally releasing the flax fiber from stalk.

• The fibers are now combed and straightened in preparation for spinning. This separates the short fibers (called tow and used for making more coarse, sturdy goods) from the longer and more luxurious linen fibers. The very finest flax fibers are called line or dressed flax, and the fibers may be anywhere from 12-20 in (30.5-51 cm) in length.

4. Spinning

• Line fibers (long linen fibers) are put through machines called spreaders, which combine fibers of the same length, laying the fibers parallel so that the ends overlap, creating a sliver. The sliver passes through a set of rollers, making a roving which is ready to spin.

• The linen rovings, resembling tresses of blonde hair, are put on a spinning frame and drawn out into thread and ultimately wound on bobbins or spools. Many such spools are filled on a spinning frame at the same time. The fibers are formed into a continuous ribbon by being pressed between rollers and combed over fine pins. This operation constantly pulls and elongates the ribbon-like linen until it is given its final twist for strength and wound on the bobbin. While linen is a strong fiber, it is rather inelastic. Thus, the atmosphere within the spinning factory must be both humid and warm in order to render the fiber easier to work into yarn. In this hot, humid factory the linen is wet spun in which the roving is run through a hot water bath in order to bind the fibers together thus creating a fine yarn. Dry spinning does not use moisture for spinning. This produces rough, uneven yarns that are used for making inexpensive twines or coarse yarns.

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• These moist yarns are transferred from bobbins on the spinning frame to large take-up reels. These linen reels are taken to dryers, and when the yarn is dry, it is wound onto bobbins for weaving or wound into yarn spools of varying weight. The standard measure of flax yarn is the cut. It is based on the measure of 1 lb (453.59 g) of flax spun to make 300 yd (274.2 m) of yarn being equal to one cut. If 1 lb (453.59 g) of flax is spun into 600 yd (548.4 m), then it is a "no. 2 cut." The higher the cut, the finer the yarn becomes. The yarn now awaits transport to the loom for weaving into fabrics, toweling, or for use as twine or rope.

4.2.3 Physical and Chemical Properties of Flax

1 Strength

Flax is one of the strongest fibres. It is especially durable being two to three times as strong as cotton. on the natural fibres, it is second in strength to silk. In linen, weight may be considered a criterion of durability. Flax also increases about 20% in strength when wet.

2. Elasticity

Linen has no significant elasticity. It is the least elastic of natural fibres. In order to fit comfortably, linen garments should neither bind nor pull at the seams.

3 Resilience

Linen is relatively stiff and has little resilience. Therefore, it wrinkles easily, which somewhat offsets its otherwise excellent qualities as a fabric for summer apparel. Due to its stiffness, linen fabrics should not have creases pressed firmly into them.

4 Absorbency

When absorbency is the main consideration, linen is preferable to cotton. It absorbs moisture and dries more quickly. This fabric takes up water rapidly. It has very good wicking properties. This makes the fibre comfortable to wear but difficult to dye and finish. It is therefore excellent for handkerchiefs and towels.

5 Density

Flax is one of the heavier cellulosic fibres with a density of 1.5 g/cc.

6 Luster

Flax has a silky luster due to the natural waxes found in the fibre. If this wax is removed by chemicals or solvents, the fibre becomes brittle and harsh.

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7 Effect of Light

Flax has good resistance to sunlight. Max is more resistant to light than cotton, but it will gradually deteriorate from exposure.

8 Effect of Heat

Linen scorches and flames in a manner similar to cotton. Linen may be safely ironed at 204°C (400').

9 Drapability

Linen has more body than cotton and drapes somewhat better.

10 Resistance to Mildew

Dry linen has good resistance to mildew, but fabrics stored in a warm, humid atmosphere support the rapid growth of the fungus. Most insects do not damage linen. It is more resistant to attack by insects and micro organisms.

11 Heat Conductivity

Linen is most suitable for summer apparel, as it allows the heat of the body to escape.

12 Cleanliness and Washability

Linen launders well and gives up stains readily. Some linen apparel requires dry cleaning because of construction and fabric finish. Care label instructions should be observed.

13 Shrinkage

Linen does not shrink a great deal; in fact, it shrinks less than cotton. But pre shrinkage finishing is desirable.

14 Reaction to Alkalis

Linen, like cotton, is highly resistant to alkalis. Linen may also be mercerized.

15 Reaction to Acids

Linen is damaged by hot dilute acids and cold concentrated acids.

16 Affinity for Dyes

Linen does not have good affinity for dyes. However, it is possible to obtain dyes linen that has good colourfastness. When buying coloured linens, look for the words "Guaranteed Fast Colour" on the label or get a guarantee of colourfastness from the store.

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17 Resistance to Perspiration

Acid perspiration will deteriorate linen. Alkali perspiration will not cause deterioration. But in either case discolouration may occur.

4.2.4 Uses

Over the past 30 years the end use for linen has changed dramatically. Approximately 70% of linen production in the 1990s was for apparel textiles whereas in the 1970s only about 5% was used for fashion fabrics.

Linen uses range from bed and bath fabrics (table cloths, dish towels, bed sheets, etc.), home and commercial furnishing items (wallpaper/wall coverings, upholstery, window treatments, etc.), apparel items (suits, dresses, skirts, shirts, etc.), to industrial products (luggage, canvases, sewing thread, etc.). It was once the preferred yarn for hand sewing the uppers of moccasin-style shoes (loafers), but its use has been replaced by synthetics.

A linen handkerchief, pressed and folded to display the corners, was a standard decoration of a well-dressed man's suit during most of the first part of the 20th century. Currently researchers are working on a cotton/flax blend to create new yarns which will improve the feel of denim during hot and humid weather.

4.3 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. Flax fibre grows in the seedpod, or boll, of the flax plant. b. Flax is the most important bast fibres. c. Retting is one of the most important steps in flax fibres preparation since it determines the colour and quality of the finished fibre. d. Dew retting method is used for producing high-quality flax fibre.

4.4 JUTE

Jute is a long, soft, shiny vegetable fibre that can be spun into coarse, strong threads. It is produced from plants in the genus Corchorus, family Malvaceae.

Jute is one of the cheapest natural fibres and is second only to cotton in amount produced and variety of uses. Jute fibres are composed primarily of the plant materials cellulose (major component of plant fibre) and lignin (major components wood fibre). It is thus a ligno-cellulosic fibre that is partially a textile fibre and partially wood. It falls into the bast fibre category

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4.4.1 Cultivation

To grow jute, farmers scatter the seeds on cultivated soil. When the plants are about 15-20 cm tall, they are thinned out. About four months after planting, harvesting begins. The plants are usually harvested after they flower, but before the flowers go to seed. The stalks are cut off close to the ground. The stalks are tied into bundles and soaked in water (retting) for about 20 days. This process softens the tissues and breaks the hard pectin bond between the bast & Jute hurd (inner woody fiber stick) and the process permits the fibres to be separated. The fibres are then stripped from the stalks in long strands and washed in clear, running water. Then they are hung up or spread on thatched roofs to dry. After 2-3 days of drying, the fibres are tied into bundles.

The suitable climate for growing jute is a warm and wet climate, which is offered by the monsoon climate during the fall season, immediately followed by summer. Temperatures ranging from 70-100 ºF and relative humidity of 70%-80% are favorable for successful cultivation. Jute requries 2"-3" of rainfall weekly with extra needed during the sowing period.

4.4.2 Retting

Retting is the process of extracting fiber from the stem or bast of the bast fiber plants. The available retting processes are: mechanical retting (hammering), chemical retting (boiling & applying chemicals), steam/vapor/dew retting, and water or microbial retting. Among them, the water or microbial retting is a century old but the most popular process in extracting fine bast fibers. However, selection of these retting processes depends on the availability of water and the cost of retting process.

To extract fine fibers from jute plant, a small stalk is harvested for pre-retting. Usually, this small stalk is brought before 2 weeks of harvesting time. If the fiber can easily be removed form the Jute hurd or core, then the crop is ready for harvesting.

After harvesting, the jute stalks are tied into bundles and submerged in soft running water. The stalk stays submerged in water for 20 days. However, the retting process may require less time if the quality of the jute is better. In most cases, the fiber extraction process of bast fibers in water retting is done by the farmers while standing under water.

When the jute stalk is well retted, the stalk is grabbed in bundles and hit with a long wooden hammer to make the fiber loose from the jute hurd or core. After loosing the fiber, the fiber is washed with water and squeezed for dehydration. The extracted fibers is further washed with fresh water and allowed to dry on bamboo poles.

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4.4.3 Properties of Jute

Good quality jute is coloured yellowish-white and silver-gray and has a lustrous appearance. Jute is usually brownish or greenish and has a unique lustre.

The individual cells in jute are shorter than those of any of the other bast fibres. Jute is the weakest of the cellulose fibres when dry and must therefore be spun into coarse yarns.

The average strength of jute is about 3.5 gm/denier. Resiliency is poor, and fabrics do not return to shape after deformation without treatment such as washing and ironing. Jute has low sunlight resistance and poor colour fastness. It is also brittle and subject to splitting and snagging. It is readily damaged by the action of weather, moisture and abrasion.

Jute can not be bleached white since disintegrates in strong bleaches; hence it is most often used in its natural colour. Chemical finishes can be used to overcome the natural odor of jute and to make it softer. Jute is similar to other cellulosic fibres in its reactions to heat and chemicals.

4.4.4 Uses

Jute is the second most important vegetable fibre after cotton; not only for cultivation, but also for various uses. Jute is used chiefly to make cloth for wrapping bales of raw cotton, and to make sacks and coarse cloth. The fibres are also woven into curtains, chair coverings, carpets, area rugs, hessian cloth, and backing for linoleum.

4.5 PINEAPPLE

The fibre form the leaf of the pineapple frequently is labeled `spina". Most of the commercial fibre comes from the Philippines. It is between 5 and 10 cm. (2 to 4") in length and is lustrous and strong. Fabrics range in hand from crisp to very soft. Delicately embroidered clothing and accessories are often made of pins, it is also a cordage fibre.

4.5.1 Properties and Uses of Pina

This natured fibre is white and especially soft and lustrous. In the Philippine Islands, it is woven into pins cloth, which is soft, durable and resistant to moisture.

It is used far ship cables, power transmission cables and driving cables. Light coloured fibres are spun into coarser cloth th ead, which are used for clothes and bags. Fine fibres are used for malting interior fabires. It is also used as a material for summer hats, brushes and paper malting material.

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4.6 HEMP

The fiber is one of the most valuable parts of the hemp plant. It is commonly called "bast", meaning it grows as a stalk from the ground. Hemp fibers can be 3 to 15 feet long, running the length of the plant. Depending on the processing used to remove the fiber from the stem, the hemp naturally may be creamy white, brown, gray, black or green.

4.6.1 Flow chart

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4.6.2 Harvesting

Smallholder plots are usually harvested by hand. The plants are cut at 2 to 3 cm above the soil and left on the ground to dry. Mechanical harvesting is now common, using specially adapted cutter-binders or simpler cutters.

The cut hemp is laid in swathes to dry for up to four days. This was traditionally followed by retting, either water retting (the bundled hemp floats in water) or dew retting (the hemp remains on the ground and is affected by the moisture in dew moisture, and by molds and bacterial action). Modern processes use steam and machinery to separate the fibre, a process known as thermo-mechanical pulping.

4.6.3 Properties

Characteristics of hemp fibre are its superior strength and durability, resistance to ultraviolet light and mold, comfort and good absorbency (8%). Hemp rope is notorious for breaking due to rot as the capillary effect of the rope-woven fibres tended to hold liquid at the interior, while seemingly dry from the outside. Hemp rope used in the age of sailing-ships was protected by tarring

4.6.4 Uses

Hemp is used for a wide variety of purposes, including the manufacture of cordage of varying tensile strength, clothing, and nutritional products. The bast fibers are can be used in 100% hemp products, but are commonly blended with fabrics such as linen, cotton or silk, for apparel and furnishings, most commonly a 55/45 Hemp/Cotton blend.

4.7 LET US SUM UP

Textiles have been made from fibres derived from banana leaves and coconut. Bast fiber or skin fiber: Fibers are collected from the skin or bast surrounding the stem of their respective plant. These fibers have higher tensile strength than other fibers. Therefore, these fibers are used for durable yarn, fabric, packaging, and paper. Some examples are flax, jute, kenaf, industrial hemp, ramie, rattan, soybean fiber, and even vine fibers and banana fibers.

Hemp fibers are mainly used for ropes and aerofoils because of their high suppleness and resistance within an aggressive environment. Hemp fibers are, for example, currently used as a seal within the heating and sanitary industries.

4.8 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • The factors influencing the characterizes of vegetable fibres • The chief vegetable fibres are structurally of four kinds. • Vegetable fibres and its extensive applications.

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4.9 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • What are the different parts of plant can be used for extracting the vegetable fibres. • Applications and end uses of vegetable fibres based on physical and chemical properties.

4.10 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. All cellulose fibres are prepared by retting process. b. The fibre from the leaf of the pineapple plant is sisal.

2 . Mention the steps for the processing of flax fibre .

Processing of Flax Fibre • Cultivating • Harvesting • Retting..... Dew retting, Pool or Dam retting, Stream retting, Vat or Mechanical retting, Chemical retting

Processing of Flax Fibre (Manufacturing Processes)

• Breaking • Scutclung • Hackling (combing) • Spinning..... Dry spinning, Wet spinning.

4.11 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile fibers, II Manmade Fibers, J. Gordon Cook. • Handbook of Fiber Science and Technology: Fiber Chemistry, Vol. IV

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LESSON-5 ANIMAL FIBRES

CONTENT 5.0 AIM AND OBJECTIVES 5.1 INTRODUCTION 5.2 SILK 5.2.1 Life cycle of silkworms 5.2.2 Sericulture 5.2.3 The Filature 5.2.4 Kinds of Silk 5.2.5 Major fiber properties 5.2.5.1 Physical properties 5.2.5.2 Mechanical properties 5.2.5.3 Chemical Properties 5.2.5.4 Other properties 5.2.6 End Uses 5.3 WOOL 5.3.1 Raw Materials 5.3.2 The Manufacturing Process 5.3.3 Differences between woolen and worsted 5.3.4 Physical and Chemical Properties of Wool 5.3.5 End Uses 5.4 CHECK YOUR PROGRESS 5.5 HAIR FIBRES 5.5.1 Mohair 5.5.2 Cashmere 5.5.3 Camel Hair 5.5.4 Alpaca 5.5.5 Lima 5.5.6 Vicuna 5.5.7 Guanaco 5.5.8 Angora 5.6 LET US SUM UP 5.7 LESSON END ACTIVITIES 5.8 POINTS FOR DISCUSSION 5.9 CHECK YOUR PROGRESS 5.10 REFERENCES

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5.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following • Meaning of animal fibres. • The methods manufacturing Silk and Hair fibrres. • Different kinds of hair fibres • Properties and Uses of animal fibres.

5.1 INTRODUCTION

Animal fibers are natural fibers that consist largely of particular proteins. Instances are silk, hair/fur (including wool) and feathers. The most commonly used type of animal fiber is hair.

Not all animal fibers have the same properties. Alpaca fiber is known for its softness, and silk for its sheen and strength. Even within a species the fiber is not consistent. Merino is a very soft, fine wool, while Cotswold is coarser, and yet both merino and Cotswold are types of sheep. This comparison can be continued on the microscopic level, comparing the diameter and structure of the fiber.

5.2 SILK

Silk is a "natural" protein fiber, some forms of which can be woven into textiles. A fine lustrous fiber composed mainly of fibroin and produced by certain insect larvae to form cocoons, especially the strong, elastic, fibrous secretion of silkworms used to make thread and fabric.

Fig 5.1

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Silk is often referred to as "the queen of the fibres. The shimmering appearance for which silk is prized comes from the fibres' triangular prism-like structure which allows silk cloth to refract incoming light at different angles. Silk is also the strongest natural fiber known to man

5.2.1 Life cycle of silkworms

The life cycle of the silk worm begins with eggs laid by the adult moth. The larvae emerge from the eggs and feed on mulberry leaves. In the larval stage, the worm is the caterpillar known as the silkworm. The silkworm spins a protective cocoon around itself so it can safely transform into a chrysalis. In nature, the chrysalis breaks through the cocoon and emerges as a moth. The moths mate and the female lays 300 to 400 eggs. A few days after emerging from the cocoon, the moths die and the life cycle continues. The cultivation of silkworms for the purpose of producing silk is called sericulture.

5.2.2 Sericulture

Breeding silkworms

• Only the healthiest moths are used for breeding. Their eggs are categorized, graded, and meticulously tested for infection. Unhealthy eggs are burned. The healthiest eggs may be placed in cold storage until they are ready to be hatched. Once the eggs are incubated, they usually hatch within seven days. They emerge at a mere one-eighth of an inch (3.2 mm) long and must be maintained in a carefully controlled environment. Under normal conditions, the eggs would hatch once a year in the spring when mulberry trees begin to leaf. But with the intervention of Seri culturists, breeding can occur as many as three times per year.

Feeding the larva

• The silkworms feed only on the leaves of the mulberry tree. The mulberry leaves are finely chopped and fed to the voracious silkworms every few hours for

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20 to 35 days. During this period the wormns increase in size to about 3.5 inches (8.9 cm). They also shed their skin, or molt, four times and change color from gray to a translucent pinkish color.

Spinning the cocoon • When the silkworm starts to fidget and toss its head back and forth, it is preparing to spin its cocoon. The caterpillar attaches itself to either a twig or rack for support. As the worm twists its head, it spins a double strand of fiber in a figure-eight pattern and constructs a symmetrical wall around itself. The filament is secreted from each of two glands called the spinneret located under the jaws of the silkworm. The insoluble protein-like fiber is called fibroin. • The fibroin is held together by sericin, a soluble gum secreted by the worm, which hardens as soon as it is exposed to air. The result is the raw silk fiber, called the bave. The caterpillar spins a cocoon encasing itself completely. It can then safely transform into the chrysalis, which is the pupa stage.

Stoving the chrysalis

• The natural course would be for the chrysalis to break through the protective cocoon and emerge as a moth. However, sericulturists must destroy the chrysalis so that it does not break the silk filament. This is done by stoving, or stifling, the chrysalis with heat.

5.2.3 The Filature

Sorting and softening the cocoons

• The filature is the factory in which the cocoons are processed into silk thread. In the filature the cocoons are sorted by various characteristics, including color and size, so that the finished product can be of uniform quality. The cocoons must then be soaked in hot water to loosen the sericin. Although the silk is about 20% sericin, only 1% is removed at this stage. This way the gum facilitates the following stage in which the filaments are combined to form silk thread, or yarn.

Reeling the filament

• Reeling may be achieved manually or automatically. The cocoon is brushed to locate the end of the fiber. It is threaded through a porcelain eyelet, and the fiber is reeled onto a wheel. Meanwhile, diligent operators check for flaws in the filaments as they are being reeled.

• As each filament is nearly finished being reeled, a new fiber is twisted onto it, thereby forming one long, continuous thread. Sericin contributes to the adhesion of the fibers to each other.

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Packaging the skeins

• The end product, the raw silk filaments, is reeled into skeins. These skeins are packaged into bundles weighing 5-10 pounds (2-4 kg), called books. The books are further packaged into bales of 133 pounds (60 kg) and transported to manufacturing centers.

Forming silk yarn

• Silk thread, also called yarn, is formed by throwing, or twisting, the reeled silk. First the skeins of raw silk are categorized by color, size, and quantity. Next they are soaked in warm water mixed with oil or soap to soften the sericin. The silk is then dried.

• As the silk filaments are reeled onto bobbins, they are twisted in a particular manner to achieve a certain texture of yarn. For instance, "singles" consist of several filaments which are twisted together in one direction. They are turned tightly for sheer fabrics and loosely for thicker fabrics. Combinations of singles and untwisted fibers may be twisted together in certain patterns to achieve desired textures of fabrics such as crepe de chine, voile, or tram. Fibers may also be manufactured in different patterns for use in the nap of fabrics, for the outside, or for the inside of the fabric. • The silk yarn is put through rollers to make the width more uniform. The yarn is inspected, weighed, and packaged. Finally, the yarn is shipped to fabric manufacturers.

Degumming thrown yarn • To achieve the distinctive softness and shine of silk, the remaining sericin must be removed from the yarn by soaking it in warm soapy water. Degumming decreases the weight of the yarn by as much as 25%.

Finishing silk fabrics (weighting) • After degumming, the silk yarn is a creamy white color. It may next be dyed as yarn, or after the yarn has been woven into fabric. The silk industry makes a distinction between pure-dye silk and what is called weighted silk. In the pure- dye process, the silk is colored with dye, and may be finished with water-soluble substances such as starch, glue, sugar, or gelatin. To produce weighted silk, metallic substances are added to the fabric during the dying process. This is done to increase the weight lost during degumming and to add body to the fabric. If weighting is not executed properly, it can decrease the longevity of the fabric, so pure-dye silk is considered the superior product. After dyeing, silk fabric may be finished by additional processes, such as bleaching, embossing, steaming, or stiffening.

5.2.4 Kinds of Silk

Silk refers to cultivated silk

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1. Wild or Tussah Silk

The silkworms that hatch from a wild species of moth live on oak leaves instead of mulberry leaves that form the food of the cultivated species. This coarser food produces an irregular and coarse filament that is hard to bleach and hard to dye. The tannin in the oak leaves gives wild sill: its tan colour. Wild silk is less lustrous than cultivated sills, as only a low percentage (about 11%) of sericin is removed in the degumming process. Wild silk fabrics are durable and have a coarse, irregular surface. They are washable and are generally less expensive than pure-dye silk.

2. Doupion Silk Doupion silk comes from two silkworms that spin their cocoons together. The yam is uneven, irregular, and large in diameter.

3. Raw Silk Raw silk refers to cultivated silk-in-the-gum. Raw silk varies in colour from gray- white to canary yellow but since the colour is in the sericin, boiled-off silk is white.

4. Reeled Silk Reeled silk is the long continuous filament, 300 to 1600 yards in length.

5. Spun Silk Spun silk refers to yarns made from silk from pierced cocoons and waste silk.

6. Waste Silk Waste silk is comprised of the tangled mass of silk on the outside of the cocoon and the fibre from pierced cocoons.

5.2.5 Major fiber properties

5.2.5.1 Physical properties

1. Shape Silk has a triangular shaped cross section whose corners are rounded.

1. Luster Due to the triangular shape (allowing light to hit it at many different angles), silk is a bright fiber meaning it has a natural shine to it.

2. Covering power Silk fibers have poor covering power. This is caused by their thin filament form.

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3. Hand When held, silk has a smooth, soft texture that, unlike many synthetic fibers, is not slippery.

4. Denier 4.5 g/d (dry) Â; 2.8-4.0 g/d (wet)

4.2.5.2 Mechanical properties

(1) Strength Silk is the strongest of all the natural fibers; however it does lose up to 20% of its strength when wet.

(2) Elongation/elasticity Silk has moderate to poor elasticity. If elongated even a small amount the fibers will remain stretched.

(3) Resiliency Silk has moderate wrinkle resistance

4.2.5.3 Chemical Properties

1. Protein Composition Silk is made up of GLY-SER-GLY-ALA-GLY and forms Beta pleated sheets. Interchaine H-bonds are formed while side chains are above and below the plane of the H-bond network. Small residue (Gly) allows tight packing and the fibers are strong and resistant to stretching. The tension is due to covalent peptide bonds. Since the protein forms a Beta sheet, when stretched the force is applied to these strong bonds and they do not break. The 50% GLy composition means that Gly exists regularly at every other position.

2. Absorbency Silk has a good moisture regain of 11%.

3. Electrical conductivity Silk is a poor conductor of electricity making it comfortable to wear in cool weather. This also means however, that silk is susceptible to static cling.

4. Resistance to ultraviolet light/biological organisms Silk can become weakened if exposed to too much sunlight. Silk may also be attacked by insects, especially if left dirty.

5. Chemical reactivity/resistance Silk is resistant to mineral acids. It is yellowed by perspiration and will dissolve in sulphuric acid.

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5.2.5.4 Other properties 1. Dimensional stability Unwashed silk chiffon may shrink up to 8% due to a relaxation of the fiber macrostructure. So silk should either be prewashed prior to garment construction, or dry cleaned. However, dry cleaning may still shrink the chiffon up to 4%.

Occasionally, this shrinkage can be reversed by a gentle steaming with a press cloth. Gradual shrinkage is virtually nonexistent, as is shrinkage due to molecular-level deformation.

5.2.6 End Uses

Silk is used for luxury apparel, household textiles. It is popular in men's neckties for its hand and drape. Silk apparel fabrics are available in a wide range of weights and constructions. The fibre is used alone and in blends with other fibres.

Silk is used in fine drapery and upholstery fabrics. Some of the most expensive handmade oriental rugs are made of silk fibres. Protection from sunlight damage may be provided by careful lining of draperies and the positioning of furniture so that the silk upholstorv is not a direct sunlight. Very fine silk filaments are used in eye surgery.

Silk sutures still are used by some surgeons. The protein fibre is believed by some to be more compatible with human tissue than sutures of other materials.

5.3 WOOL

Wool is the fiber derived from the fur of animals of the Caprinae family; principally sheep.Wool was probably the first animal fiber to be made into cloth. The art of spinning wool into yarn developed about 4000 B.C.

No one knows when man started using wool as a textile fibre. The dense, soft, often curly hair forming the coat of sheep and certain other mammals, such as the goat and alpaca, consisting of cylindrical fibers of keratin covered by minute overlapping scales and much valued as a textile fabric.

5.3.1 Raw Materials

In scientific terms, wool is considered to be a protein called keratin. Its length usually ranges from 1.5 to 15 inches (3.8 to 38 centimeters) depending on the breed of sheep. Each piece is made up of three essential components: the cuticle, the cortex, and the medulla.

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The cuticle is the outer layer. It is a protective layer of scales arranged like shingles or fish scales. When two fibers come in contact with each other, these scales tend to cling and stick to each other. It's this physical clinging and sticking that allows wool fibers to be spun into thread so easily. The cortex is the inner structure made up of millions of cigar-shaped cortical cells. In natural-colored wool, these cells contain melanin. The arrangement of these cells is also responsible for the natural crimp unique to wool fiber. Rarely found in fine wools, the medulla comprises a series of cells (similar to honeycombs) that provide air spaces, giving wool its thermal insulation value. Wool, like residential insulation, is effective in reducing heat transfer.

5.3.2 The Manufacturing Process

The major steps necessary to process wool from the sheep to the fabric are: shearing, cleaning and scouring, grading and sorting, carding, spinning, weaving, and finishing.

1. Shearing Sheep are sheared once a year usually in the springtime. A veteran shearer can shear up to two hundred sheep per day. The fleece recovered from a sheep can weigh between 6 and 18 pounds (2.7 and 8.1 kilograms); as much as possible, the fleece is kept in one piece. While most sheep are still sheared by hand, new technologies have been developed that use computers and sensitive, robot- controlled arms to do the clipping.

2. Grading and sorting Grading is the breaking up of the fleece based on overall quality. In sorting, the wool is broken up into sections of different quality fibers, from different parts of the body. The best quality of wool comes from the shoulders and sides of the sheep and is used for clothing; the lesser quality comes from the lower legs and is used to make rugs. In wool grading, high quality does not always mean high durability.

Wool is also separated into grades based on the measurement of the wool's diameter in microns. These grades may vary depending on the breed or purpose of the wool. For example: • < 17.5 - Ultra fine merino • 17.6-18.5 - Superfine merino • < 19.5 - Fine merino • 19.6-20.5 - Fine medium merino • 20.6-22.5 - Medium merino • 22.6 < - Strong merino

Or

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• < 24.5 - Fine • 24.5-31.4 - Medium • 31.5-35.4 - Fine crossbred • 35.5 < - coarse crossbred

3. Cleaning and scouring

Wool taken directly from the sheep is called "raw" or "grease wool." It contains sand, dirt, grease, and dried sweat (called suint); the weight of contaminants accounts for about 30 to 70 percent of the fleece's total weight. To remove these contaminants, the wool is scoured in a series of alkaline baths containing water, soap, and soda ash or a similar alkali. The byproducts from this process (such as lanolin) are saved and used in a variety of household products. Rollers in the scouring machines squeeze excess water from the fleece, but the fleece is not allowed to dry completely. Following this process, the wool is often treated with oil to give it increased manageability.

5.3.3 Differences between woolen and worsted

In the spinning operation, the wool roving is drawn out anti twisted into yarn. Woolen V are chiefly spun on the mule spinning machine. Worsted yarns are spun on any kind of spinning machine mule, ring cap or flyer.

The differences between woolen and worsted yarns are as follows:

Woolen yarn Worsted yarn

Short staple Lang staple Carded only Carded and combed Slack twisted Tightly twisted Weaker Stronger Bulkier Finer, smoother, even fibres Softer Harder

5.3.4 Physical and Chemical Properties of Wool

1. Strength

Wool fibres are weak but wool fabrics are very durable. The durability of wool is the result of the excellent elongation and elastic recovery of the fibres. Fibre strength is not always an indication of durability since flexibility of the fibre and its resistance to abrasion is also important. The tear strength of wool is poor. Wool is fair abrasion resistance. Flexibility of wool is excellent. They can be bent back on themselves 20,000 times without breaking.

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2. Resilience

Wool is a very resilient fibre. Its resiliency is greatest when it is dry and lowest when it is wet. It a wool fabric is crushed in the hand, it tends to spring back to its original position when the hand is opened. Because wool fibre has a high degree of resilience, wool fabric wrinkles less than some others; wrinkles disappear when the garment or fabric is steamed. Good wool is very soft and resilient, poor wool is harsh. When buying a wool fabric, grasp a handful to determine its quality.

3. Heat Conductivity As wool fibres are poor conductor of heat, they permit the body to retain its normal temperature. Wool garments are excellent for winter clothing and are protective on damp days throughout the year. The scales on the surface of a fibre and the crimp in the fibre create little pockets or air that serve as insulative barriers and give the garment greater warmth.

4. Absorbency Initially, wool tends to be water-repellent. One can observe that droplets of water on the surface of wool fabrics are readily brushed off. Wool can absorb about 20% of its weight in water without feeling damp; consequently, wool fabrics tend to feel comfortable rather than clammy or chilly. Wool also dries slowly.

5. Cleanliness and Washability Dirt tends to adhere to wool fabric. Consequently, wool requires frequent dry cleaning or laundering if the fabric is washable. Extreme care is required in laundering. Wool is softened by moisture and heat, and shrinking and felting occur when the fabric is washed. Since wool temporarily loses about 25% of its strength when wet wool fabrics should never be pulled while wet.

To control the possibility of shrinking or stretching when laundering a wool sweater or a similar garment, wash it in cold water with an appropriate detergent. To dry the garment, roll it in a towel, squeeze gently to remove as much moisture as possible then spread it out to its original shape on a towel or heavy cardboard.

6. Effect of Heat Wool becomes harsh at 212°F (100°C) and begins to decompose at slightly higher temperatures. Wool has a plastic quality in that it can be expressed and shaped at steam temperature, whether in fabric as for slacks and jackets, or in felt, as for hats.

7. Effect of Light Wool is weakened by prolonged exposure to sunlight.

8. Resistance to Mildew Wool is not ordinarily susceptible to mildew, but if left in a damp condition, mildew develops.

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9. Reaction to Alkalies Wool is quickly damaged by strong alkalies. The alkali test can be used to identify wool and wool blends. The wool reacts to the alkali by turning yellow, then becoming stick and jellylike, and finally going into solution. If the fabric is a blend, the wool in the blend will disintegrate, leaving only the other fibres. Mild alkali-in warm or cool water-can is used in scouring the raw wool fibres to remove grease.

