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General Introduction to Textiles A textile is a flexible material comprised of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw wool fibres, linen, cotton, or other material on a spinning wheel to produce long strands known as yarn.[1] Textiles are formed by weaving, knitting, crocheting, knotting, or pressing fibres together (felt). The words fabric and cloth are 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.

Mankind has been endowqed with a resltess nature and is always eager to improve and beautify its own self as well as to embellish and decorate its surroundings. This spirit also applies to Textiles that has always been a symbol of social stature, dignity, prestige of a personwearing those. It is only therefore only natural that a lot of human energy and ingenuity has gone into the improvement of apparel and also the hometextiles for their quality of attractiveness and comfort. At the same time , constant efforts were also made for reduction in their cost of production so as to expand their distribution. History of transfer of human clothing from skins and barks to woven fabrics is obscure but the earliest efforts made for decoration of dresses with dyeing and printing precesses are fairly well known. There is a general consensus among the researchers that dyeing and printing of fabric is as old as its weaving. According to the Greek mythology, Ariadne the Goddess for spinning and weaving is daughtr of idon the dyer of wool. Sources and Types of textiles Textiles can be made from many materials. These materials come from four main sources: animal, plant, mineral, and synthetic. In the past, all textiles were made from natural fibres, including plant, animal, and mineral sources. In the 20th century, these were supplemented by artificial fibres made from petroleum. 1 PROJECT SPECIAL FINISHES

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Textiles are made in various strengths and degrees of durability, from the finest gossamer to the sturdiest canvas. The relative thickness of fibres in cloth is measured in deniers. Microfibre refers to fibres made of strands thinner than one denier. Animal textiles Animal textiles 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 dirtproof. Woollen refers to a bulkier yarn produced from carded, nonparallel 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. 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, vicua 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. Wadmal is a coarse cloth made of wool, produced in Scandinavia, mostly 1000~1500CE. Silk is an animal textile made from the fibres of the cocoon of the Chinese silkworm. This is spun into a smooth, shiny fabric prized for its sleek texture. Plant textiles Grass, rush, hemp, and sisal are all used in making rope. In the first two, the entire plant is used for this purpose, while in the last two, only fibres from the plant are utilized. Coir (coconut fibre) is used in making twine, and also in floormats, doormats, brushes, mattresses, floor tiles, and sacking. Straw and bamboo are both used to make hats. Straw, a dried form of grass, is also used for stuffing, as is kapok. Fibres from pulpwood trees, cotton, rice, hemp, and nettle are used in making paper. Cotton, flax, jute, hemp and modal are all used in clothing. Pia (pineapple fibre) and ramie are also fibres used in clothing, generally with a blend of other fabrics such as cotton. Acetate is used to increase the shininess of certain fabrics such as silks, velvets, and taffetas. Seaweed is used in the production of textiles. A water-soluble fibre known as alginate is produced and is used as a holding fibre; when the cloth is finished, the alginate is dissolved, leaving an open area

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Tencel is a man-made fabric derived from wood pulp. It is often described as a man-made silk equivalent and is a tough fabric which is often blended with other fabrics - cotton for example. Mineral textiles Asbestos and basalt fibre are used for vinyl tiles, sheeting, and adhesives, "transite" panels and siding, acoustical ceilings, stage curtains, and fire blankets. Glass Fibre is used in the production of spacesuits, ironing board and mattress covers, ropes and cables, reinforcement fibre for composite materials, insect netting, flameretardant and protective fabric, soundproof, fireproof, and insulating fibres. Metal fibre, 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 Synthetic textiles

A variety of contemporary fabrics. From the left: evenweave cotton, velvet, printed cotton, calico, felt, satin, silk, hessian, polycotton. All synthetic textiles are used primarily in the production of clothing. Polyester fibre is used in all types of clothing, either alone or blended with fibres such as cotton. Aramid fibre (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 fibres 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 activewear, bras, and swimsuits. Olefin fibre is a fibre used in activewear, linings, and warm clothing. Olefins are hydrophobic, allowing them to dry quickly. A sintered felt of olefin fibres is sold under the trade name Tyvek. 3 PROJECT SPECIAL FINISHES

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Ingeo is a polylactide fibre 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 fibre used in clothing embellishment General uses of Textiles 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 1. carpeting 2. upholstered furnishings 3. window shades 4. towels 5. covering for tables 6. beds and other flat surfacesand in art. In the workplace, they are used in industrial and scientific processes such as filtering. 1. Miscellaneous uses include 2. flags 3. backpacks 4. tents 5. nets 6. cleaning devices, such as handkerchiefs 7. transportation devices such as balloons, kites, sails, and parachutes 8. strengthening in composite materials such as fibre glass and industrial geotextiles 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 1. 2. 3. 4. 5. 6. 7. 8. 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 bullet proof vests.

In all these applications stringent performance requirements must be met. Woven of threads coated with zinc oxide nanowires, laboratory fabric has been shown capable of "self-powering nanosystems" using vibrations created by everyday actions like wind or body movements.

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The History of Textiles Early humans started wearing the skins of a wide variety of mammals that they killed for food. The skins provided both protection and decoration. Over the millennia, through experimentation, mankind began to build up a range of animal and plant fibres that could be used for clothing, fabric, matting and cordage. Some of these natural materials were more readily available and had a widespread use, others such as yucca leaves were more specific to an area and had a limited use. Clothing and Fabric - Animal skins such as wolf, bear, dear, leopard, moose, rabbit, buffalo and seal. Animal fibres such as silkworm, sheep, goat, camel, rabbit, alpaca, human hair and feathers. Plant fibres such as cotton, flax, ramie, jute, hemp and yucca leaves. Matting and Cordage Animal fibres such as goat and human hair. Plant fibres such as flax, esparto grass, bark, vines, hemp and corn straw. Certain fibres, because of their properties and availability became more important. Linen developed from the wild flax of Mesopotamia, cotton from the area around the River Indus and from Southern Mexico, silk from Northern China and wool from sheep that were originally domesticated in Western Asia as early as 9000BC. These ancient sheep were not woolly, as we know them today, but possessed a hairier coat. Woolly breeds did not appear until about 3000BC. A history of textiles should probably start with wool, a fibre that was successfully made into fabric as far back as the Stone Age some 1.75 million years ago. By the later Stone Age the art of using vegetable dyes from the arbutus plant and from elderberries was discovered, and by the Bronze Age even more complex dyeing operations such as the application of woad had been introduced. The art and craft of dyeing using natural dyes developed to a remarkable extent with colours being obtained from plants such as madder, saffron and weld, as well as those from the animal world such as Tyrian purple from molluscs and cochineal from insects. One interesting point worth noting is that there were very few natural green dyes available up until the mid 19th century and the birth of the synthetic dye industry. Anyone wanting green had therefore to apply blue and yellow colour to a fabric in two stages. Yellow natural dyes tend to fade to a dirty brown and so that is why Medieval tapestries have blue trees and grass. Serviceable woollen fabrics have been found in Iraq dating back to 4200BC indicating a thriving trade in wool. It was evidently from Central Asia that sheep and wool were introduced into other areas of the world. Because sheep adapt easily to their environment, many variations of shape, fleece, or other characteristics have developed. The ancestor of the finest wool-bearing sheep is the Spanish Merino, which was bred from a number of earlier breeds, including that introduced into Spain by the Phoenicians. Merinos have become the foundation of the modern global wool raising industry.

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By early Roman times, around 700BC, wool dyeing had been established as a recognised craft. In Britain, the woollen industry had from the Middle Ages become the major industry in the land. As far back as the 14th century, Edward III commanded that the Lord Chancellor should sit on a sack of wool as a reminder of the importance of the trade. At the time, surplus wool was exported to Europe through the network of traders known as the Hanseatic League. Imports included wine from the Rhineland and finished textiles from Bruges. Edward realised that more revenue could be gained by exporting cloth and so he encouraged expert weavers from Flanders to settle here. In medieval towns across the country the trade was partitioned into spinning, weaving, fulling and merchant tailoring, controlled to a great extent by craft guilds who imposed standards and laid down working methods. This system was unchanged until independent clothiers appeared during Tudor times. These capitalists bought wool from the farmer then had it spun up into yarn and woven by others before fulling, dyeing and finishing the cloth on their own premises. Across Europe, especially in the Low Countries, powerful urban guild weavers effectively limited the cottage weaving of yarn, holding up the price of cloth. By the 16 th Century the effect of cheap labour had turned England into a major exporter of fabric. The mechanisation of the textile industry in the late 18th and early 19th century changed the woollen industry forever. The adaptation of the new inventions, so effective in transforming the cotton industry, came later to the woolen industry as it was then a more difficult fibre to process mechanically. Investment was particularly strong in Yorkshire, initially around Huddersfield and Halifax and then on to Bradford, which also had the added advantage of a thriving coal industry. A convenient source of energy for the new steam engines which by then were 6 PROJECT SPECIAL FINISHES

