ANTIBACTERIAL PROPERTIES OF NANO SILVER FINISH CELLULOSE FABRIC


By: Mohammad Mirjalili, Niloofar Yaghmaei and Marjan Mirjalili

In the present study, an attempt has been made to impart antimicrobial finishing to the cellulose fabric using nano silver solution at various concentrations (5, 10, 15, 20 and 25 ml) and an eco-friendly crosslinking agent by the exhaustion technique. Curing conditions were varied, keeping curing temperatures at 110°C and 100°C and curing times to 1 and 2 min. To assess the quality of the finished fabric, various properties such as washing fastness and zone of inhibition were studied. The zones of inhibition have been studied using Escherichia coli bacteria to determine antimicrobial activity of the fabric; the surface characteristics of these fabrics have been studied by scanning electron microscopy (SEM).
In the case of the treated commercial cotton fabric product, the zones of inhibition are at a minimum of 14 mm and a maximum of 18 mm for Gram-negative bacteria. SEM study and antibacterial tests of the silver-finished fabrics indicated that, generally, silver nanoparticles were well dispersed on the fabric surface. Antibacterial test was used to estimate the biological activity of the treated fabrics, and Gram-negative bacteria (Escherichia coli) were used for this purpose. The washing fastness of finished textiles was investigated in terms of ISO 105 CO3-1982 standard. The results obtained proved the good and long-lasting bacteriostatic efficacy of silver nanoparticles applied during the finishing of cotton and viscose.

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Antibacterial properties of nano silver finish cellulose fabric

CRITICAL SOLUTIONS IN THE DYEING OF COTTON TEXTILE MATERIALS


Over the decades there have been several papers on the coloration of cotton-based textiles. The number of articles dealing with the processing of cotton, including preparation, dyeing, and finishing, may be in the thousands. An investigation of the possible causes of problems occurring in the coloration of textiles revealed that a comprehensive review of case studies and scientific analysis would be a welcome addition to the already rich pool of knowledge in this area.

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Critical_Solutions_in_the_Dyeing_of_Cotton_Textile_Materials-libre

Cloth Finishing


Cloth Finishing

( Originally Published Early 1900’s )

Importance of cloth finishing.-Cloth finishing is one of the chief arts in the textile industry. The appearance of the goods is often of first concern, and the appearance of any fabric is largely due to the methods of finishing.

BLEACHING

Bleaching is one of the most usual and important among the finishing processes. It has for its object the whitening or decolorizing of the textile fiber to which it is applied. Fibers, as they come from the plant, from the back of the sheep, or from the cocoon, are usually somewhat colored or stained. Some of them, like tussah silk or Egyptian cotton, are highly colored. This natural coloring of the fiber may be undesirable in many fabrics; hence, bleaching is employed to clear the fiber of this color. Again, most fibers accumulate stains of various kinds during the early processes of manufacture as, for example, in the spinning and weaving. This discoloration cannot be entirely removed by simple washing; hence, the bleaching process is applied to clear the fabric. In like manner, when the calicoes or other prints come from the printers, the white background between the colored figures may be soiled, spotted, or otherwise discolored; again, a light bleach is applied, but not enough appreciably to injure the color in the figures.

Bleaching agents.-There are two classes of bleaching substances, oxygen and sulphurous acid. Under certain conditions oxygen destroys the coloring matters entirely. Sulphurous acid probably does no more than change the color to white, leaving the coloring substances still in the textile. An object once bleached white by oxygen is not likely to turn yellow or to change back to its original color; whereas textiles bleached in sulphurous acid quite frequently do change back again after a time, especially when in contact with certain chemicals such as alkalies or soaps.

Grassing.-The oldest bleaching method is that of “grassing,” still used to a certain extent in Europe for bleaching linens. The linen fabrics are laid on the grass or ground for weeks. The oxygen of the air and that given off by green plants slowly attacks and destroys the little yellow color particles in the flax fiber. Slowly the linen becomes whiter and whiter until finally it is fully bleached. The particular value of the grass bleach over all others is its slowness. This guarantees permanence. Furthermore, the “grassing” process is not likely to be carried on a bit further than necessary. The oxygen which attacks the coloring matter may ultimately attack the cellulose in the fiber and does do so in chemical bleacheries unless the fabric is removed at the proper time. A few moments’ delay, therefore, in a chemical bleachery means great damage to the cloth; whereas a few days either one way or the other in grass bleaching makes practically no difference. Cotton also was at one time bleached in this manner, but the more rapid chemical oxygen bleachers have entirely superseded grass bleaching for this textile.