10. Reaction to Acids Although wool is damaged by hot sulphuric acid, it is not affected by other acids, even when heated. Acids are used in the manufacture of wool fabrics to remove cellulose impurities, such as leaves or burrs, that may still be in the fabric after weaving. This treatment is called carbonizing.

11. Affinity for Dyes Because of their high affinity for dyes, wool fabrics dye well and evenly. The use of chrome dyes assures fastness of colour. A variety of other dyes may be effectively used.

12. Resistance to Perspiration Wool is weakened by alkali perspiration. Garments should be dry cleaned or washed with care to avoid deterioration and odor. Perspiration, generally, will cause discolouration.

13. Flammability Wools burns very slowly and it self-extinguishing. It is normally regarded as flame-resistant. For curtains, carpets and upholstery to be used in trains, planes, ships, hotels and other public buildings, wool is often given a flame- retardant finish.

14. Press Retention Wool also has good press retention. It takes and holds creases well. Creases are set by use of pressure, heat and moisture. During pressing the fibre molecules adjust themselves to the new position by forming new cross-linkages. Creases in wool are not permanent, however, since they can be removed by moisture.

5.3.5 End Uses

Overcoats, suits, dresses and underwear are commonly made from wool. In addition to clothing, wool has been used for carpeting, felt, wool insulation and upholstery. Wool felt covers piano hammers and it is used to absorb odors and noise in heavy machinery and stereo speakers.

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5.4 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. Wool is a natural protein fibre. b. Merino goat produces the best wool. c. Wool may be classified into fluet groupings according to the quality of the wool produced. d. Silk is a continuous-filament cellulose fibre produced by the silkworm. e. The process of unwinding the filament from the cacoon is called sorting. f. Cultivated silk is less lustrous than wild silk.

2. Identify basic two animal fibers, their characteristics, and uses.

Wool: The fiber that forms the coat (fleece) of sheep. The primary sources are Australia, South America, New Zealand, and United Kingdom. a. Characteristics (1) Natural insulator; warmest of all natural fibers (2) Soft and resilient (3) Naturally flame retardant (4) Absorbs moisture more slowly than cotton (5) Will shrink if machine washed or dried unless chemically treated (6) Affected by moths b. Some common uses (1) Sweaters, tailored suits (2) Coats (3) Blankets (4) Upholstery (5) Rugs, carpets

Silk: The fine, lustrous fiber that comes from a cocoon spun by a silkworm. The silkworm forces two fine streams of a thick liquid out of tiny openings in its head. These streams harden into filaments or fibers upon contact with the air. Silk is primarily produced in Asia (especially Thailand, China, India), and Madagascar. a. Characteristics (1) Luxurious appearance and feel (2) Strongest of all natural fibers (3) Drapes nicely (4) Expensive (5) Easily spots if fabric becomes wet (6) Weakens with exposure to sun and perspiration

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b. Some common uses (1) Wedding gowns (2) Lingerie (3) Men’s ties (4) Tailored garments (of raw silk) (5) Home furnishings (raw silk)

5.5 HAIR FIBRES

The hair of certain species of other mammals such as goats, alpacas, and rabbits may also be called wool.Hair fibres that have qualities of wool are obtained from certain kinds of throughout the world. The hair of these animals has been so adapted by nature for the climate in which they live that the cloth produced from the fibre gives warmth with Lightweight. Most specialty wools are obtained from the goat, camel and rabbit families.

Good family Camel family Others Angora rabbit - Angora goat - mohair Camel's hair angora Cashmere goat - cashmere Llama Fur fibres Alpaca Musk ox-giviut Vicuina

Guanaco 5.5.1 Mohair

Mohair, the fibre of the Angora goat, is produced in Turkey, South Africa and the United States. Texas is the largest producer of mohair. The goats are sheared twice a year, in the early fall and early spring.

The raw fleece from the Angora goat is quite long and is of a slightly yellowish or grayish tint, however, when the fleece is washed it comes out a lustrous white. The fibre length is 4 to 6 inches for half a year or 8 to 12 inches for a full year. Mohair fibres have a circular cross section. It is more uniform in diameter than wool fibre. Mohair shows almost no scales.

Mohair is the most resilient natural fibre. It has none of the crimp found in sheep's wool, giving it a smoother surface which is more resistant to dust and more lustrous than wool. Mohair is very strong and has good amity for dyes. It does not attract or hold dirt particles.

The coarse hairs are used for interlinings for ties, suits and coats; the fine hairs are used in woolens and worsted for clothing; the medium quality fibres are used in upholstery and rugs. Mohair is blended with wool, silk; cotton and rayon are also used in combination with these fibres.

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5.5.2 Cashmere

The Cashmere goat is native to the Himalaya Mountain region of Kashmir in India, Mongolia and China. The Cashmere goat is smaller than the Angora goat.

The fleece of this goat has long, straight, coarse outer hair of little value, is made into luxuriously soft wool like yarns. The fibres rang in colour from white to gray to brownish gray. The hair is combed by hand from the animal during the molting season, and care is taken to separate the coarser hair from the fine fibres. Only a small part of the fleece is the very fine fibre, probably not more than 4 oz. per goat. Because supply of the fibre is limited and demand for it is high, cashmere fibre is quite expensive.

Cashmere is more sensitive to the action of alkali than wool. Cashmere is used in high-quality apparel. Fabrics are warm, buttery in hand, and have beautiful draping characteristics. It is used for such garments as sweaters, sports jackets, suits and over coats when a luxurious, soft fabric is desired. It is often blended with wool to reduce the cost of the product.

5.5.3 Camel Hair

This textile fibre is obtained from the two-humped Bactrian camel, which is native to all parts of Asia (Mongolia and Tibet). Each animal sheds about 2.7 kg. (5 lbs.) of fibre per year. Camel hair fabrics are ideal for comfort particularly when used for overcoating, as they are especially warm but lightweight. The best quality is expensive when used alone. It is often minted with wool, thus raising the quality of the wool fabric by adding the fine qualities of camel hair. The price of a mixed cloth is naturally much less than that of a fabric that is 1camel hair. In the textile industry, camel hair is divided into three grades. Grade 1 is the soft and silky light tan under hair found close to the skin of the camel. This is short staple or roil, of from 1'/." to 3%" (30-90 mm.). Formerly, it was the only true camel hair used in the manufacture of apparel. In wood roils represents the less valuable short-staple; in the hair fibres, the short fibres are the prized product and are only used in high-grade apparel fabrics. Grade 2 is the intermediate growth, consisting of short hairs and partly of coarse outer hairs, ranging from 1%" to 5" (40-125 mm.) in length. Grade 3 consists entirely of coarse outer hairs measuring up to 15" (380 mm) in length and in colour from brownish black to reddish brown. It is coarse, tough, stiff and wiry. It is used in artists' brushes industrial fabric, blankets, press cloths, ropes, cordage and some lower grade apparel fabrics.

5.5.4 Alpaca The alpaca is a domesticated animal of the South American branch of the camel family. The alpaca is a small animal about three and one-half feet high and looks like an overt own poodle. The fleece is quite long, reaching almost to the ground. The animals are clipped every second year and yield four to eight pounds of fibres per animal.

61 B.Sc. CDF – Fibre to Fabric

The fibre is valued for its silky beauty as well as for its strength. The hair of the alpaca is stronger than ordinary sheep's wool, is water-repellent, and how a high insulative geniality. The staple is 6 to 11"(150-250 mm.) in length and is noted for its softness, fineness and luster. The natural colours of alpaca are white, light fawn, light brown, dark brown, gray, black and piebald.

5.5.5 Lima

The llama is a domesticated animal native to the same geographic area as the alpaca. Fibres are shorn from the animal once a year, and they are similar in length and diameter to alpaca fibres. The fibres are both coarse and fine and are difficult to separate. Most fabrics produced from llama fibres are made by South America Indians, although some fibre is sold abroad for blending with sheep's wool.

5.5.6 Vicuna

The vicuna is the wild animal of the South American branch of the camel family. The vicuna is a small about three feet high (90 cm.) and weight 75 to 100 Ibs. (35 - 45 kg,). A single animal yields only ' lb. (IM gm.) of hair, thus forty animal are required to provide enough hairy for the average coat. To species the vicuna is now under the protection of the Peruvian and Bolivian governments. Vicuna is the softest, finest, rarest and most expensive of all textile fibres. The fibre is short, very lustrous and a light cinnamon colour.

5.5.7 Guanaco

The guanaco, native to southern Argentina where it is both wild and domesticated, is related to the llamand alpaca. The fibre is extremely soft and silky. It is so light, resilient, and warm and the colour is a honey beige. Because of these characteristics and its limited availability, it is expensive. It generally is blended with wool, frequently lamb's wool, so not mask the fibre's soft

5.5.8 Angora

Angara is the hair rabbit, which was raised originally in North Africa and France, United States, Italy and Japan. Each rabbit produces only a few ounces of hair, and since the rabbits are difficult to raise and produce a small yield the total quantity of Angora is very limited and very expensive.

Angora is fairly long, fine, fluffy, soft, smooth, lustrous, slippery and resilient. It requires special processing to spin it properly. It is pure white in colour. It is used primarily far items such sweaters, mittens, baby cloths, millinery and yarns for knitting or knitted fabrics.

5.6 LET US SUM UP

With animal fibers, and natural fibers in general, the individual fibers look different, whereas all synthetic fibers look the same. This provides an easy way to differentiate between natural and synthetic fibers under a microscope. The animal fibers used most commonly both in the manufacturing world as well as by the hand spinners are wool and silk.

62 B.Sc. CDF – Fibre to Fabric

5.7 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Find the principal component of animal fibres • Analyze the length of hair fibres • Uses of animal fibres in the field of textile

5.8 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points

• The size and shape of the scales is unique to each fibres. • The reason for high crimp in wool fibres • Find the differences of varies types of silk

5.9 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. Mohair, the fibre of the Cashmere goat, is produced in Turkey, South Africa and the United States. b. Mohair is very strong and has good affinity for dyes. c. Cashmere is used in high-quality apparel.

5.10 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile fibers, II Manmade Fibers, J. Gordon Cook. • Handbook of Fiber Science and Technology: Fiber Chemistry, Vol. IV

63 B.Sc. CDF – Fibre to Fabric

LESSON-6 RAYON

CONTENT

6.0 AIM AND OBJECTIVES 6.1 INTRODUCTION 6.2 VISCOSE RAYON 6.2.1 Physical and Chemical Properties of Rayon 6.2.2 Major Rayon Fiber Uses 6.3 ACETATE RAYON 6.3.1 Physical and Chemical Properties of Acetate 6.4 LET US SUM UP 6.5 LESSON END ACTIVITIES 6.6 POINTS FOR DISCUSSION 6.7 CHECK YOUR PROGRESS 6.8 REFERENCES

6.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following

• Meaning of Regenerated fibres. • Manufacturing techniques of rayon fibres. • Properties and Uses of Viscose and Acetate fibres.

6.1 INTRODUCTION

There are two main categories of man-made fibers: those that are made from natural products (cellulosic fibers) and those that are synthesized solely from chemical compounds (noncellulosic polymer fibers). Rayon is a natural-based material that is made from the cellulose of wood pulp or cotton. This natural base gives it many of the characteristics low cost, diversity, and comfort that have led to its popularity and success. Today, rayon is considered to be one of the most versatile and economical man-made fibers available.

64 B.Sc. CDF – Fibre to Fabric

6.2 VISCOSE RAYON

The process of manufacturing viscose rayon consists of the following steps mentioned, in the order that they are carried out: 1. Cellulose, 2. Steeping, 3. Pressing, 4. Shredding, 5. Aging, 6. Xanthation, 7. Dissolving, 8. Ripening, 9. Filtering, 10. Degassing, 11. Spinning, 12. Drawing, 13. Washing, 14. Cutting.

The various steps involved in the process of manufacturing viscose are shown in Fig. 6.1, and clarified below.

Figure 6.1: Process of manufacture of viscose rayon fiber 1. Cellulose Purified cellulose for rayon production usually comes from specially processed wood pulp. It is sometimes referred to as dissolving cellulose or dissolving pulp to distinguish it from lower grade pulps used for papermaking and other purposes. Dissolving cellulose is characterized by a high a -cellulose content, i.e., it is composed of long-chain molecules, relatively free from lignin and hemicelluloses, or other short-chain carbohydrates.

65 B.Sc. CDF – Fibre to Fabric

2. Steeping The cellulose sheets are saturated with a solution of caustic soda (or sodium hydroxide) and allowed to steep for enough time for the caustic solution to penetrate the cellulose and convert some of it into soda cellulose, the sodium salt of cellulose. This is necessary to facilitate controlled oxidation of the cellulose chains and the ensuing reaction to form cellulose xanthate.

3. Pressing The soda cellulose is squeezed mechanically to remove excess caustic soda solution.

4. Shredding The soda cellulose is mechanically shredded to increase surface area and make the cellulose easier to process. This shredded cellulose is often referred to as white crumb.

5. Aging

The white crumb is allowed to stand in contact with the oxygen of the ambient air. Because of the high alkalinity of white crumb, the cellulose is partially oxidized and degraded to lower molecular weights. This degradation must be carefully controlled to produce chain lengths short enough to give manageable viscosities in the spinning solution, but still long enough to impart good physical properties to the fiber product.

6. Xanthation

Fig 6.2

The properly aged white crumb is placed into a churn, or other mixing vessel, and treated with gaseous carbon disulfide. The soda cellulose reacts with the CS2 to form xanthate ester groups. The carbon disulfide also reacts with the alkaline medium to form inorganic impurities which give the cellulose mixture a characteristic yellow color and this material is referred to as yellow crumb. Because accessibility to the CS2 is greatly restricted in the crystalline regions of the soda cellulose, the yellow crumb is essentially a block copolymer of cellulose and cellulose xanthate.

7. Dissolving The yellow crumb is dissolved in aqueous caustic solution. The large xanthate substituents on the cellulose force the chains apart, reducing the interchain hydrogen bonds and allowing water molecules to solvate and separate the chains, leading to solution of the otherwise insoluble cellulose. Because of the

66 B.Sc. CDF – Fibre to Fabric

blocks of un-xanthated cellulose in the crystalline regions, the yellow crumb is not completely soluble at this stage. Because the cellulose xanthate solution (or more accurately, suspension) has a very high viscosity, it has been termed viscose.

8. Ripening

The viscose is allowed to stand for a period of time to ripen. Two important processes occur during ripening: Redistribution and loss of xanthate groups. The reversible xanthation reaction allows some of the xanthate groups to revert to cellulosic hydroxyls and free CS2. This free CS2 can then escape or react with other hydroxyl on other portions of the cellulose chain. In this way, the ordered, or crystalline, regions are gradually broken down and more complete solution is achieved. The CS2 that is lost reduces the solubility of the cellulose and facilitates regeneration of the cellulose after it is formed into a filament.

9. Filtering

The viscose is filtered to remove undissolved materials that might disrupt the spinning process or cause defects in the rayon filament.

10. Degassing

Bubbles of air entrapped in the viscose must be removed prior to extrusion or they would cause voids, or weak spots, in the fine rayon filaments.

11. Spinning - (Wet Spinning)

The viscose is forced through a spinneret, a device resembling a shower head with many small holes. Each hole produces a fine filament of viscose. As the viscose exits the spinneret, it comes in contact with a solution of sulfuric acid, sodium sulfate and, usually, Zn++ ions. Several processes occur at this point which cause the cellulose to be regenerated and precipitate from solution. Water diffuses out from the extruded viscose to increase the concentration in the filament beyond the limit of solubility. The xanthate groups form complexes with the Zn++ which draw the cellulose chains together. The acidic spin bath converts the xanthate functions into unstable xantheic acid groups, which spontaneously lose CS2 and regenerate the free hydroxyls of cellulose. (This is similar to the well-known reaction of carbonate salts with acid to form unstable carbonic acid, which loses CO2). The result is the formation of fine filaments of cellulose, or rayon.

12. Drawing

The rayon filaments are stretched while the cellulose chains are still relatively mobile. This causes the chains to stretch out and orient along the fiber axis. As the chains become more parallel, interchain hydrogen bonds form, giving the filaments the properties necessary for use as textile fibers.

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13. Washing

The freshly regenerated rayon contains many salts and other water soluble impurities which need to be removed. Several different washing techniques may be used.

14. Cutting

If the rayon is to be used as staple (i.e., discreet lengths of fiber), the group of filaments (termed tow) is passed through a rotary cutter to provide a fiber which can be processed in much the same way as cotton.

6.2.1 Physical and Chemical Properties of Rayon

1. Strength The tensile strength of viscose rayon is greater than that of wool, but is only about half as great as that of silk. Viscose rayon is also weaker than cotton and linen and its strength is reduced 40 to 70% when wet. The strength is controlled by stretching, which causes a greater orientation of the molecules. Viscose is easily stretched when wet and swollen. If dried in a stretched condition, it will relax and shrink upon again becoming wet.

2. Elasticity Viscose rayon has greater elasticity than cotton or linen but less than wool or silk.

3. Drapability Viscose rayon possesses a marked quality of drapability because it is a relatively heavyweight fabric. The filament can be made as coarse as desired depending on the holes in the spinneret.

4. Resilience Viscose rayon lacks the resilience natural to wool and silk and creases readily; but it should be remembered that the resistance of a fabric to creasing depends on the kind of yarn, weave, and finishing process.

5. Heat Conductivity Viscose rayon is a good conductor of heat and is therefore appropriate for summer clothing. Spun rayon fabrics, however, are adaptable to winter apparel because they can be napped.

6. Absorbency Viscose rayon is a one of the most absorbent of all textiles. It is more absorbent than cotton or linen. The combination of high heat conductivity and high absorbency of rayon makes it very suitable for summer wear.

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7. Cleaning and Washability Because of its smoothness, viscose, rayon fibre helps to produce hygienic fabric that shed dirt. Some viscose rayon fabrics wash easily, and depending on the finish that may be given to them, they will not become yellow when washed or dry cleaned. Regular rayon fabrics have limited washability because of the low strength of the fibre when wet. When laundered, a mild soap or detergent and warm water should be used.

8. Shrinkage Viscose rayon fabrics tend to shrink more than cotton fabrics of similar construction. Knitted fabric always shrinks more than flat woven fabrics because of the nature of the construction. When spun viscose rayon is blended with wool, the great amount of shrinkage characteristic of the wool is reduced.

9. Affect of Heat Since viscose rayon is a pure cellulose fibre, it will burn in much the same manner as cotton. Application of heat at 300°F (150°C) causes viscose rayon to lose strength; above 350°F (177°C), it begins to decompose.

10. Effect of Light Viscose rayon has generally good resistance to sunlight, though prolonged exposure of intermediate tenacity rayon results in faster deterioration and yellowing.

11. Resistance to Mildew Like cotton, viscose rayon has a tendency to mildew. Moths are not attracted to cellulose. Consequently, moth-proffering treatments are not necessary for viscose rayon. Resistance to other insects is also similar to that of cotton.

12. Reaction to Alkalies Viscose rayon is fairly resistant to alkalies and oxidizing agents but tends to be harmed to a greater extent by alkalies than are cotton or linen. A mild soap and warm water is recommended when laundering such garments.

13. Reaction to Acids Viscose rayon reacts to acids in a manner similar to cotton. It is harmed by acids. Being pure cellulose, the fabric is disintegrated by hot dilute and cold concentrated acids.

14. Affinity for Dyes Viscose rayon has good affinity for most cotton dyes. Viscose rayon fabrics absorb dyes evenly and can be dyed with a variety of dyes, such as direct, acid, chrome and disperse. Coloured viscose rayons have a high resistance to sunlight. This property makes them suitable for window curtains.

69 B.Sc. CDF – Fibre to Fabric

15. Resistance to Perspiration Viscose rayon is fairly resistant to deterioration from perspiration. The colour, however, is not usually as resistant as the fabric and will fade if not solution-dyed.

6.2.2 Major Rayon Fiber Uses

• Apparel: Accessories, blouses, dresses, jackets, lingerie, linings, millinery, slacks, sport shirts, sportswear, suits, ties, work clothes • Home Furnishings: Bedspreads, blankets, curtains, draperies, sheets, slipcovers, tablecloths, upholstery • Industrial Uses: Industrial products, medical surgical products, nonwoven products, tire cord • Other Uses: Feminine hygiene products

6.3 ACETATE RAYON

• Cellulose + Glacial Acetic Acid + Acetic Anhydride + Sulphuric acid (Cotton linter, wood pulp) • Frimary Cellulose Acetate + Water • (Cellulose tri-acetate) • Secondary Cellulose Acetate + Acetone • Acetate Spinning Solution . • Dry Spinning in Warm Air Acetate Filament

70 B.Sc. CDF – Fibre to Fabric

Fig. 6.3: Acetate flow chart Cotton linters or wood chips are converted into sheets of pure cellulose. The cellulose is steeped in glacial acetic acid and aged for a period of time under a controlled temperature. After aging, it is thoroughly mixed with acetic anhydride. A small amount of sulphuric acid is then added as a catalyst to facilitate a reaction producing a thick, clear liquid solution of cellulose acetate. After further aging, water is added, and causing the cellulose acetate to precipitate as white flasks. The flasks are dried, dissolved in acetone, and filtered several times to remove impurities. The result is clear, white spinning solution of the consistency of syrup.

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If delustered yarn is required, titanium dioxide, a delusterant, is added at this stage to produce the desired degree of brightness: bright, semi dull, or dull. Dyestuff may be added to the spinning solution to provide superior colour- fastness. After the delusterant has been added, the spinning solution is forced through a spinneret and into a cabinet of heated air that evaporates the acetone and solidifies the filament. The filaments are then ready for winding on spools, cones, or bobbins ready for shipping to the mills for weaving or knitting. Staple fibres are cut, crimped, lubricated, dried, and baled for shipment.

6.3.1 Physical and Chemical Properties of Acetate

The properties of acetate fabrics will vary to some extent depending on the type of yam used (filament, textured, or spun), on the type of fabric construction, and on the finish.

1. Strength Acetate is not a strong fibre. It is weaker than any rayon and is, in fact, one of the weakest textile fibres. It loses much of its strength when wet.

2. Elasticity Acetate is more elastic than any rayon.

3. Resilience Acetate is more wrinkle resistant than any rayon; consequently, the fabric will tend to return to its original shape much better than will rayon after it is pulled or crumpled. After washing, acetate garments should be carefully hung to permit the yams to relax to their original shape.

4. Durability Acetate fabrics have good body and flexibility and therefore drape very nicely.

5. Heat Conductivity Acetate does not have as high a rate of heat conductivity as rayon and therefore is warmer. Acetate is consequently more useful for linings and warmer clothing, particularly if it is spun acetate.

6. Absorbency Acetate is not very absorbent. It absorbs only half as much moisture as the rayon’s. Acetate fabric gets wet mostly on the surface and will not become saturated; therefore; they dry quickly. This makes acetate very suitable for shower curtains, umbrellas, and rain coats. It is also suited for bathing suits, particularly at the seashore because salt water does not have any deteriorating effect on acetate. On the other hand, acetate is uncomfortable in warm, humid weather because of its low absorbency. Acetate garments, such as blouses and lingerie, worn next to the skin feel clammy and uncomfortable because they do not absorb atmospheric humidity.

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7. Cleanliness and Washability Acetate fibre smoothness helps to produce hygienic fabrics that shed dirt and wash easily. They will not become yellow when washed or dry cleaned. Since acetate temporarily loses some strength when wet such fabrics must be handled with care when washed. When laundered, a mild soap or detergent and warm water should be used. The garments should not be rubbed rigorously but should be handled gently and squeezed to remove the water. They will dry readily and should be hung so that the water wilt drip off. Acetate garments dry clean well.

8. Effect of Bleaches White acetate remains white, and acetate fabrics need not be bleached. If bleaching is desired, it should be done with a very mild solution of hydrogen peroxide or a very dilute solution of sodium hypochlorite.

9. Shrinkage Acetate fabrics will shrink less than any rayon. Sometimes they are given a shrink resistant finish.

10. Effect of Heat Acetate fabrics need less ironing than rayon fabrics. A warm iron will easily smooth out an acetate fabric, particularly if the fabric is a little damp. If the from is too hot, it will melt the acetate causing it to stick to the iron and make the fabric stiff.

11. Effect of Light Acetate is more resistant to the effect of light than cotton or any rayon. Over a period of time, acetate will be weakened from exposure to light.

12. Resistance to Mildew Acetate is highly resistant to mildew. It is ideal for fabrics exposed to moisture, such as shower curtains.

13. Reaction to Alkalies Strong alkalies should not be used on acetate since they cause a chemical change in the fibre.

14. Reaction to Acids Acetate is more resistant to acids than pure cellulose, but it will be decomposed by concentrated solutions of strong acids.

15. Resistance to Perspiration Acetate fabrics are fairly resistant to deterioration by perspiration, but the colour will be affected if it has not been solution-dyed.

73 B.Sc. CDF – Fibre to Fabric

6.4 LET US SUM UP

There are several types of rayon fibers in commercial use today, named according to the process by which the cellulose is converted to the soluble form and then regenerated. Rayon fibers are wet spun, which means that the filaments emerging from the spinneret pass directly into chemical baths for solidifying or regeneration.

Viscose rayon is made by converting purified cellulose to xanthate, dissolving the xanthate in dilute caustic soda and then regenerating the cellulose from the product as it emerges from the spinneret. Most rayon is made by the viscose process.

6.5 LESSON END ACTIVITIES

The students may do the following activities based on this lesson.

• Collect both viscose and acetate rayon finds the difference • Analyze the development of viscose rayon and its special application.

6.6 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points

• Development of viscose rayon based on its special application. • Chemical composition and structure of different rayon • Difference in manufacturing Regenerated filament and regenerated fibre.

6.7 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. Rayon is a general teen for man-made filaments prepared from various solutions of modified cellulose. b. Rayon’s are used in only continuous form. c. Viscose rayon is more absorbent than cotton or linen. d. Acetate rayon is not a pure cellulosic product. e. Acetate rayon dissolves in acetone.

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2. Explain the manufacturing of viscose rayon

Production method

Regular rayon (or viscose) is the most widely produced form of rayon. This method of rayon production has been utilized since the early 1900s and it has the ability to produce either filament or staple fibers. The process is as follows:

• Cellulose: Production begins with processed cellulose • Immersion: The cellulose is dissolved in caustic soda • Pressing: The solution is then pressed between rollers to remove excess liquid • White Crumb: The pressed sheets are crumbled or shredded to produce what is known as "white crumb" • Aging: The "white crumb" aged through exposure to oxygen • Xanthation: The aged "white crumb" is mixed with carbon disulfide in a process known as Xanthation • Yellow Crumb: Xanthation changes the chemical makeup of the cellulose mixture and the resulting product is now called "yellow crumb" • Viscose: The "yellow crumb" is dissolved in a caustic solution to form viscose • Ripening: The viscose is set to stand for a period of time, allowing it to ripen • Filtering: After ripening, the viscose is filtered to remove any undissolved particles • Degassing: Any bubbles of air are pressed from the viscose in a degassing process • Extruding: The viscose solution is extruded through a spinneret, which resembles a shower head with many small holes • Acid Bath: As the viscose exits the spinneret, it lands in a bath of sulfuric acid resulting in the formation of rayon filaments • Drawing: The rayon filaments are stretched, known as drawing, to straighten out the fibers • Washing: The fibers are then washed to remove any residual chemicals • Cutting: If filament fibers are desired the process ends here. The filaments are cut down when producing staple fibers.

6.8 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile fibers, II Manmade Fibers, J. Gordon Cook. • Handbook of Fiber Science and Technology: Fiber Chemistry, Vol. IV

75 B.Sc. CDF – Fibre to Fabric

LESSON-7 SYNTHTIC FIBRES

CONTENT

7.0 AIM AND OBJECTIVES 7.1 INTRODUCTION 7.2 NYLON 7.2.1 Basic Concepts of Nylon Production 7.2.2 Manufacturing of Nylon 7.2.3 Physical and Chemical Properties of Nylon 7.2.4 Major End Uses 7.3 CHECK YOUR PROGRESS 7.4 POLYSTER 7.4.1 Manufacturing of Polyester 7.4.2 Physical and Chemical Properties of Polyester 7.4.3 Major End Uses 7.5 ACRYLIC 7.5.1 Manufacturing of Acrylic 7.5.2 Properties of Acrylic 7.5.3 Uses of Acrylic 7.6 LET US SUM UP 7.7 LESSON END ACTIVITIES 7.8 POINTS FOR DISCUSSION 7.9 CHECK YOUR PROGRESS 7.10 REFERENCES

7.0 AIM AND OBJECTIVES

After going through this unit, you should be able to have a clear idea of the following • Meaning of synthetic fibres. • Manufacturing techniques of nylon, polyester and acetate. • Properties and Uses of synthetic fibres.

76 B.Sc. CDF – Fibre to Fabric

7.1 INTRODUCTION

The first truly synthetic fibre was nylon, which originated from research work in the United States and represented a radically different chemical structure and potentially new properties for textiles. Nylon is a general name, which covers materials with a range of qualities, including the two most important clothing types, nylon 6 and nylon 66. All nylon is made from products derived from coal tar or oil and possesses some very unusual properties, including high strength and luster. Certain nylons may be textured and bulked to produce particular tactile qualities in cloth. Other fibres discovered more recently (1941) include the class known as polyester. This largely British invention has, in its Terylene form, many similarities to nylon. Acrylic fibre, produced alongside polyester after 1950, represented the first realistic wool substitute. Its warmth has led it to be used widely for knitwear. Other fibres among the true synthetics include modacrylics and elastomers. The latter are currently extremely popular as Lycra, its stretch properties being utilized in sports clothing.

7.2 NYLON

Any synthetic plastic material composed of polyamides of high molecular weight and usually, but not always, manufactured as a fibre. Nylons were developed by Du Pont in the 1930s. The successful production of a useful fibre by chemical synthesis from compounds readily available from air, water, and coal or petroleum stimulated expansion of research on polymers, leading to a rapidly growing family of synthetics.

7.2.1 Basic Concepts of Nylon Production

• The first approach: combining molecules with an acid (COOH) group on each end are reacted with two chemicals that contain amine (NH2) groups on each end.

This process creates nylon 6, 6, made of hexamethylene diamine with six carbon atoms and acidipic acid, as well as six carbon atoms.

• The second approach: a compound has an acid at one end and an amine at the other and is polymerized to for a chain with repeating units of(-NH- [CH2]n-CO-)x. o In other words, nylon 6 is made from a single six-carbon substance called caprolactam. o In this equation, if n=5, then nylon 6 is the assigned name. (May also be referred to as polymer)

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7.2.2 Manufacturing of Nylon

• Carbon + Nitrogen + Hydrogen + Oxygen (coal) (air) (water) (air) + • Adipic Acid and Hexamethylene Diamine • Amide (Nylon Salt) • Heated in Vaccum (Loss of Water) • Nylon Super Polymer ™ Heated • Nylon Spinning Solution (Polyamide) ™ Dry Spinning (Cool Air) ™ Drawing and Stretching • Nylon Filament

Fig 7.1 Flow Diagram for a Process Used to Manufacture Nylon

Nylon is actually a group of related chemical compounds. It is composed of hydrogen, nitrogen, oxygen and carbon in controlled proportions and structural arrangement. Variations can result in types of nylon plastics, such as combs, brushes, and gears.