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available. The industry quickly died off in traditional woollen processing areas such as East Anglia and the West Country. Around 3000BC there was an explosion of invention with fibres like cotton, silk and flax becoming more widely used. Spinning and weaving were already well established as domestic crafts. Before the invention of the Spinning Wheel and the later Saxony Wheel, spinning was a slow and tedious task. The spinning of one pound of heavy cotton yarn taking several weeks and one pound of woollen blanket yarn about one week. Spinning would be done between the finger and thumb using a simple spindle and whorl. Even the direction of the rotation was in ancient times dictated more often than not by local tradition. Such was the importance of textiles to a community. Traditional Spinning Wheel

Weaving was a much less tedious task consuming a spinners weekly output in a matter of hours. Even so handloom weaving was an awkward process with the shuttle bearing the yarn being passed slowly across the warp from one hand to the other. Ancient looms were generally one of five types used throughout the world. All basically doing the same job. These were the horizontal ground loom of ancient Egypt, the vertical framed loom and warp weighted looms of Europe, the simple backstrap loom of the Americas and the widely used treadle loom. Even though the process was slow and laborious these looms, in the hands of an expert, could produce wonderfully complex patterned fabrics with very fine yarn. The art of hand knitting, an alternative to weaving, was practised from the Middle Ages, its origins being unknown. But it was not until the invention of the frame for knitting stockings by William Lee in the year 1589 that knitted garments came to the fore. The 7 PROJECT SPECIAL FINISHES

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knitting frame was essentially a weft knitting machine that produced stitches at more than six times the speed of a hand knitter. Knitting did not change again until 1775 when the warp knitting machine was invented, and again in the mid 19th Century when the all important latch needle was introduced. Apart from the introduction of the wheel driven spindle which helped to speed up spinning, the production of fabric changed little until the Industrial Revolution. The earliest known Old World textiles are linens from Turkey dating back to 6500BC. By 3400BC the manufacture of linen from flax was already an established art in Egypt where both fine and coarse canvas-like linen cloth have been found in burial chambers. The wealthier and more important the person the finer the linen. Some mummies have been found wrapped in as much as 900 metres of very fine linen. The use of linen spread from Egypt through the Mediterranean basin and was carried to north west Europe by the Romans. France, the Low Countries and Ireland became famous for their linen. Ireland especially had an ideal damp climate for spinning and weaving. Linen Wrapping from Tutenkamuns Tomb

Surprisingly, up until the 17th century only small amounts of flax were grown in England. This was due in part to competition from the wool industry. The arrival around this time of linen workers from the continent stimulated a demand for the fibre which was met by importation largely from Russia. Evidence of the origins of silk production are a little vague, but it is known that dyed silk ribbons and fabric were in use in China before 3000BC. More conclusive evidence is 8 PROJECT SPECIAL FINISHES

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available around 2600BC with the existence of the earliest written records of the use of dyestuffs. Trade in silk opened up during the Shang dynasty around 1700BC. Early examples of silk being found as far afield as Scandinavia. By the time of the Roman Empire, during the Han dynasty, the Silk Road was well established and sericulture had been introduced into Bactria and India to help relieve the increased demand. Trade could be very lucrative, for example, Purpura (Murex - mollusc) dyed silk garments were only for the very rich, with such garments costing their weight in gold.

The Silk Road from Changan in China through Lanzhou, Wuwei, and Dunhuang. Into Pakistan, Afghanistan, Iran and Iraq and onto the Mediterranean. Most of the early Chinese production of silk was not for export and much of the silk leaving the country was given away as annual tributes or gifts. Chinese emigration eventually spread the knowledge of sericulture across to Korea and Japan. By the time of the Tang dynasty in about 600AD foreign silks from as far a field as Persia were finding their way back to China. It is interesting to note that the first true factory in England was a silk mill, not wool or cotton as you would expect, constructed in 1718 on the River Derwent near Derby by John and Thomas Lombe. The mill was six storeys high, employed 300 men and was driven by water power. It was a full fifty years ahead of its time. Cotton, arguably the most important and widely used fibre today dates back again to about 3000BC. Early fabrics being found in Indian tombs. Written descriptions in Hindu hymns dating from around 1400BC of the manufacture of cotton yarn and the weaving of the cloth, suggest that by then the fabric had an important place in Indian culture. It was 9 PROJECT SPECIAL FINISHES

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also produced by the early Chinese civilisations and there is evidence of cotton production in pre-Inca Peru (before 2000BC). By the time of Alexander the Great, production techniques had already become quite sophisticated, the beautiful printed cottons of India being worth a mention in his records of conquest. The cultivation of cotton spread to Egypt and the Mediterranean basin. By the 12th century, Venice had become a major cotton manufacturing city, processing cotton from the Mediterranean area into cloth for sale across Europe. Cotton manufacturing eventually spread to Germany in the Middle Ages together with the increased cultivation of dye plants such as woad. The fibre was first imported into England in the 16th century but it was not until the mid 18th century that production increased significantly through a series of inventions which transformed the manufacturing process. The earlier inventions were aimed at merely improving the productivity of the home workers. Increased demand for cotton made it more difficult to supervise the work and quality control became more of a concern, as did the embezzlement of materials. The obvious answer to these problems, together with the increasing size and complexity of the textile machinery itself , was to establish factories where all the manufacturing could be done, and controlled, under one roof. By the 18th century there was a sudden interest in the mechanisation of all manufacturing processes. In the textile industry, which was a domestic industry at the time, the main bottleneck in production was the speed at which yarn could be spun. The invention of the Spinning Jenny by James Hargreaves in 1764 improved productivity significantly enabling a single operator to spin eight threads at once. However, the thread produced was coarse and did not have the strength required for producing warp threads on looms (warp threads are tensioned and require considerably more strength than weft threads) The real breakthrough came in the 1771 when Richard Arkwright successfully established a mill based on the use of the automatic continuous spinning machine called the Waterframe. The power for the factory, which was located by the river Derwent in Derbyshire, being supplied by a water wheel. As the mill became more successful Arkwright built homes for the workers around the mill. The resulting village of Cromford was the first planned workers village consisting in the main of three storey terraced houses. The top storey which was connected by doors along the whole row of houses, was used by the employees to make stockings during the evenings. The main advantage of the Waterframe was that it could produce a stronger, higher quality thread. The final step in the early mechanisation of spinning came with the invention by Samuel Crompton in 1779 of the mule. This was a hybrid machine which combined the roller drafting of the water frame with the running twist of the jenny. Fine yarns could now be produced consistently. The importance of the water wheel in the early development of the cotton industry can be shown clearly by the fact that in the late 18th century there were nearly 100 cotton mills within a 10 mile radius of Ashton-under-Lyne, all on the river Tame and all powered by water. Water mills had been introduced to Britain as far back as Roman times, but on a much smaller scale. However, by the Domesday census of 1086 there were 5600 of them used for grinding grain, processing wool, hammering metal and making paper. 10 PROJECT SPECIAL FINISHES

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It was not until the early 20th century that real progress was made in the synthesis of polymeric synthetic fibres. In the late 1920s Carothers was given a remit by E.I Du Pont De Nemours Inc to conduct fundamental research into macromolecular materials. In 1928 he discovered the reaction that produces a synthetic polyamide. Over the next seven years this process was refined and by 1935 a pilot process for a condensation polymer from hexamethylene diamine and adipic acid, or nylon 66, was operating. The two chemical components are first mixed in methanolic solution and the nylon salt settles out. A concentrated solution of this salt is heated under pressure in an inert atmosphere to about 270C. Steam is then bled off and the residue is heated further under vacuum to complete the polymerisation. Nylon was the first major synthetic fibre and from 1938 to 1972 was in the greatest production by weight. Carothers also demonstrated a number of high molecular weight plastics made from acids and alcohols in the early 1930s, and patented a workable system in 1935. However, he was making more progress with polyamides and so this work, which was the first step towards polyester, was dropped. In England, during the early years of the Second World War, Whinfield and Dixon conducted research on the terephthalic acid and ethylene glycol system which became the basis for the highly successful polyester fibre. Their choice of polymer condensation reaction gave a product that overcame difficulties with chemical stability experienced by earlier researchers. Acrylonitrile was known as a chemical substance as far back as 1893, but because of difficulties in dissolving it for spinning no progress was made in converting it to a useable fibre until 1925. It was around this time that melt spinning was invented. There were still problems however, due to the very viscous nature of the polyacrylonitrile melts. Again it wasnt until the Second World War that progress was made. Researchers in the USA developed a solvent spinning system using dimethyl formamide which produced satisfactory synthetic fibres of the acrylic type. This was marketed as Orlon. Ultimately, two spinning systems were developed, both still in use, a dry evaporative method and a wet method using solvent dissolved polymer extruded into a water bath. The developments already discussed provided the basis for the expansion of the textile industry. More recent improvements in spinning and weaving technology, such as open end spinning (Vyzkumny Ustav Bavinarsky, 1966) and shuttleless weaving (rapier, air jet, water jet) have helped to increase the efficiency, range, speed and quality of processing.