Chemical bleaching.-The principal chemicals used in oxygen bleaching are chloride of lime, hydrogen peroxide, sodium peroxide, and potassium permanganate. All these substances are heavily charged with oxygen. In the bleaching process, this oxygen is set free, and this free oxygen attacks the coloring matters in unbleached goods. The bleaching powder of commerce is chloride of lime, the principal bleaching substance used for cotton and for all other vegetable fibers excepting jute. It is, however, entirely unsuitable for wool and silk. Hydrogen peroxide is the best bleaching substance of all. It may be used on any sort of fiber, for it attacks nothing but the coloring matter. It is frequently used in removing stains and also in bleaching hair. But for general textile bleaching purposes it is too expensive, and is hard to keep in concentrated form for even a short time. It is used extensively, however, in bleaching wool mousselines that are to be printed. Hydrogen peroxide produces a much better result than sulphurous acid, the common bleaching substance for wool. When cheaper means of producing peroxide are discovered, this chemical is bound to take front rank among the bleaching agents. Potassium permanganate is another oxygen-loaded chemical that is sometimes used in bleaching woolens. Sodium peroxide is a compound somewhat cheaper to produce than hydrogen peroxide, and contains a large amount of live, active oxygen. It is a rather new bleaching agent, but is already used to a certain extent on wool and silk, especially tussah silk.

Sulphur bleach.-Sulphurous acid bleach is applied in the form of either a gas or a liquid. The gas is produced by burning sulphur in the air. The fumes that arise from burning sulphur are sulphurous acid gas. The liquid is produced by saturating water with this gas. Sulphur bleach is used mainly for animal fibers (wool and silk) and jute. The most common method employs the gas rather than the liquid. Rooms called sulphur chambers are built out of brick especially for this purpose. The fabric or yarn is brought into this chamber and hung up damp in loose folds while sulphur is burned in pots on the floor. The rising fumes saturate the damp textiles, the dampness materially assisting, and the fibers gradually whiten. In large wool bleacheries the cloth is run through the sulphur chamber on rollers, bleaching on the way. The process is inexpensive and results in a beautiful white. Its tendency to make wool harsh is corrected by washing in soap and water. When the wool is mixed with cotton there is danger of the cotton’s being destroyed by the acid. The sulphur bleach is ordinarily used for wool and silk.

Chloride of lime.-In cotton bleaching, chloride of lime is the most common chemical used. Cotton is generally bleached in the piece or fabric form. The usual exceptions are sewing cotton, absorbent cotton, and jeweler’s cotton. The last two are bleached in the state of loose fibers. When the cotton comes from the looms it is still in the natural color, although somewhat altered by the sizing in the warp and by the dirt; grease, and dust accumulated in the machinery. The cloth is now said to be “in the gray.” It is, however, more of a dirty yellow than gray, and presents a soft, flabby, fuzzy, unattractive appearance. It is now ready for the bleaching process.

The bleaching process.-The cloth is first run through a washing machine to remove as much of the discoloration and dirt as possible. Next, most fabrics are either sheared or singed; that is, they are run through machines which either cut off or burn off the fuzziness that is always found on cloth direct from the loom. The shearing process is performed by a machine that works on the same principle as a lawn mower, cutting all loose ends and fibers very close to the body of the cloth. The singeing is done by very quickly passing the cloth over a line of gas jets, or over a red-hot plate, where the heat burns off the fuzz but has no time to burn the fabric itself. Recently, singeing has been successfully performed by electricity. Cloth is sometimes singed on both sides, sometimes on only one. The shearing and singeing processes leave the cloth apparently smooth.

As a rule, cotton cloths are then bleached. There are four common methods, or “bleachers” as they are called: “madder bleach,” “Turkey red bleach,” “market bleach,” and “rapid bleach.” Of these the madder bleach is the most thorough. The others differ from the madder bleach mainly in degree of thoroughness. Goods to be dyed in deep colors need less whitening; hence, they are given, for example, the Turkey red bleach. Goods to be dyed black need almost no bleaching; for these the rapid bleach is sufficient. The market bleach is really the rapid bleach with the addition of blueing and other substances to cover up defects in the process.

The bleaching industry.-Cotton bleaching is often conducted as a separate industry. In England this is quite the rule. The cloth is sent from the weaving concerns to the bleacheries to be bleached on commission or at so much a yard. Sometimes the products of the loom are purchased by converters who hire others to do all the finishing processes, including bleaching. Occasionally bleachers buy the cloth in the gray, bleach it, and again market it. In this country bleaching and dyeing works are usually associated, and both are frequently under the same management as the cotton mills. This joining together or integration of related industries is typical of American business organization, not only in the textile industries, but also in many other great businesses, such as steel production and meat packing.

How the bleacheries handle cotton goods.-Piece goods arrive at the bleacheries in bolts or rolls of an average length of fifty yards. Each of these is stamped with the owner’s name, the length of the bolt, and other necessary particulars. The ends of several hundred rolls are first stitched together to form one long sheet sometimes as much as twenty-five miles long.

Moistening and bowking.-When all is ready, the cloth is moistened, run through a six-to eight-inch ring to rumple it and form it into the shape of a rope, and in this form if is laid away in coils for several hours in bins to soften the sizing in the warp. Next, the cloth is turned into a covered tank called a kier, in which is a weak solution of caustic soda or milk of lime. The liquid is kept moving through the tank by means of pumps. Here the cloth is stirred for about eight or ten hours, a process which removes all fats and wax found in the cloth, such, for example, as the natu ral wax found around the cotton fibers. All of this must be thoroughly removed before bleaching if the cloth is to be made snow white. The mixture in the “kier” is called the “lime boil,” and this particular part of the process is called “bowking.” The process concludes with a thorough washing in pure, fresh water.