By a series of chemical steps beginning with such raw materials as coal, petroleum, or such cereal byproducts as oat hulls or corncobs, two chemicals called hexamethylene diamine and adipic acid are made. These are combined to form nylon salt. Then, since the nylon salt is to be shipped to the spinning mill, it is dissolved in water for easily handling. At the spinning mill, it is heated in large evaporators until a concentrated solution is obtained. The concentrated nylon salt solution is then transferred to an autoclave, which is like a h e

78 B.Sc. CDF – Fibre to Fabric

pressure cooker. The heat combines the molecules of the two chemicals into giant chainlike ones, called linear super polymers. The linear super polymer is then allowed to flow out of a slot in the autoclave onto a slowly revolving casting wheel. As the ribbons of molten nylon resin are deposited on the wheel, they are sprayed with cold water, which hardens them to milky white opaque ribbons. The ribbons are removed from the casting wheel to a chipper, which transforms them into flakes.

Nylon flakes are blended and poured into the hopper of the spinning machine to insure uniformity in the final nylon yarn. Through a value in the bottom of the hopper, the nylon flakes fall onto a hot grid, which melt, them? The molten nylon is pumped through a send filter to the spinneret. The spinneret has one or more holes, depending on the purpose for which the yarn is to be made. As the filaments come out of the spinneret and hit the air, they solidify. This filament can be changed, however, by stretching or cold drawing, the filaments from two to seven times their original length. The amount of stretching is dependent on the diameter, elasticity, and strength desired. As the filaments are stretched, they become more and more transparent. The polyamide molecules straighten out, become parallelized, and are brought very close together. Up to a point, the nylon becomes stronger, more elastic, more flexible and more pliable.

7.2.3 Physical and Chemical Properties of Nylon

1. Strength Nylon is produced in both regular and high tenacity strengths. Although one of the lightest textile fibre, it is also one of the strongest. The strength of nylon will not deteriorate with age.

2. Elasticity Nylon is one of the most elastic fibre that exists today, though it does not have the exceptional elastic quality of spandex fibre. After being stretched, nylon has a strong natural tendency to return to its original shape, and has its own limit to elasticity. If stretched too much, it will not completely recover its shape. Spun nylon is not as elastic as filament nylon.

3. Resilience Nylon has excellent resilience. Nylon fabrics retain their smooth appearance, and wrinkles from the usual daily activities fall out readily.

4. Shrinkage Nylon has good dimensional stability and retains its shape after being wet.

5. Drapability Fabrics at nylon yarn have excellent draping qualities. Lightweight sheers may have a flowing quality, medium-weight dress fabrics can drape very nicely, and heavier weight jacquards also drape well.

79 B.Sc. CDF – Fibre to Fabric

6. Heat Conductivity Nylon fabrics may or may not conduct heat well. The warmth or coolness of a nylon garment depends on the weave of the fabric and on the type of yarn used. The smoothness, roundness, and fineness of nylon filaments permit the manufacture of very smooth, very fine yarns, which can be packed very closely when weaving the fabric. If nylon fabric is woven compactly, it will not be porous. The tight construction will not permit air to circulate through the fabric, and the heat and moisture of the body will not readily pass through it but will built up between the fabric and the body: so, the wearer will feel very warm.

7. Absorbency Nylon does not absorb much moisture. Fabrics made of nylon filament yarns will not readily wet through the material-most of the water remains on the surface and runsoff the smooth fabric, which therefore dries quickly. Such fabrics are useful for rain coats and shower curtains. Spun nylon fabrics, however, will not dry quickly. Nylon's low absorbency has a disadvantage in that the fabric feels clammy and uncomfortable in warm, humid weather.

8. Cleanliness and Washability Because of nylon's smooth surface, dirt and stains often come clean merely using a damp cloth. To wash nylon garments by hand or washing machine, use lukewarm water at 100°F (38°C) and a detergent or soap with a water softener.

Nylon filament fabrics dry very quickly. They need little or no ironing because the garments are usually heat set to retain their shape, pleats or creases. Spun nylon has a tendency to pill or form balls, on the surface of the fabric. To minimize thus, such fabrics should not be rubbed. They should be washed gently, preferably by hand. Brushing with a soft brush will reduce the pilling.

9. Effect of Heat Like acetate, nylon will melt if the iron is too hot, therefore, the iron should be set at the proper heat level. It does not burn readily but melts to form glossy beads formation.

10. Effect of Light Bright nylon is more resistant to the effects of sunlight than most other fibres. Dull nylon will deteriorate a little more quickly than bright nylon; however, even dull nylon has good resistance to light.

11. Resistance to Mildew and Insects Mildew has absolutely no effect on nylon. Mildew may form on nylon, but it will not weaken the fabric. Moths and other insets will not attack nylon because it has no attraction for them.

80 B.Sc. CDF – Fibre to Fabric

12. Reaction to Alkalies Nylon is substantially inert to alkalies. No reaction with soap, alkalis and alcohols.

13. Reaction to Acids Nylon is decomposed by cold concentrated solutions of such mineral acids as hydrochloric, sulphuric and nitric acids. A boiling dilute 5% solution of hydrochloric will destroy nylon

7.2.4 Major End Uses

• Apparel - swimwear, active wear, intimate apparel, foundation garments, hosiery, blouses, dresses, sportswear, pants, jackets, skirts, raincoats, ski and snow apparel, windbreakers, children’s wear. • Home Fashions - carpets, rugs, curtains, upholstery, draperies, bedspreads • Other - Luggage, back packets, life vests, umbrellas, sleeping bags, tents.

7.3 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. The diameter of the individual nylon filaments is dependent on the rate of delivery from the pump to the spinneret. b. Nylon has poor resilience and strength. c. Fabrics of nylon filament yarn have excellent draping qualities.

2. Give the manufacturing sequence and properties of nylon. • Carbon + Nitrogen + Hydrogen + Oxygen (coal) (air) (water) (air) + • Adipic Acid and Hexamethylene Diamine • Amide (Nylon Salt) • Heated in Vaccum (Loss of Water) • Nylon Super Polymer ™ Heated • Nylon Spinning Solution (Polyamide) ™ Dry Spinning (Cool Air) ™ Drawing and Stretching • Nylon Filament

81 B.Sc. CDF – Fibre to Fabric

Properties • Lightweight • Exceptional strength • Good drapeability • Abrasion resistant • Easy to wash • Resists shrinkage and wrinkling • resilient, pleat retentive • Fast drying, low moisture absorbency

7.4 POLYSTER

Polyester is a synthetic fiber derived from coal, air, water, and petroleum. Developed in a 20th-century laboratory, polyester fibers are formed from a chemical reaction between an acid and alcohol. In this reaction, two or more molecules combine to make a large molecule whose structure repeats throughout its length. Polyester fibers can form very long molecules that are very stable and strong.

7.4.1 Manufacturing of Polyester

• Terephthalic Acid + Ethylene Glycol o Polymerization • Polyester + Highly Heated • Polyester Spinning Solution o Melt or Dry Spinning (Cool Air) • Filament o Drawing and Stretching • Polyester Filament

82 B.Sc. CDF – Fibre to Fabric

Fig 7.1 Flow Diagram Polyester Process

1. Polymerization • To form polyester, dimethyl terephthalate is first reacted with ethylene glycol in the presence of a catalyst at a temperature of 302-410°F (150- 210°C). • The resulting chemical, a monomer (single, non-repeating molecule) alcohol, is combined with terephthalic acid and raised to a temperature of 472°F (280°C). Newly-formed polyester, which is clear and molten, is extruded through a slot to form long ribbons.

2. Drying

• After the polyester emerges from polymerization, the long molten ribbons are allowed to cool until they become brittle. The material is cut into tiny chips and completely dried to prevent irregularities in consistency.

3. Melt spinning

• Polymer chips are melted at 500-518°F (260-270°C) to form a syrup-like solution. The solution is put in a metal container called a spinneret and forced through its tiny holes, which are usually round, but may be pentagonal or any other shape to produce special fibers. The number of holes in the spinneret determines the size of the yarn, as the emerging fibers are brought together to form a single strand.

83 B.Sc. CDF – Fibre to Fabric

• At the spinning stage, other chemicals may be added to the solution to make the resulting material flame retardant, antistatic, or easier to dye.

4. Drawing the fiber

• When polyester emerges from the spinneret, it is soft and easily elongated up to five times its original length. The stretching forces the random polyester molecules to align in a parallel formation. This increases the strength, tenacity, and resilience of the fiber. This time, when the filaments dry, the fibers become solid and strong instead of brittle. • Drawn fibers may vary greatly in diameter and length, depending on the characteristics desired of the finished material. Also, as the fibers are drawn, they may be textured or twisted to create softer or duller fabrics.

5. Winding

• After the polyester yarn is drawn, it is wound on large bobbins or flat- wound packages, ready to be woven into material.

7.4.2 Physical and Chemical Properties of Polyester

1. Strength Polyester fibres may be characterized as relatively strong fibres. Fabrics of regular tenacity polyester filament yarns are very strong and durable. The high- tenacity polyester filament yarns used for tires and industrial purposes are extremely strong; some types are the strongest of all textiles except glass, aramid etc. The staple fibres also vary in strength depending on the type of fibre.

2. Elasticity Polyester fibres do not have a high degree of elasticity. In general, polyester fibre is having a high degree of stretch resistance. Thus property makes polyester suited for knitted garments; sagging and stretching that would ordinarily occur are reduced. Fabrics of polyester fibre have good dimensional stability.

3. Resilience Polyester fibre has a high degree of resilience. Not only does a polyester fabric resist wrinkling when dry, it also resists wrinkling when wet. And heat set polyester fibre is suitably resilient for .use in carpets.

4. Drapability Fabrics of polyester filament yarn have satisfactory draping qualities. Staple polyester can produce spun yarn that is more flexible and softer, thereby imparting the draping quality. Drapability of fabrics of blended polyester staple will depend upon the type and proportion of blend in the yam as well as the fabric construction.

84 B.Sc. CDF – Fibre to Fabric

5. Heat Conductivity Fabrics of polyester fibre are better conductors of heat. The basic polyester filament fibre is round. This results in a smoother yarn woven into fabrics with fewer air spaces and less insulation. Polyester staple fibre is crimped and this does provide greater insulation in the yarns and fabrics.

6. Absorbency Polyester is one of the least absorbent fibres. This low absorbency has two important advantages. Polyester fabrics will dry very rapidly since almost all the moisture will lie on the surface rather than penetrate the yarns. Fabrics of polyester fibre are therefore well suited for water-repellent purposes, such as rainwear. Furthermore, this low absorbency means that polyester fabrics will not stain easily. Many substances lie on the surface and can be wiped or washed off easily.

7. Cleanliness and Washability Since polyester fibres are smooth and have a very low absorbency, many stains lie on the surface and can easily be washed by hand or machine. Strong soaps are not needed. When ironing polyester fabrics, it is best to use low to medium heat.

8. Effect of Bleaches Polyester fabrics maybe safety bleached because polyester had good resistance to deterioration by household bleaches. If the polyester has an optical brightener, no bleaching is necessary.

9. Shrinkage Polyester fabrics shrink as much as 20% during wet-finishing operations. Finished polyester woven and knitted fabric will not shrink. They have excellent dimensional stability.

10. Effect of Heat Depending upon the type, pohester will get sticky at 440 to 468°F (227-242°C). Therefore, if ironing is needed, it should be done at lower temperatures. At temperature in the range of 480 to 554°F (249290°C), polyester will melt and flame.

11. Effect of Light Polyester has good resistance to sunlight. Fabrics of polyester are therefore well suited for outdoor use. Over a prolonged period of exposure to direct sunlight, however, there will be a gradual deterioration of the polyester fibre. When exposed to sunlight behind glass, polyester shows a considerable increase in resistance to sunlight, it has a marked superiority over most other fibres under these conditions and is very well suited for curtains.

85 B.Sc. CDF – Fibre to Fabric

12. Resistance to Mildew and Insects Polyester fabrics are absolutely resistant to mildew. They will not be stained or weakened. Mildew should readily wash off the fabrics without any deterioration to it.

13. Reaction to Alkalies At room temperature, polyester has good resistance to weak alkalies and fair resistance to strong alkalies. This resistance is reduced with increased temperature. At boiling temperature, it has poor resistance to weak alkalies and dissolves in strong alkalies.

14. Reaction to Acids Depending upon the type, polyester has excellent to good resistance to mineral and organic acids. Highly concentrated solution of a mineral acid, such as sulphuric acid, at relatively high temperatures will result in degradation.

15. Affinity for Dyes Polyester can be dyed with appropriate disperse, azoic, and developed dyes at high temperatures, producing a good range of shades that have good-to-excellent wash fastness and fair-to-good light fastness.

16. Resistance to Perspiration Polyester has no significant loss of strength from continued contact with either acid or alkaline perspiration.

7.4.3 Major End Uses • Apparel - essentially every form of clothing, dresses, blouses, jackets, separates, sportswear, suits, shirts, pants, rainwear, lingerie, childrenswear • Home Fashions - curtains, draperies, floor coverings, fiber fill, upholstery, bedding.

7.5 ACRYLIC

Acrylic fibers are synthetic fibers made from a polymer (Polyacrylonitrile) with an average molecular weight of ~100,000. To be called acrylic in the U.S., the polymer must contain at least 85% acrylonitrile monomer. Typical co monomers are vinyl acetate or methyl acrylate.

7.5.1 Manufacturing of Acrylic

The term acrylic comes from the chemical composition of the fibre; the word modacrylic comes from "modified acrylic". Dimethylfromamide or dimethylacetamide is used as a solvent. Some fibres can be spun from acetone.

86 B.Sc. CDF – Fibre to Fabric

After the polymer is dissolved, it must be filtered to remove impurities and undissolved polymer. The solution is spun by either a wet-spinning or a dry- spinning system. Bi component acrylic fibres are formed at the spinneret.

After coagulation, the fibre is drawn to produce fibre properties. Fibre crimp is also developed before the fibre is cut into staple.

7.5.2 Properties of Acrylic

The acrylic fibres are stronger than wool and acetate but weaker than most of the other fibres. Elongation and recovery of the fibres are also variable. The acrylic fibres have good resilience. They do not wrinkle easily, and any wrinkles that are formed in garments usually disappear after the fabric relaxes.

They are more absorbent than polyester but less absorbent than nylon. The low moisture regain indicates that the fibres generate static electricity.

Acrylic fibres burn with a yellow flame. They form a hot gummy residue that drips away from the burning material. The molten drip solidifies to a hard, brittle black bead. The reaction of the original modaerylics to heat was one of the major reasons for their popularity. The fibres were difficult to ignite, and they self-extinguished. The ash was a hard black char. The fibres could be treated so that some were more sensitive to heat than others.

Weak alkalies do not affect acrylics. Concentrated alkalies degrade acrylics. Cold, concentrated nitric acid dissolves acrylic fibres, and other concentrated acids weaken them. Dilute acids do not harm the fibres. 'I the acrylic fibres are not affected by household organ,: solvents.

Acrylic has excellent resistance to sunlight. Even prolonged exposure does not affect fibre strength. Most acrylic fibres are dyed with disperses dyes.

7.5.3 Uses of Acrylic

The primary markets for acrylic is in apparel and home furnishings. The fibres are usually soft and light in weight. In apparel, the fibre may be used alone or in blends with cotton, wool. rayon, and polyester. Apparel in which acrylic fibre are likely to lie found include socks, knit sweaters, and sportswear fabrics.

Blankets, carpets and upholstery fabrics are made form act lie fibres and acrylic blends. The farbics have wool like hand but are not affected by moths. Household fabrics made from acrylic fibres are especially popular where exposure to sunlight is a problem.

87 B.Sc. CDF – Fibre to Fabric

7.6 LET US SUM UP

Most synthetic fibres are now made from petrochemicals and do giant polymers resemble plastics in structure. The first commercially successful plastic fibre is nylon. Since then many synthetics, including acrylics, aramids, olefins, and polyesters, have been developed. With synthetics, as with rayon’s and acetates, fibre-forming liquids are extruded as filaments into an environment that causes them to solidify. They are then treated to yield such qualities as heat and moisture resistance, ease of dyeing, and stretchability.

7.7 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Find the differences between nylon 6 and nylon 6, 6 • Nylon can be made to form fibres, filaments, bristles, or sheets to be manufactured into yarn, textiles, and cordage, and it can also be formed into molded products. collect the available samples.

7.8 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • History and development of synthetic fibre. • Polyester and its uses in the manufacture of many products • Molecular chain arrangement of nylon

7.9 CHECK YOUR PROGRESS

1. Answer True (T) or False (F). a. Acrylic is a noncellulosic polymer. b. All synthetic fibres are prepared by retting process. c. Monofilament yarns are stronger than multifilament yarns. d. Polyester is composed of hydrogen, nitrogen, oxygen and carbon in controlled proportions and structural arrangement. e. Acetate is more resistant to acids than pure cellulose

2. Give the manufacturing sequence and properties of polyester • Terephthalic Acid + Ethylene Glycol o Polymerization • Polyester + Highly Heated • Polyester Spinning Solution

88 B.Sc. CDF – Fibre to Fabric

o Melt or Dry Spinning (Cool Air) • Filament o Drawing and Stretching • Polyester Filament

Properties • Strong • Crisp, soft hand • Resistant to stretching and shrinkage • Washable or dry-cleanable • Quick drying • Resilient, wrinkle resistant, excellent pleat retention (if heat set) • Abrasion resistant • Resistant to most chemicals • Because of its low absorbency, stain removal can be a problem

7.10 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Handbook of Textile fibers, II Manmade Fibers, J. Gordon Cook. • Handbook of Fiber Science and Technology: Fiber Chemistry, Vol. IV

89 B.Sc. CDF – Fibre to Fabric

90 B.Sc. CDF – Fibre to Fabric

UNIT - III

91 B.Sc. CDF – Fibre to Fabric

92 B.Sc. CDF – Fibre to Fabric

LESSON-8 INTRODUCTION TO SPINNING

CONTENT 8.0 AIM AND OBJECTIVES 8.1 INTRODUCTION 8.1.1 History 8.2 DEFINITION 8.2.1 Objects 8.3 CLASSIFICATION OF SPINNING 8.3.1 Mechanical Spinning Methods 8.3.2 Chemical spinning 8.4 MATERIALS USED 8.5 COTTON SPINNING SYSTEM 8.5.1 Classification of Yarn Forming Operations for Cotton Yarns 8.6 GINNING AND BALING 8.6.1 Purpose of ginning 8.6.2 Gin Types 8.6.3 Baling 8.7 MIXING AND BLENDING 8.7.1 Purposes of Blending 8.8 LET US SUM UP 8.9 LESSON END ACTIVITIES 8.10 POINTS FOR DISCUSSION 8.11 CHECK YOUR PROGRESS 8.12 REFERENCES

8.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • Spinning is the process of converting fibers into yarns • Process sequence of manufacturing cotton fibre into yarn. • Number of different spinning methods • Pre-cleaning of raw material • Blending of different fibers

93 B.Sc. CDF – Fibre to Fabric

8.1 INTRODUCTION

Spinning is an ancient textile art in which plant, animal or synthetic fibers are twisted together to form yarn (or thread, rope, or cable). For thousands of years, fiber was spun by hand using simple tools, the spindle and distaff. Only in the early Medieval era did the spinning wheel increase the output of individual spinners, and mass-production only arose in the 18th century with the beginnings of the Industrial Revolution. Hand-spinning remains a popular handicraft.

The fabrication of yarn (thread) from either discontinuous natural fibers or bulk synthetic polymeric material. In a textile context the term spinning is applied to two different processes leading to the yarns used to make threads, cords, ropes, or woven or knitted textile products.

8.1.1 History

The earliest spinning probably involved simply twisting the fibers in the hand. Later a stick, called a spindle, was used to add the twist and hold the twisted fiber. Usually a whorl or weight stabilizes the spindle. The spindle is spun and twists the fiber until it becomes yarn. The spindle may be suspended or supported. Later the spinning wheel was developed which allowed continuous and faster yarn production. Spinning wheels may be foot, hand or electrically powered. The hand-turned spinning wheel called a charkha was prevalent in India and was used by Gandhi and his followers.

Modern powered spinning, originally done by water or steam power but now done by electricity, is vastly faster than hand-spinning. New techniques including Open End spinning or rotor spinning can produce yarns at rates in excess of 40 meters per second per spinning head.

8.2 DEFINITION

Spinning is the art of producing continuous, twisted Strands, of a desire size, from fibrous materials. In a broad sense, the term is used to include all the operations through which cotton fibers are passed until they become yarn. It is customary to speak of a "spinning mill" to distinguish it from a "weaving mill" or a “finishing plant”. In a narrow sense, spinning applies only to that operation which takes roving, further draws and twists it, and produces yarn.

8.2.1 Objects

1. Mixing • The term mixing refers to the bringing together of two or more varieties of the same basic fibre • For example, Egyptian cotton fibre combined with American cotton fibre, so that the final yarn remains 100% cotton

94 B.Sc. CDF – Fibre to Fabric

2. Blending • Blending refers to the bringing together of fibres from different origins • For example, wool and silk or cotton and polyester

3. Cleaning and fibre separation • All bales of raw fibres contain a variety of impurities that need to be removed • The first process is to divide and split the bales into smaller and smaller loose bunches, to remove dust, seeds and unwanted debris • Some fibre types are then washed or scoured • Others can be combed or carded to further separate and clean the fibres

4. Fibre alignment • This process follows carding and combing • Several slivers or groups of carded or combed fibres are combined to form a single sliver of straightened fibres • The process is called drawing

5. Drafting and twisting • Drafting is the process of gently drawing out the sliver to reduce it's linear density or thickness • Exactly how this is done and what machinery is used depends on the required yarn quality and count • The final process is to insert the required amount of twist into the single yarn

8.3 CLASSIFICATION OF SPINNING

Spinning can be classified in two methods based on its yarn production technique. 1. Mechanical Spinning 2. Chemical Spinning

8.3.1 Mechanical Spinning Methods

• There are a large number of different spinning methods • Here we will look at some of the most relevant,ring spun, rotor spun, twistless, wrap spun and core spun yarns

1. Ring spun yarns • The most popular method of staple fibre yarn production • The fibres are twisted around each other to give strength to the yarn

95 B.Sc. CDF – Fibre to Fabric

2. Rotor spun yarns • Similar to ring spinning • Generally rotor spun yarns are only made from short staple fibres • Rotor spinning produces a more regular, smoother yarn than ring spinning • Rotor spun yarn is weaker than ring spun

3. Twistless yarns • Rather than being twisted, the fibres are held together by some form of adhesive • The glued fibres are often laid over a continuous filament core

4. Wrap spun yarns • The yarns are made from staple fibres bound by another yarn • The binding yarn is usually a continuous man-made filament yarn • They can be made from either short or long staple fibres

5. Core spun yarns • Core spun yarns have a central core wrapped with staple fibres • They are produced in one operation at the time of spinning • For example, a cotton outer for handle and comfort, with a filament (often polyester) core for added strength, (lots of sewing threads) or cotton over an electrometric core (shirring elastic)

8.3.2 Chemical spinning

The term spinning is also used for the production of monofilaments from synthetic polymers for example, polyamides or nylons, polyesters, and acrylics or modified natural polymers, such as cellulose-rayon.

These semi synthetic and fully synthetic fibres can be produced by the suitable following methods. 1. Dry spinning 2. Wet spinning 3. Melt spinning

96 B.Sc. CDF – Fibre to Fabric

8.4 MATERIALS USED

Yarn can be made from a wide variety of materials: • Plant fibers: cotton, flax (to produce linen), bamboo, ramie, hemp, nettle, raffia, yucca, coconut husk, banana trees, and soy • Animal fibers: wool, goat (angora, or cashmere goat), rabbit (angora), llama, alpaca, dog, cat, camel, yak, qiviut (from Musk Ox), and silk • Synthetic fibers fibers: nylon, rayon (derived from wood pulp), acetate, polyester, tencel (derived from wood pulp), and ingeo (derived from corn) • Mineral fibers: asbestos

8.5 COTTON SPINNING SYSTEM

Spinning is process of manufacturing cotton fibre into yarn. This includes the general operations of opening, picking, carding, drawing, roving and ring spinning in the production of the so called "carded yams". For "combed yams", three steps culminating in `combing' are included after the carding operation.

1. Ginning Ginning is the process of separating the lint cotton from the seed.

2. Blending A Process or processes concerned primarily with the mixing of various lots of fibres to produce a homogeneous mass. Blending is normally carried out to mix fibres, which may or may not be of similar physical or chemical properties, market values, or colours. Blending is also used to ensure consistency of end product.

3. Opening Covers the initial treatments given to raw cotton. the separation and opening up of the cotton to remove compression because of baling and shipping. Heavier impurities are also removed from the stock.

4. Picking The final operation in the cotton system preparation line, in which the cotton flocks are opened mechanically, cleaned, and formed into a lap of specified mass per unit area, for feeding to a carding machine.

5. Carding The process in yarn manufacture in which the fibres are brushed up, made more or less parallel have considerable portions of foreign matter removed, and are put into a manageable form known as sliver.

6. Drawing Operations by which slivers are blended. doubled. or leveled, and by drafting reduced to a sliver or a roving suitable for spinning.

97 B.Sc. CDF – Fibre to Fabric

7. Combing The straightening and parallelizing of fibres and the removal of short fibres and impurities by using a comb or combs assisted by brushes and rollers.

8. Roving A loose assemblage of fibres drawn into a single strand, with very' little twist. It is an intermediate state between sliver and yarn.

9. Spinning The final operation in cotton yarn manufacture. It completes the working of the cotton fibres into a commercial, fine, coherent yarn sufficiently twisted so that it is now ready for weaving purposes.

10. Doubling The number of laps, slivers, slubbings. or rovings fed simultaneously into a machine for drafting into a single end. Doubling is employed to promote blending and regularity.

11. Twisting Process of combining two or more parallel single or ply yams by twisting together to produce a ply-yarn or cord. Ply yarns result from twisted single yarns and cords and cables from twisted ply yarns. Twisting is also employed to obtain greater strength and smoothness, increased uniformity in yam.

8.5.1 Classification of Yarn Forming Operations for Cotton Yarns

Yarn Forming Operations

98 B.Sc. CDF – Fibre to Fabric

8.6 GINNING AND BALING

8.6.1 Purpose of ginning

Ginning should be considered as the first actual mill processing of cotton, because generally this is the first mechanical process to which raw cotton is subjected, unless the cotton has been harvested by machine. The complete ginning operation consists of any preliminary cleaning and drying of the cotton, separation of the seed from the cotton fibres, often referred to as lint, and pressing and wrapping the cotton into a bale of approximately 500 lb. This latter process is known as baling.

The amount of pre-cleaning or pre-diving which may be necessary depends on the condition of the cotton as it is brought from the fields to the gin. Methods of harvesting usually determine what amount of pre-cleaning will be necessary; cleanly hand-picked cotton requires no pre-cleaning. While roughly hand- snapped or mechanically stripped cotton requires a considerable amount of pre- cleaning before reaching the actual operation of separating the seed from the lint.

8.6.2 Gin Types

There are two types of gin in operation today:

1. The saw gin and the roller gin. The saw gin is used for short and medium staple cottons; 2. The roller gin is used primarily for long-staple cottons.

Fig 8.1 Roller gin

99 B.Sc. CDF – Fibre to Fabric

8.6.3 Baling

After the cotton is ginned it is necessary to package or bale the stock for the purpose of transporting it. The first step takes place at the gin, where the cotton is compressed layer by layer and a cover or jute or cotton bagging is wrapped around and the whole bale secured by six flat strap-iron ties.

8.7 MIXING AND BLENDING

Mixing is the process of intermingling of various verities of cotton, to prepare the raw material for the spinning process.

The long continuous filament fibers can't be used for blending because they're too long and too difficult to handle. Also, natural fibers, such as wool and cotton, with which many manufactured fibers are blended, are very short. Therefore, before blending, man-made fibers are first cut into short fibers, called staple fibers. The staple fibers can more easily be twisted with the shorter natural fibers, or with staple fibers of another manufactured fiber.

Staple fibers are created by extruding many continuous filaments of specific denier from the spinneret and collecting them in a large bundle called a "tow". A tow may contain over a million continuous filaments. The tow bundle is then crimped, in much the same way a curling iron is used to crimp a woman's hair, and is then mechanically cut into staple fibers, usually ranging in length from 1 to 6-1/2 inches, depending how they are to be used.

8.7.1 Purposes of Blending

Blending of different fibers is done to enhance the performance and improve the aesthetic qualities of fabric. Fibers are selected and blended in certain proportions so the fabric will retain the best characteristics of each fiber. Blending can be done with either natural or manufactured fibers, but is usually done using various combinations of manufactured fibers or manufactured and natural fibers.

For example, polyester is the most blended manufactured fiber. Polyester fiber is strong, resists shrinkage, stretching and wrinkles, is abrasion resistant and is easily washable. Blends of 50 to 65% polyester with cotton provides a minimum care fabric used in a variety of shirts, slacks, dresses, blouses, sportswear and many home fashion items A 50/50 polyester/acrylic blend is used for slacks, sportswear and dresses. And, blends of polyester (45 to 55%) and worsted wool creates a fabric which retains the beautiful drape and feel of 100% wool, while the polyester adds durability and resistance to wrinkles.

100 B.Sc. CDF – Fibre to Fabric

8.8 LET US SUM UP

In spinning, separate fibers are twisted together to bind them into a long, stronger yarn. Characteristics of the yarn vary based on the material used, fiber length and alignment, quantity of fiber used and degree of twist.

Natural fibers, such as wool, cotton, or linen, are generally found as short, entangled filaments. Their conversion into yarn is referred to as spinning. After a carding operation on the raw material to disentangle the short filaments, the filaments are drawn (drafted) to promote alignment in an overlapping pattern and then twisted to form, by mechanical interlocking of the discontinuous filaments, a resistant continuous yarn.

8.9 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Make the flow chart for the sequence of operation for different spinning systems. • Based on the end use and application of delivery material, analyze the spinning methods.

8.10 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Analyze the spinning methods based on the end use and application • Find the sequence of operation for different spun yarn.

8.11 CHECK YOUR PROGRESS

1. List the sequence of operation involved in spinning and gives a short note on each.

Preparing the fibers Fibers are shipped in bales, which are opened by hand or machine. Natural fibers may require cleaning, whereas synthetic fibers only require separating. The picker loosens and separates the lumps of fiber and also cleans the fiber if necessary. Blending of different staple fibers may be required for certain applications. Blending may be done during formation of the lap, during carding, or during drawing out. Quantities of each fiber are measured carefully and their proportions are consistently maintained.

101 B.Sc. CDF – Fibre to Fabric

Carding

The carding machine is set with hundreds of fine wires that separate the fibers and pull them into somewhat parallel form. A thin web of fiber is formed, and as it moves along, it passes through a funnel-shaped device that produces a ropelike strand of parallel fibers. Blending can take place by joining laps of different fibers.

Combing

When a smoother, finer yarn is required, fibers are subjected to a further paralleling method. A comblike device arranges fibers into parallel form, with short fibers falling out of the strand.

Drawing out

After carding or combing, the fiber mass is referred to as the sliver. Several slivers are combined before this process. A series of rollers rotating at different rates of speed elongate the sliver into a single more uniform strand that is given a small amount of twist and fed into large cans. Carded slivers are drawn twice after carding. Combed slivers are drawn once before combing and twice more after combing.

Twisting

The sliver is fed through a machine called the roving frame, where the strands of fiber are further elongated and given additional twist. These strands are called the roving.

Spinning

The predominant commercial systems of yarn formation are ring spinning and open-end spinning. In ring spinning, the roving is fed from the spool through rollers. These rollers elongate the roving, which passes through the eyelet, moving down and through the traveler. The traveler moves freely around the stationary ring at 4,000 to 12,000 revolutions per minute. The spindle turns the bobbin at a constant speed. This turning of the bobbin and the movement of the traveler twists and winds the yarn in one operation.