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Textile Fibre Usage and Production Before any conclusions can be made as to the best options for improving environmental sustainability in the textile industry, trends in fibre usage and production need to be analysed. It is no use recommending the use of a fibre if it is likely that it will always remain in a minority as far as popularity and options for use. Production of textiles in the years from 1750 to 1900 was limited mainly to the natural fibres, cotton, wool, silk and flax. Restrictions on flax growing in England during the Middle Ages led to a growth in the production of flax in Ireland which became the worlds largest producer of linen. In the late 18th Century more efficient flax spinning machinery became available, and a number of new factories were built in England, but the popularity and price of cotton goods restricted the use of linen to sailmaking, sacking and furniture. The woollen industry, which had been established in the Middle Ages was based on the domestic system. With spinning often done by farm women and the weaving by the men when the farm work was slack. Leeds in Yorkshire eventually became the main centre for the trade of wool cloth to be finished. By the mid 18 th century the town was producing and trading about 80000 pieces of broadcloth per year. In Britain the sudden expansion of the cotton industry can clearly be seen in the amounts of cotton fibre imported between 1700 and 1800. In 1700 there was barely 1000 tonnes of fibre imported, by 1780 this had climbed to about 3000 tonnes. Over the next twenty years with the introduction of widespread mechanisation, there was a nine fold increase to about 26000 tonnes. By this time the Lancashire textile industry employed about 250000 workers which accounted for 36% of the working population of the north west. The cotton industries location was no accident. The availability of large quantities of water from the Pennines for both power and cloth processing, the proximity of substantial coal supplies for the later transfer to steam power, the salt for bleaching from Cheshire and the good communications by road, canal and rail to ports like Liverpool and Manchester, all added to the attractiveness of the region. The silk industry developed slowly in Britain and it was only in the late 17 th and early 18th century that significant amounts of cloth were produced. Silk factories were established in Macclesfield, Stockport, Chesterfield, Manchester, Norwich and London. By about 1850 the industry employed about 130000 people in Britain. Small by comparison to cotton, but significant. If only the evolution of man-made fibres and natural fibres and their respective share in the world production of fibres are considered, this leads to the conclusion that man-made fibres tend to take the place of natural fibres. An obvious conclusion since synthetic fibres alone have risen from zero in the 1920s to over one third of the market in the early 1990s.

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However, this is not the case. The production of cotton, and even wool to a certain extent, have kept pace with the demand for synthetics. Since 1900, global cotton production has risen from about 3.5 million tones per year to 18.0 million tonnes per year with no signs of tailing off. Wool production doubled between the years 1900 to 1960, from about 1.5 million tonnes to 3.0 million tonnes per year, but since then production has been relatively static. The demand for silk has been fairly constant since the First World War, at the relatively low level of about 50000 to 60000 tonnes per year, with a dip during the Second World War when production in Japan, the main silk producer at the time, collapsed. Man-made cellulosics grew from a global production of 22000 tonnes in 1920 to nearly 2.5 million tonnes in 1956. Since then production has remained pretty static due to the introduction of other, more useful and attractive, synthetic fibres. Production of wholly synthetic man-made fibres really started in the late 1930s, grew slowly and then took off explosively in the 1960s, rising from 830000 tonnes in 1961 to 4178000 tonnes by 1968. Current world production of synthetics is running at about 18 million tonnes per year with polyester having the largest share of the synthetic market. The principal factor in making polyester the worlds most-used man-made fibre has been the dominant position of polyester/cotton blended fabrics in world markets. In the Far East investment in polyester-fibre plants has been particularly strong.

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Trends over the last thirty years or so therefore suggest that cotton is holding its own and that polyester has grown to be by far the most popular man-made fibre. This is likely to hold true in the short to medium term. Any significant reduction in environmental impact will therefore not come about because of the use of one fibre in preference to another, purely on the basis of a slightly lower cradle to grave impact. There are environmental problems of one kind or another with all of the major fibres in current use. The answer must therefore be to improve processing, to minimise wastage, and to develop new or alternative chemicals and dyes with lower environmental impacts and toxicity. If we look at textile usage in slightly more detail, then in terms of fibre production the global market share of the principal textile fibres in 1994 was approximately as follows :-

The predominance of cotton for the natural fibres, and polyester for the manmade fibres clearly shows up. The two accounting for some 65% of the total textile market. The Others category contain the polyamides. Within the textile industry there exists only limited options for fibre substitution. This is particularly true of the synthetic fibres which have been developed to satisfy a need. For example, nylon is dominant in womens hosiery, some areas of lingerie and carpets, whilst polyester is dominant in the heavy workwear and minimum care apparel markets. The consumption of fibres by end use gives a further indicator of trends in usage and subsequent wastage. This following example gives a breakdown of use in the EC for the year 1988/89. For the sake of simplicity all fibre usage has been expressed in terms of four fibre types and five usage categories. Each usage category adds up to 100%. 14 PROJECT SPECIAL FINISHES

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Use Apparel Carpets Domestic Industrial Tyres

Synthetic 42.6 84.7 42.1 55.6 39.4

Cellulosic 10.9 0.5 12.3 21.9 59.3

Cotton 32.9 1.4 42.2 21.3 1.3

Wool 13.9 3.4 3.4 1.1 0.0

The apparel category is dominated by polyester and cotton, with a smaller but significant volume of viscose and wool. A similar pattern is true of the domestic category, although the requirement for wool here is only tiny. Carpets use mainly nylon and wool. Industrial fibre usage is dominated by synthetics, which are used across a wide range of applications, from conveyor belts and geotextiles through to medical uses. Tyre production, which is also an industrial usage, but such an important one that it has been separated out here, requires both synthetics and cellulosics for tyre backing materials. It is important to note that the car industry accounts for about 35 to 40% of the total fibre consumed by these last two categories. The organised recovery of waste textiles can be traced back as far as the old clothiers, many of whom were farmers involved in all stages of textile production. However, the practice of recovering waste is probably as old as the art of spinning and weaving. Shoddy and mungo was invented, as such, by Benjamin Law in 1813. He was the first to take old clothes and grind them down into a fibrous state that could be re-spun into yarn. The shoddy industry which was centred around the towns of Batley, Morley, Dewsbury and Ossett in West Yorkshire, concentrated on the recovery of wool from rags. The importance of the industry can be gauged by the fact that even in 1860 the town of Batley was producing over 7000 tonnes of shoddy. At the time there were 80 firms employing a total of 550 people sorting the rags. These were then sold to shoddy manufacturers of which there were about 130 in the West Riding. Waste cotton garments could not be pulled apart without creating too short a fibre and so waste cotton was generally used as a filling material and for cleaning cloths. The shades of recovered wool produced by the shoddy trade, especially in the early days, tended because of the nature of the process, and the source of the garments, to be dull. There were lots of greys, blues, and blacks obtained from old uniforms. A lot of this went back into uniforms producing a complete cycle of use. As more and more fibre blends and cotton appeared, and competition from the Italian recycling industry became stiffer, there was a tendency for the English rag trade to move towards garment sorting and the selling of second hand clothing to the third world. Today there are only about ten rag pulling companies left in the UK, even so, there is still a lot 15 PROJECT SPECIAL FINISHES

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of textile waste produced. Typical figures for the waste produced at each stage of processing gives an idea of the potential for the minimisation and the recovery of waste. Fibrous/Fabric Waste Production

It is worth noting that even in these days of increased environmental awareness, about a million tonnes of textiles are landfilled each year in the UK. Key Inventions and Inventors John Kay (1704 1780) Flying Shuttle The son of a Lancashire farmer, John Kay patented his idea, the Flying Shuttle, in 1733. This new addition significantly improved the age old process of handloom weaving which relied on the yarn being passed from one hand to the other. The invention involved knocking a shuttle back and forth across the loom by means of a set of cords. This enabled weavers to produce wider fabrics at faster speeds. Failure to get payment for the use of his idea and the destruction of his house in Bury by angry weavers, afraid that the 16 PROJECT SPECIAL FINISHES