8.12 REFERENCES

• Fibre Science 5Th Edition, Joseph J Preal, Fairchild Publications, New York 1990. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993

102 B.Sc. CDF – Fibre to Fabric

LESSON-9 OPENING AND CLEANING

CONTENT

9.0 AIM AND OBJECTIVES 9.1 INTRODUCTION 9.2 OPENING AND CLEANING 9.2.1 Types of opening and cleaning 9.2.2 Blending Feeders 9.2.3 Porcupine Opener 9.2.4 Path of Cotton through the Picker (Scutcher) 9.3 CHECK YOUR PROGRESS 9.4 CARDING 9.4.1 Objects of Carding 9.4.2 Principle of Carding 9.4.3 Path of Cotton through the Card 9.5 LET US SUM UP 9.6 LESSON END ACTIVITIES 9.7 POINTS FOR DISCUSSION 9.8 CHECK YOUR PROGRESS 9.9 REFERENCES

9.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following: • Open the compressed layer of cotton • To blend different varieties of cotton in the desired proportion. • To extract the impurities present in the raw material. • To convert the mass of cotton fibre into a uniform thick sheet of cotton lap

103 B.Sc. CDF – Fibre to Fabric

9.1 INTRODUCTION

There are the two basic classes of yarn, namely spun yam and continuous filament yam. Spun yarn is an assemblage of relatively short fibres while continuous filament yarn is a grouping of virtually endless parallel continuous filaments.

In the case of spun yarns, to understand the problem of opening cotton, it is necessary to consider the condition of the cotton in the bale. Due to the way cotton is run into the gin box and then tamped, a cotton bale is made up of a series of sheets or layers. When compressed, these layers become quite firmly necked. Even when the bands are removed from the bale, these layers are very much packed together. In this condition, it is not possible to clean cotton or use it for manufacturing. It must be loosened and separated into small tufts or bunches for further processing.

9.2 OPENING AND CLEANING

Opening is the process of tearing apart the compressed and matted cotton until it is very much loosened and separated into small tufts of fiber. Carried to the extreme limit, opening can be the separation of the compressed cotton into its individual fibers.

The mechanical opening of cotton is carried on in three different classes of machinery. 1. The opening machines, 2. The picking machines and 3. The carding machines.

The machinery specially designated as opening machinery includes • Bale breakers, • Hopper feeders, • Buckley openers, • Vertical openers, and • Horizontal openers.

The purposes of the opening machinery are: first, to open the cotton and, second, to clean it. At the start the opening is paramount and little cleaning is expected, but as the cotton progresses, the importance of cleaning becomes greater. It is difficult to separate opening and cleaning because, until the cotton is opened, it cannot be cleaned. Thus, some mills may consider that opening is merely an incidental feature of cleaning. However, it is necessary to open cotton; regardless of how clean it is, before any suitable fibre arrangement can be made. So, opening should he considered a separate operation in cotton manufacture.

104 B.Sc. CDF – Fibre to Fabric

9.2.1 Types of opening and cleaning

All opening and cleaning machines may be broadly classified in to the following types: • Loose feeding and cleaning, • Semi fast gripped and controlled.

There are three types of opening 1. Hopper type 2. Cylinder type 3. Beater type

In cleaning, the machines may classify based on the following types: • Major cleaning points • Minor cleaning points

9.2.2 Blending Feeders

It is a hoper type. There may be three to six blending feeders before the opening line. It purposes is to loosen the closely packed stock making a series of small bunches.

Fig 9.1

105 B.Sc. CDF – Fibre to Fabric

It is shown in Fig. 9.1 it consists of a hopper with a horizontal endless apron for a bottom and an inclined endless apron carrying many spikes for the front side. An excess of cotton is prevented from passing out by a revolving cylinder covered with spikes near the upper end of the spiked apron. Another cylinder is arranged outside the hopper to remove the cotton carried out of the hopper by the spiked apron.

The bottom apron constantly carries the cotton forward against the pinned elevating apron. In this way a supply of cotton is constantly pressed against the pins of the elevating apron. The pins of the apron collect cotton and carry it upward and over the front of the hopper. To prevent an excessive amount of cotton being carried out of the hopper, a spike roll is placed parallel with the elevating apron and not far from it. The spike roll travels in the opposite direction to the elevating apron and so tends to strike off large bunches or any excess of cotton carried by the elevating apron.

When the stock in the hopper becomes a rolling mass, it is carried forward by the bottom apron, upward by the elevating apron and then backward as it reaches the top of the mass or as it is struck down and backward by the spike roll.

The elevating apron moves downward on the outside of the hopper. The pins are inclined downward. Another cylinder, having four or six leather-faced wooden strips across its face, is set parallel with and close to the elevating apron. This '` stripping roll “turns in the same direction as the apron but at a higher surface speed. Consequently the cotton is brushed off the points and drops down to some conveyor which carries it to the next operation.

Under the stripping (or doffing) roll of this feeder, is a series of steel bars over which the cotton passes as it leaves the elevating apron. Below these grid bars is a large space, entirely enclosed, serving as a dead air, dirt collecting section. As the cotton is opened to a greater extent than in the bale breakers, there is a greater opportunity to clean it. While but a small percentage of dirt can be taken out at this place, the cost of removal is very slight.

The hopper of this feeder is enclosed, except for the feed opening just above the bottom apron. A suction fan is mounted on the top of the feeder hopper and draws air from it, thus carrying away dust, fly and dirt which would other wise be carried along with the cotton or throne out into the opening room.

As illustrated in Fig. 9.1 this hopper feeder is supplied cotton through the small hopper at the left. Passing by the swinging automatic door and under the ends of the feelers or rakes, the cotton is carried into the hopper proper. When the hopper is properly filled, the rakes are forced back against the rod girt, which supports them and prevents breaking and bending. When the rake is against the rod girt, the feeler lever, connected to the end of the feeler shad outside the hopper, operates the micro switch which sends current to the red light.

106 B.Sc. CDF – Fibre to Fabric

9.2.3 Porcupine Opener

Fig 9.2

It is a beater type opening machine. A Buckley opener is a machine for opening and cleaning cotton with the air of a "Buckley Beater" The objects of this process are first, to continue the opening of the cotton; and second to separate the heavy dirt from the cotton.

The Buckley opener is built around a Buckley beater in a horizontal position. A common Buckley Dater consists of sixteen circular plates rigidly mounted on a central shaft. There are fillers between the plates to prevent cotton from winding around the shaft; Steel fingers are attached to each plate at uniformly spaced distances. These fingers are bent at different angles so that the entire width of the beater has a uniform distribution of these fingers.

The delivery usually lends to a condenser, or screen section. The simplest type of Buckley opener feeds the cotton through a pair of feed rolls horizontally in line with the center of the beater, as shown in Fig. 9.2. The cotton is carried downward and forward for about one-half the circumference of the beater and is then discharged approximately; one-half the circumference of the beater is enclosed by bars

The opening done by the Buckley opener is the result of holding the cotton in the feed rolls, and pulling away bunches with the fingers of the beater. As the fingers are arranged to cover the full width of the feed roll in one revolution, they are constantly pulling at different places and so pulling apart the large bunches of cotton tuft.

107 B.Sc. CDF – Fibre to Fabric

9.2.4 Path of Cotton through the Picker (Scutcher)

Breaker pickers and single process pickers are fed with hopper feeders. The feeder is made the same width as the picker, usually 40 inches. The feeder drops cotton on to a short lattice apron which carries it to the picker feed rolls as a continuous, reasonably even flow. Usually a wooden roll, about 8 inches in diameter, is placed above the apron just back of the feed rolls. This roll presses the loose cotton and prevents it from climbing over the top of the feed rolls, directing it right into the proper position

Fig 9.3

A cross section of a breaker picker equipped with a hopper feeder is shown in Fig. 9.3 The cotton is carried out of the hopper and dropped on the short feed apron. It passes under the wooden compressing roll, through a pedal feed and to two feed rolls. As it passes beyond the feed rolls, the rapidly revolving beater strikes it and pulls it away from the mass held in the rolls. The cotton is carried through about 120 degrees by the beater and is then thrown off towards the screens.

The fan, below the screens, draws a current of air up through the grid bars, the beater chamber and flue, the screen surfaces and out the screen ends and down through flues on the outside of the machine. This air current carries the cotton to the screens where it is deposited in a fairly uniform sheet. The screens, turning slowly, deliver this loosely formed sheet to the condensing roll. It, then, passes through the calendar rolls and is wound up between the lap rolls on the lap arbor.

108 B.Sc. CDF – Fibre to Fabric

9.3 CHECK YOUR PROGRESS

1. List any five opening machinery. • Bale breakers, • Hopper feeders, • Buckling openers, • Vertical openers and • Horizontal openers.

2. Define the opening.

Opening is the process of tearing apart the compressed and matted cotton until it is very much loosened and separated into small tuffs of fibre. (or) Opening covers the initial treatments given to raw cotton, the separation and opening up of the cotton to remove compression because baling and shipping.

9.4 CARDING

9.4.1 Objects of Carding • To unwind and open the lap into very small tufts. • To extract vegetable impurities and all other trash particles from the cotton. • To open the cotton, even to the separation of one fibre from the all. • To condense the fibre ioto sliver form. • To deposit the sliver in to can.

9.4.2 Principle of Carding

There are two main principle of carding.

1. Stripping - Stripping action (Fig 9.4) takes place between cylinder and licker-in.

• The direction of the both licker-in and cylinder wires are inclined in the same direction. This is called Point to back arrangement. • Surface speed of the cylinder is about 2000 feet per minute and twice the surface speed of the licker-in.

109 B.Sc. CDF – Fibre to Fabric

Cylinder

Fig 9.4 Stripping action

2. Carding- Carding action(Fig 9.5) between cylinder and flats.

Fig 9.5 Carding action

• The wires point in opposite directions. This called point to point arrangement. • The tufts of cotton down to individual fibres, and remove some short fibres

9.4.3 Path of Cotton through the Card

In Fig. 9.6 it will be seen that the fibres pass over the feed plate and are carried downward to the right by the licker-in. This opens up the lap a great deal because the surface speed of the licker-in is in the vicinity of 1000 feet per minute, while the feed roll surface speed is in the vicinity of 1 foot per minute.

110 B.Sc. CDF – Fibre to Fabric

The cylinder strips the cotton from the licker-in opposite. The feed plate and carries it upward and over the top to the right. The surface speed of the cylinder is about 2000 feet per minute. As this is about twice the surface speed of the licker-in and, as the points of both the licker-in and the cylinder incline upward, this is a definite "stripping action."

The flats enclose the top of the cylinder, leaving but a very narrow space between the tips of their wire and that of the cylinder. The wires point in opposite directions, thus being arranged for "carding action." This is where the real carding process takes place. The surface speed of the flats is about 3 inches per minute in the same direction as the cylinder. The clearance between the flats and the cylinder is in the vicinity of .010 of an inch. So, the cotton is carded between these two, very close, wire-covered surfaces which separate the tufts of cotton down to individual fibres, and remove some short fibres and dirt to the flats, where they remain.

The slow motion of the flats is used to carry then forward, so that they may be stripped of accumulated fibre and dirt and returned to action. The motion is slow enough so it doe, not affect the carding action but fast enough to prevent loading the flats with too much fibre.

Beyond the flats, the cylinder carries the cotton downward to where it is transferred to the doffer. The surface of the doffer moves at a slow speed, averaging around 72 feet per minute, and in the same direction as the cylinder, where they approach each other. The two surfaces are generally set about .007 of an inch apart. The ginner generally considers this a stripping point but a study of the wire arrangement and directions will show that the action is carding.

Fig 9.6

111 B.Sc. CDF – Fibre to Fabric

After making half a turn on the doffer, the fibers come up under the doffer comb. This comb vibrates very rapidly, and, as it moves downward, the points move against the back of the doffer wire, producing a definite stripping action, The point of the comb will be about 0.010 of an inch away from the doffer wire. This stripping action removes a thin film of fibres the width of the card.

The web is much too thin to attempt to handle it and so the entire width is carried forward to a funnel-shaped "trumpet," where it is drawn through a small hole by a pair of calendar rolls and "condensed" to a sliver. The fibres retain this rope-like form due to the pressure resulting from passing through the trumpet. It is carried upward and into the coiler.

The coiler is a cast-iron stand attached to the front of the card. It has a foot projecting from one side of the bottom to hold the roving can and a top projecting over the foot with a device for coiling the sliver in a regular arrangement in the can. There is a small trumpet in the top of the coiler, a pair of small calendar rolls to draw the silver through it and a revolving plate gear carrying an inclined tube, through which the sliver passes. The "tube gear" turns, arranging the sliver in a coil in the can. At the same time, the can table turns the can so that each coil is a little to one side of the preceding coil. The result is a series of coils in a spiral, making a regular, compact arrangement in the can from which the sliver may be withdrawn without tangling.

9.5 LET US SUM UP

Most cotton contains an appreciable quantity of dirt due to the field conditions and the handling in gathering. This dirt must be removed before malting goods of average quality or better. Opening or loosening the tunes makes possible the removals of the dirt. So, opening and cleaning are generally carried on together.

9.6 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • The students may get more idea when they go through a spinning mill and follow the sequence of operation and passage of material through opening and cleaning machine. • Collect the samples of both feed and delivery material of different opening and cleaning machine and analyze them.

9.7 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Find the process sequence of cotton fibre based on its properties. • Discus why carding is the heart of a spinning mill? Or • Give the reason for “Card well Spin well”.

112 B.Sc. CDF – Fibre to Fabric

9.8 CHECK YOUR PROGRESS

1. What are the objects of carding?

• To open the cotton more completely, • To clean the cotton (dirt, neps, and short fibres) • To produce a silver

2. Discus why carding is the heart of a spinning mill?

Before the spinning of yarn the material has to thoroughly cleaned and this will be attain in the carding machine. Because spinning is the art of producing continuous, twisted strands, of a desire size, from fibrous materials.

The cleaning, that is the removal of dirt, is possible because of the complete opening being done. There are two important points for this type of cleaning first, where the cotton is fed (at the licker-in), and second, where the cotton is brushed between the carding surfaces (between the cylinder and flats).

9.9 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993

113 B.Sc. CDF – Fibre to Fabric

LESSON-10 YARN FORMATION

CONTENT

10.0 AIM AND OBJECTIVES 10.1 INTRODUCTION 10.2 DRAWING 10.2.1 Object of drawing 10.2.2 Principles of drawing 10.2.3 Drawing machine functions 10.3 COMBING 10.3.1 Objects 10.3.2 Degree of Combing 10.3.3 Process detail 10.3.4 Comb Actions 10.4 ROVING 10.4.1 Object 10.4.2 Common names 10.4.3 Operation on Roving Frame 10.5 CHECK YOUR PROGRESS 10.6 SPINNING FRAME 10.6.1 Object of Ring frame 10.6.2 Passage of Material through Ring Frame 10.7 LET US SUM UP 10.8 LESSON END ACTIVITIES 10.9 POINTS FOR DISCUSSION 10.10 CHECK YOUR PROGRESS 10.11 REFERENCES

114 B.Sc. CDF – Fibre to Fabric

10.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • The process of making fibrous material into yarn or thread. • As many as eight strands of sliver are blended together in the drawing process. • Roving frames draw or draft the slivers out even more thinly and add a gentle twist as the first step in ring spinning of yarn. • Ring spinning machines further draw the roving and add twist making it tighter and thinner until it reaches the yarn thickness or “count” needed for weaving or knitting fabric.

10.1 INTRODUCTION

In a Yarn formation position of a spinning sequence a longitudinal fibre array first is refined in a drafting process, and the refined fibre array then is subject to a twist imparting process, and is taken off the twist-imparting zone as a yarn. • Drawing out, • Twisting, and • Winding of fibers into a continuous thread or yarn.

10.2 DRAWING

After carding or combing, the fiber mass is referred to as the sliver. Several slivers are combined before this process. Drawing is the process where the fibres are blended and straightened. Multiple cans of sliver are drawn together at the draw frame to make the resulting sliver more uniform. The number of drawing passages utilized depends on the spinning system used and the end product.

10.2.1 Object of drawing

Doubling • To feed and combine 6 or 8 card slivers side by side through draw frame to produce one sliver. • Doubling is the process improves uniformity or regularity of the final sliver by averaging out the weight variation existing in sliver fed to draw frame. Drafting • Attenuate the feed sliver until the required size is obtained in delivery sliver. • Straightening and parallelization of fibre is achieved by drafting rollers. Condensing • To condense the thin fleece or web delivered from the front roller into single sliver. • Deposition of sliver in the form of coils in a can with the help of coiler mechanism.

115 B.Sc. CDF – Fibre to Fabric

10.2.2 Principles of drawing

The drawing process is: • First, to improve the uniformity of the slivers treated and • Second, to straighten the fibres composing the slivers, malting them more nearly parallel to each other.

A series of rollers rotating at different rates of speed elongate the sliver into a single more uniform strand. The straightening action of roller drawing (Fig 10.1) is the result of holding a large mass of fibres in rolls moving at one speed and pulling away some of the protruding fibres with rolls moving at a higher rate of speed. As adjacent fibres are more or less entangled with each other, increasing the speed of one fibre causes it to drag by the others. The result of having one fibre slip past another is that each tends to cling to the other and the contacting ends are straightened out.

Fig 10.1

The amount of straightening depends upon how much one set of rolls moves faster than the other set of rolls

10.2.3 Drawing machine functions

The first object, improving the uniformity of slivers, is accomplished by "doubling." "Doubling" is the practice of feeding two or more strands at once, to produce one strand. It is customary, with different types of drawing frames, to double 4, 6, S or 16 ends, with rare Cases of doubling 5 or 7 ends. In an effort to improve the uniformity, the drawing operation is often repeated. On the theory that if the first doubling improves the uniformity, and a second operation will carry the improvement even further. Two processes of drawing are quite as good as those produce when three processes of drawing are used. So, most mills are using but two processes of drawing. Many mills have reduced drawing to one process.

116 B.Sc. CDF – Fibre to Fabric

Using a second process of drawing, directly after the first process, will show a continued improvement in uniformity measured by one yard lengths. But the increase is not as great as during the first drawing.

The second object straightening the fibres and making them more nearly parallel. is accomplished by the draft or roller drawing. As the fibres progress through the machine; they are drawn along at increasing speeds. As one pair of rolls draws the fibre away from the preceding pair of rolls, the speed of the fibre is increased and it is pulled away from those moving less rapidly.

10.3 COMBING

Combing is the process that follows carding in the preparation of fibers for spinning, lays the fibers parallel, and removes noils (short fibers). The modern combing machine is a specialized carding machine. Combing produces a fine sliver suitable for drawing out and spinning into strong, smooth yarn. The process, used for long staple cottons and worsted yarn, is expensive, since up to 25% of the card sliver is eliminated. Combing is an intermittent operation. The shorter fibers, neps and dirt are removed and the fibers are made quite straight and parallel.

10.3.1 Objects

The objects of combing are as follows: • First, to remove short fibers from the cotton; • Second, to remove any neps and dirt remaining with the cotton and third to straighten the fibers and so make them parallel to each other.

10.3.2 Degree of Combing

In some cases, combing is classified by the amount of noil removed. Where the percent of noil is not over 10% it is often spoken of as "semi-combing". In these cases, the removal of short fibers is at a minimum and while it improves the quality of the stock, the greatest value of the operation is the straightening of the fibers.

"Regular combing", is the term applied to those cases which represent the common procedure, where the noil amounts to between 10 and 20 percent.

"Double combing", applies when the combed sliver is taken back to the sliver lapper and put through the combing operations a second time. This is rarely done but when the procedure is followed the noil will be between 20 and 30 percent. It is obvious that the double combing is used only when the highest quality products of the finest counts are desired.

117 B.Sc. CDF – Fibre to Fabric

10.3.3 Process detail

For the purpose of detailed study, combing may be considered a series of independent operations, each of which may be studied as an isolated mechanical action, where all are so timed and located that the cotton passes through one after the other as a continuous operation.

If, instead of tying to understand the comb as a whole, the student will, at the start, study each action until familiar with it and then go back and review the entire machine as a summary to all the individual studies, he will fmd that much less time is necessary to thoroughly absorb all the details of the intricate combing process.

The separation of combing into its various actions gives the following list, taking the actions in order of occurrence:

• Feeding, which introduces the ribbon laps in a series of short lengths. • Nipping, which grips the fibers between two parallel jaws as a means of holding fibers while the short fibers, neps and dirt are being removed. • Combing, which passes many rows of closely spaced needles through the fibers held by the nippers, as the means of removing short fibers, neps and dirt. • Detaching, which consists of; (a) moving the previously combed cotton backward sothe newly combed fibers may overlap the others, and (b) drawing those fibers which project the farthest from the lap in the nippers, away from the lap. • Top combing, which draws the back end of the detached fibers through a row of closely spaced needles, thus straightening and cleaning them and preventing short fibers from being carried along by contact with the long fibers. • Condensing, which passes the web from the detaching rolls through a trumpet forming it into a sliver. • Drawing, which passes the slivers from all the heads, as a narrow sheet, through a series of drawing rolls to reduce them to a normal weight of sliver.

1. Nippers The nippers, the nipper cam and the connecting levers used in actuating the nippers. The lower nipper, often called the nipper plate, is fixed in position. The upper nipper, often called the nipper knife, rises and falls to cause opening and closing. The position of nipper knife is regulated by moving the frame, as for the nipper plate.

118 B.Sc. CDF – Fibre to Fabric

2. Cylinder Combing Cylinder combing is the operation in which the comb removes much of the short fibers, neps and dirt. Because of this operation, the cotton fibers are very much straightened. Cylinder combing consists in passing many rows of fine, closely spaced needles through the fringe of fibers projecting from the nippers.

3. Top Combing The function of the top comb is to comb the portion of the fibers held in the nippers during the cylinder combing. As it is impossible for the cylinder to comb the entire length of the fiber, the top comb is located so that it will comb the tail end of the fibers as they are being drawn away by the detaching rolls.

4. Detaching The purpose of the detaching mechanism is to grasp the combed fibers which project farthest from the nippers and draw them away, overlapping the previously detached cotton to produce a continuous sheet of fibers

10.3.4 Comb Actions (Fig 10.2)

The feed rolls have just turned forward a short distance, the nipper knife is moving downward and the half lap is nearly ready to start combing. The end of the lap is still in the top comb as a result of the last top combing action, but the last groups of fibers detached have been carried forward until their ends are up in the detaching rolls.

The nippers closed before the combing action started. As they closed, the lap was forced down out of the top comb directly into the path of the needles of the half lap. The top comb and the detaching rolls are still inactive.

After the last needles of the half lap left the cotton, the detaching rolls turned backward a short distance. This caused a thin web of combed fibers to hang down at the back of the steel detaching roll. As the segment came to the leather detaching roll, all three detaching rolls started turning forward. When the segment came in contact with the leather roll, it lifted it, and these two parts grasped the most forward fibers. These fibers being drawn from the lap and being led on to the previously detached cotton, thus forming the "piecing".

119 B.Sc. CDF – Fibre to Fabric

Fig 10.2 As the fibers are being detached from the lap held in the nippers, the pull of the detaching rolls causes the lap to form a nearly straight line from the feed rolls to the bite of the detaching roll and segment. This causes the fibers which are being detached to pass through the needles of the top comb and so provides the top combing action. Meanwhile, fibers not actually gripped in the detaching bite are retarded from passing forward by the friction in the top comb. Any fibers tangled with or adhering to fibers being detached either are not drawn forward or are collected in a crumpled up form behind the top comb.

10.4 ROVING

In preparation for ring spinning, the sliver needs to be condensed into a finer strand, known as a roving, before it can be spun into a yarn. Because ring spun yarn is made in a linear process (sliver to roving to yarn), the yarn is stronger. The sliver is fed through a machine called the roving frame, where the strands of fiber are further elongated and given additional twist. These strands are called the roving.

120 B.Sc. CDF – Fibre to Fabric

10.4.1 Object

The main object of speed frame:

• Drafting: To reduce the thickness of material and parallelization to make the product more even. • Twisting: To import twist to the material. • Winding: To wind the rove on the bobbin. • Building: To build the material on the bobbin in a suitable shape (Cylindrical body with conical edges)

10.4.2 Common names

These were commonly named as follows: 1. Slubber 2. Intermediate (First Intermediate) 3. Fine (Fly Frame, Speeder, Second Intermediate) 4. Jack

The term "fly frame" is frequently applied as a general term for all roving frames but is also used for the specific operation listed here as a fine frame.

10.4.3 Operation on Roving Frame

The work of a roving frame may be divided into a number of separate operations, each of which is almost independent of the others and yet so timed and tied in with the others that the whole makes a unit. These operations and their objects are: • Drawing, to reduce the size of the strand. • Twisting, to give the necessary strength. • Laying, to put the coils on the bobbins in a regular arrangement. • Winding, to put successive layers on the bobbins at the proper rate of speed. • Building, to shorten successive layers to make conical ends on the package of roving.

1. Drawing

As the basic ideas on which all of the roving drafting equipment works are still those of the regular, three roll system, this section treats, fast, of the regular draft equipment, after which various systems for long draft are considered. The object of drawing, in the roving process, is to reduce the bulk of the strand to a suitable size for spinning.

121 B.Sc. CDF – Fibre to Fabric

2. Twist Twisting, in roving, is the operation of revolving the strand about its own axis so that the fibres are arranged in a spiral form and thus bind each other together.

The object of using twist in roving is to give the strand sufficient strength to withstand the strain of turning the bobbin on which it is wound, in the creel of the next operation. Unfortunately, as the strand is drawn on the roving frame, its bulk is so reduced that it has practically no strength. Consequently, if the strand is to be unwound through Cunning the bobbin by pulling on the roving, the strength must be materially increased. The purpose of twisting is limited to this one phase of the problem. As increased twist reduces the productive capacity of the machine, it is generally used in as limited quantities as possible.

Fig 10.3 Twisting is accomplished by the "flyer", (Fig 10.3) which is carded on the spindle. As the strand is delivered at the front rolls, it is led downward and forward to the top of the flyer, through the flyer and on to the bobbin. The flyer revolves rapidly and carries the roving around with it. The result is that the front roll is delivering a narrow ribbon of fibers in a fixed plane; the flyer, holding the other and of the exposed strand, turns rapidly and twists it. The twist runs quickly up to the front roll as t h e is nothing to prevent. As rapidly as the front roll delivers a new length of ribbon, the flyer makes additional turns and they run back to the front roll. For any given condition, the flyer speed and the front roll speed are fixed, which gives a constant ratio between the turns of twist and the inches delivered at the front roll. This is the 'Twists per Lich".

122 B.Sc. CDF – Fibre to Fabric

3. Spindles (Fig 10.4)

Fig 10.4

In all modern frames, there are two lines of spindles directly in front of, and just below the drawing rolls. The two lines of spindles are staggered to reduce floor space necessary and to make it easier to leach the back line. The spacing of spindles is, given as the "space" of the frame, which is the distance between spindles of one line, measured from center to center. Another way of classifying the spindle spacing is by the "gauge", which is the distance for a given number of spindles, including both front and back spindles. While this seems a very arbitrary figure to the beginner, it will soon be seen that the distance in inches is from center to center of roll stands and that the number of spindles is the number supplied by one section of the front roll.

4. Lay

Lay refers to the arrangement of the coils of roving wound around the bobbin in any given layer. The lay may be "close" or "open", depending upon whether succeeding coils are crowding each other or are so spaced that they do not touch. The closeness of the lay is measured in "coils per inch", which means just what the expression says: - the number of coils that are wound around the bobbin, in any one layer, in the distance of one inch parallel with the axis of the bobbin.

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The object of the laying operation is to put the successive coils of roving side by side in a regular, uniformly spaced arrangement, which forms a helix around the previously built package. The problem is somewhat increased by the continually increasing diameter of the bobbin, as layer after layer is put on, making each successive layer on a different diameter.

10.5 CHECK YOUR PROGRESS

1. What is meant by drawing?

Drawing is the process of progressively pulling or sliding fibres by each other which causes a reduction in the size of the strand but does not break it apart. (or) Drawing is operation by which slivers are blended, doubled, or leveled, and by drafting reduced to a sliver or a roving suitable for spinning.

2. What are the objects of drawing?

The objects of drawing are to improve the uniformity of the slivers treated, and to straighten the fibres composing the slivers, making them more nearly parallel to each other.

3. Define the twisting in roving.

Twisting, in roving, is the operation of revolving the strand about its own axis so that the fibres are arranged in a spiral form and thus bind each other together.

10.6 SPINNING FRAME

The ring frame was invented in 1828 by the American John Thorp and is still widely used today. This system involves hundreds of spindles mounted vertically inside a metal ring. Many natural fibers are now spun by the open-end system, where the fibers are drawn by air into a rapidly rotating cup and pulled out on the other side as a finished yarn.

Fig 10.5

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The predominant commercial systems of yarn formation are ring spinning Fig 10.5 and open-end spinning. In ring spinning, the roving is fed from the spool through rollers. These rollers elongate the roving, which passes through the eyelet, moving down. The traveler moves freely around the stationary ring at 4,000 to 12,000 revolutions per minute. The spindle turns the bobbin at a constant speed. This turning of the bobbin and the movement of the traveler twists and winds the yarn in one operation.

10.6.1 Object of Ring frame

The spinning frame may perform four basic operations. Each is continuous and all are carried on simultaneously. These operations are as follows: -

• Drafting: reducing the bulk of the strand to the desired size. (In a few instances, mostly for waste yams, drawing may not take place). • Twisting: causing the fibers to spiral around each other and bind themselves together to give the desired strength. • Winding: coiling the twisted strand of yam around the bobbin as rapidly as it is delivered by the drafting rolls. • Building: regulating the pattern of winding of the yam to give a package of a desired shape and size to suit the requirements of the use of the yam.

While each of these operations will be considered separately, it is important to keep in mined the relationship of each to the others.

10.6.2 Passage of Material through Ring Frame:

The supply package, roving bobbins are placed in this creel with the help of the skewers as shown in Fig 10.5. In modern frame instead of this type, umbrella creels are used. The roving from each bobbin is drawn outward and downward through a roving guide and through a traversing guide by the movement of the back pair of draft rollers.

The purpose of traversing guide is to allow the material to the full width of the roller, so as to avoid the damage to the drafting rollers.

The roving strand passes through the back pair, middle pair and finally through the front pair, gets drafted thus results a ribbon of fibres without any twist. As soon as the fibre emerges from the front rollers, they are twisted together by the rotation of traveler and are pulled downward at sharp angle through the yarn guide (lappet guide) which is directly over the centre of the spindle and the cop.

The yarn then passed about vertically downward to the traveler on the ring where it makes approximately right angled turn to pass horizontally to the cop. Between the yarn guide and the cop and yarn is revolved by the rotation of the traveler on the surface of the ring and gets twisted.

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The spindles are driven by the tin roller. The tin roller in turn receives the drive form the motor. Each spindle is separated by a device called separators (thin metal plate of steel or aluminum). This is to avoid lashing of ends by the ballooning effect. The yarn thus wound on the bobbin is made to required shape by suitable building mechanism.

Fig 10.5

10.7 LET US SUM UP

In spinning, separate fibers are twisted together to bind them into a long, stronger yarn. Characteristics of the yarn vary based on the material used, fiber length and alignment, quantity of fiber used and degree of twist.

126 B.Sc. CDF – Fibre to Fabric

10.8 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Students are advice to visit any one spinning mill and analyze the feed and delivery material of each machine • The development of ring spinning can be come to know by different journals and magazine.

10.9 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • How we say the capacity of the spinning mill? • Ring spinning system and its modern development. • The necessity of combing and how it delivery material differ from carded material.

10.10 CHECK YOUR PROGRESS

What is meant by spinning?

Spinning is the art of producing continuous, twisted strands, of a desire size, from fibrous materials. (or)

The final operation in cotton yarn manufacture. It completes the working of the cotton fibres into a commercial, fine, coherent yarn sufficiently twisted so that it is now ready for weaving process.