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Lewis Paul (circa1700 1759) - Carding Machine Lewis Paul invented a Roller Spinning machine in 1738, and in 1748 a hand driven carding machine. Both inventions had their limitations when tried out in industrial conditions, but they provided later inventors and entrepreneurs, Arkwright in particular, with a useful starting point from which to develop further ideas. James Watt (1736 1800) Rotary Steam Engine James Watt was already a renowned engineer and instrument maker when in 1763 whilst reparing a Newcomen engine he discovered a way of making it more efficient. The new engine cooled the used steam in a condenser separate from the main cylinder. The invention was ideal for pumping water out of mines and was significantly more powerful than existing engines. Watt continued to develop the engine and in 1782 came up with the design for a rotary motion engine which would be ideal for driving machinery. By 1783 Richard Arkwright was already using a Watt steam engine in one of his textile mills, and by 1800 over 500 had been purchased. James Hargreaves (1720 1788) Spinning Jenny James Hargreaves, a weaver from Blackburn, had the idea for an improved spinning machine when the family spinning wheel was accidentally knocked over. He saw the potential for a whole row of spindles worked off a single wheel. In 1764 he built the first Spinning Jenny which could spin eight threads at once. By 1770, because the invention had not been patented, the machine had been copied and improved by others to enable eighty threads to be spun at once. The invention of the Jenny caused uproar amongst the traditional Lancashire spinners, a group of whom marched on his house and destroyed his equipment. Richard Arkwright (1732 1792) Water Frame The idea for the Water Frame came from work originally done by a clockmaker from Warrington called John Kay. Arkwright, a wig maker from Preston employed Kay, who had run out of funds, to make the new machine. Arkwright made improvements to the spinning frame which involved three sets of paired rollers that turned at different speeds, producing a strong twisted yarn, and set up a factory by the River Derwent using what was now called the Water Frame. The name change came about because the spinning frame had become too large to be manually operated and so the power of the water wheel had to be used. The invention of the Water Frame produced a need for more cardings. Arkwright turned his attention to this new bottleneck in production. The carding machine invented by Lewis Paul in 1748 was improved by Arkwright in 1775. The new machine incorporated a crank and comb mechanism producing a continuous film of fibre. Arkwright went on to build factories in Lancashire, Staffordshire, Derbyshire and Scotland. The later factories using the rotary steam engine invented by 17 PROJECT SPECIAL FINISHES

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James Watt instead of water power. On his death in 1792 Richard Arkwright was a very wealthy man with an estimated fortune in excess of 500 000.

Samuel Crompton (1753 1827) Spinning Mule The Spinning Mule, devised by Samuel Crompton in 1779, was a hybrid of the earlier Spinning Jenny and the Water Frame. The Mule which was initially a small hand operated machine produced a strong, yet fine and soft yarn. By the 1790s a larger steam or water powered version was being built with over 400 spindles. Sadly because Crompton was too poor to apply for a patent he sold the rights to a Bolton manufacturer and made no money from the subsequent sale of his invention. Edmund Cartwright (1743 1823) Power Loom Cartwright, the well educated son of a Nottingham landowner became interested in the new textile industry when visiting a factory owned by Richard Arkwright. In 1784, with the help of a carpenter and blacksmith, he began working on a machine that would improve the speed and quality of weaving. A basic version of the Power Loom was patented in the following year. The invention revolutionised weaving, changing it from a manual process into a mechanical one. The weaver now spent most of his time repairing broken threads. The invention was improved by William Horrocks of Stockport between 1803 and 1814, and subsequently by Richard Roberts of Manchester who effectively invented the definitive power loom. Joseph Jacquard (1752 1834) Jacquard Loom Jacquard, the son of a silk weaver from Lyons, was a failed businessman when in 1801 he developed a loom that used a series of punched cards to control a complex pattern of warp threads. Further work on the idea produced the familiar looped arrangement of cards for the repeat patterns used in cloth and carpet designs. The invention now enabled intricate patterns to be woven without the continual intervention of the weaver. Jacquard Loom

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One interesting effect of this invention was the adaptation by Charles Babbage of the card system invented by Jacquard in his work to produce an automatic calculator, which eventually led to the development of computers and computer programming. William Perkin (1838 1907) Synthetic Dyes William Perkin studied at the Royal College of Chemistry under von Hoffman and at the tender age of 18 discovered the first synthetic dye, mauveine. He went on to set up his own business and within five years had made his fortune. At 35 he retired from business but continued to experiment leading to the discovery of coumarin, the first synthetic perfume. Other Key Developments 1785 Bell develops roller or cylinder printing. 1786 Bertholet develops method for using chlorine water for commercial bleaching. The use of hydrogen peroxide follows shortly after. 1797 Bancroft invents a process for steam fixation of prints. 1828 John Thorp patented the first ringframe for spinning yarn. 1834 Runge with his work on the distillation of coal tar paved the way for later work done in developing aniline dyes. 19 PROJECT SPECIAL FINISHES

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1862 The first soluble azo dye synthesised by Martius and Lightfoot. 1868 Graebe and Liebermann synthesised alizarin, a synthetic substitute for madder a widely used vegetable dye. 1878 Von Baeyer successfully synthesised indigo. 1884 The first direct cotton dye Congo Red was created by Bottinger. 1886 Northrop automatic bobbin changing loom first used. 1891 The first commercial rayon plant was built by Chardonnet at Besancon, France. 1901 Bohn synthesised Indanthrene Blue RS, the first anthraquinone vat dye. 1951 Polyester manufactured commercially at the DuPont plant in North Carolina. 1953 - Cibalan Brilliant Yellow 3GL introduced. This led the way to fibre reactive dyes. ICI introduced the Procion range of reactives by 1956. Textile processing techniques In order to determine the true environmental impact of textile processing, the main types of machinery in current use , together with typical processing routes needs to be described. The pollutants and waste generated by processes together with typical levels or concentrations, emitted or discharged help to provide a more detailed picture of textiles. For convenience, the whole textile chain has been split in to the seven main sections. These are fibre production, fibre to fabric, preprative treatments, textile coloration, finishing processes, fabric after and recycling and disposal Fibre production- this includes the details on cotton growing, sheep rearing, sericulture and the generation of man made fibres Fibre to fabric-which contains information on the types of machinery used in spinning, weaving, knitting and non-woven production Preprative treatments- which includes details of processes such as singeing, desizing, scouring, and bleaching Textile coloration- contains different methods used for dyeing and printing. Finishing processes- includes information on coating and lamination, wet chemical finishing and mechanical finishing processes.

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SPECIAL FINISHES 21 Fabric aftercare- which contains information on different types of commercial laundry and dry leaning machineries. Recycling and disposal- looks at the processes involved in textiles, the segregation techniques and different end-uses.

These stages are explained in several CLASSES ahead.

Classes of Textiles The textiles covers various stratas amd have a gfreat impact on every day life of human beings. In order to determine the true environmental impact of textile processing, the main types of machinery in current use, together with typical processing routes need to be described. The pollutants and waste generated by processes together with typical levels or concentrations, emitted or discharged help to provide a more detailed picture of textiles. For convenience, the whole textile chain has been split in to the seven main sections. These are fibre production, fibre to fabric, preprative treatments, textile coloration, finishing processes, fabric after and recycling and disposal. 1. Fibre production- this includes the details on cotton growing, sheep rearing, sericulture and the generation of man made fibres 2. Fibre to fabric-which contains information on the types of machinery used in spinning, weaving, knitting and non-woven production 3. Preprative treatments- which includes details of processes such as singeing, desizing, scouring, and bleaching 4. Textile coloration- contains different methods used for dyeing and printing. 5. Finishing processes- includes information on coating and lamination, wet chemical finishing and mechanical finishing processes. 21 PROJECT SPECIAL FINISHES

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SPECIAL FINISHES 6. Fabric aftercare- which contains information on different types of commercial laundry and dry leaning machineries. 7. Recycling and disposal- looks at the processes involved in textiles, the segregation techniques and different end-uses.

However a simpler way of describing the above chain can be:Ginning Spinning Weaving Pretreatment Dye/Print FINISH

Dispose

End use

Ginning It is the process in which the cotton fibres are separated from their seeds and refined a bit. Moreover it is used to effectively bring the cotton fibre in the form that can be easily used by the next big stage of Spinning. Otherwise the attached cotton seed and many other impurities may not allow the effective formation of yarn

A typical spinning Mill 22 PROJECT SPECIAL FINISHES

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Spinning It is the process in which the cotton yarn is produced. Not only cotton but many other types of fibres may-be used for the production of yarn. For example the silk filament is used for the production of silk yarn. Similarly the jute threads or many other regenerated and synthetic fibres in the fluid form are used for the preparation for their respective type. In case of cotton yarn, it can be carded, combed, single ply, double ply and so on

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Spinning process in Pakistan is done in two technologies 1. Ring spun yarn 2. Open end spun yarn

Ring spun yarn 24 PROJECT SPECIAL FINISHES

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Open end spinning Weaving The term weaving means to weave or to bring the yarn in a form that make up fabric, by either the interlacement of warp and weft or by the interloping of yarn(commonly called knitting)

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Wet-processing This is the anther entirely different stage of textile sector. It involves various complicated and important stages, and can be divided as such: Pretreatments 1. singe 2. desize 3. scour 4. bleach 5. mercerize Dyeing/Printing

Finishing End use

Pretreatments The term pretreatments include all operations of preparing the textile material, such as fibres yarn and woven, knit and non-woven fabrics and garments for the subsequent processes for dyeing printing and finishing. For all practical purposes the pretreatments are carried out along with dyeing and printing and their equipments is part of the wetprocessing plant. 26 PROJECT SPECIAL FINISHES

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The main objective of pretreatments is to impart textile materials a uniform and high degree of absorptivity to aqueous liquor with the minimum possible damage to the fibrous material. The pretreatments of cotton fabrics, for example, should remove natural all impurities like pectins, wax, protein and husk as well as sizing chemicals comprising of softeners and adhesives. Besides high and uniform absorptivity, the textile material should have adequate degree of whiteness so as not to mar the The process of pretreatment refers to the application of chemicals and axillaries on the textiles to the features such as Removal of waxes, pectins, jute strings, rags, Remove hairy fibres on the fibre surface Absorbancy Lusture Ability to absorb dye Removal of pigments Whiteness Swelling of the fibre structure Emerizing(optional) Fibre alignment The above results are obtained in a continuous range of machines, of which each have a specific operation and working. Singeing-cum-Desizing It is the process of removing protruding fibres from the surface of the fabric. Textiles are normally singed in order to improve their surface appearance and wearing properties. The burning-off of protruding fibre-ends, which are not firmly bound in the yarn, results in a clean surface which allows the structure of the fabric to be clearly seen. Un-singed fabrics soil more easily than singed fabrics. Similarly, the risk of cloudy dyeing with singed articles dyed in dark shades is considerably reduced than un-singed articles. Although textile materials can be singed in yarn, knitted or woven forms, singeing of woven fabrics is much more common as compared to other forms. Two main methods of singeing are direct flame singeing and indirect flame singeing. The important direct flame singeing parameters are: Singeing position Flame intensity Fabric speed Distance between the fabric and the burner Moisture in the fabric coming for singeing If any one or more of the above parameters are not optimal, the result may be faulty singeing. There may be singeing faults which are optically demonstrable and are quite easily remedied during the actual working process. 27 PROJECT SPECIAL FINISHES

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Special burners, two of which are provided for the machine. These burners have a particular combustion chamber and are provided with water-cooling arrangement. The cloth can be threaded so as to allow singeing of either one or both sides. It is essential to note that the gas consumption per meter of fabric is less as compared with a machine of conventionaldesign. Both burners are titled away simultaneously (by 45) by electro-magnets. The Burners can be easily cleaned as a special arrangement has been provided. Slit width and flame length adjustments are provided. Non-return valve is incorporated in burner, which isolates the supply line from the burner chamber. High Singeing speeds, infinitely variable between 80 mtrs. To 150 mtrs/min. Excellent and uniform singeing effect with economical gas consumption. Burners turning away automatically when the machine stops. Efficient dust extraction device. Pre-heating Cylinders of Stainless Steel Construction. Water Cooled adjustable rollers immediately after the Burners to obtain soft, medium or high singeing effect Steam quenching device also provided on request. Desizing desizing refers to the removal of starches and sizes from the fabric before the fabric is set for upcoming processes. Desizing can be carries by various purposes, some of which are mentioned Enzyme Desizing Enzyme desizing is the most widely practiced method of desizing starch. Enzymes are high molecular weight protein biocatalyst that are very specific in their action. Enzymes are named after the compound they break down, for example, Amylase breaks down amylose and amylopectin, Maltase breaks down maltose and Cellulase breaks down cellulose. For desizing starch, amylase and maltase are used. Cellulase, on the other hand, is used for finishing cotton fabrics. Amylase will degrade starch into maltose, a water soluble disaccharide and Maltase will convert maltose into glucose, a simple sugar. Desizing with Acids Mineral acids will hydrolyze starch by attacking glucosidic linkages. Acid hydrolysis lowers the molecular weight and eventually reduce starch to glucose. Hydrochloric and 28 PROJECT SPECIAL FINISHES

SPECIAL FINISHES 29 sulfuric acids can be used. One problem with acid desizing is that cellulose fibers are also degraded which is why the method is not used much. One advantage with using acids is that cotton fibers can be demineralized more easily. Insoluble salts are solubilized by acids making the removal of such troublesome metals such as iron more thorough. De-sizing compartment with 12 /16 mtrs. Contents can be provided with a suitable squeezing mangle.

Sr No 1 2 3 4 5 6 7 8 9 10 11 12

Description TENSION UNIT WITH GUIDE ROLLERS & BARS S.S. PRE-DRYING CYLINDER (OPTIONAL) PRE-BUSHING UNIT WITH SUCTION SINGEING CHAMBER WITH EXHAUST WATER-COOLED ROLLER WATER-COOLED BURNER CARBURETOR WITH BLOWER STEAM QUENCHING DEVICE POST BRUSHING WITH SUCTION (OPTIONAL) DE-SIZING UNIT ST-12/ST-15 SQUEEZING MANGLE 3 TONS. MAIN DRIVE (A.C. CONTROLLER) MOTOR WITH FREQUENCY

Scouring 29 PROJECT SPECIAL FINISHES

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Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing. Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils. Mill grease used to lubricate processing equipment mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced. The process of removing these impurities is called Scouring. Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water soluble components. Certain organic solvents will readily dissolve oils fats and waxes and these solvents can be used to purify textiles. Removal of impurities by dissolution is called Extraction. There are commercial processes where textiles are cleaned with organic solvents. Fabrics processed this way are said to be "Dry Cleaned". Although not widely used as a fabric preparation step, it is an important way of removing certain difficult to remove impurities, where a small amount of residuals can cause downstream problems. Garment dry-cleaning is more prevalent. For fabrics that do not have to be desized, solvent scouring is an effective way of removing fiber producer finishes, coning and knitting oils. Knitted fabrics made from nylon, polyester, acetate and acrylics, are particularly amenable to this method of preparation. Wool grease is effectively removed by solvent scouring. Solvent Extractions are particularly useful in the laboratory for determining the amount of processing oils added to man-made fibers and the residual amounts of oils and waxes left by aqueous scouring. Properly controlled, fabrics can be produced with very little residual matter. Schematic of a Continuous Scouring Range

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Bleaching the process of whitening or depriving objects of colour, an operation incessantly in activity in nature by the influence of light, air and moisture. The art of bleaching, of which we have here to treat, consists in inducing the rapid operation of whitening agencies, and as an industry it is mostly directed to cotton, linen, silk, wool and other textile fibres, but it is also applied to the whitening of paper-pulp, bees'-wax and some oils and other substances. The term bleaching is derived from the A.-S. blaecan, to bleach, or to fade, from which also comes the cognate German word bleichen, to whiten or render pale. Bleachers, down to the end of the 18th century, were known in England as " whitsters," a name obviously derived from the nature of their calling. The operation of bleaching must from its very nature be of the same antiquity as the work of washing textures of linen, cotton or other vegetable fibres. Clothing repeatedly washed, and exposed in the open air to dry, gradually assumes a whiter and whiter hue, and our ancestors cannot have failed to notice and take advantage of this fact. Scarcely anything is known with certainty of the art of bleaching as practised by the nations of antiquity. Egypt in early ages was the great centre of textile manufactures, and her white and coloured linens were in high repute among contemporary nations. As a uniformly wellbleached basis is necessary for the production of a satisfactory dye on cloth, it may be assumed that the Egyptians were fairly proficient in bleaching, and that still more so were the Phoenicians with their brilliant and famous purple dyes. We learn, from Pliny, that different plants, and likewise the ashes of plants, which no doubt contained alkali, were employed as detergents. He mentions particularly the Struthium as much used for bleaching in Greece, a plant which has been identified by some with Gypsophila Struthium. But as it does not appear from John Sibthorp's Flora Graeca, edited by Sir James Smith, that this species is a native of Greece, Dr Sibthorp's conjecture that the 31 PROJECT SPECIAL FINISHES