10.11 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Spun yarn technology, Vol I,II,III

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LESSON-11 YARN

CONTENT 11.0 AIM AND OBJECTIVES 11.1 INTRODUCTION 11.2 DEFINITION 11.2.1 Types of Yarns 11.3 CLASSIFICATION OF YARN 11.3.1 Yarn Twist 11.3.1.1 Direction of twist 11.3.1.2 Twists per inch 11.3.1.3 Amount of twist 11.4 COMPLEX (FANCY, NOVELTY) YARNS 11.4.1 Main parts of fancy yarn 11.4.2 Types of Fancy Yarn 11.5 SEWING THREAD 11.5.1 Sewing thread functions 11.5.2 Sewing thread availably 11.5.3 Sewing thread properties 11.6 LET US SUM UP 11.7 LESSON END ACTIVITIES 11.8 POINTS FOR DISCUSSION 11.9 CHECK YOUR PROGRESS 11.10 REFERENCES

11.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following

• Fibers or filaments formed into a continuous strand for use for the manufacture of thread. • Yarns twist to give them strength and smoothness.

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11.1 INTRODUCTION

Yarn is a long continuous length of interlocked fibers, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery and rope making. Thread is a type of yarn intended for sewing by hand or machine.

The characteristics of spun yarn depend, in part, on the amount of twist given to the fibers during spinning. A fairly high degree of twist produces strong yarn; a low twist produces softer, more lustrous yarn; and a very tight twist produces crepe yarn.

11.2 DEFINITION

Yarn consists of several strands of material twisted together. Each strand is, in turn, made of fibers, all shorter than the piece of yarn that they form. These short fibers are spun into longer filaments to make the yarn. Long continuous strands may only require additional twisting to make them into yarns.

11.2.1 Types of Yarns

Staple (spun) yarn -made from short, staple fibers that must be held together by some means (usually twisting) in order to be formed into a long, continuous yarn. Natural fibers except silk are staple fibers; manufactured fibers and silk are usually filament but can be cut into staple lengths.

Filament - made from long, continuous strands of fiber. (May be monofilament or multifilament). Silk and manufactured fibers come in filament form.

11.3 CLASSIFICATION OF YARN

Yarns are also classified by their number of parts. • Single yarn - made from a group of filaments or staple fibers twisted together; if untwisted, it will separate into the individual fibers • Ply yarn – (Fig 11.1)two or more single yarns are twisted together to make a single yarn; if untwisted, it will separate into the single yarns which will separate into individual fibers

Fig 11.1 2-Ply and 3-Ply Yarns

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• Cord yarn –(Fig 11.2) two or more ply yarns are twisted together; if untwisted, it will separate into the plied yarns which will then separate into single yarns which will separate into individual fibers. • Novelty (fancy, complex) yarns - yarns that have a decorative effect; not uniform in size and appearance. • Core-spun yarns - yarns that have a central core of one fiber around which is wrapped or twisted an exterior layer of

Fig 11.2

11.3.1 Yarn Twist

11.3.1.1 Direction of twist (Fig 11.3)

When fibers are twisted to make a yarn, they are twisted to the right or left. This twisting is called S or Z twist. Most yarns are made with a Z twist. The direction of twist does not usually affect the characteristics of the yarn or fabric.

Fig 11.3 Z- and S-twist yarn

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11.3.1.2 Twists per inch

The number of twists per inch can, in plied yarns, be determined by counting the number of bumps in one inch, and divide by the number of singles (the strands plied together to make the yarn).

In the industry the number of twists per inch is calculated as:

TPI= T.M. * • Where, T.M. is Twist multiplier or K (twist factor). • Twist factor has been established by experiments and practice that the maximum strength of a yarn is obtained for a definite value of K.

11.3.1.3 Amount of twist

Twist is needed in yarn to hold the fibers together, and is added in both the spinning and plying processes. The amount of twist varies on the fiber, thickness of yarn, preparation of fiber, manner of spinning, and the desired result. Fine wool and silk generally use more twist than coarse wool, short staples more than long, thin more than thick, and short drawn more than long drawn.

The amount of twist in a yarn helps to define the style of yarn- a yarn with a lot of air such as a woolen yarn will have much less twist than a yarn with little air, like a worsted yarn. It also affects the stretchiness of the yarn, strength, the halo of the yarn, and many other attributes. Filling or weft yarns usually have fewer twists per inch because strength is not as important as with warp yarns, and highly twisted yarns are, in general, stronger. Warp yarns have to be stronger so that they can withstand the tension of the loom.

The amount of twist affects the characteristics and properties of a yarn including appearance, behavior and durability.

• Generally, higher twist creates yarns that are Stronger More firms Smaller in diameter Smoother Resistant to snagging and abrasion Resilient Good conductors of heat

• Generally, lower twist creates yarns that are Weaker Softer Larger in diameter Fuzzy

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Prone to snag and abrade Crush easily Resistant to heat transfer

Filament yarns often have little or no twist because they are continuous and strong; the fibers will not break or separate from the yarn as easily as spun (staple) yarns

11.4 COMPLEX (FANCY, NOVELTY) YARNS

• Complex yarns are made to create decorative effects in the fabrics into which they are woven. • Usually weaker than simple yarns. • Usually woven into the filling direction of the fabric. • Yarns usually exhibit more snagging and wear. • These are yarns that differ from normal yarns, in appearance, texture and handle • They constitute a vast range of types, many specifically designed for hand knitters

Novelty yarns can be further split into two categories, fancy and metallic yarn.

Fancy yarns • Fancy yarns can be made from staple or filament fibres. • They are intentional produced to have a distorted or irregular construction. • Popular effects include knops, snarls, loops and slubs.

Metallic yarns • Usually produced from aluminium sheets laminated with plastic film, cut into thin ribbons. • Or can be core spun, for example a polyester core with a metallic outer.

11.4.1 Main parts of fancy yarn:

There are three main parts are involved in the fancy yarn. 1. Core (ground) yarn 2. Effect yarn 3. Binder yarn

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Fig 11.4

• Novelty, fancy and decorative yarns are used in both woven and knitted fabrics. • Knots, snarls, loops and other irregularities can be introduced to create textured surface effects. • Fancy yarns usually have a base or core yarn which is a conventional plain yarn, this yarn is combined with the effect yarn shown in Fig 11.4. • The effect yarn can be held in place with a binding yarn.

11.4.2 Types of Fancy Yarn

There are many types of fancy, novelty and decorative yarns produced. They can be produced in many ways. • Different coloured fibres can be blended together then spun as one yarn. • Colour can be applied by printing or dyeing pattern onto roving or yarn. • Spots of coloured fibre can be twisted in with the base yarn. • Two or more threads of different, softness, thichness, weight, colour or fibre content can be twisted together. • Raised textures can be introduced by controling the amount and direction of twist. • Fancy yarns can be natural or man-made or a combination of both.

1. Boucle, gimp and loop yarns (Fig 11.5)

These yarns are made by feeding one or more effect yarns faster than the core yarn while spinning

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Fig 11.5

• Boucle has a hard twisted core yarn, the effect yarn is rapidly twisted round the core so that excess yarn forms an irregular wavy, bumpy surface • Gimp is much the same as boucle, but the excess yarn forms a more regular surface • Loop yarn is the result of the excess soft spun yarn being formed into well shaped circular loops on the hard spun core

2. Snarl yarns (Fig 11.6) • Snarl yarns are made in a similar way to loop yarns • Except the effect yarn has a high, lively twist, so that the excess bits snarl and double up on themselves and twist together

Fig 11.6

• Just like the lengths of cord we make on a door-knob 3. Knop or button yarns (Fig 11.7)

Fig 11.7

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• These yarns are also made by feeding the yarns at different rates while spinning • But this time the excess yarn of one or more of the components forms bunches • These can be at regular or irregular intervals

4. Slub yarns (Fig 11.8)

Fig 11.8

• Slub yarn is charactorised by having, alternating short places of thin, firm twist yarn, with places of very thick, loose twist yarn • The differnt areas can be at regular or irregular intervals

5. Marl yarns (Fig 11.9)

Fig 11.9

• Marl yarns are made by twistng together two or more ends of different coloured yarns • The effect pattern is one of regular diagonal stripes of each colour

6. Spiral and corkscrew yarns (Fig 11.10)

Fig 11.10

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• These are plied yarns where one yarn wraps around the other, rather than the yarns being twisted together • A spiral yarn has a higher twist than a corkscrew yarn • A spiral yarn usually has a thinner yarn wrapped round a thicker core • A corkscrew yarn has a softer bulkyer yarn wrapped round a thin, firm yarn

7. Chenille yarns (Fig 11.11)

Fig 11.11

• Chenille yarns have a soft, fuzzy cut pile which is bound to a core • These yarns can be spun, but the machinery required is much specialized • For this reason, these yarns are usually woven on a loom • The effect yarn forms the warp, which is bound by a weft thread • The weft thread is spaced out at a distance of twice the required length of pile • The warp is then cut half way between each weft thread.

11.5 SEWING THREAD

Sewing thread is found everywhere, in common apparel, home furnishing, sports wear and shoes, in automotive items like air bags and seat belts as well as in various other technical applications. The sewing seam performances of the sewing thread are influenced by material to be sewn, sewing techniques and the end use desired.

11.5.1 Sewing thread functions

Sewing thread covers two main functions; the most important is obviously joining the different fabrics and give the product the necessary strength in the area of its highest stress – the invisible seams. The second function is refining products with decorative stitching. In both cases one thing is often underestimated: Sewing Thread may account only for 0,5% of fiber amount within a garment, however, it shares fairly more than 50% of responsibility for the final quality of a garment.

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The requirements can be defined as: • The ability of sewing thread to meet functional requirements of producing desired seam effectively. • Ability to provide desired aesthetics and serviceability in the seam. • Cost of the sewing thread and that of resultant seam.

11.5.2 Sewing thread availably

Sewing thread is available as: • Spun yarn (Cotton or PES spun) • Core spun (PES/Cotton; Poly/Poly) • Flat filament threads (PES, Nylon, etc.) • Textured filament (Draw-textured or air-textured) • Special threads mainly for technical applications

11.5.3 Sewing thread properties

1. Functional requirements

Tensile properties: Sewing thread should have high tenacity with moderate tension. For better loop formation characteristics, the elastic modulus of the sewing thread should be high.

Friction: There should be uniformity of friction over long length. Factors are responsible for giving maximum possible tension fluctuation of the yarn components in the cross section and the length.

Passage through needle eye: There should be no sudden shocks when thread passes through the eye of the needle. Needle temperature is critical for sewing thread of man made fibres.

Free from knots and faults: Sewing thread should be free from knots and faults to give smooth performance.

2. Serviceability

During sewing, threads are subjected to abrasion over needles and fabric threads. There is a lose of strength during and after sewing during fabric use. Sewing thread should have high abrasion resistance so that lose strength is minimum. For a good serviceability, seam must be firm. A seam strength test could be performed. Different stitches are applied to different application. Fabric properties affect seam strength along with loop and abrasion strength of sewing thread and the amount damage due to sewing. To avoid puckering of garments around the seams, the thread shrinkage should be generally less then 2% during washing.

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3. Aesthetic Colour, shade, luster, smoothness, fitness are some of aesthetic related characteristics of sewing threads. Certain amount of hairiness in sewing thread has to positive effect on sewing but this effect has to be sacrificed for appearance. There is a tendency to use dyed sewing thread for appearance.

4. Cost consideration From the raw material aspect, sewing thread of natural silk is expensive. A higher melting sewing thread may be expensive. but, it should have a judicious use in the sense that the fabric for which it is used should also have a high melting points as the hot needles not only attack the sewing thread but the fabric also.

5. Other sewing thread properties In addition to the essential properties, some of the applications may be required for sewing threads to have special properties like, resistance to flexing in seams in shoes, discontinuous surface to provide grip and avoid slippage in the seam for high seam strength applications.

11.6 LET US SUM UP

The characteristics of spun yarn depend, in part, on the amount of twist given to the fibers during spinning. A fairly high degree of twist produces strong yarn; a low twist produces softer, more lustrous yarn; and a very tight twist produces crepe yarn.

More twist produces stronger yarn; low twist produces softer, shinier yarn. Two or more single strands may be twisted together to form ply yarn. Knitting yarns have less twist than weaving yarns. Thread, used for sewing, is a tightly twisted ply yarn.

11.7 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • To visit any one spinning mill and analyze the Yarn are manufactured. • Find the factors influencing the thread properties. • Analyze the difference between sewing thread with other yarn.

11.8 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points

• The necessary parameter required to manufacture a sewing thread • Based on the end use, analyze the manufacturing procedure for different yarn.

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11.9 CHECK YOUR PROGRESS

1. Discuss the parts of fancy yarn. 1. Core (ground) yarn 2. Effect yarn 3. Binder yarn • Fancy yarns usually have a base or core yarn which is a conventional plain yarn, this yarn is combined with the effect. • The effect yarn can be held in place with a binding yarn.

2. Write short notes on twist.

Fibers are twisted to make a yarn, they are twisted to the right or left. This twisting is called S or Z twist. Most yarns are made with a Z twist.

The number of twists per inch can, in plied yarns, be determined by counting the number of bumps in one inch, and divide by the number of singles (the strands plied together to make the yarn). If the picture to the right, for example, was of an inch of 2 ply yarn, then the number of twists per inch would be 6 dived by 2, or three, as there are six bumps, and it is a two ply.

11.10 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Spun yarn technology, Vol I,II,III

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140 B.Sc. CDF – Fibre to Fabric

UNIT- IV

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142 B.Sc. CDF – Fibre to Fabric

LESSON-12 WEAVING PREPARATORY PROCESS

CONTENT

12.0 AIM AND OBJECTIVES 12.1 INTRODUCTION 12.1.1 Sequence of Operations 12.1.2 Winding Machines 12.1.3 Yarn Traversing 12.1.4 Weaving Preparatory Flow Chart 12.1.5 Warp Preparation 12.2 WARP WINDING (CONING) 12.2.1 Object of warp winding 12.2.2 Working of warp winding machine 12. 3 WARPING 12.3.1 Object 12.3.2 Warping machine 12.4 CHECK YOUR PROGRESS 12.5 SLASHING OR WARP SIZING 12.5.1 Object 12.5.2 Reasons for Sizing 12.5.3 Sizing 12.6 LET US SUM UP 12.7 LESSON END ACTIVITIES 12.8 POINTS FOR DISCUSSION 12.9 CHECK YOUR PROGRESS 12.10 REFERENCES

12.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • Process sequence of weaving operation • Preparation of the warp yarn • The main purposes of warp winding • The main purposes of sizing

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12.1 INTRODUCTION

In general, weaving involves the interlacing of two sets of threads at right angles to each other: the warp and the weft.

The selection of suitable yarns and the preparation of yarn for weaving have a considerable influence upon the efficiency with which the weaving operation itself can be performed. For maximum efficiency, yam breakage at the loom must be reduced to a minimum and this is only possible if: (a) Care is taken to select yarn of uniform quality; (b) The yarn is wound on to a suitable package in the best possible way; and (c) The yarn has adequate treatment before use.

There requirements apply to varying extents to both warp and filling. The preparation of the warp differs from the preparation of the filling and it is necessary to deal with each of them separately. However, winding is common to both and may be considered in general terms.

12.1.1 Sequence of Operations

In fabric manufacture, the sequence of operations is as follows: 1. Yarn production. 2. Yarn preparation. • Warp • Filling 3. Weaving 4. Fabric finishing.

12.1.2 Winding Machines

The package may be rotated by one of three methods: 1. Surface contact between the outer surface of the yam on the package and a drum or roller. This gives a constant surface speed to the package and the yam is taken up at an approximately constant speed. 2. Directly driving the package at a constant angular speed. This causes the yarn take-up speed to vary as the size of the package changes. 3. Directly driving the package at varying speed. To give constant yarn speed, it is necessary to cause the rotational speed to vary inversely with the package radius.

12.1.3 Yarn Traversing There are three fundamentally different types of packages: (1) The parallel wound package; (2) The near-parallel wound package; and (3) The cross-wound package.

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12.1.4 Weaving Preparatory Flow Chart

Yarn Production

Warp winding Winding Weft winding

Warping

Sizing

Drawing-in & Denting-in

Looming

12.1.5 Warp Preparation • The essential features of a good warp are as follows: • The yarn must be uniform, clean, and as free from knot as possible. • The yarn must be sufficiently strong to withstand the stress and friction of weaving without excessive end breakage. • Knots should be of standard type and size, enabling them to pass easily through the heddles and reeds of the loam. • The warp must be uniformly sized and the amount of size added must be sufficient to protect the yam from abrasion at the heddles and reed so as to prevent the formation of a hairy surface on the warp threads. • The ends of the ware must he parallel and each must be wound on to the loom beam at an even and equal tension.

12.2 WARP WINDING (CONING)

As a warp consists of a multitude of separate yarns or ends, in making an appropriate package (known as a beam) the ends must lie parallel and this determines the type of yarn package that must be used.

One of the main purposes of warp winding is to transfer yarn from the spinner's or double's package (Figure 12.1) to another suitable for use in the creel of a warping machine or for dyeing. Warping requires as much yam as possible on each package and also a package which has been wound at comparatively high tension, but dyeing requires a soft wound package so that dye can penetrate; a compromise is sometimes needed, therefore, in the matter of winding tension.

145 B.Sc. CDF – Fibre to Fabric

Fig 12.1

12.2.1 Object of warp winding

The main Object of warp winding is to take yarn from small packages (Ring cop) and convert into large package like cones and cheeses. Ring cops contain small amount of yarn in lengthwise and weight of the ring cops is very low. It can exhaust quickly in further process, than cones.

A second main purpose of warp winding is to make it possible to inspect the yam and to remove any thick or thin places, slubs, neps or loose fibres. This clearing-operation applies mainly to staple fibre yarns where such faults are more prevalent.

12.2.2 Working of warp winding machine

The supply packages of this cone winding machine is normally ring cops which are mounted in an upright position on the creel and extends the entire length of the machine on either side of it.

The yarn from each supply package is drawn through a thread guide or yarn delivery roller. Here, the yarn wind one or two winds in between this two rollers to impart some amount of tension before the yarn going to tensioner of course there is a balloon breaker in between the cop and the thread guide to break the balloon formation there by avoiding breakages of yarn.

Normally, washer type tensioner is used. The tensioning device consists of a pair of metal washers fitted loosely in a short spindle. The amount of tension given to the yarn will depend on the weight of these washers and count of yarn etc., generally for the course count the amount of tension given to the yarn is 300 grains for medium counts the tension will be 100 grain and for the fine counts the tension will be 55 grains.

The yarn from the tensioner, passed between the slub catchers. Normally snick plate type slub catcher is used on the high speed cone winding machine, which arrests slubs, neps,snaris thick places etc., present in the yarn. The slub catcher can be set according to the counts of the yarn wound. For a coarser type of yarn double slub catcher is used.

146 B.Sc. CDF – Fibre to Fabric

The setting will depend on the count of the yarn. For carded yarn the clearance in the slub catcher will be 2 times, the diameter of the uarn and for combed yarn the setting will be 1.5 times the diameter of the yarn.

The yarn from the slub catcher passes under the broken thread stop motion wire, which lifts the cone when a yarn breakes or the supply bobbin becomes exhausted.

And then, the yarn passes over the grooved drum are mounted at regular intervals on winding drum shaft, which are provided with ball bearings. The no. of drums per machine may be 20 to 120. Each shaft is driven by a separate motor so that the drums on any one side can run independently of these on the other side. The function of the grooved drum is, wind the yarn on the cone and at the same time gives a traverse movement to the yarn. The grooves on the drum guide the yarn which is always in these grooves and moves in the same direction.

The machine is further fitted with a conveyor one on each side. The conveyor carries empty supply bobbins and deposits them into a suitable container kept at the end of the machine.

12. 3 WARPING

Warping is process preparatory to actual weaving or knitting. Since the early days of cotton cloth manufacturing, it has been found necessary to wind cotton yarn from relatively small spinning bobbins onto larger packages such as spools or cones of various types and sizes in order to make a warp.

Fig 12.2

12.3.1 Object

The object of warping is to lay the number of ends required for the warp into a horizontal sheet of yam of specified length under uniform tension with the yarns spaced evenly across the specified width.

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12.3.2 Warping machine

Supply package

Thy yams are taken from large supply packages placed in a creel and are wound on a beamer. The supply packages are usually in the form of large cones holding about 60,000 yards of yarn, or cheeses from the automatic spoolers holding 2.5 to 3 pounds of yarn shown in the fig 12.2.

Creel

The metal creel consists of a series of vertical bars each carrying nine to twelve cones or cheeses. The upper and lower ends of the vertical bars carry the cheese containers and are connected to endless, sprocket chains, run ring lengthwise of the creel. These chains extend along the outside of the creel around sprockets at both ends of each creel section and back on the inside, carrying a continuous series of cheese containers on both the outside and inside of each section. This permits the filling or receptacles on the inside of the creel with yarn while the warper is in operation.

Containers

With cheeses, containers or receptacles are used which will prevent ballooning of the rapidly running threads and also lint accumulation. They are equipped with a spring detent, which engages the groove inside the Bakelite sleeve and fixes the cheese in a concentric position.

The cheeses are held stationary in the containers and the yarn is pulled off over the ends. When the yarn has been wound off the cheeses on the outside, a small one-quarter H. P. motor moves the empty containers to the inside of the creel. This same movement brings the full containers from the inside to a running position on the outside of the creel. Electric fans are mounted to prevent lint accumulation.

Electric End Stop-Motion

The electric drop wires in the creel gates function when a thread or end breaks. The wire falls from the running position, making an electrical connection inside the bar holding the drop wires. Completion of the circuit through an electromagnet on top of the machine releases a powerful spring which actuates a string brake, stopping the rotation of the warper beam in time to avoid burying the loose, broken end. At the same time all other drop wires assume a leaning position, thereby placing sufficient tension on each strand of yarn to pull out any kinks that may form due to any overrun of the yarn. This tension remains on the yarn during the slow-speed starting of the warper but is removed as the machine gets into high speed.

148 B.Sc. CDF – Fibre to Fabric

Comb

The ends which were picked up from each vertical row of cheeses at the time of creeling and left hanging loose are now in position to be carried forward to the beamer and laid into the single comb divided into sections of nine dents each. The ends from several vertical rows are usually brought forward at one time by the creel girl and passed to the warper tender or beamer. The latter, standing in from of the warper, lays the ends into a special comb which is so designed as to permit laying them in quickly and without error. As the ends are carried forward, they automatically drop into place behind their respective electric drop wires. The entire operation described above, i.e., turning the creel, changing the beam and laying the new ends into the comb consumes less than fifteen minutes under ordinary circumstances.

12.4 CHECK YOUR PROGRESS

1. Give the importance of winding. • Spinners package contain small amount of yarn in lengthwise and weight of the ring cops is very low. It can exhaust quickly in further process • Winding is to take yarn from small packages (Ring cop) and convert into large package like cones and cheeses. • Remove any thick or thin places, slubs, neps or loose fibres.

2. Writ shorts on types of warping with necessary diagram. There are two main types of warping: (a) Beam warping and (b) Section warping. (a) Beam warping is used for long runs of grey fabrics and simple patterns where the amount of colored yarn involved is less than about 15 per cent of the total. This is sometimes referred to as direct warping.

Fig 12.3

149 B.Sc. CDF – Fibre to Fabric

(a) Beam warping is used for long runs of grey fabrics and simple patterns where the amount of colored yarn involved is less than about 15 per cent of the total. This is sometimes referred to as direct warping.

(b) Section warping is used for short runs, especially of fancy patterned fabrics where the amount of colored yarn is greater than about 15 per cent of the total. Ihe broad principle: of this type of warping is shown in Figure 12.3 This is sometimes referred to as indirect warping or pattern warping.

12.5 SLASHING OR WARP SIZING

The process of weaving necessitates keeping the warp threads under considerable tension and subjects them to the abrasive action of the heddles and other moving parts of the loom. This is especially true where tightly woven, firm cotton cloths are being woven on modem high-speed looms. To prevent excessive warp breakage under these conditions and insure maximum production, the warp threads are sized. This operation, frequently called slashing, consists of coating the warp yarns with a smooth, tough film whose chief ingredient is starch.

12.5.1 Object

It is necessary to size the warp yam for several reasons, namely: • To strengthen the yarn by causing the fibres to adhere together: • To make the outer surface of the yam smoother so that hairs protruding from one yarn in the warp should not become entangled with hairs protruding from a neighboring yam; • To lubricate the yarns so that there is less friction when they rub together in the weaving process.

12.5.2 Reasons for Sizing

The primary purposes of sizing are to increase loom production and reduce warp breaks. Other objectives in some cases include adding to the weight of the goods and giving the proper feel. These are of importance when the goods are sold in the grey or loom state. Ease of removal may have considerable influence on the size mix used because, when the material is dyed, bleached or given a special finish after weaving the size must be removed by a desizing operation.

To give good abrasion resistance and protect the fibers, it is essential that the size bind the fibers together and prevent individual fibers from sticking out of the yarn. Thus, a properly sized warp will have a smooth appearance in marked contrast to the fuzzy, hairy appearance of the usual unsized yarns. Thus laying of the fibers also serves to cover up certain yarn defects such as corkscrews and nebs. The starch films must penetrate the yarns sufficiently to hold the outer fibers together in a smooth film, but most not penetrate the yarn too much or it will the flexibility and make the yarn stiff and brittle.

150 B.Sc. CDF – Fibre to Fabric

12.5.3 Sizing

The various parts of the modern slasher are: • The warp magazine creel. • The size box with stretch level and temperature control. • The cylinder dryer, enclosure and air exhaust. • The split rods, measuring clock and expansion comb. • The beaming end and press roll.

Fig 12.3

Creels

Three types of creels are in use in sizing, namely (a) The upright creel, (b) The horizontal creel and (c) The new magazine creel.

The upright creel saves floor space, because it permits the vertical stacking of the back beams one above the other. The horizontal creel allows for the placement of the back beams one behind the other, horizontally and at a low level, allowing the operator to get at them easily. If different width beams are used, the widest beam is placed nearest the slasher and the narrowest in back.

The magazine creel is a new development and its assembly consists of two identical creels, mounted on trucks riding on metal tracks. The empty or used- up creel and its 12 to 16 beam are pushed to one side and the Bill, prepared magazine creel is pushed into position behind the size box.

Stretch Control Assembly

Back of the size boxes is the stretch control assembly consisting of a 4-inch diameter measuring and drawl roll and a 9-inch diameter stretch control roll (cloth covered) and a 4-inch diameter press roll. This group of rolls draws the

151 B.Sc. CDF – Fibre to Fabric

warp yarn from all section beams to the first size box. The large arc of contact of the cloth-covered draw roll exerts a through grip on the entering warp yarns and equalizes the tension of the yarn sheets drawn from different section beams. By means of change gears, the stretch control can be set to produce and maintain a definite amount of stretch, usually from 1.5 to 2.25 per cent.

Size Boxes

The size boxes, of which there are two in the latest slashers, are built of heavy copper or Monel metal. steam jacketed and strongly braced at all points. One is used for the top sheet of yarn, the other for the lower; these are kept separate and then combined at the third or drying cylinder. Each vat or box contains a ribbed or solid immersion roll which can be raised or lowered, and two 9-inch heavy copper size rolls mounted in tightly sealed anti-friction bearings. The squeeze rolls are made of cast iron and covered with sheeting, slasher felt or rubber, as required.

The position, air cylinder and valve assembly on the squeeze rolls in a new and valuable improvement which reflects in more uniform size penetration, more even drying and less shedding in weaving. It has three distinct advantages: 1) It increases the pressure far in excess of the pressure due to gravity, 2) It raises and lowers the rolls for washing purposes and 3) It reverses the roll positions to improve the uniformity of the size application and increase the life of the roll coverings.

The temperature of size box is controlled by regulating the admission of steam into the box or its steam jacket by means of an air-operated temperature recorder and a diaphragm steam valve.

Dryers

Four 5-foot cylinders are used and threaded up as shown in Figure 12.3. The cocker slasher is a multi-cylinder machine (23 or 30 in diameter cylinders), employing as many as five, seven or nine cylinders. All drying cylinders are equipped with automatic pressure and vacuum relief safety valves. The drainage of the steam condensate within the cylinder is affected by a bucker system which, after collecting the condensate, discharges it’s through a joint, which is self-sealing, leak-proof.

Drive

The beam is friction driven, regulated by a hand wheel or, as in the case of a press roll and automatic tension device connected to the hydraulic control used to adjust the cone discs within the Reeves drive. When the loom beam is starting, the press roll is in the high position and, as the beam fills, the press roll assumes lower positions.

152 B.Sc. CDF – Fibre to Fabric

Doffing

When the beam is full, the friction clutch is disengaged and slows down the beam, produces a slight tension on the wasp while being doffed, and an empty beam is put in place.

12.6 LET US SUM UP

In many cases the first textile operation is the preparation of the lengthwise ends system (warped or beamed yarns) of the textile structure by warping or beaming operations. There are several basic methods to produce beamed yarns/strands

The first method used mostly for the direct warping: a large and predetermined number of ends pulled from a creel are wound onto a large spool (beam) placed onto a warper to produce section beams.

Another method is sizing: a predetermined number of ends pulled from a creel are directly slashed and wound onto a beam. Then the slashed beams to produce the loom beams.

12.7 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Visit any one sizing unit and analyze the process details. • Go through the journals and magazine and see the development of winding machines and its automations. • Find the capacity of creel in warping and sizing.

12.8 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Development of winding machines and its automations. • Capacity of creel in warping and sizing. • The importance sizing in looming process.

12.9 CHECK YOUR PROGRESS

1. Write the object of sizing and its necessity. • To strengthen the yarn by causing the fibres to adhere together: • To make the outer surface of the yam smoother so that hairs protruding from one yarn in the warp should not become entangled with hairs protruding from a neighboring yam; • Purposes of sizing are to increase loom production and reduce warp breaks.

153 B.Sc. CDF – Fibre to Fabric

12.10 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Watson’s Textile Design and colour, Grosichkli.Z. Newness Butter, orths,London, 1980.

154 B.Sc. CDF – Fibre to Fabric

LESSON-13

DRAWING –IN & WEFT PREPARATION

CONTENT 13.0 AIM AND OBJECTIVES 13.1 INTRODUCTION 13.2 DRAWING-IN AND TYING-IN 13.2.1 Drawing-in 13.2.2 The Reed Plan or Denting-In 13.2.3 Tying-in 13.3 WEFT PREPARATION 13.3.1 Flow of operation 13.3.2 Object 13.3.3 Conditioning of Filling 13.3.4 Working of warp winding machine 13.4 LET US SUM UP 13.5 LESSON END ACTIVITIES 13.6 POINTS FOR DISCUSSION 13.7 CHECK YOUR PROGRESS 13.8 REFERENCES

13.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • The process of drawing and its type • The arrangement of the warp ends in the reed dents • Warp Tying-in and its types • Weft yarn preparations and machine

13.1 INTRODUCTION

The earliest looms, from the 5th millennium BC, consisted of bars or beams forming a frame to hold a number of parallel threads in two alternating sets. By raising one set of these threads (which together formed the warp), it was possible to run a cross thread (a weft, or filling) between them. A shuttle carried the filling strand through the warp.

155 B.Sc. CDF – Fibre to Fabric

Modern looms are of two types, those with a shuttle (the part that carries the weft through the shed) and those without; the latter draw the weft from a stationary supply.

13.2 DRAWING-IN AND TYING-IN

13.2.1 Drawing-in

This is the process of drawing every warp end through its drop wire, heddle eye and dent as shown in Figure 13.1 Drawing-in can be performed manually or by means of automatic machines.