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Struthium of the ancients was the Saponaria qfficinalis, a plant common in Greece, is certainly more probable. Cotton is bleached in the raw state, as yarn and in the piece. In the raw state, and as yarn, the only impurities present are those which are naturally contained in the fibres and which include cotton wax, fatty acids, pectic substances, colouring matters, albuminoids and mineral matter, amounting in all to some 5% of the weight of the material. Both in the raw state and in the manufactured condition cotton also contains small black particles which adhere firmly to the material and are technically known as " motes." These consist of fragments of the cotton seed husk, which cannot be completely removed by mechanical means. The bleaching of cotton pieces is more complicated, since the bleacher is called upon to remove the sizing materials with which the manufacturer strengthens the warp before weaving A. Bleaching Mechanism Sodium hypochlorite is the salt of a moderately strong base (OCl-) and a weak acid (HOCl). Solutions are therefore alkaline. The species present in a solution can be understood from the following: Note: Hypochlorous acid (HOCl) is the active bleaching agent. B. Effect of pH pH has a profound effect on bleaching with hypochlorite. 1. If caustic is added to the solution, the equilibrium shifts to the left favoring the formation of the hypochlorite ion (OC1-) at the expense of hypochlorous acid (HC1O). Under strongly alkaline conditions (pH > 10), little to no bleaching takes place. 2. When acid is added, the equilibrium shifts to the right and the HOCl concentration increases. At a pH between 5 and 8.5, HOCl is the major specie present so very rapid bleaching takes place. However, rapid degradation of the fiber also takes place. 3. When the pH drops below 5, chlorine gas is liberated and the solution has no bleaching effectiveness at all. 4. The optimum pH for bleaching is between 9 and 10. Although the concentration of HOCl is small, it is sufficient for controlled bleaching. As HOCl is used up, the equilibrium conditions continue to replenish it. This pH range is used to minimize damage to the fiber. Sodium carbonate is used to buffer the bleach bath to pH 9 to 10. C. Effect of Time and Temperature Time and temperature of bleaching are interrelated. As the temperature increases, less time is needed. Concentration is also interrelated with time and temperature. Higher concentrations require less time and temperature. In practice, one hour at 400 C is satisfactory for effective bleaching. D. Effect of Metals Copper and iron catalyze the oxidation of cellulose by sodium hypochlorite degrading the fiber. Fabric must be free of rust spots or traces of metals otherwise the bleach will damage the fabric. Stainless steel equipment is required and care must be taken that the 32 PROJECT SPECIAL FINISHES

SPECIAL FINISHES 33 water supply be free of metal ions and rust from pipes. Prescouring with chelating agents becomes an important step when bleaching with hypochlorites. Recommended recipes:-

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Mercerizing The term applied to a process, discovered in 1844 by John Mercer, a Lancashire calico printer, which consists in treating cotton (and to a limited extent other plant fibres) with strong caustic soda or certain other reagents, whereby morphological and chemical changes are brought about in the fibre. Thus, if a piece of bleached calico be immersed in caustic soda of 50 Tw. strength (sp. gr. 1.25), it rapidly changes in appearance, becoming stiff and translucent, but when taken out and well washed in running water it loses these properties and apparently reverts to its original condition. On closer examination, however, the fabric is found to have shrunk considerably both in length and breadth, so as to render the texture quite different in appearance to that of the original calico; it is also considerably stronger, and if dyed in the same bath along with some of the untreated fabric is found to have acquired a greatly increased affinity for colouring matters. This peculiar action is not restricted to caustic soda, similar effects being obtained with sulphuric acid of 105 Tw., nitric acid of 83 Tw., zinc chloride solution of 145 Tw., and other reagents. Mercer assumed that a definite compound, corresponding to the formula C12H20010.Na20 is formed when the cotton is steeped in caustic soda, and that this is decomposed by subsequent washing with water into a hydrated cellulose C12H20010H20, which would account for the fact that in the air-dried condition mercerized cotton retains about 5% more hygroscopic moisture than ordinary cotton. This view is strengthened by the observation that when cotton is immersed in nitric acid of 83 Tw. it acquires similar properties to cotton treated with caustic soda. If, after immersion in the nitric acid, it is squeezed and then dried (without washing) in a vacuum over burnt lime, it is found to have formed a compound which corresponds approximately to the formula C 6 H 10 0 5 .HNO 3, which is decomposed by water into free nitric acid and a hydrated cellulose. When viewed under the microscope, mercerized cotton is seen to have undergone considerable morphological changes, in asmuch as the lumen or central cavity is much reduced in size, while the fibre has lost its characteristic band-shaped appearance and becomes rounded. In Mercer's time the process, which he himself termed "sodaizing" or "fulling," never acquired any degree of corn mercial success, partly on account of the expense of the caustic soda required, but mainly on account of the great shrinkage (20 to 25%) which took place in the cloth. An important application of the process in calico printing for the production of permanent crimp or "crepon" effects, which was originally devised by Mercer, was revived in1890-1891and is still largely practised by calico printers (see Textile Printing). Another application, also dependent upon the shrinking action of caustic soda on cotton, was patented in 1884 by Depoully, and has for its object the production of crimp effects on piece-goods consisting of wool and cotton or silk and cotton. In the manufacture of such goods cotton binding threads are introduced at definite intervals in the warp or weft, or both, and the piece is passed through cold caustic soda, washed, passed through dilute sulphuric acid, and washed again till neutral. The cotton contracts under the influence of the caustic soda, while both wool and silk remain unaffected, and the desired crimped or puckered effect is thus obtained. 34 PROJECT SPECIAL FINISHES

SPECIAL FINISHES 35 By far the most important application of the mercerizing process is that by which a permanent lustre is imparted to cotton goods; this was discovered in 1889 by H. A. Lowe, who took out a patent for his process in that year, this being supplemented by a further patent in 1890. Since Lowe's invention did not receive sufficient encouragement, he allowed his patents to lapse and the process thus became public property. It was not until 1895, when Messrs Thomas & Prevost repatented Lowe's invention, that actual interest was aroused in the new product and the process became a practical success. Their patent was subsequently annulled on the ground of having been anticipated. The production of a permanent lustre on cotton by mercerizing is in principle a very simple process, and may be effected in two ways. According to the first method, the cotton is treated in a stretched condition with strong caustic soda, and is then washed, while still stretched, in water. After the washing has been continued for a short time the tension relaxes, and it is then found that the cotton has acquired a permanent lustre or gloss similar in appearance to that of a spun silk though not so pronounced. According to the second method, which constitutes but a slight modification of the first, the cotton is immersed in caustic soda of the strength required for mercerizing, and is then taken out, stretched slightly beyond its original length, and then washed until the tension slackens. Not all classes of cotton are equally suited for being mercerized. Thus, in the case of yarns the most brilliant lustre is always obtained on twofold or multifold yarns spun from long-stapled cotton (Egyptian or Sea Island). Single yarns made from the same quality of cotton are only slightly improved in appearance by the process, and are consequently seldom mercerized; and the same applies to twofold yarns made from ordinary American cotton. In piece-goods, long-stapled cotton also gives the best results, but it is not necessary that the yarn used for weaving should be twofold. In the great majority of cases, the mercerizing of cotton, whether it be in the yarn or in the piece, is done before bleaching, but sometimes it is found preferable to mercerize after bleaching, or even after bleaching and dyeing. The strength of the caustic soda employed in practice is generally between 55 and 60 Tw. The temperature of the caustic soda hasj a material influence on its action on the cotton fibre, very much stronger solutions being required to produce the same effect at elevated temperatures than at the ordinary temperature, while, on the contrary, by lowering the temperature it is possible to obtain a good lustre with considerably weaker lyes. Cotton yarn may be mercerized either in the hank or in the warp, and a great number of machines have been patented and constructed for the purpose. The simplest form of machine for hanks consists essentially of two superposed strong steel rollers, on which the hanks are placed and spread out evenly. The upper roller, the bearings of which run in a slotted groove, is then raised by mechanical means until the hanks are taut. Caustic soda of 60 Tw. is now applied, and the upper roller is caused to revolve slowly, the hanks acting as a belt and causing the lower roller to revolve simultaneously. After about three minutes the caustic soda is allowed to drain off and the hanks are washed by spurt pipes until they slacken, when they are taken off and rinsed, first in dilute sulphuric acid (to neutralize the alkali and facilitate washing), and then in water till neutral. The hanks are then bleached in the ordinary way and may be subsequently dyed, no diminution being 35 PROJECT SPECIAL FINISHES

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brought about in the lustre by these operations. Cotton warps are usually mercerized on a machine similar in construction to a four box dyeing machine (see Dyeing), but with the guiding rollers and their bearings of stronger construction and the squeezers at each end of the first box with a double nip (three rollers). The first box contains caustic soda, the second water, the third dilute sulphuric acid, and the fourth water. For the continuous mercerizing of cotton in the piece much more complicated and expensive machinery is required than for yarn, since it is necessary to prevent contraction in both length and breadth. The mercerizing range in most common use for pieces is constructed on the same principle as the stentering machine used in stretching pieces after bleaching, dyeing or printing, and consists essentially of two endless chains carried at either end by sprocket wheels. The chains carry clips which run in slotted grooves in the horizontal frame of the machine, which is about 40 ft. in length. The clips close automatically and grip the cloth on either side as it is fed on to the machine from the mangle, in which it has been saturated with caustic soda. The stretching of the piece begins immediately on entering the machine, the two rows of clips being caused to diverge by setting the slotted grooves in such a manner that when the piece has travelled about one-third of the length of the machine it is stretched slightly beyond its original width. At this point the piece meets with a spray of water, which is thrown on by means of spurt pipes; and in consequence the tension slackens and the mercerizing is effected. When the piece arrives at the end of the machine the clips open automatically and release it. Thence it passes through a box containing dilute sulphuric acid, and then through a second box where washing with water is effected. In most large works the caustic soda washings, which were formerly run to waste or were partly used up for bleaching, are evaporated down in multiple effect evaporators to 90 Tw., and the solution is used over again for mercerizing. Cotton mercerized under tension has not as much affinity for colouring matters as cotton mercerized without tension, and although the amount of hygroscopic moisture which it retains in the air-dried condition is greater than in the case of ordinary untreated cotton, it is not so great as that held by cotton which has been mercerized without tension. By drying cotton which has been mercerized with or without tension at temperatures above 100 C. its affinity for colouring matters is materially decreased. The cause of the lustre produced by mercerizing has been variously explained, and in some cases antagonistic views have been expressed on the subject. When viewed under the microscope by reflected light, the irregularly twisted band-shaped cotton fibre is seen to exhibit a strong lustre at those points from which the light is reflected from the surface. Cotton mercerized without tension shows a similar appearance. In the yarn or piece the lustre is not apparent, because the innumerable reflecting surfaces disperse the light in all directions. If, however, the cotton has been mercerized under tension, being plastic while Dyeing

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SPECIAL FINISHES 37 A colorant is a substance capable of imparting its colour to a given substrate, such as paint, paper or cotton, in which it is present. Not all colorants are dyes. A dye must be soluble in the application medium, usually water, at some point during the coloration process. It will also usually exhibit some substantivity for the material being dyed and be absorbed from the aqueous solution. Most textile dyeing processes initially involve transfer of the coloured chemical, pores, or between fibre polymer molecules, depending on the internal structure of the fibre. or its precursor, from the aqueous solution onto the fibre surface; a process called adsorption. From there, the dye may slowly diffuse into the fibre. This occurs down The process of applying dyes on to the substrate(fabric) such that the dyes are applied in the solution form, called dye liquor. There are various classes of dyes depending on the type of substrate, and the method of application varies accordingly Normally the dyes used in the industry for the dyeing of cotton, or other cellulosic, proteinic, regenerated, or synthetic fabrics are following Direct dyes Reactive dyes Vat dyes Sulphur dyes Azoic dyes Disperse dyes Acid or Anionic dyes, pre-mettalised or mordant dyes Basic or cationic dyes

Direct dyes Direct cotton dyes have inherent substantivity for cotton, and for other cellulosic fibres. Their aqueous solutions dye cotton usually in the presence of an electrolyte such as NaCl or Na2SO4. Direct dyes do not require the use of a mordant and, as their name implies, the dyeing procedure is quite simple. The goods go into the bath followed by the dissolved dyes. The bath is then gradually heated, usually to the boil, and additions of salt promote dyeing. Many direct dyes are relatively inexpensive. They are available in a full range of hues but are not noted for their colour brilliance. Their major drawback is their poor to moderate fastness to washing. This limits their use to materials where good washing fastness is not critical. The light fastness of dyeings with direct dyes on cellulosic fibres varies from poor to fairly good, although some copper complex direct dyes have very good light fastness. As usual, the deeper the colour of the dyeing, the lower the fastness to wet treatments, and the higher the fastness to light. Various aftertreatments of the dyeings improve the fastness to washing. In some cases, however, such aftertreatments decrease the light fastness. They also invariably cause a change in hue that makes shade correction and colour matching more 37 PROJECT SPECIAL FINISHES

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difficult. Cotton, and other cellulosic fibres, are dyed with direct, sulphur, vat, reactive or azoic dyes more types than for any other fibre. Each of these classes of dye has its own application methods, dyeing characteristics, cost, fastness properties and colour range, and therefore its own particular advantages and disadvantages. Within each group, application and performance properties vary considerably so the choice of which dyes to use is often not easy. Direct dyes generally cannot meet todays more stringent washing fastness requirements for apparel and linens. In recent years, their share of the market has gradually declined in favour of reactive dyes. The latter have very good washing fastness on cellulosic materials and often have bright colours. Reactive dyes The idea of immobilizing a dye molecule by covalent bond formation with reactive groups in a fibre originated in the early 1900s. Various chemicals were found that reacted with the hydroxyl groups of cellulose and eventually converted into coloured cellulose derivatives. The rather forceful reaction conditions for this led to the false conclusion that cellulose was a relatively unreactive polymer. Possibly because of this, a number of dyes now known to be capable of covalent bond formation with groups in wool and cotton were not initially considered as fibre-reactive dyes, despite the good fastness to washing of their dyeings. In 1955, Rattee and Stephen, working for ICI in England, developed a procedure for dyeing cotton with fibre-reactive dyes containing dichlorotriazine groups. They established that dyeing cotton with these dyes under mild alkaline conditions resulted in a reactive chlorine atom on the triazine ring being substituted by an oxygen atom from a cellulose hydroxyl group. This is shown where CellOH is the cellulose with a reactive hydroxyl group, DyeCl is the dye with its reactive chlorine atom, and CellO Dye the dye linked to the cellulose by a covalent bond. The role of the alkali is to cause acidic dissociation of some of the hydroxyl groups in the cellulose, and it is the cellulosate ion (CellO) that reacts with the dye.

The dyeing had very good fastness to washing. The only way the fixed dye can bleed from the cotton is after hydrolysis of the covalent bond between the dye and the cellulose. This requires conditions more forceful than those met with in ordinary washing in hot water. Within about five years of this important development, all the major dyestuff manufacturers were marketing reactive dyes for cotton, and also for wool. Reactive dyes, particularly those used for dyeing cotton, have become one of the major classes of dye because of their good washing fastness, their bright shades and their versatile batch and continuous dyeing methods.

Vat dyes 38 PROJECT SPECIAL FINISHES

SPECIAL FINISHES 39 Vat dyes are one of the oldest types of dye. Vat dyes in particular give dyeing on cellulosic fibres with the best overall fastness properties. Because of the popularity of blue jeans, Indigo is still one of the most important of all dyes in present use. Natural Indigo was obtained by extraction from leaves, by fermentation in wooden vats, the origin of the term vatting. Today, Indigo is synthesised from manufactured intermediates. Its application involves reduction to the water-soluble leuco compound, dyeing the cotton and re-oxidation of the leuco dye in the fibres to the insoluble pigment, the three basics steps involved in vat dyeing. Vat dyes are water-insoluble pigments. They are called dyes because chemical reduction in alkaline solution converts the pigment into a water-soluble leuco form with substantivity for cotton. The vat pigment and the leuco compound often have quite different colours blue and pale yellow in the case of Indigo so the progress of the reduction is often easy to observe. After dyeing with the leuco compound, the pigment is regenerated in the dyed cotton by oxidation. The overall process therefore involves three key steps: (1) reduction of the pigment to the soluble leuco compound, a process called vatting; (2) absorption of the leuco compound by the cotton during dyeing; (3) oxidation of the absorbed leuco compound in the cotton, reforming the insoluble pigment inside the fibres. The use of strongly alkaline solutions (pH 1214) for vatting and dyeing limits the use of most vat dyes to cellulosic fibres Sulphur dyes Sulphur dyes are a type of vat dye used for dyeing cellulosic fibres. The insoluble pigment is converted into the substantive leuco compound by reduction with sodium sulphide and the leuco form is subsequently oxidised inside the fibre. Sulphur dyes are manufactured by heating organic materials with sodium polysulphide in aqueous or alcoholic solution, or by baking with sodium sulphide and sulphur. A variety of organic compounds are used including amines, nitro compounds, and phenols and their derivatives. These dyes almost always contain loosely bound sulphur and liberate hydrogen sulphide when treated with acidic solutions of reducing agents such as stannous chloride. The chemistry of sulphur dyes is very complex and little is known of the molecular structures of the dyestuffs produced. The Colour Index only gives the structures of the starting materials that are used to produce these dyes and even then the information can be quite misleading. Two products manufactured from the same starting materials are 39 PROJECT SPECIAL FINISHES