Fig 13.1

Manual Drawing-in

The warp beam is taken from the slashing room to the drawing-in area, where there are frames on which the drop wires, harness frames and reed are supported in the order in which they are found on the loom.

A length of warp yarn, just enough to each to the other side of the frame, is unwound. Leasing of the warp at this stage simplifies separation of the yarns. In normal practice, two operations sit facing each other across the frame and the operator facing the reed (the drawer-in) passes a hooked needle through the heddle eyes and drop wines. The needle hook is then exposed to the second operator (the reacher-in) on the other side of the frame; the reacher-in selects the correct yarn in its proper order and puts it on the hook so that when the needle is pulled out the yarn is threaded through the two loom parts. This is done according to a plan known as the drawing-in draft. The yarns are then threaded through the reed dents as required by the denting plan or reed plan.

156 B.Sc. CDF – Fibre to Fabric

Machine Drawing-in

Hand drawing-in is a time consuming operation, and it has been made fully automatic. There are two systems available, namely: • Three machines each performing a single operation; a wire-pinning machine, a drawing-in machine and a reed-denting machine. • One machine for drawing the warp through all the elements.

The machine used in these process employ a pattern chain to control a selector finger which selects the warp treads separately and delivers them to a hook which draws them through the required element. The machines are very expensive and require a special type and shape of heddle. Accessories are needed to facilitate the preparation of the machine for drawing-in. Examples include a pattern punching machine and a heddle counter to determine the number of heddles required on every harness frame. A certain level of efficiency and continuous use of equipment are necessary if the use of such machines is to be economically justification able. A modern warp drawing machine may be able to handle some 6000 ends per hour, but the speed achieved is dependent on the specific conditions. Machines are available to deal with one or two warps, flat or leased, and with different widths.

13.2.2 The Reed Plan or Denting-In

The reed plan indicates the arrangement of the warp ends in the reed dents. It is general practice to draw more than one warp end in a reed dent. This allows the use of reasonable wire dimensions and number. Normally 2 ends/dent for the body of the fabric and 4 ends/dent tot the selvage is a reasonable combination However, in many cases, 3 or 4 ends/dent are used. The reed plan can be either regular or irregular depending on whether or not the same number of ends per dent is used regularly across the width of the body of the ware. Some designs require the use of different numbers of ends per dent in the body of the fabric to produce certain effects in the fabric.

13.2.3 Tying-in

Tying-in used when a fabric is being mass produced. The tail end of the warp from the exhausted warp beam is tied to the beginning of the new warp. Two types of machine are used: 1. Stationary machines. The tying-in takes place in a separate room away from the loom. 2. Probable machines. These are used at the loom.

Stationary machines have the disadvantage that they necessitate moving the exhausted beam and all its part from the loom and taking it to and from the tying-in department. However, they have the disadvantage of permitting maintenance of the loom to be carried out.

157 B.Sc. CDF – Fibre to Fabric

The time taken to tie-in a complete depends mostly upon the total number of ends in that warp, but it is also affect by secondary factors which tend to retard productivity. For example, a color stripe must be tied in proper register and the operator will have to stop tying if there has been a broken end in order to adjust the machine to give proper register. The count and type of yarn (together with the reed and heddle details) determine the type of knot to be used and this affects the rate of knotting. Also the nature of the yarn can affect the breakage rate during knotting, and thus influence the total time needed for tying-in.

The capacity of warp-tying machines has remained unchanged for years. A capacity of about 600 knots/min appears to be the maximum. The machine can deal with flat warp or leased warp and with a warp width of about 5 yd. The sequence of operations is normally as follows: • The machine selects the warp ends from the new beam. • It selects the corresponding end from the old beam. • It ties the two ends together and moves to the next.

Following the tying-in process, all knots are pulled through to the cloth roller, the drop wires heddles and reed; the loom is now ready for operation.

13.3 WEFT PREPARATION

Staple yarns are commonly rewound after spinning to permit the removal of faults and to provide package sizes suited to the machines available. Filament yarn is not spun of on a spinning frame as used for staple yarns. It may be received in the form of packages known as tubes, cops, cones, cakes, or cheeses which can vary greatly in size. Hence it is necessary to rewind the yarn onto pirn of the required size.

Fig 13.2

Pirn winding is usually carried out on automatic pirn or semi automatic pirn winders. These machines are automatic in the sense that when a pirn is filled with yarn, an automatic device stops the rotation of the spindle, the full pirn is ejected, a new empty pirn is automatically place on the spindle and winding recommences to continue until the pirn is full, when the cycle is repeated.

158 B.Sc. CDF – Fibre to Fabric

13.3.1 Flow of operation

13.3.2 Object

• Removal of slubs and weak places during processing which otherwise would impair the running of the loom. • The production of tighter packages having more yards per pirn. This reduces the number of pirn changes in the loom. • Greater uniformity of pirn used on the loom. This improves the uniformity of the fabric.

13.3.3 Conditioning of Filling

This process is the same whether pirn are made on spinning or twister frames, or wound on a pirn It involves the wetting or steaming of the filling yarn to stabilize it so that it will weave satisfactorily. An unconditioned yarn is usually "lively"; if allowed to go slack, it will snarl as shown in Figure 13.3

Fig 13.3 Yarn Snarl

159 B.Sc. CDF – Fibre to Fabric

13.3.4 Working of warp winding machine

The supply package in the form of a cone is mounted in an inverted position at the top of the machine.

Magazine

A circular magazine accommodates a large number of empty pirns and can feed the empty pirn to the winding position if required. This is effected by means of a chute mechanism and empty pirn carrier. Here the operator has to arrange the empty pirns on the circular magazine.

Tensioner

The material from the cone is passed through a twin disc type tensioner. Two discs are arranged together by means of a pressure plate with a knob. The knob is graduated from 0 to 9. The tension on the yarn is adjusted by rotating the knob.For finer counts, the tension on the yarn is more and for coarser counts the tension on the yarn is less. Higher the dial reading more is the tension and vice-versa.

Stop motion

The yarn is then passed over a broken thread stop motion wire which stops the unit whenever end breaks or the supply package exhausts.The operator has to take the ends form the cone and pirn and has to tie the ends by means of a hand knotter.

Thread guide

Then the material is passed a thread guide which acts as a traverse guide and finally on to the pirn is axially in between two holders, one at the base and one at the tip. This arrangement eliminates the vibration of the pirns. Winding is carried out by rotating the pirn and traversing is carried out by the traverse guide. The traverse guide whose driving end is situated inside on oil tight box, itself for varying lengths of traverse by the lifting a bar situated at the front of the machine. The yarn leaving the traverse guide goes to the pirn on which it is finally wound.

Doffing

The majority of high speed pirn winders is built and works on the unit principles. The work involved in doffing the full pirns replacing it by an empty pirn and restarting are carried out automatically and systematically.

Electric power

All the units are driven by an electric motor. But this motor does not interface with individual units. Each unit receives its motion through a friction disc. Stopped pulley drive to pirns enables easy adjust in speeds when the count is changed.

160 B.Sc. CDF – Fibre to Fabric

Feeler arrangement

A feeler arrangement controls the diameter of the pirn by a set screw adjustment. After attaining the predetermined diameter, the feeler wheel assembly mechanically moves forward towards the tip of the pirn, with the revolving winding pirn and so traversing is carried throughout the surface of the pirn. Further the machine is equipped with an adjustable bunch building motion.

Pirn building

To prevent sloughing off pirns in the shuttle during weaving an attachment enables a differential binding and coiling of yarn and there by locks the yarn at the nose of the pirn during its building up.

An oscillating fan is placed over the machine to prevent accumulation of fluffs etc.

13.4 LET US SUM UP

Weaving is an ancient textile art and craft that involves placing two sets of threads or yarn called the warp and weft of the loom and turning them into cloth. In looming process we are using tying in machine. The tail end of the warp from the exhausted warp beam is tied to the beginning of the new warp.

13.5 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Visit any one weaving unit and analyze the process details of pirn winding. • Go through the journals and magazine and see the development of weft winding machines and its automations.

13.6 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Development of weft winding machines and its automations. • Analyze the various types knotting machine and its working.

13.7 CHECK YOUR PROGRESS

1. Define drawing-in and denting-in

Drawing-in This is the process of drawing every warp end through its drop wire, healed eye.

161 B.Sc. CDF – Fibre to Fabric

Denting-In

The reed plan indicates the arrangement of the warp ends in the reed dents.

2. Illustrate the object of weft winding. • Cones or Cheeses are converted as pirn for the suitable package of shuttle. • During the removal of slubs and weak places during processing which otherwise would impair the running of the loom. • The production of tighter packages having more yards per pirn. This reduces the number of pirn changes in the loom. • Greater uniformity of pirn used on the loom. This improves the uniformity of the fabric.

13.8 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Watson’s Textile Design and colour, Grosichkli.Z. Newness Butter, Worths,London, 1980.

162 B.Sc. CDF – Fibre to Fabric

LESSON-14 LOOMING

CONTENT 14.0 AIM AND OBJECTIVES 14.1 INTRODUCTION 14.2 LOOM 14.2.1 Classification of loom 14.2.2 The fundamental parts 14.2.3 Basic Mechanisms 14.2.4 Passage of material through loom 14.3 PRIMARY MOTIONS IN WEAVING 14.3.1 Shedding 14.3.2 Picking 14.3.2.1 Shuttle 14.3.3 Beating-up 14.3.3.1 Reed 14.4 SECONDARY MOTION 14.4.1 Take-up motion 14.4.2 Left-off motion 14.5 OTHER LOOM MECHANISMS 14.6 LET US SUM UP 14.7 LESSON END ACTIVITIES 14.8 POINTS FOR DISCUSSION 14.9 CHECK YOUR PROGRESS 14.10 REFERENCES

14.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • To know the functions and parts of a loom. • The mechanisms involved to manufacture a fabric. • Basic principle and concept of using the mechanisms in looming operations.

163 B.Sc. CDF – Fibre to Fabric

14.1 INTRODUCTION

Production of fabric by interlacing two sets of yarns so that they cross each other, normally at right angles, usually accomplished with a hand- or power- operated loom. In weaving, lengthwise yarns are called warp and crosswise yarns are called weft, or filling. Most woven fabrics are made with their outer edges finished in a manner that avoids raveling (because the weft yarn turns around instead of ending in a cut end). These edges, called selvages, run lengthwise, parallel to the warp yarns.

14.2 LOOM

A loom is a machine or device for weaving thread or yarn into textiles. In practice, the basic purpose of any loom is to hold the warp threads under tension to facilitate the interweaving of the weft threads. The precise shape of the loom and its mechanics may vary, but the basic function is the same.

14.2.1 Classification of loom

So far, only looms using a weft-carrying shuttle have been considered. These looms have a wide degree of versatility and fall into four main classes: 1. Hand looms: still used in relatively large quantities for the production of all types of fabrics in the less-developed countries, but also used in the United Kingdom for the production of certain classic brocades, tapestries, and tweeds; 2. Non-automatic power looms; these machines are being used in ever- decreasing numbers, especially in the developed countries, but they seem likely to retain a certain usefulness in the production of specialist fabrics, such as industrial fabrics woven from heavy coarse wefts on wide looms; 3. Conventional automatic looms: machines that have gained world-wide popularity because of their advantages of versatility and relative cheapness; and 4. Circular looms; strictly limited in their application (i.e., tubular fabrics for hose-pipes and sacks), but they do achieve the ideal of high wefi-insertion rates from relatively low shuttle speeds because insertion of the weft is continuous.

164 B.Sc. CDF – Fibre to Fabric

14.2.2 The fundamental parts

Fig 14.1

The fundamental parts of all looms are the warp beam, a cylinder on which the warp threads are wound; heddles (rods or cords), each with an eye through which is drawn a warp thread; the harness, a rectangular frame set with a series of heddles operated to form a shed between the warp threads for the insertion of the weft threads; the reed, a comb like frame that pushes the filling yarn firmly against the finished cloth after each pick, or row; the breast beam, over which the cloth is wound creating a tension with the warp beam; the cloth beam, on which the cloth is rolled as it is constructed; and the shuttle, if it is not a shuttle less loom.

14.2.3 Basic Mechanisms

In order to interlace warp and weft threads to produce fabric on any type of weaving machine, three operations are necessary: 1. Shedding: separating the warp threads, which run down the fabric, into two layers to form a tunnel known as the shed. 2. Picking: passing the weft thread, which traverses across the fabric, through the shed; and 3. Beating-up: pushing the newly inserted length of weft, known as the pick, into the already woven fabric at a point known as the fell.

These three operations are often called the primary motions of weaving and must occur in a given sequence, but their precise timing in relation to one another is also of extreme importance and will be considered in detail later.

Two additional operations are essential if weaving is to be continuous:

1. Warp control (or let-off): this motion delivers warp to the weaving area at the required rate and at a suitable constant tension by unwinding if from a flanged tube known as the weaver's beam; and

165 B.Sc. CDF – Fibre to Fabric

2. Cloth control (or take-up): this motion withdraws fabrics from the weaving area at the constant rate that will give the required pick-spacing and then winds it onto a roller.

In order to give some reality to these generalities, the diagram in Fig14.2 shows the passage of the warp through a loom.

14.2.4 Passage of material through loom

The yarn from the warp beam passes round the back rest and comes forward through the drop wires of the warp stop-motion to the heads, which are responsible for separating the ware sheet for the purpose of shed formation. It then passes through the reed, which olds the threads at uniform spacing and is also responsible for beating-up the weft thread that has been left in the triangular warp shed formed by the two warp sheets and the reed. Temples hold the cloth form at the fell to assist in the formation of a uniform fabric, which then passes over the front rest, round the take-up roller, and onto the cloth roller.

The mechanisms of a power-driven loom receive their motion from shafts that traverse from side to side in the loom and are driven from a motor. Their relative speeds are of importance since they govern the mechanism that they drive.

Fig 14.2

166 B.Sc. CDF – Fibre to Fabric

14.3 PRIMARY MOTIONS IN WEAVING

Thus, it is apparent that there are three primary motions on all cotton looms: 1) The dividing of the warp ends into two groups, known as shedding, 2) The passage of the shuttle containing the filling through this opening across the cloth, known as picking, and 3) The pushing of the loose filling pick up next to the previous filling pick to form the cloth, known as beating-up.

14.3.1 Shedding

A simple cam-shedding motion is illustrated in Fig14.1 One of the two cams mounted on the bottom shaft depresses a bowl and treadle. The treadle is fulcrummed towards the back of the loom so that its front end will move down and pull its corresponding healds shaft (Fig 14.3) down because they are joined by a series of connections. Further connections above the heald shafts cause the roller motion to rotate partially so that the other heald shaft and its treadle will be raised. As the cam unit continues to rotate, the second cam will cause the whole motion to be reversed.

Fig 14.3

In weaving plain-weave fabrics, only two heald shafts are theoretically needed, the odd ends being drawn through the eyes of the healds on one heald shaft and the even ends being drawn through the eyes of the other shaft.

14.3.2 Picking

It has already been mentioned that the two picking mechanisms operate on alternate picks. The cams that activate them are mounted on the bottom shaft of the loom and are set at 180° to one another.

As the cam rotates it will eventually push a bowl attached to the back end of the picking shaft in an upward direction. The partial rotation that this movement

167 B.Sc. CDF – Fibre to Fabric

gives to the picking shaft will create a sharp inward movement of the lugs straps, which are wrapped round the picking sick at their outer end. Since the picking stick is fulcrummed at its lower end. then the upper end will move quickly inwards, and the picker mounted near to the top of the stick will project the shuttle across the loom.

14.3.2.1 Shuttle

Fig 14.4 The shuttle (Fig14.4) is a rectangular piece of wood, tapered at each end to a point so that entry into a partly opened shed is easier and more accurate. The main body of the shuttle is hollowed out to accommodate the package known as the pirn, which contains the weft yarn. The insides of the walls of the shuttle are lined with fur, bristles, or loops to control the yarn as it unwinds from the pirn.

There is a clamp arrangement at one end of the shuttle to hold the pirn steady during weaving (or alternatively the pirn is mounted on a spindle), and at the other end of the shuttle there is a unit known as the shuttle eye, in which there is a arrangement to control the weaving tension of the weft thread as it is delivered from the shuttle. A groove along the front wall of the shuttle prevents the weft from being trapped between the shuttle and the shuttle-box front, and a second groove along the base reduces abrasion by the shuttle on the bottom warp sheet as it traverses the loom from one box to the other.

14.3.3 Beating-up

The sley must reciprocate for the reed to push the weft into the fell of the cloth, and the two sley swords therefore extend down from the race board to a fulcrum point known as the rocking shaft.A connecting rod (crank arm) is connected to the back of each of the two sley swords by a pin (sword pin) just below the level of the race board, and its other end fastens round the bend in the crankshaft, which is known as the crank. As the crankshaft rotates, the crank arm and thus the top end of the sley are made to reciprocate with a movement that approximates to simple harmonic motion.

168 B.Sc. CDF – Fibre to Fabric

14.3.3.1 Reed

Fig 14.5 The reed (Fig14.5) is a closed comb of flat metal strips, which are uniformly spaced at intervals corresponding to the required spacing of the warp ends. The top and bottom baulks of the reed, which close the comb, can be made of wood wrapped with string and set in pitch (pitch-baulk reed) to produce a cheaper product, or alternatively the wire may be soldered in position on a metal bar (all- metal reed) to produce a unit of much greater accuracy. The spaces between the metal strips through which the ends pass are known as dents. The main functions of the reed are to hold the warp threads at uniform spacing and to beat-up the newly picks of weft in addition to supporting the shuttle during its traverse of the loom.

14.4 SECONDARY MOTION

In addition to these three primary motions, there are two secondary or contributing motions, the left-off motion, by which warp yarn is fed into the loom std. the take-up motion, which controls the rate at which the completed cloth is taken away by the sand roll

14.4.1 Take-up motion (Fig 14.6)

Strict control of the rate of cloth withdrawal from the fell is essential if uniform pick-spacing and thus regular cloth appearances are to be achieved, and for this purpose a take-up motion is incorporated.

169 B.Sc. CDF – Fibre to Fabric

Fig 14.6 Cloth wind up systems

14.4.2 Left-off motion (Fig 14.7)

Uniform tension in the warp sheet is essential during weaving, and this is achieved by controlling the rate at which the warp beam is allowed to rotate by the let-off motion.

Fig 14.7

14.5 OTHER LOOM MECHANISMS

A series of other mechanisms is used in the interests of productivity and quality. The warp-protector motion will stop the loom to prevent excessive damage to the warp threads, cloth and reed if a shuffle becomes trapped between the top and bottom shed lines and the reed by failing to complete its traverse. Warp and weft stop-motions will stop the loom almost immediately a warp end or a weft breaks. Automatic replacement of the weft package in the shuffle, when almost all the _yarn on the pirn has been used up, is achieved with the aid of a detecting-feeler motion and a bobbin or shuttle-transfer mechanism. Furthermore, it is possible to vary the weft being inserted by having more than one shuttle-box in a unit at the end of the sley. The shuttle in each shuttle-box may contain a weft of different colour or character, and the appropriate shuttle-box is positioned opposite the race board just before insertion of the pick.

170 B.Sc. CDF – Fibre to Fabric

14.6 LET US SUM UP

The weaving machine or loom provides the means to interlace warped and filling yarns according to a weave pattern to form a fabric structure. • The yarn’s system in the fabric is in a lengthwise direction and is referred to as the warp. It is supplied to the weaving machine on a loom beam. Warped yarns are often called ends. • The yarns crossing the warp are referred to as weft or filling. On the new loom generation; they are inserted in the fabric by means of weft feeder allowing a regular unwinding.

The weaving process is made of 5 basic mechanisms:

Mechanism 1: The let-off motion distributes the warp to the loom. Mechanism 2: A warp shedding mechanism moves the warped yarn up and down according to the weave pattern. Mechanism 3: A filling insertion system introduces the filling between the openings of the warped yarns (also called shed) carried out by the shedding mechanism. Filling glass products are basically inserted with modern picking system:

• Air jet. • Water jet • Rapier • Projectiles • Needle (loom for narrow fabrics). Mechanism 4: A read moved by the beat up motion beats the filling between the warped yarns against the fabric in formation. Mechanism 5: A fabric take-up regulates the filling density and the woven fabric is wound on a tube on the loom or with a separate winding device. All of these motions must be synchronized, so that they work in harmony if looms of any type are to function properly.

14.7 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Visit any one weaving unit and the passage of material through a loom. • Find the working principles of different mechanisms used in looming operation. • Go through the journals and magazine and see the development of weaving machines and its automations.

171 B.Sc. CDF – Fibre to Fabric

14.8 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Development of weaving machines and its automations. • Difference between shuttle loom with shuttle less loom. • Working principles of different mechanisms used in looming operation.

14.9 CHECK YOUR PROGRESS

1. The Mechanisms used in looming process: • Shedding: separating the warp threads, which run down the fabric, into two layers to form a tunnel known as the shed. • Picking: passing the weft thread, which traverses across the fabric, through the shed; and • Beating-up: pushing the newly inserted length of weft, known as the pick, into the already woven fabric at a point known as the fell. • Let-off : this motion delivers warp to the weaving area at the required rate and at a suitable constant tension. • Take-up: this motion withdraws fabrics from the weaving area at the constant rate.

2. Draw a loom with yarn passage and indicate different weft insertion systems.

172 B.Sc. CDF – Fibre to Fabric

3. Write short on weaving.

Weaving: The process of interlacing one or more sets of yarns at right angles on a loom. a. Warp yarns: Yarns that run lengthwise in woven fabric. b. Weft yarns: Yarns that run crosswise in woven fabric. c. Grain: The direction of the lengthwise and crosswise yarns or threads in a woven fabric. d. Bias: The diagonal grain of a fabric. The bias provides the greatest “give” or stretch in the fabric.

14.10 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Watson’s Textile Design and colour, Grosichkli.Z. Newness Butter, Worths,London, 1980.

173 B.Sc. CDF – Fibre to Fabric

LESSON-15 WOVEN FABRIC BASIC DESIGN

CONTENT 15.1 AIM AND OBJECTIVES 15.2 INTRODUCTION 15.2.1 Weave representation 15.3 BASIC WEAVES 15.3.1 Plain weave 15.3.1.1 Ornamentation of Plain Cloth 15.3.1.2 Variations of the Plain Weave 15.3.2 Twill Weave 15.3.3 Satin and Sateen Weaves 15.4 LET US SUM UP 15.5 LESSON END ACTIVITIES 15.6 POINTS FOR DISCUSSION 15.7 CHECK YOUR PROGRESS 15.8 REFERENCES

15.1 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • Woven fabrics weave or structure. • The warp and filling are interlaced. • The three fundamental basic weaves.

15.2 INTRODUCTION

Woven fabrics are classified as to weave or structure according to the manner in which warp and weft cross each other. The three fundamental weaves, of which others are variations, are the plain, twill, and satin.

174 B.Sc. CDF – Fibre to Fabric

15.2.1 Weave representation

The fabric weave or design is the manner in which the warp and filling are interlaced. The pattern or repeat is the smallest unit of the weave which when repeated will produce the design required in the fabric. There are many ways of representing a weave, a most familiar method being to use square design paper. The use of thread diagrams and cross-sections is another effective method of representation.

On the design paper, the vertical rows of squares represent warp ends and the horizontal rows of squares represent filling picks. A mark in a small square indicates that at this particular intersection, the warp end is shown of the face of the fabric with the pick beneath. It is normal to use a filled in square to indicate that the end is over the pick and a blank square to indicate that the pick is over the end.

15.3 BASIC WEAVES

Three basic weaves are, 1. Plain, 2. Twill, and 3. Satin.

15.3.1 Plain weave

In plain weave the warp and weft are aligned so that they form a simple criss- cross pattern. Each weft thread crosses the warp threads by going over one, then under the next, and so on. The next weft thread goes under the warp threads that its neighbor went over, and vice versa. Plain weave is also known as "tabby weave" or "taffeta weave."

From fig15.1 it can be seen that the plain weave repeats on 2 ends x 2 picks. Plain fabric comprises a high percentage of the total production of woven fabrics and it can be produced on a loom with 2 harnesses. It has the highest number of interlacing as compared with other weaves and therefore it produces the finest fabrics.

175 B.Sc. CDF – Fibre to Fabric

Fig 15.1

15.3.1.1 Ornamentation of Plain Cloth

The appearance of a plain fabric can be changed in many ways, which can be summarized as follows:

1. The use of color

In the warp direction color stripes are produced along the length of the fabric; in the filling direction, color stripes are produced across the width of the fabric. We used in both warp and filling directions a check effect is produced.

2. Changing Yarn and Fabric Counts

Stripes and check effects can be produced by using different fabric count or yam count in one or both directions. Also rib effects can be produced by using different yarn counts and different tensions.

3. Changing the Yarn Twist

Using combinations of different twist levels and directions in the warp or filling (or both warp and filling), different effects can be produced in the fabric due to the changes in orientation of the fibers. Also different amounts of twist produce different shrinkage characteristics in different parts of the fabric and so change the appearance.

4. Different Finishing Techniques Treatments such as dyeing, mercerizing with caustic soda or coating can change the characteristics of the plain fabric.

15.3.1.2 Variations of the Plain Weave

Some fabrics are considered to be derivatives of the plain weave. These are, in effect, extensions of the simple interlacing and, like plain weave; they can be produced on a loom with two harnesses.

1. Warp Rib Weave

In this the extension of the plain weave is in the warm drection, as shown by Figure 15.2; the warp weaves in the same order as in the plain fabric, namely, every two adjacent ends weave opposite to each other.

176 B.Sc. CDF – Fibre to Fabric

Fig 15.2 2. Filling Rib Weave

Fig 15.3 In this case groups of ends are woven with each group in direct opposition to the adjacent groups. The repeat is always on 2 picks x any number of ends as shown in Figure 15.3. The ribs produced in the fabric run in the direction of the warp. It is usual to use coarse warp and fine filling to emphasize the rib. The fabrics are normally stronger than the plain fabrics because of the low crimp level.

3. Basket Weave (Matt Weave)

In this weave the extension is made in both directions so that groups of ends and picks are woven in the same way as single ends and picks are woven in the plain weave. The weave is denoted in the manner used for rib weaves, i.e. as 2 up 2 down basket or 2 x 2 baskets in Figure 15.4.

Fig 15.4

177 B.Sc. CDF – Fibre to Fabric

15.3.2 Twill Weave

It is made by passing the weft threads over one warp thread and then under two or more warp threads, over one and under two or more, and so on, with a "step" or offset between rows that creates the characteristic diagonal pattern. Because of this structure, twills generally drape well. Examples of twill fabric are chino, denim, gabardine, tweed and serge.

Twill Weave, the second basic weave, is characterized by diagonal lines running at angles varying between 15° and 75°. A twill weave is denoted by using numbers above and below a line (such as 2 up 1 down twill). At Figure 15.5 the 2 up 1 down twilll and the Figure 15.6 the 1 up 2 down Will are shown; these represent the smallest possible repeat of twill weaves, and one is the opposite side of the other. The repeat is always on a number of ends and picks equal to the addition of the two numbers above and below the line denoting the weave. A 2 up 1 down twill or a 1 up 2 down twill repeats on 3 ends x 3 picks. If the number above the line is greater than the number below the line, the weave is known as warp face twill. If the opposite is true, it is filling face twill. There is a third alternative in which the number of above and below the line are equal (such as 2 up 1 down twill); this is called balanced twill. Most twill fabrics are made with warp face weaves

Fig 15.5

Fig 15.6

The twill weave is always given a direction; a right-hand twill is one in which the twill line runs from bottom left to top right and a left-hand twill is one in which the twill line runs from bottom right to top left. The angle of the twill is

178 B.Sc. CDF – Fibre to Fabric

determined by the amount of shift in the points of interlacing. A twill weave when has more than one pick shift and one end shift is called steep twill; if the shift is more than one end and one pick it is called a reclining twill. A steep twill will have twill angles more than 45° and a reclining twill have angles less than 45° as shown in Fig15.6. However, the angle of the twill line in the fabric depends on the number of picks and ends/in. in the fabric. A 45° twill woven with the same yarn in warp and filling,

Fig 15.6 15.3.3 Satin and Sateen Weaves

This is the third basic weave, in which the interlacing points are arranged in a similar way to twill weaves but without showing the twill line. The satin weave is a warp face weave and the sateen is a filling face weave. Sateen are sometimes called filling satins weave. Figure 15.7 shows a 5-ends (or 5 harness) satin and Figure 15.8 shows 5-end sateen. In this case, the repeat is on 5 ends x 5 picks and it is clear that one design is the backside of the other. There are two different ways of arranging the interlacing points, one by using a counter (or move number) of 2 picks and the second by using 3 picks as counter. It can be seen that in warp face satin the ends float over all the picks but one in the repeat. The interlacing can be arranged to be in the right-hand direction or in the left- hand direction as shown in Figure 4.7(b).For every number of ends and picks in the repeat there is more than one arrangement for the interlacing points.

Fig 15.7

179 B.Sc. CDF – Fibre to Fabric

Fig 15.8

Although the satin weave is the backside of the sateen weave produced on the same number of harnesses, it is not tine to say that the fabric produced as a satin can be used as sateen. This is mainly because for a satin fabric to be smooth and lustrous, the ends/inch must be higher than the picks/in., but the opposite is true for sateen fabrics. The sateen fabrics we normally softer and more lustrous than satins, but satins are usually stronger than lateens. In both fabrics, if a heavy construction of filament yarns is used, the fabric tends to be stiff and does not drape easily. However, the length of the float can balance the effect of the construction, but longer floats have disadvantages in that they have an adverse effect on fabric serviceability. Long float satins and lateens are useful in jacquard designing or in combination with other weaves, bur are rarely used elsewhere.

15.4 LET US SUM UP

Weaving is an ancient textile art and craft that involves placing two sets of threads or yarn called the warp and weft of the loom and turning them into cloth. This cloth can be plain (in one color or a simple pattern), or it can be woven in decorative or artistic designs,

The three basic weaves are plain or tabby (weft threads go over one warp thread, then under one), twill, and satin. Fancy weaves, such as pile, Jacquard, dobby, and leno, require more complicated looms or special loom attachments.

15.5 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Draw the three basic weaves in different repeat size. • By using the basic steps of ornamentation of plain weave, create different types of plain weave. • Design a 10 x 10 satin or sateen with different move number.

180 B.Sc. CDF – Fibre to Fabric

15.6 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Give the possibility of creating 8 x 8 satin or sateen with different move number. • Create different types of plain weave by using its derivatives • What repeat size?

15.7 CHECK YOUR PROGRESS 1. What are all basic weaves?

Three basic weaves are, • Plain, • Twill, and • Satin.

2. Define twill weave.

Twill Weave, the second basic weave, is characterized by diagonal lines. The twill weave is always given a direction; a right-hand twill is one in which the twill line runs from bottom left to top right and a left-hand twill is one in which the twill line runs from bottom right to top left.

3. Illustrate the common weaves

Common weaves

(1) Plain weave: The simplest weave in which the weft (crosswise) yarn is passed over then under each warp (lengthwise) yarn. A basket weave is one variation, with the weft yarn passing over two and fewer than two warp yarns each pass. Examples: chiffon, seersucker, taffeta

(2) Twill weave: A weave in which the weft yarn is passed over and under one, two, or three warp yarns beginning one warp yarn back on each new row. Used for durability, this weave produces a diagonal design on the surface. Examples: denim, gabardine

(3) Satin weave: A weave that produces a smooth, shiny-surfaced fabric resulting from passing the weft yarn over and under numerous warp yarns to create long floats. Examples: sateen, satin

15.8 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Watson’s Textile Design and colour, Grosichkli.Z. Newness Butter, Worths,London, 1980. • Watson’s Advanced Textiel Design, Grosicki.Z. Newness butter worth, Bombay

181 B.Sc. CDF – Fibre to Fabric

LESSON-16 WOVEN FABRIC FANCY DESIGN

CONTENT 16.0 AIM AND OBJECTIVES 16.1 INTRODUCTION 16.2 PILE WEAVE 16.2.1 Warp pile 16.2.1.1 Velvet 16.2.2 Weft pile 16.2.2.1 Velveteen and Corduroys 16.3 DOUBLE CLOTH 16.3.1 Rules for Arrangement of Perfect Stitching 16.4 LENO 16.5 SWIVEL 16.6 LAPPET 16.7 DOBBY 16.8 JACQUARD 16.8.1 Types of Jacquards 16.9 LET US SUM UP 16.10 LESSON END ACTIVITIES 16.11 POINTS FOR DISCUSSION 16.12 CHECK YOUR PROGRESS 16.13 REFERENCES

16.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • Basic concept of fancy wave • Pile weave and its types • The importance and the basic principles of dobby and jacquard.

182 B.Sc. CDF – Fibre to Fabric

16.1 INTRODUCTION

The three fundamental weaves, of which others are variations, are the plain, twill, and satin. Pile fabrics have an additional set of yarns drawn over wires to form loops, and may be cut or uncut. Warp-pile fabrics include terry and plush; weft-pile, velveteen and corduroy. In double-cloth weave two cloths are woven at once, each with its warp and filling threads, and combined by interlacing some yarns or by adding a fifth set. The cloth may be made for extra warmth or strength, to permit use of a cheaper back, or to produce a different pattern or weave on each surface, e.g., steamer rugs, heavy over coating, and machine belting. Velvet is commonly woven as a double cloth. In swivel weaving, extra shuttles with a circular motion insert filling yarns to form simple decorations, such as the dots on Swiss muslin. Figure weaves are made by causing warp and weft to intersect in varied groups. Simple geometric designs may be woven on machine looms by using a cam or a dobby attachment to operate the harnesses. For curves and large figures each heddle must be separately governed. The Jacquard loom attachment permits machine weaving of the most complicated designs.

16.2 PILE WEAVE

Pile weave is a form of textile created by weaving. Pile fabrics used to be made on traditional hand weaving machines. The warp ends that are used for the formation of the pile are woven over metal rods or wires that are inserted in the shed (gap caused by raising alternate threads) during weaving. The pile ends lie in loops over the inserted rods. When a rod is extracted the pile ends remain as loops on top of the base fabric. The pile ends laying over the rod may be left as 'loop pile', or cut to form 'cut pile' or velvet.

On mechanical looms the technology of 'wire weaving' still exists, using modern technology and electronics. This weaving technique allows users to obtain both loop pile and cut pile in the same fabric. Other techniques involve the weaving of two layers of fabric on top of each other, whereby the warp ends used for the pile are inserted in such a way that they form a vertical connection between the two layers of fabric. By cutting the pile ends in between the two layers one obtains two separate pile fabrics. With this technique only the cut pile effect can be obtained. This is known as 'face-to-face weaving'. Both 'wire weaving' and 'face- to-face' weaving are used for the manufacturing of upholstery and furnishing fabrics as well as in rug making.

16.2.1 Warp pile

In warp pile fabrics the face effect is produced by raising an extra warp above the ground fabric in a series of loops. If the loops are uncut, the fabric is called terry cloth. Bath toweling is a familiar form of terry cloth. If the loops are cut and the fibers stand erect from the ground, then the pile characteristic of velvet is formed. In double shuttle looms, two fabrics are woven one over the other face

183 B.Sc. CDF – Fibre to Fabric

to face. The raised warp pile surface is formed by holding the two fabrics apart as they are woven with gauge wires and cutting the pile ends which interlace between the two fabrics. Figure 16.1 (A) and (B) illustrate cross sections of a double plush fabric before and after cutting.

Fig 16.1 (A)

Fig 16.1 (B) 16.2.1.1 Velvet

Velvet is a rich looking, fairly light weight cut pile material used chiefly for dresses, hats and trimmings. Plush is much like velvet but the pile is longer and coarser and it is usually a heavier material used for upholstery, robes and caps. Plush upholstery material is often designed so that the pile stands out as a pattern. Examine any plush upholstery material to get a general idea as to the depth and body of the pile. Silk, rayon, mohair, cotton, and combinations of these are used in weaving velvet and plush.

16.2.2 Weft pile

Fabrics are woven with an extra filling are called weft pile

16.2.2.1 Velveteen and Corduroys

These fabrics are woven with an extra filling which may be arranged 1 ground, 2 piles; 1 ground, 3 piles; or greater preparation. The ground filling weaves with the warp to form the cloth is woven to produce the raised surface. The fabric is then brushed and sheared to form the characteristic soft velvet faced surface. Plain weave, filling rib weaves, and small twill weaves are generally used for the ground interlacing. Velveteen pile weaves are based on plain and twill weaves with raisers indicated on alternate ends. Corduroy pile weaves are based on

184 B.Sc. CDF – Fibre to Fabric

plain weave on consecutive ends which may be reversed on alternate cords to form a rounded appearance. The width of the cords is varied by changing the space between the stitching points of the pile weave. Corduroys and velveteen are made of cotton or of cotton and rayon mixtures. The corduroys are warm, long wearing and comparatively inexpensive so they are widely used for boys clothing, men's suits and trousers and for coat linings where warmth is important.

16.3 DOUBLE CLOTH

Double cloth or double weave (also double cloth, double-cloth) is a type of woven textile in which two or more sets of warps and one or more sets of weft or filling yarns are interconnected to form a two-layered cloth. The movement of threads between the layers allows complex patterns and surface textures to be created.

In contemporary textile manufacturing[2], the term "double cloth" or "true double cloth" is sometimes restricted to fabrics with two warps and three wefts, made up as two distinct fabrics lightly connected by the third or binding weft, but this distinction is not always made, and double-woven fabrics in which two warps and two wefts interlace to form geometric patterns are also called double cloths.

Double-faced fabrics are a form of double cloth made of one warp and two sets of wefts or (less often) two warps and one weft. These fabrics have two right sides or faces and no wrong side, and include most blankets, satin ribbons, and interlinings.

These weaves are used chiefly in the manufacture of woolen and worsted suiting and over coating. A double cloth consists of two independent fabrics woven one on top of the other and may or may not be stitched together. In fabrics woven for increased thickness and weight, the two clothes are stitched by having the back warp interweave with the face filling or by having the face warp interweave with the back filling or a combination of both. When arranging these weaves on design paper, face warp and filling threads are treated separately from the back warp and filling threads. A perfect stitch must be made if possible to cover the stitching points.

16.3.1 Rules for Arrangement of Perfect Stitching • A back end may be raised over a face pick between two raiser of the face weave and next to a raiser of the back weave. This is called a raiser stitch. • A face end may be lowered under a back pick between two sinkers of the face weave and next to a sinker of the back weave. This is called a sinker stitch.

16.4 LENO

In gauze and leno weaving certain ends - termed crossing ends – are passed from side to side of what are termed standard ends, and are bound in by the weft in these positions. The crossing and standard ends may be arranged with

185 B.Sc. CDF – Fibre to Fabric

each other in various proportions, as 1-and-1, 1-and-2, 1-and-3, 2-and-2, 2- and-3 etc., but an essential condition is that each group of crossing and standard ends must be placed in one split of the reed. A crossed system of interlacing can be obtained when the entire warp is brought from one beam, and in some cases this is essential in order to produce the desired effect.

Very frequently, however, effects with such a difference in the take up are produced that it is necessary for the two series of ends to be brought from separate beams. The warp may consist entirely of crossing interlacing alternately with straight interlacing in any required order. There is, therefore, almost unlimited scope for the production of variety of effect in striped, checked, and figured fabrics by combining gauze or leno with practically any other system of interweaving.

The fabrics produced by this method are employed for curtaining, shirting’s and for blouse and dress materials as well as for various industrial uses such as filter cloths, screens and sieves. Their great merit lies in a very considerable stability of the interlacing combined with its open nature. The size of the interstices can be determined precisely and will remain stable and uniform even under a degree of pressure.

16.5 SWIVEL

The term swivel is sometimes applied to the type of loom in which several narrow fabrics, such as hat-bands, ribbons, tapes, etc., are independently formed alongside each other. In this machine a separate shuttle is employed for each fabric, but there is no fly shuttle, and the goods are not generally described as small wares.

In broadloom swivel weaving, however, a number of small shuttles work in conjunction with an ordinary fly shuttle, the latter inserting a ground weft which forms with the warp a foundation cloth upon which the swivel shuttles produce figures in extra weft. The chief purpose of the swivel arrangement is to produce the ornament with the least possible waste if the extra yarn. Each figure, and in some cases each part of a figure in a horizontal line of the cloth, is formed by a separate shuttle; the extra weft thus being introduced only where required, with little material extending between the figures on the reverse side of the cloth. In addition to the great saving of the figuring yarn, the swivel method has the advantage over the ordinary system of extra weft figuring that each shuttle may control a distinct colour, while the figures have a richer and fuller appearance on account of the weft being thrown more prominently on to the surface. The addition of the swivel mechanism, however, makes the loom much more complex, consequently there is reduced speed and output. The cloths are woven wrong side up, and there is, therefore, the disadvantage that defects caused by broken threads more readily escape observation; but, on the other hand, weaving the cloths right side up would necessitate the bulk of the warp being raised on the swivel picks.

186 B.Sc. CDF – Fibre to Fabric

Compared with lappet figuring, in which the floats of a thread cannot be stitched between the extremities, swivel figuring produces much neater effects, as any for of weave development can be applied to a figure. Effects are readily produced that appear and handle very similarly to styles in which the pattern is formed after weaving by embroidery.

16.6 LAPPET

Lappet fabrics can be basically classified as extra warp structures in which the extra material forms an opaque figure on an open, semi-transparent ground. The fabrics are particularly popular in the Middle East where they are often used as shawls and other traditional items of attire. Due to the difficulties of manufacture however, they are produced by only a small number of specialist firms.

The ground weave is usually plain and is constructed in two or four healds with the aid of a negative tappet assembly. The ornamentation of ground fabric consists of crammed or cord ends, coloured stripes and other such devices which do not call for the use of additional shedding mechanisms in the form of dobbies or jacquards. On this plain ground the extra warp threads, known as whip threads figure in a manner entirely foreign to warp threads by traversing horizontally across the ground ends, each such traverse forming one float of a figure which is built from a succession of these transverse laps. As the crosswise movement of the whip thread takes place under the ground warp line, and the action occurs picks, two points become obvious: (1) The fabric is woven face side down (2) No interlacing of the float is possible in the middle of its traverse.

The float can be bound only at each extremity which clearly imposes a certain limit on the extent of each traverse.

16.7 DOBBY

A Dobby Loom is a type of floor loom that controls the warp threads using a device called a dobby. Dobby is short for "draw boy" which refers to the weaver's helpers who used to control the warp thread by pulling on draw threads.

Fabrics requiring more than six harnesses to weave are usually provided with dobby looms. Dobby looms are used for the production of fancy goods, fancy shirting’s; terry towels, handkerchiefs. Dobby looms are equipped with a dobby head mechanical for controlling the movements of the harnesses. The dobby head consists of a series of levers each lever operated independently so that it can raise or lower its harnesses on any pick without reference to other harness lever. Dobbs looms are built for sixteen, twenty-five and thirty harnesses.

187 B.Sc. CDF – Fibre to Fabric

16.8 JACQUARD

Jacquard is the term applied to a machine invented by Joseph Marie Jacquard, a mechanic of Lyons, France for the purpose of providing looms with a superior head motion.

With the invention of the jacquard, it is possible to have an innumerable number of interlacing in a fabric, because. on a jacquard machine, each warp end is controlled independently of the others.

Cardboard cards are used with perforations in the card to control the operation of the interlacing of each warp end. Thus, the field of designing intricate and novel cloth fabrics is extended so as to permit the duplication of practically on design in cloth.

16.8.1 Types of Jacquards

Jacquard machines while operating on the same principles and essentially the same in construction are divided into different types according to their uses. • The American index jacquard is used in the manufacture of rugs. • The French index jacquard is the most common type as this machine is used extensively in many different textile mills and fulfills the average requirements in jacquard weaving. • A Fine index jacquard is a type often used, especially in the silk and rayon industry, when a large number of warp ends are to be woven. The fine index jacquard is like the French index. Only more compact, and contains a greater number of hooks; that is, it is capable of controlling a greater number of warp ends.

16.9 LET US SUM UP

To plan a weave structure for a fabric, one must have knowledge of the various methods of interlacing threads to form cloth and some understanding of the mechanism of the loom. If color is used, the designer must have insight into the problems of planning color combinations and knowledge of how color arrangements are provided for on a loom.

Figures and designs are put on the fabrics to embellish them. Figured fabric may be structural designs or applied designs.

188 B.Sc. CDF – Fibre to Fabric

16.10 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Collect different samples of pile fabric and analyze the fabric particulars. • Find the difference between dobby and jacquard. • Go through the specialty of double cloth.

16.11 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • How the velvet is differing from velveteen? Discuss the different process parameters. • Give the minimum and maximum capacity of dobby and jacquard • Collect the sample of double cloth and analyze it.

16.12 CHECK YOUR PROGRESS

1. Discuss pile fabrics.

Pile fabrics are characterized by a soft face covering which generally conceals the interlacing of the warp and filling. • In warp pile fabrics the face effect is produced by raising an extra warp above the ground fabric in a series of loops. If the loops are uncut, the fabric is called terry cloth. • The loops are cut and the fibers stand erect from the ground, then the pile characteristic of velvet is formed. • Velveteen is the fabrics are woven with an extra filling yarn.

189 B.Sc. CDF – Fibre to Fabric

2. Give the rules for arrangement of perfect stitching. • A back end may be raised over a face pick between two raiser of the face weave and next to a raiser of the back weave. This is called a raiser stitch. • A face end may be lowered under a back pick between two sinkers of the face weave and next to a sinker of the back weave. This is called a sinker stitch.

16.13 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Watson’s Textile Design and colour, Grosichkli.Z. Newness Butter, Worths,London, 1980. • Watson’s Advanced Textiel Design, Grosicki.Z. Newness butter worth, Bombay

190 B.Sc. CDF – Fibre to Fabric

UNIT – V

191 B.Sc. CDF – Fibre to Fabric

192 B.Sc. CDF – Fibre to Fabric

LESSON-17 KNITTING

CONTENT 17.0 AIM AND OBJECTIVES 17.1 NTRODUCTION 17.2 PRINCIPLES OF KNITTING 17.2.1 Types of Knitting 17.3 COMMON KNITTING TERMS 17.4 KNITTING ELEMENTS 17.5 KNIT, TUCK AND MISS POSITIONS 17.6 PASSAGE OF MATERIAL 17.7 CHECK YOUR PROGRESS 17.8 KNITTED STRUCTURE 17.8.1 Plain stitch 17.8.2 Rib stitch 17.8.3 Purl Fabric 17.9 WARP KNITTING 17.9.1 Types 17.10 CHARACTERISTICS OF KNITTING YARNS 17.11 LET US SUM UP 17.12 LESSON END ACTIVITIES 17.13 POINTS FOR DISCUSSION 17.14 CHECK YOUR PROGRESS 17.15 REFERENCES

17.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • To know the basic principles of knitting • The classification of knitting • Different knitting elements and its functions • Knitted yarn and requirements

193 B.Sc. CDF – Fibre to Fabric

17.1 INTRODUCTION

Knitting is a method by which thread or yarn may be turned into cloth. Knitting consists of loops called stitches pulled through each other. The active stitches are held on a needle until another loop can be passed through them.

In hand knitting, there are generally two needles used, the loops being transferred from one needle to the other to produce rows of connected loops to form a fabric. In machine knitting there is a needle for every loop and new loops are put on where the old loops vacate.

17.2 PRINCIPLES OF KNITTING

Knitting is the art of constructing a fabric with needles by interlooping one or more yarns in several series of connected loops, hanging on and supporting one another. A woven fabric has two sets of threads which cross each other at right angels, producing a fabric that is relatively inelastic. A knitted fabric has but one thread, or possibly a series of threads, and the fabric is composed of series of interlooped loops. Since these loops can be distorted to a certain degree in any direction and since nearly all knitting yarns are more or less elastic, a knitted fabric is quite elastic.

Fig 17.1

A loop is the curved form into which the yarn is drawn by the knitting needles. One complete stitch is composed of two loops, the needle loop which is formed around the needle, the sinker loop which is formed around the edge of the sinker, the wall between two needle slots or another needle. Actually then, the stitch is composed of one whole loop (the needle loop) and two halves (the sinker loop). Figure 17.1 shows a stitch.

17.2.1 TYPES OF KNITTING

There are two major varieties of knitting: 1. Weft knitting and 2. Warp knitting.

194 B.Sc. CDF – Fibre to Fabric

A weft-knitted fabric consists of horizontal, parallel courses of yarn and requires only a single yarn. By contrast, warp knitting requires one yarn for every stitch in the course, or horizontal row; these yarns make vertical parallel Wales. Warp knitting is resistant to runs, and is common in lingerie fabric such as tricot.

Warp knitting is generally done by machine, whereas weft knitting may be done by machine or by hand. Knitting machines use a different mechanical system to produce results nearly identical to those produced by hand-knitting.

17.3 COMMON KNITTING TERMS

1. Knitting- The making of fabric on more than one needle by interlooping a thread or several parallel threads.

2. The Loop-The basic shape into which yarn is formed in the process of knitting. All knitted fabric is made up of a succession of loops.

Fig 17.2

3. Formation of Loop- A needle is inserted through each one of the original loops and draws a yarn through the original loop to form a loop of the next course. This newly formed loop takes the place of the original loop on the needle, remaining there until the needle pulls the next yarn through it. This operation is repeated continuously.

195 B.Sc. CDF – Fibre to Fabric

4. Needle and Sinker Loops-The yarn lies in the plane of the fabric in what is called a snake curve, and the loops which are drawn through the previously formed loops by the needle are called needle loops. But since the yarn is continuous there must be connecting loops of opposite curvature; these are called sinker loops because during the feeding of yarn in sinker-top type knitting machines, these loops are formed over thin plates called sinkers.

5. Course-Any one thread formed into successive loops. (See Figs. 17.3)

Fig 17.3

6. Length of Course In circular knitting, a course follows a continuous helical (spiral) path in the tube of the fabric from beginning to end. However, in practice, the length of a course is taken as one complete circuit of the fabric and successive circuits are regarded as separate courses.

7. Wale- A vertical chain of loops in the lengthwise direction of the fabric, formed by one needle, is a wale. (See Fig 17.4 )

Fig 17.4

196 B.Sc. CDF – Fibre to Fabric

17.4 KNITTING ELEMENTS

The knitting elements system of circular knitting machines may be divided into: • The primary knitting elements, such as the needles and sinkers which actually form the stitches, and • The secondary knitting elements which actuate the needles and sinkers. Such secondary knitting elements are the cylinder, cams, and pattern wheels.

17.5 KNIT, TUCK AND MISS POSITIONS

As needles approach a yarn feeding carrier, they may be placed by pattern wheels and cams in any one of three different positions relative to that carrier. These three positions are called: 1. Knit Position 2. Tuck Position 3. Miss Position

Fig 17.5

1. Knit Position-The knit position or latch-clearing position is the peak height to which a needle may be raised. (See Fig 17.5 ) As it is lifted by the raising cam, the loop already on the needle, held down by the sinkers, forces the needle latch open as the needle rises. 2. Tuck Position- The tuck position is illustrated in Fig 17.5. The needle is raised so that the previous needle loop opens the latch, but not so high that the loop slides below and off the latch. The previous needle loop remains on the latch as the needle takes the fed yarn in its hook. Since the needle was not raised sufficiently high to cause the previous loop to slide below the latch, then as the needle is drawn into cast-off position, the previous needle loop is not cast off in the normal manner. Instead, as the needle descends, the previous needle loop is returned to the hook of the needle joining the newly fed yarn. 3. Miss Position - The lowest position in which the needle is placed as it approaches the yarn carrier is one in which it is not high enough to take the fed yarn. This is called the welt or “miss” or non-knitting position.

197 B.Sc. CDF – Fibre to Fabric

17.6 PASSAGE OF MATERIAL

A circular knitting machine with one set of needles, in a circular arrangement. In a flat machine, the beds are at ring angles to each other and inclined at 45 degrees from the horizontal. In the circular rib knitting machine, one set of needles is vertical and the other horizontal, still maintaining the right angle relation. These machines knit stitch in a tubular form.

Fig 17.6

1. Feed

A single thread in a weft-knitting machine can feed all the needles in use. In the commonest form of machine, each loop in a row (or "course") is formed in synchronism with the thread- laying: at any moment, therefore, successive needles are at different points of their loop-forming cycle. To obtain high productivity, it is necessary to oscillate the needles rapidly, and to multiply the number of knitting points round the machine.

198 B.Sc. CDF – Fibre to Fabric

2. Yarn Guide A yarn guide conveys the yarn to the needles at the proper place. There is a lag in the action of the yarn guide. A friction device causes the yarn guide to lag behind the vertex of the needle action so that when the yarn is fed the needles are on their way down and therefore pull the yarn evenly.

3. Yarn Tension Device The yarn tension device is used just for this purpose, to take up any slack in the yarn and to keep an even tension on the yam during knitting.

4. Needle The Latch Needle needles are used in the circular knitting machine. This type of needle is composed of a flattened wire shank with a wedged out hook at one end and a latch set into the shank of the needle so that it will swing on a rivet and cover the point of the hook, thus forming an eye in the needle. The other end of the needle has a butt formed by a bending of the continuation of the flattened wire shank. This butt projects from the slot in which the needle is held in the machine and is the means by which the needle is moved to cause the needle to knit. The latch needle is self- operating once a loop is placed within the hook. No auxiliary device is needed to cause the latch to form the eye.

5. Latch Openers Brushes or other types of latch openers are placed just in front of the yarn guide to open the latches of the needles when they rise so that they will take one new yam. They are especially useful when fancy stitches which involve empty needles are made.

6. Cylinder Because of the positions of the needles, the beds assume different forms. The vertical needles are arranged in a bed which is a hollow cylinder with the needle slots cut in the outside surface.

7. Cam The cylinder stitch cam is labeled and is mounted on a post which is forced upward by a spring on its lower end, while a set screw prevents its rising above a certain level. Adjustment of the stitch cam is made through the setscrew. The raising cam is a rigid block forcing the needles to a fixed height causing the cylinder needles to knit. The cast-off cam, located on the back side of the machine in relation to the knitting position, is mounted on a post which may be operated through levers. In the normal position, the cast-off cam has no effect upon the knitting action of the needles. When the cam is raised, it causes the cylinder needles to cast off their loops. The other cam blocks perform duties indicated by their names.

199 B.Sc. CDF – Fibre to Fabric

17.7 CHECK YOUR PROGRESS

1. Define knitting and its types.

Knitting: Constructing fabric by looping yarns together. a. Weft knits: Knits made with only one yarn that runs crosswise forming a horizontal row of interlocking loops. (1) Cut edges will curl. (2) Weft knits run if snagged. (3) Examples: jersey, ribbed knits, sweater knits b. Warp knits: Knits made with several yarns creating loops that interlock in the lengthwise direction. (1) Do not ravel (2) Have selvage edges (3) Examples: tricot, raschel knits

2. Explain Course and Wales

Fig 17.7

• A course is a series of adjacent loops running across the fabric forming a line width-wise (filling-wise) of the fabric shown in fig 17.7

• A wale is a series of loops, made by one needle, hanging on and supporting one another, forming a line length-wise (warp-wise) of the fabric.

17.8 KNITTED STRUCTURE

All knitted fabric is based on one of three basic structures. Whatever stitch is used or decorative pattern designed the fabric structure will be either plain fabric, rib fabric or purl fabric.

200 B.Sc. CDF – Fibre to Fabric

17.8.1 Plain stitch

Plain stitch (fig 17.8) is made by one series of needles side by side drawing all the loops in one direction. Some stationary device must be inserted between needles over which to from the stitch. The length of the stitch, and the consequent texture of the fabric, is controlled by the distance the needle draws the new loop below these fixed devices. In some machines these devices are sinkers, but in the flat machine fixed walls, called "jacks", between the needles are used as a medium over which to draw the stitch.

Fig 17.8

The plain fabric may be identified by its smooth face with lines running length- wise, caused by the wales; and its comparatively rough back with lines running width-wise of the fabric. It is fairly elastic, especially width-wise. It has a tendency to curl when flat or when cut from a tube. It will ravel or run in either direction.

17.8.2 Rib stitch

A rib stitch is one in which loops in the same course are drawn to opposite sides of the fabric. The resultant fabric is known as a ribbed fabric. A rib stitch is made on two sets of needles working together. An examination of a ribbed fabric will show that one wale occurs between two wales on the opposite side of the fabric. The needles must be staggered to produce this condition. Since alternate needles approach each other at approximately 90°, they must be staggered in order not to strike. In hand knitting, a ribbed fabric is produced by "purling" alternate stitches. Rib or ribbed stitch is shown in Figure 17.9

Fig 17.9

201 B.Sc. CDF – Fibre to Fabric

The rib fabric is the same in appearance on the face and back with pronounced ribs or wales clinging close together. The accordion action of the staggered wales makes rib stitch very elastic. It does not curl when flat or when cut from a tube. It will ravel or nun in one direction only, the direction in which it is knit.

17.8.3 Purl Fabric

The purl fabric, sometimes known as Links and Links fabric, is one in which successive courses are drawn to opposite sides of the fabric. Figure 17.10 shows the purl stitch. Like plain stitch it is produced on a single set of needles, but instead of drawing all courses of loops in one direction, alternate courses are drawn in opposite directions.

It might be said that the purl fabric is a modified plain stitch similar to the cardigans being modified rib stitches. The only difference is that a special machine is required to knit purl stitch so that tendency is to call purl stitch a separate type. Purl stitch is the same stitch that is known as plain or "garter" stitch in hand knitting. Both sides of the purl fabric are alike.

Fig 17.10

The identifying characteristics are horizontal lines on back and face similar to the lines on the back of plain fabric. Purl fabric is about as elastic as plain fabric widthwise, but has considerably more elasticity lengthwise. One of its disadvantages is its tendency to stretch lengthwise unless tightly knit. The purl fabric has no tendency to curl in either direction.

17.9 WARP KNITTING

Warp knitting (fig 17.11) is a family of knitting methods in which the yarn zigzags along the length of the fabric, i.e., following adjacent columns ("wales") of knitting, rather than a single row ("course"). For comparison, knitting across the width of the fabric is called weft knitting.

202 B.Sc. CDF – Fibre to Fabric

Fig 17.11

Since warp knitting requires that the number of separate strands of yarn ("ends") equals the number of stitches in a row, warp knitting is almost always done by machine, not by hand.

17.9.1 Types Warp knitting comprises several types of knitted fabrics, including tricot, raschel knits, and milanese knits. All warp-knit fabrics are resistant to runs and relatively easy to sew.

• Tricot is very common in lingerie. • Milanese is stronger, more stable, smoother and more expensive than tricot and, hence, is used in better lingerie. • Raschel knits do not stretch significantly and are often bulky; consequently, they are often used as an unlined material for coats, jackets, straight skirts and dresses.

17.10 CHARACTERISTICS OF KNITTING YARNS

A good knitting yarn should have the following characteristics in the order of their relative importance:- • Uniformity of diameter • Flexibility • Elasticity • Strength.

Uniform in Diameter

A good knitting yarn should be as uniform in diameter as is possible. A knitted fabric reveals variations in diameter far more than any other method of fabrication. The peculiar loop formation places a greater length of yarn within a relatively small space in the fabric. Because of this peculiarity, a thick or thin place in the yarn is magnified in appearance.

203 B.Sc. CDF – Fibre to Fabric

Because uniformity of diameter is of such importance, everything is done to improve the appearance of uniformity in a knitting yam. That is one reason that a great many knitting yarns are plied, to increase the probability of uniformity. Single ply knitting yarns are usually very slightly twisted to make a yarn which will be lofty and appear, at least, more uniform that the same yam with more twist.

Flexibility

Flexibility is necessary in a knitting yarn in order that the yarn will form loops readily. A knitted fabric consists of a series of interlooped yarns. A stiff, wiry yarn resists the formation of loops and is not a good knitting yarn. The soft twist given knitting yarns also tends to increase its flexibility.

Elasticity

Elasticity in a knitting yarn is not necessary to actually cause it to knit but does improve the ultimate knitted fabric. Elasticity is that property which causes a yarn to assume its original length after being stretched by any tension less than its elastic limit. The tendency of an elastic yarn to assume its original length after tension is applied, causes it to react similarly in the knitting action. This elasticity creates a more compact, smaller looped and more elastic knitted fabric.

Strength

The relative important of strength in a knitting yarn is less than any other characteristic. Contrary to popular belief the action of knitting is comparatively easy on the yarn. A very weak yarn, providing it has sufficient of the afore- mentioned characteristics, will it readily. A yarn which is dried out or brittle will not knit but that is not because it lacks strength but because it lacks flexibility and elasticity. The relative unimportance of strength as a characteristic in a knitting yarn allows a yarn to be spun with soft twist to improve its flexibility, elasticity and uniformity.

17.11 LET US SUM UP

Knitting is the art of constructing a fabric with needles by interlooping one or more yarns in several series of connected loops, hanging on and supporting one another. A woven fabric has two sets of threads which cross each other at right angels, producing a fabric that is relatively inelastic. A knitted fabric has but one thread, or possibly a series of threads, and the fabric is composed of series of interlooped loops. Since these loops can be distorted to a certain degree in any direction and since nearly all knitting yarns are more or less elastic, a knitted fabric is quite elastic.

204 B.Sc. CDF – Fibre to Fabric

17.12 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Visit any one knitting unit and go through the method of fabric formation. • Collect the various types of knitting elements uses in knitting. • Analyze the characteristics of different knitting fabric structure.

17.13 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Compare the properties of plain, rib and purl structure. • Go through the different types of needle selection mechanisms. • Differentiate various types of needle.

17.14 CHECK YOUR PROGRESS

1. Draw plain knit structure and explain the fabric properties.

The plain fabric may be identified by its smooth face with lines running length- wise, caused by the wales; and its comparatively rough back with lines running width-wise of the fabric. It is fairly elastic, especially width-wise. It has a tendency to curl when flat or when cut from a tube. It will ravel or run in either direction.

2. List the factors which influence the selection of a particular fabric-making process.

Weaving. If the requirements are for a dense, inelastic fabric, for a fabric using very cheap yarn, for a fabric with a complex rectangular pattern (e.g. a suiting, especially with a large multicolor check), weaving is generally the preferred choice.

205 B.Sc. CDF – Fibre to Fabric

Weft Knitting. This process is particularly suitable for garments where rigidity is not required, such as hosiery, underwear and leisure wear. It is also a way making garment blanks that need no cutting, or only minimal cutting. No yarn preparation (with the occasional exceptions of coning and lubrication) is necessary, and the conversion cost is low.

Warp Knitting. This is at its best in the production of low-cost filament fabrics, whose properties can be determined by design; examples are lingerie, shirts, sheets, nets and power nets. The resultant fabrics are naturally crease-shedding and do not need ironing if the fabric has been made from a thermoplastic fibre.

3. Write short notes on knitting principles. • Fabric is produced with needles by interlooping one or more yarns in several series of connected loops, hanging on and supporting one another. • A knitted fabric has one thread, or possibly a series of threads, and the fabric is composed of series of interlooped loops.