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unlikely to have similar properties even though they may have the same CI number. The actual dyestuffs produced from the same materials by different processes may have quite different dye contents, dyeing characteristics and environmental impacts. Because of the large amounts of sodium sulphide used in the manufacture and application of these dyes, much of which will eventually be found in the effluent, they pose a significant environmental problem. In this respect, sulphur dyestuffs produced in the developed Western nations are much more environmentally friendly. A variety of structural units have been proposed for various sulphur dyes. It is generally accepted that these dyes are polymeric having sulphur containing aromatic heterocyclic units such as thiazines and thiazoles linked by di- or polysulphide bonds. On treatment of an aqueous dispersion of the insoluble pigment with sodium sulphide, the sulphide links are reduced forming individual heteroaromatic units with thiol groups. These are soluble in the alkaline solution in the form of thiolate ions that have low to medium substantivity for cellulose. Over-reduction is possible if other groups are affected and the more powerful hydros is rarely used as the reducing agent. After dyeing of the cellulosic material, the thiolate ions in the fibres can be re-oxidised back to the polymeric pigment with di-sulphide bonds linking the aromatic units. Sulphur dyes often have dull yellow vats and sulphide and polysulphide solutions are usually pale yellow. For these reasons, the colour content of a given product cannot be assessed by the usual spectrophotometric method and it is necessary to prepare dyeings and compare their colours Azoic dyes These usually are water-insoluble mono- or bisazo compounds precipitated in the fibre by reaction of a diazonium ion with a suitable coupling component. The name azoic dye is somewhat confusing, since many soluble dyes are also azo dyes. The name azoic combination is preferable. The production of dyeings with Para Red, one of the first azoic combinations (1880), illustrates the basic principle of dyeing with this type of dye. Cotton fabric was first impregnated with an alkaline solution of 2-naphthol. It was dried and then padded with an acidic solution of diazotised p-nitroaniline (2). A deep red pigment formed in the cotton fibres (3). A final soaping at the boil removed pigment particles adhering to the fibre surfaces. This gave the optimum fastness to washing, light and rubbing, although these were not outstanding. Intermediate drying was necessary because 2-naphthol has poor substantivity for cotton and tended to bleed out of the wet fabric into the diazonium ion bath causing pigment formation, particularly on the fibre surfaces. The introduction of coupling components with much higher substantivity for cotton overcame this problem, and also decreased the migration of the coupling component to the yarn surfaces during the intermediate drying. Azoic combinations are still the only class of dye that can produce very deep orange, red, scarlet and bordeaux shades of excellent light and washing fastness. The pigments produced have bright colours, and include navies and blacks, but there are no greens or bright blues. The actual hue depends on the choice of the diazonium and coupling 40 PROJECT SPECIAL FINISHES

SPECIAL FINISHES 41 components. Their use on cotton today is more and more limited, largely because of the success of fibre-reactive dyes for cotton. Black shades on polyamide, polyester and acetate fibres are also often azoic combinations. For azoic dyeing of these artificiallymade fibres, a dispersion of the primary amine and coupling component is used. The fibres absorb these like disperse dyes. The amine is then diazotised in the fibre and reacts with the aoupling component to give the azo pigment. Disperse dyes Cotton can be dyed with anionic direct, sulphur, vat, reactive and azoic dyes. These types of dyes, however, are of little use for the dyeing of synthetic fibres. Disperse dyes, on the other hand, are non-ionic. They dye all the synthetic and cellulose acetate fibres using a direct dyeing technique. Only the dyeing temperature varies from one fibre to another. They are thus one of the major classes of dyestuff. The development of disperse dyes for dyeing secondary cellulose acetate fibres in the early 1920s was a major technological breakthrough. Their major use today is for the coloration of polyesters, the most important group of synthetic fibres. What is a disperse dye? These non-ionic dyes are relatively insoluble in water at room temperature and have only limited solubility at higher temperatures. They do, however, possess substantivity for hydrophobic fibres such as nylon and polyester, in which they are quite soluble. As their name implies, these dyes are present in the dyebath as a fine aqueous suspension in the presence of a dispersing agent. The water dissolves a small amount of the dye in monomolecular form. The hydrophobic fibres then absorb the dye from the solution. Because these dyes are non-ionic organic compounds of relatively low molecular weight, many sublime on heating and dyeing by absorption of the dye vapour is also possible. When cellulose diacetate fibres first appeared in 1921, few of the available ionic dyes were able to successfully colour them. Secondary acetate fibres absorb little water, do not swell and have only small pores. In addition, their surface potential is much more negative than that of cotton and therefore they repel anionic dyes. Although cellulose diacetate fibres will absorb some cationic dyes, and a few acid dyes, there is little or no penetration of the dye unless the fibre is pre-swollen. The dyeings produced using ionic dyes also have poor fastness properties. Acid, pre mettalised or mordant dyes Despite their different names, these three types of dye have many features in common. They dye both protein and polyamide fibres using similar dyeing methods. In the Colour Index, they are classified as acid dyes or mordant dyes. The name acid dye derives from the use of an acidic dyebath. Most pre-metallised and mordant dyes are acid dyes. In the case of mordant dyes, the dyeings are aftertreated with a suitable metal ion mordant, usually chromium. In fact, mordant dyes are often referred to as chrome dyes. The metal in pre-metallised dyes is incorporated into the dye molecule during the manufacturing process. The dyeing properties of acid dyes vary widely. The acids used in the dyebath range from sulphuric acid (dyebath pH < 2.0) to ammonium acetate (dyebath pH > 6.5). Acid dyes are usually sodium salts of sulphonic acids, or less frequently of carboxylic acids, and are 41 PROJECT SPECIAL FINISHES

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therefore anionic in aqueous solution. They will dye fibres with cationic sites. These are usually substituted ammonium ion groups in fibres such as wool, silk and nylon. These fibres absorb acids. The acid protonates the fibres amino groups, so they become cationic. Dyeing involves exchange of the anion associated with an ammonium ion in the fibre with a dye anion in the bath. Acid dyes have molecular weights in the range 3001000 g mol1. The dyes with larger molecules have higher substantivity for wool or nylon. Such dyes have slower diffusion in the fibre and therefore less ability to migrate and dye level. The more hydrophobic, high molecular weight dyes therefore have better fastness to wet processes. Their absorption by wool and nylon also involves the interaction o the dye with hydrophobic groups in the fibre. Dyeing is therefore not solely a consequence of simple ionic attraction. The colour gamut of acid dyes is complete, including greens and blacks. The dyes are available as powders, grains and liquids for continuous dyeing, and as fine dispersions of the less soluble types. The selection of acid dyes for dyeing a particular material is not an easy matter, given the wide range of textile products and fastness properties demanded. Manufacturers recommend groups of selected acid dyes for each type of application. Compatible dyes are selected to have similar rates of dyebath exhaustion, when applied together by the recommended procedure, and similar fastness properties. Basic or Cationic dyes Many of the initial synthetic dyes, such as Mauveine, had free basic amino groups capable of reacting with acids. They were therefore originally named basic dyes. Molecules of these dyes are invariably organic cations and the are preferably called cationic dyes. They usually have brilliant colours and high tinctorial strength; some are even fluorescent. Many basic dyes are now obsolete because of their very poor light fastness on natural fibres but a few are still used for dyeing paper and leather and for making inks Cationic dyes will dye fibres with anionic sites by a process of ion exchange. This is usually a simple direct dyeing process. Anionic auxiliary products must be avoided as they may precipitate cationic dyes in the form of an organic salt. In dyeing protein fibres with cationic dyes, acids retard dye absorption by suppressing the dissociation of the anionic carboxylate groups in the fibres, thus making the fibre more cationic and inhibiting adsorption of dye cations. Cationic dyes have very low substantivity for cotton unless excessive oxidation has generated anionic carboxylate groups. For dyeing cotton with cationic dyes, the cotton was usually mordanted with tannic acid fixed with tartar emetic. The insoluble, anionic tannin attracts coloured dye cations , just as it repels dye anions when on a nylon surface after backtanning.

Printing 42 PROJECT SPECIAL FINISHES

SPECIAL FINISHES 43 Printing is the method of application of dye on to the substrate in the paste form. Printing various designs, shapes and figures of spectacular geometry on the fabric, resulting in the fanciness of the fabric. Printing can be done with various ways, each depending on the machinery used, method used, and the selection of paste. For the printing purposes, the dyes that can be used in the paste form, or the dyes that are mostly used are Pigments Reactive Vat Disperse These can be used separately or in the combination with each other. One important difference between dyeing and printing is that there is no concept of dye liquor in priniting. The dye which is in