17.15 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Knitting Technology, Spencer D.J.Perganion Bross, Oxford 1982. • D.B.Ajgonkar, “ principles of knitting”’ Universal publishing Corporation, 1998 • “Warp Knit Machine Elements, Wilkens 1997.

206 B.Sc. CDF – Fibre to Fabric

LESSON-18 NON WOVEN

CONTENT 18.0 AIM AND OBJECTIVES 18.1 INTRODUCTION 18.2 FIBERS USED 18.3 WEB FORMATION 18.4 DRY-LAID NONWOVENS 18.4.1 Fiber Selection 18.4.2 Fiber Preparation 18.4.3 Web Formation 18.4.4 Layering 18.4.5 Bonding and Stabilization of Webs 18.4.5.1 Mechanical Bonding 18.4.5.2 Thermal Bonding 18.4.5.3 Chemical Bonding 18.4.5.4 Hydro entanglement 18.5 WET-LAID NONWOVENS 18.6 MELT BLOWN TECHNOLOGY 18.6.1 Process 18.7 SPUNBOND TECHNOLOGY 18.7.1 Flow of operation 18.7.2 Process 18.8 LAMINATING 18.9 APPLICATIONS 18.10 LET US SUM UP 18.11 LESSON END ACTIVITIES 18.12 POINTS FOR DISCUSSION 18.13 CHECK YOUR PROGRESS 18.14 REFERENCES

207 B.Sc. CDF – Fibre to Fabric

18.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • Basic concept and sequence of operation of non oven fabrics. • List operation and the different technique involved the production of nonwoven • Application of nonwoven fabrics

18.1 INTRODUCTION

Nonwovens are a class of textiles/sheet products, unique in industry, which is defined in the negative; that is, they are defined in what they are not. Nonwovens fabrics are different than the conventional textile fabrics and paper. Nonwovens are not based on yarns and (with frequent exceptions) do not contain yarns. They are based on webs of individual fibers. Nonwovens are different than paper in that nonwovens usually consist entirely or at least contain a sizeable proportion of long fibers and/or they are bonded intermittently along the length of the fibers. Although paper consists of fiber webs, the fibers are bonded to each other so completely that the entire sheet comprises one unit. In nonwovens we have webs of fibers where fibers are not as rigidly bonded and to a large degree act as individuals

18.2 FIBERS USED

Fibers are the basic element of Nonwovens. Manufacturers of Nonwovens products can make use of almost any kind of fibers. These include traditional textile fibers, as well as recently developed hi-tech fibers. The selection of raw fibers, to considerable degree, determines the properties of the final nonwoven products. The selection of fibers also depends on customer requirement, cost, process ability, changes of properties because of web formation and consolidation. The fibers can be in the form of filament, staple fiber or even yarn. The following table shows the significant fibers used in the Nonwovens industry all over the world. Fibers used in Nonwoven industry

TRADITIONAL TEXTILE FIBERS HI-TECH FIBERS

PET Aramid (Nomex/Kevlar)

Polyolefin (PP/PE) Conductive Nylon

208 B.Sc. CDF – Fibre to Fabric

Nylon Bi-component (side-by-side, sheath-core, segmented pie and sea-island) Cotton Melamine (heat & flame resistant) Rayon Super absorbent Wool Hollow fibers Lyocell Spandex fibers (polyether) Modacrylic Fusible co-PET fiber PA-6 support/matrix fiber Glass micro-fiber Chlorofiber Antibacterial fiber Stainless steel Rubber thread PTFE Nanofibers

18.3 WEB FORMATION

All nonwoven fabrics are based on a fibrous web. The characteristics of the web determine the physical properties of the final product. These characteristics depend largely on the web geometry, which is determined by the mode of web formation. Web geometry includes the predominant fiber direction, whether oriented or random, fiber shape (straight, hooked or curled), the extent of inter- fiber engagement or entanglement, crimp and z-direction compaction. Web characteristics are also influenced by the fiber diameter, fiber length, web weight, chemical and mechanical properties of the polymer.

The choice of methods for forming webs is determined by fiber length. Initially, the methods for the forming of webs from staple-length fibers were based on the textile carding process, whereas web formation from short fibers was based on papermaking technologies. Though these technologies are still in use, newer methods have been developed. For example, webs are formed from long, virtually endless filament directly from bulk polymers; both web and fibers are produced simultaneously. • Dry-laid Nonwovens • Wet-laid Nonwovens • Melt Blown Technology • Spunbond Technology • Nanofiber Nonwovens

209 B.Sc. CDF – Fibre to Fabric

18.4 DRY-LAID NONWOVENS

This technique involved the following steps:

18.4.1 Fiber Selection

These fibers are long enough to be handled by conventional spinning equipment. The fibers are 1.2 to 20cm or longer, but not continuous.

18.4.2 Fiber Preparation

Fiber preparation consists of mechanical and pneumatic processes of handling from the bale to the point where the fiber is introduced into the web-forming machine. • Bale opening • Blending • Coarse opening • Fine opening • Web-former feeding

18.4.3 Web Formation

There are two types of web formation methods are followed here • Mechanical Web Formation (Carding or Garnetting) • Aerodynamic Web Formation (Air-Lay)

18.4.4 Layering

Web formations can be made into the desired web structure by the layering of the webs from either the card or garnet. Layering can be accomplished in several ways to reach the desired weight and web structure.

1. Longitudinal Layering:

More than once cards are involved in here. Carded webs from all the cards (placed in a sequence one after the other) are laid above one another on a conveyor belt and later bonded. Properties of the bonded webs are anisotropic in nature because of the unidirectional arrangements of fibers. This technique can only be used for making light textiles.

2. Cross layering:

It can be done by using two different devices (cross lappers); vertical and horizontal cross lapper. Vertical lapper consists of a pendulum conveyor after the doffer roll on a card (as shown in fig. 8). Pendulum conveyor reciprocates and lays the carded web in to folds on another conveyor belt.

210 B.Sc. CDF – Fibre to Fabric

3. Perpendicular layering:

This technique has an advantage over longitudinal and cross layering because of the perpendicular and oriented fibers in the fabric. The bonded webs have high resistance to compression and show better recovery after repeated loading.

18.4.5 Bonding and Stabilization of Webs

18.4.5.1 Mechanical Bonding

1. Needle punching

Needle punching is a process of bonding nonwoven web structures by mechanically interlocking the fibers through the web. Barbed needles, mounted on a board, punch fibers into the web and then are withdrawn leaving the fibers entangled. The needles are spaced in a non-aligned arrangement and are designed to release the fiber as the needle board is withdrawn.

Needle punch process

The needle punch process is illustrated in fig.18.1 Needle punched nonwovens are created by mechanically orienting and interlocking the fibers of a spun bonded or carded web. This mechanical interlocking is achieved with thousands of barbed felting needles repeatedly passing into and out of the web.

Fig 18.1

The needle board: The needle board is the base unit into which the needles are inserted and held. The needle board then fits into the needle beam that holds the needle board into place. The feed roll and exit roll. These are typically driven rolls and they facilitate the web motion as it passes through the needle loom.

211 B.Sc. CDF – Fibre to Fabric

Fig 18.2

The bed plate and stripper plate: The web passes through two plates, a bed plate on the bottom and a stripper plate on the top. Corresponding holes are located in each plate and it is through these holes the needles pass in and out. The bed plate is the surface the fabric passes over which the web passes through the loom. The needles carry bundles of fiber through the bed plate holes shown in fig 18.2. The stripper plate does what the name implies; it strips the fibers from the needle so the material can advance through the needle loom.

The correct felting needle can make or break the needle punched product. The proper selection of gauge, barb, point type and blade shape (pinch blade, star blade, conical) can often give the needle puncher the added edge needed in this competitive industry

2. Stitch Bonding

Stitch bonding is a method of consolidating fiber webs with knitting elements with or without yarn to interlock the fibers. There are a number of different yarns that can be used. Kevlar is used for strength in the fabric for protective vests. Lycra® is used for stretch in the fabric. Home furnishings are a big market for these fabrics. Other uses are vacuum bags, geo textiles, filtration and interlinings. In many applications stitch-bonded fabrics are taking the place of woven goods because they are faster to produce and, hence, the cost of production is considerably less.

18.4.5.2 Thermal Bonding

Thermal bonding is the process of using heat to bond or stabilize a web structure that consists of a thermoplastic fiber. All part of the fibers act as thermal binders, thus eliminating the use of latex or resin binders. Thermal bonding is the leading method used by the cover stock industry for baby diapers. Polypropylene has been the most suitable fiber with a low melting point of approximately 165°C. It is also soft to touch. The fiber web is passed between heated calendar rollers, where the web is bonded. In most cases point bonding

212 B.Sc. CDF – Fibre to Fabric

by the use of embossed rolls is the most desired method, adding softness and flexibility to the fabric. Use of smooth rolls bonds the entire surface of the fabric increasing the strength, but reduces drape and softness.

18.4.5.3 Chemical Bonding

Bonding a web by means of a chemical is one of the most common methods of bonding. The chemical binder is applied to the web and is cured. The most commonly used binder is latex, because it is economical, easy to apply and very effective. Several methods are used to apply the binder and include saturation bonding, spray bonding, print bonding and foam bonding. i) Saturation ii) Foam bonding iii) Spray bonding iv) Print bonding v) Powder bonding

18.4.5.4 Hydro entanglement

Hydro entanglement is a process of using fluid forces to lock the fibers together. This is achieved by fine water jets directed through the web, which is supported by a conveyor belt. Entanglement occurs when the water strikes the web and the fibers are deflected. The vigorous agitation within the web causes the fibers to become entangled.

18.5 WET-LAID NONWOVENS

Wet-laid nonwovens are nonwovens made by a modified papermaking process. That is, the fibers to be used are suspended in water. A major objective of wet laid nonwoven manufacturing is to produce structures with textile-fabric characteristics, primarily flexibility and strength, at speeds approaching those associate with papermaking. Specialized paper machines are used to separate the water from the fibers to form a uniform sheet of material, which is then bonded and dried. In the roll good industry 5-10% of nonwovens are made by using the wet laid technology.

18.6 MELT BLOWN TECHNOLOGY

Melt blowing (MB) is a process for producing fibrous webs or articles directly from polymers or resins using high-velocity air or another appropriate force to attenuate the filaments. The MB process is one of the newer and least developed nonwoven processes. This process is unique because it is used almost exclusively to produce micro fibers rather than fibers the size of normal textile fibers. MB micro fibers generally have diameters in the range of 2 to 4 µm, although they may be as small as 0.1 µm and as large as 10 to 15 µm. Differences between MB nonwoven fabrics and other nonwoven fabrics, such as degree of softness, cover or opacity, and porosity can generally be traced to differences in filament size.

213 B.Sc. CDF – Fibre to Fabric

18.6.1 Process

The most commonly accepted and current definition for the MB process is: a one-step process in which high-velocity air blows a molten thermoplastic resin from an extruder die tip onto a conveyor or take-up screen to form a fine fibrous and self-bonding web.

The MB process is similar to the spun bond (SB) process which converts resins to nonwoven fabrics in a single integrated process. The schematic of the process is shown MB in figure 18.3. A typical MB process consists of the following elements: • Extruder, • Metering pumps, • Die assembly, • Web formation, and • Winding.

Extruder

The extruder is one of the important elements in all polymer processing. It consists of a heated barrel with a rotating screw. Its main function is to melt the polymer pellets or granules and feed them to the next step/element. The forward movement of the pellets in the extruder is along the hot walls of the barrel between the flights of the screw. The melting of the pellets in the extruder is due to the heat and friction of the viscous flow and the mechanical action between the screw and the walls of the barrel. There are four different heaters in the extruder, which are set in incremental order.

Fig 18.3

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Metering Pump

The metering pump is a positive-displacement and constant-volume device for uniform melt delivery to the die assembly. It ensures consistent flow of clean polymer mix under process variations in viscosity, pressure, and temperature. The metering pump also provides polymer metering and the required process pressure. The metering pump typically has two intermeshing and counter- rotating toothed gears.

Die Assembly

The die assembly is the most important element of the melt blown process. It has three distinct components: • Polymer-feed distribution, • Die nosepiece, and • Air manifolds.

Web Formation

As soon as the molten polymer is extruded from the die holes, high velocity hot air streams (exiting from the top and bottom sides of the die nosepiece) attenuate the polymer streams to form micro fibers. As the hot air stream containing the micro fibers progresses toward the collector screen, it draws in a large amount of surrounding air (also called secondary air) that cools and solidifies the fibers. The solidified fibers subsequently get laid randomly onto the collecting screen, forming a self-bonded nonwoven web.

Winding

The melt-blown web is usually wound onto a cardboard core and processed further according to the end-use requirement. The combination of fiber entanglement and fiber-to-fiber bonding generally produce enough web cohesion so that the web can be readily used without further bonding. However, additional bonding and finishing processes may further be applied to these melt- blown webs.

18.7 SPUNBOND TECHNOLOGY

Spun bond fabrics are produced by depositing extruded, spun filaments onto a collecting belt in a uniform random manner followed by bonding the fibers. The fibers are separated during the web laying process by air jets or electrostatic charges. The collecting surface is usually perforated to prevent the air stream from deflecting and carrying the fibers in an uncontrolled manner. Bonding imparts strength and integrity to the web by applying heated rolls or hot needles to partially melt the polymer and fuse the fibers together. Since molecular orientation increases the melting point, fibers that are not highly drawn can be

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used as thermal binding fibers. Polyethylene or random ethylene-propylene copolymers are used as low melting bonding sites. Spun bond products are employed in carpet backing, geo textiles, and disposable medical/hygiene products. Since the fabric production is combined with fiber production, the process is generally more economical than when using staple fiber to make nonwoven fabrics

18.7.1 Flow of operation

18.7.2 Process

• Spinning • Web Formation • Bonding

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Fig 18.4

Spinning

Spun bonding combines fiber spinning with web formation by placing the bonding device in line with spinning. In some arrangements the web is bonded in a separate step which, at first glance, appears to be less efficient. However, this arrangement is more flexible if more than one type of bonding is applied to the same web.

The spinning process is similar to the production of continuous filament yarns and utilizes similar extruder conditions for a given polymer. Fibers are formed as the molten polymer exits the spinnerets and is quenched by cool air. The objective of the process is to produce a wide web and, therefore, many spinnerets are placed side by side to generate sufficient fibers across the total width. The grouping of spinnerets is often called a block or bank. In commercial production two or more blocks are used in tandem in order to increase the coverage of fibers.

Before deposition on a moving belt or screen, the output of a spinneret usually consists of a hundred or more individual filaments which must be attenuated to orient molecular chains within the fibers to increase fiber strength and decrease extensibility. This is accomplished by rapidly stretching the plastic fibers immediately after exiting the spinneret. In practice the fibers are accelerated

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either mechanically or pneumatically. In most processes the fibers are pneumatically accelerated in multiple filament bundles; however, other arrangements have been described where a linearly aligned row or rows of individual filaments is pneumatically accelerated.

Web Formation

The web is formed by the pneumatic deposition of the filament bundles onto the moving belt. A pneumatic gun uses high-pressure air to move the filaments through a constricted area of lower pressure, but higher velocity as in a venture tube. In order for the web to achieve maximum uniformity and cover, individual filaments must be separated before reaching the belt. This is accomplished by inducing an electrostatic charge onto the bundle while under tension and before deposition. The charge may be induced triboelectrically or by applying a high voltage charge.

Bonding

Many methods can be used to bond the fibers in the spun web. Although most procedures were developed for nonwoven staple fibers, they have been successfully adapted for continuous filaments. These include mechanical needling, thermal bonding, and chemical bonding. The last two may bond large regions (area bonding) or small regions (point bonding) of the web by fusion or adhesion of fibers. Point bonding results in the fusion of fibers at points, with fibers between the point bonds remaining relatively free.

Other methods used with staple fiber webs, but not routinely with continuous filament webs include stitch bonding, ultrasonic fusing, and hydraulic entanglement. The last method has the potential to produce very different continuous filament structures, but is more complex and expensive. The choice of a particular bonding technique is dictated mainly by the ultimate fabric applications; occasionally a combination of two or more techniques is employed to achieve bonding.

18.8 LAMINATING

Laminating is the permanent jointing of two or more prefabricated fabrics. Unless one or other of the fabrics develops adhesive properties in certain conditions, an additional medium is necessary to secure bonding.

• Wet laminating: Adhesives used in the wet process are dissolved or dispersed in a suitable solvent. The simplest form of wet laminating consists of applying the adhesive to one of the lengths of material that is to be joined, and to put the second length on it with the required amount of pressure. Then drying, hardening or condensing the material that has been joined together is carried out. The solvents can be macromolecular natural or synthetic substances and water.

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• Dry laminating: All Kinds of thermoplastics are used for dry laminating. These include powders, plastisols, or melt adhesives, and are applied to the substrates that are to be joined together using suitable machinery. Dry laminated non-woven fabrics have a soft feel.

18.9 APPLICATIONS

Non-woven materials are nowadays mainly produced from man-made fibers. Two synthetic polymers dominate the market: polypropylene (PP) and polyesters (mainly PET). Nonwovens are often application-designated as either durable or disposable. For example, nonwovens used as house wraps to prevent water infiltration are durable nonwovens. Nonwovens used as facings on baby diapers are disposable or single-use nonwovens.

Non-woven materials are used in numerous applications, including:

Hygiene • Baby diapers • Feminine hygiene • Adult incontinence products • Wipes • Bandages and wound dressings • Medical • Isolation gowns • Surgical gowns • Surgical drapes and covers • Surgical scrub suits • Caps

Technical • Roll roofing and shingle reinforcement • Insulation backing • Battery electrode separators • Vinyl flooring reinforcement • Plastic surface reinforcement (veils) • Wall coverings • Honeycomb structural components • Ceiling tile facings • Circuit board reinforcement • Electrical insulation • Filters • Gasoline, oil and air - including HEPA filtration • Water, coffee, tea bags

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Geo textiles • Soil stabilizers and roadway underlayment • Agriculture mulch • Pond and canal water barriers • Sand infiltration barrier for drainage tile

Other • Carpet backing, primary and secondary • Composites • Marine sail laminates • Table cover laminates • Backing/stabilizer for machine embroidery • Insulation (fiberglass batting) • Pillows, cushions, and upholstery padding • Batting in quilts or comforters • Consumer and medical face masks • Tarps, tenting and transportation (lumber, steel) wrapping • Disposable clothing (foot coverings, coveralls)

18.10 LET US SUM UP

Non-woven fabric is typically manufactured by putting small fibers together in the form of a sheet or web, and then binding them either mechanically (as in the case of felt, by interlocking them with serrated needles such that the inter-fiber friction results in a stronger fabric), with an adhesive, or thermally (by applying binder (in the form of powder, paste, or polymer melt) and melting the binder onto the web by increasing temperature).

18.11 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Make flow chart for the flow of operation for the non woven fabric manufacturing. • Find the different technique and sequence of operation for producing non woven fabric. • Collect the different fabrics samples of non woven fabric.

18.12 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Find the difference in manufacturing the non woven fabric with other fabric. • The special steps to be followed during the manufacturing of non woven fabric by different techniques.

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18.13 CHECK YOUR PROGRESS

1. Give the uses of nonwoven. • Nonwoven fabrics are finding increasing usage in reusable apparel and other products, thus replacing the traditional knits and woven. • Nonwovens are widely used as interlinings in blouses, jackets, shirts, and waistbands. • Nonwovens have been introduced into the outdoor sporting markets for fishing and hunting apparel. • Medical textiles are being constructed as reusable but with special barrier materials to protect the surgeon and those in the operating room.

2. Steps to be followed to manufacturing the non woven fabric Manufacturers of Nonwovens products can make use of the basic element • Selection of fibres • Fibre preparations • Web formations • Bonding

3. Draw the floe of operation in spun bonding technique.

18.14 REFERENCES

• Nonwoven Bonded Fabrics, 1985. Lunenschloss, J. and Albrecht , W. • Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Princlples of Nonwovens, INDA, Cary, NC (1993)

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LESSON-19

OTHER FABRICS

CONTENT 19.0 AIM AND OBJECTIVES 19.1 INTRODUCTION 19.2 FELT 19.2.1 Raw Materials 19.2.2 The Manufacturing 19.3 BRAID 19.4 TATTING 19.4.1 Technique 19.5 CROCHET 19.6 CALICO 19.7 NETTING 19.8 LET US SUM UP 19.9 LESSON END ACTIVITIES 19.10 POINTS FOR DISCUSSION 19.11 CHECK YOUR PROGRESS 19.12 REFERENCES

19.0 AIM AND OBJECTIVES

After going through this lesson, you should be able to have a clear idea of the following • Knowledge of different fabric producing methods and its types. • Knowledge of the structure of the main construction of felted fabric. • Methods and the differences between tatting and crochet.

19.1 INTRODUCTION

There are some methods are available to form a fabric apart from weaving, knitting and nonwoven which may or may not follow the principles of weaving and knitting.

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• Net - Net is a device made by fibers woven in a grid-like structure, as in fishing net, a soccer goal, a butterfly net, or the court divider in tennis • Felt - Felt is a non-woven cloth that is produced by matting, condensing and pressing fibers. The fibers form the structure of the fabric. • Felting - The process of making felt is called felting. • Crochet - The word crochet describes the process of creating fabric from a length of cord, yarn, or thread with a hooked tool. • Crochet hook - A crochet hook is a type of needle, usually with a hook at one end, used to draw thread through knotted loops.

19.2 FELT

Felt is a dense, non-woven fabric and without any warp or weft. Instead, felted fabric is made from matted and compressed fibers or fur with no apparent system of threads. Felt is produced as these fibers and/or fur is pressed together using heat, moisture, and pressure. Felt is generally composed of wool that is mixed with a synthetic in order to create sturdy, resilient felt for craft or industrial use. However, some felt is made wholly from synthetic fibers.

19.2.1 Raw Materials

Felt is produced from wool, which grips and mats easily, and a synthetic fiber that gives the felt some resilience and longevity. Typical fiber combinations for felt include wool and polyester or wool and nylon. Synthetics cannot be turned into felt by themselves but can be felted if they combine with wool.

Other raw materials used in the production of wool include steam, utilized during the stage in which the material is reduced in width and length and made thicker. Also, a weak sulfuric acid mixture is used in the thickening process. Soda ash (sodium chloride) is utilized to neutralize the sulfuric acid.

19.2.2 The Manufacturing

Process • Since some felts use more than one type of fiber, the fibers must be mixed and blended together before any processing begins. To do this, the raw fibers are put into an opener with a big cylinder studded with steel nails that combine the fibers into a mass. • Next, these blended fibers must be carded. Carding machines are huge cylinders that mat the fibers into a web. Hopper-feeders allow a specific weight of fiber to pass into the cylinder in order to create a standardized web. The fibers in the web are pulled by the wires, or carded, so that they are parallel to one another.

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• Generally, at least two carding machines are used in the manufacturing process, each refining the web as it creates a new one. A transporter moves one web from the first carding machine to a second. The web is then fed into the second machine. This second carder generates a new web that is thicker and fully carded. • At the end of the second carding, a comb removes the carded web from the machine and rolls it up. There are two ways to remove the web from the machine: a cross-lapper may be used in which the web is perpendicularly rolled up, or across the direction of the fibers; or a vlamir may be utilized, in which the web is rolled parallel to the direction of the fibers. • Next, several different webs are combined to create one thick web. Four rolls of web are rolled up but are layered so that their fibers alternate in direction based on the way the webs were rolled, either cross-lapped or rolled using a vlamir. These four rolls are considered a standard single roll, sometimes referred to as a batt. This batt is considered a standard roll of material. Batts are layered in order to create different thicknesses of felt. • The batts of felted material must be hardened or matted together in order to create thick, densely-felted material. The first step in this process is subjecting the batts to heat and moisture. In order to do so, the batts are passed through a steam table. • Now, the separate batts must be matted together and shrunk in length and width in order to create a dense felt. These batts must be subjected to heat, moisture, and pressure in order to be matted densely. First, the wetted batts are fed into a plate-hardener that shrinks the width of the fabric. The plate-hardener consists of a large, square flat bed with a large plate that drops down over the batts of wet, hot batts, exerting pressure on the material and compressing it. At the same time, the plate-hardener oscillates from edge to edge, further matting the fiber to a specific width. • Next, the batts are fed into a fuller or fulling machine, which shrinks the length to a specific measurement. As it shrinks, the felt becomes more dense. The batts are fed through a set of upper and lower steel rollers that are covered with hard rubber or plastic and are molded with treads much like a car tire, enabling them to move across the batts. The felt is continuously wetted with a hot water and sulfuric-acid solution. The upper rollers remain stationary as the lower rollers are moved upwards to put pressure on the fabric and push it against the upper rollers. All of the rollers, both upper and lower, move together forward and backward. The pressure, the acid, the hot water, and the movement cause the batts to shrink in length, making the felt even more dense. For example, a single piece of felt that is 38 yd (34.7 m) long may come out of the fuller at only 30 yd (27.4 m) in length. • The wet felt has sulfuric acid residue and must be neutralized. To do so, the felt is run through neutralizing tanks filled with a soda ash and warm water solution. This process is carefully timed so that specific yard lengths and widths are in for an exact amount of time.

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• The neutralized felt is then run through a refulling machine in which heavy rollers run over the surface of the fabric one last time to smooth out any irregularities. • If felts are to be dyed, the wet pieces are taken to a dye vat. Some industrial grades are not dyed but go directly to drying.

19.3 BRAID

To interweave three or more strands, strips, or lengths of in a diagonally overlapping pattern. A braid is an interweaving or twinning three or more separate strands in a diagonally overlapping pattern. The strands may be of one or more materials. Braids are commonly involved in hairstyling and rope making. Simple braids with more than three strands can be flat or tubular and generally contain an odd number of strands. Complex braids have been used to create hanging fiber artworks. A braid is similar to a plait, which covers any type of knot forming a repeated pattern.

Fig 19.1

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In fiber optics and electrical and electronic cables, braid is a tubular sheath made of braided strands of metal placed around a central cable for mechanical protection or grounding purposes. Such braids are also used after flattening for bonding large components together. The numerous smaller wires comprising the braid are much more resistant to cracking under repeated motion and vibration than is a cable of larger wires.

19.4 TATTING

Tatting is a technique for handcrafting a particularly durable lace constructed by a series of knots and loops. Tatting can be used to make lace edging as well as doilies, collars, and other decorative pieces. The lace is formed by a pattern of rings and chains formed from a series of lark's head (or half-hitch) knots, called double stitches (ds), over a core thread. Gaps can be left between the stitches to form picots, which are used for practical construction as well as decorative effect.

19.4.1 Technique

1 Shuttle tatting 2 Needle tatting 3 Cro-tatting

1. Shuttle tatting

Tatting with a shuttle (Fig 19.2) is the earliest method of creating tatted lace. A tatting shuttle facilitates tatting by holding a length of wound thread and guiding it through loops to make the requisite knots.

Fig 19.2

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It is normally a metal or plastic pointed oval shape less than 3 inches long, but shuttles come in a variety of shapes and materials. Shuttles often have a point or hook on one end to aid in the construction of the lace. Antique shuttles and unique shuttles have become highly sought after by collectors

2. Needle tatting

Fig 19.3

A tatting needle is a long, blunt needle that does not change thickness at the eye of the needle. The needle used must match the thickness of the thread chosen for the project. Rather than winding the shuttle, the needle is threaded with a length of thread.

3. Cro-tatting

Cro-tatting combines needle tatting with crochet. The cro-tatting tool is a tatting needle with a crochet hook at the end. One can also cro-tat with a bullion crochet hook or a very straight crochet hook. In the nineteenth century, "crochet tatting" patterns were published which simply called for a crochet hook. One of the earliest patterns is for a crocheted afghan with tatted rings forming a raised design.

19.5 CROCHET

Crocheting differs largely from knitting in that there is only one loop, not the multitude as knitting has. Also, instead of knitting needles, a crochet hook is used. Other than that it is vaguely similar, and is often mistaken for knitting. Lace is commonly crocheted, as well as a large variety of other items. Process

Crocheted fabric is begun by placing a slip-knot loop on the hook, pulling another loop through the first loop, and repeating this process to create a chain of a suitable length. The chain is either turned and worked in rows, or joined to the beginning of the row with a slip stitch and worked in rounds. Rounds can also be created by working many stitches into a single loop. Stitches are made by pulling one or more loops through each loop of the chain. At any one time at the end of a stitch, there is only one loop left on the hook. Tunisian crochet, however, draws all of the loops for an entire row onto a long hook before working them off one at a time.

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19.6 CALICO

Calico is a type of fabric made from unbleached, and often not fully processed, cotton. Also referred to a type of Printing.

19.7 NETTING

Netting is an open-mesh form of fabric construction that is held together by knots or fused thermoplastic yarns at each point where the yarns cross one another. There are several types of mesh; they are square, hexagonal, and octagonal. The range of mesh sizes is from coarse and opens to fine and shear. Netting may be made of any kind of fiber and may be given a soft or stiff sizing. Net fabrics are relatively fragile and require care in handling and cleaning. Torn net fabrics cannot be satisfactorily mended because the repair would be apparent. If the sizing is water soluble, the fabric should be dry-cleaned. There is a variety of netting; some are produced under specific trademarks. Among the best known standard fabrics are noted here. • Bobbinet is a thin to medium weight hexagonal netting. A typical use is for bridal ceils. • Malines is a very thin, diaphanous diamond-shaped net named after the city of Belgium, its origin. • Tulle is a fine, stiff netting of hexagonal mesh. It is generally used for trimming or over draping of dress goods.

19.8 LET US SUM UP

• Crochet is a process of creating fabric from yarn or thread using a crochet hook. Crochet differs from knitting in that only one loop is active at one time and that a crochet hook is used instead of knitting needles. • Braiding of fiber yarn creates a strand or rope that is thicker and stronger than the strands would have been separately. • Tatting is a technique for handcrafting a particularly durable lace constructed by a series of knots and loops. • Felt is a non-woven cloth that is produced by matting, condensing and pressing fibers. The fibers form the structure of the fabric. • Netting is an openwork fabric, patterned with open holes in the work, made by machine or by hand.

19.9 LESSON END ACTIVITIES

The students may do the following activities based on this lesson. • Collect various samples and structure of netted fabric. • If possible try to do tatting and crochet.

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19.10 POINTS FOR DISCUSSION

Here the students are asked to discuss about the following points • Find the history of felting because it’s very interesting. • Discuss the various methods available to form a netted fabric. • Go through the working principle of a braiding machine.

19.11 CHECK YOUR PROGRESS

1. List the types of braiding.

Basically the braided fabrics are grouped in to categories. 1. Round braid 2. Flat braid

2. The raw materials used for felting is... • Felt is produced from wool and a synthetic fiber. • Typical fiber combinations for felt include wool and polyester or wool and nylon.

3. Write short notes on netting and braiding. a. Nets. Made by knotting, twisting, or looping yarns. Example: lace b. Braided fabric. Created by interlacing three or more yarns to form a regular diagonal pattern down the length of the resulting cord. Examples: decorative trims, shoelaces

4. Define netting and its types.

Netting is an open-mesh form of fabric construction that is held together by knots or fused thermoplastic yarns at each point where the yarns cross one another.

Types: • Bobbinet is a thin to medium weight hexagonal netting. A typical use is for bridal ceils. • Malines is a very thin, diaphanous diamond-shaped net named after the city of Belgium, its origin. • Tulle is a fine, stiff netting of hexagonal mesh. It is generally used for trimming or over draping of dress goods.

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19.12 REFERENCES

• Fibre to Fabric, Cormann B.P, International student’s edition, Mc Graw Hill Book Co., Singapore 1985. • Sewing and Kniting – A Reader’s Digest step by step guide, Reader’s Digest New York 1993 • Riego de la Branchardiere, Eléanor. Crochet Book, 9th Series or Third Winter Book, London:

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