Brown sour.-The next step, known variously as the “brown sour,” “gray sour,” or “lime sour,” follows the washing. The cloth is passed into tanks of water containing sulphuric or hydrochloric acid, sometimes both. This souring process counteracts the action of any caustic soda or lime that may remain in the cotton fiber from the previous treatment. Here a knowledge of the chemistry of bleaching is absolutely essential. The proportion of acid in the “brown sour” must be just sufficient to destroy the alkali in the fiber. If not strong enough, the alkali will not all be destroyed and will continue to cause trouble throughout the entire life of the cloth. If too much acid is used, then not only will the alkali be destroyed, but the cotton fiber will be endangered as well. Much of the poor cotton cloth in the market owes its lack of strength to poor bleaching methods. Linen is more sensitive to these chemical changes than cotton; hence the difficulty of getting good chemically bleached linens. The acid or souring bath is followed by a washing in pure water.

Lye boil.-In the full madder bleach the cloth after the acid bath is usually passed into a second alkali bath containing hot lye and resin soap. This is called the “lye boil.” After three hours of boiling under pressure, with the alkali liquor forced through every part of the cloth by means of pumps, all of the fats and acids in the fiber have been ex tracted and changed into soapsuds. The invariable washing in pure water follows.

Chemicking.-The cloth is now ready to be transferred into the real bleaching bath, the chloride of lime solution, or “chemick,” as bleachers name it. Through this bath the cloth is passed back and forth, the liquid being forced through every part of it. After one or two hours this part of the process is completed. The cloth is removed and passed between heavy wooden rollers, which press out the excess of the chloride of lime solution. The cloth is then coiled or piled in bins so as to be exposed to the air. It is here that the real bleaching takes place. The chloride of lime absorbed in the fiber has a strong affinity for air and for water. Both are attracted, and in the chemical processes that follow a certain amount of oxygen is crowded out of the air and water, and this free, active oxygen attacks the coloring matters and destroys them. Now again the proportions must be scrupulously adjusted so that not too much or too little oxygen is produced. Too much would result in an oxidation or destruction not only of the color particles, but also of the cotton fiber itself.

White souring.-The chemicking or bleaching is followed by washing in pure water and afterward by treatment in a weak acid bath known as the “white sour.” In this bath all action of the chloride of lime is stopped. Then follows another most careful washing in water to remove every particle of acid, whereupon the bleaching process is ended. The cloth is opened up flat, spread out, beaten, stretched or tentered, and dried over hot rollers. It is now ready for dyeing, for printing, for mercerizing, or, if to remain in the white, for the final finishing processes of sizing and calendering. Dyeing, printing, and mercerizing have already been described; hence, we need only give our attention to the final finishing processes.

CLOTH DRESSING

Whether the cloth shall be made soft or stiff, dull or glossy, and so on, depends upon the finish applied and the materials used. Certain sizings fill up the spaces between the threads in the fabric, stiffen the fabric, and give it greater weight and body. Other sizing materials give stiffness without adding weight. Some give weight without stiffness. Some help to make the fabric glossy, others to give the cloth some special appearance in imitation of a different fiber. It would take a volume to give in detail an account of how these various effects are obtained. Such a description is not necessary here. A fair idea of the possibilities of cloth finishing can be obtained by a study of fabrics themselves, especially with the help of a small magnifying glass and with such tests as boiling and rubbing.

Dressing materials,-The materials used in cotton finishing or dressing include starches, glue, fats, casein, gelatin, gluten, minerals, and antiseptic substances. The starches give stiffness and weight; glue gives tenacity to the starches and other materials. Minerals, such as clay, are used to give weight. Fats give the qualities of softness and help make the fabric more elastic. Wax, stearin, and paraffin are frequently used to develop a high luster in the calendering or pressing processes. Antiseptic substances such as zinc chloride, salicylic acid, and zinc sulphate are added to prevent the starches and fats used in the dressing from molding or putrefying.

Starches.-The starchy substances commonly used include wheat flour, wheat starch, potato starch, rice starch, and cornstarch. Sometimes the starch is baked until brown before using. In this form it is called dextrin or British gum. Dextrin gives a softer dressing than any other starchy material. Wheat and corn starches produce the stiffest effects. Potato starch comes between the two extremes. Starch is sometimes treated for a couple of hours with caustic soda at about the freezing point. At the end of this time the excess of alkali is neutralized with acid. The result is a gum, called apparatine, which stiffens the cloth and does not wash out so easily as most other stiffening substances. Starch treated with acid produces glucose, and this is used largely as a weighting or loading material.

Fats.-Among the fats used are tallow, stearin, several different kinds of oils and waxes, and paraffin. These are sometimes added to the starches to reduce the stiffness of the fabrics. Glycerin and magnesium chloride are frequently added for the same reason. Fats may be added to waterproof the cloth, although waterproofing is usually accomplished by rubberizing; that is, by soaking the cloth in a solution of crude rubber or caoutchouc.

Minerals.-The minerals are added for various reasons. China clay increases the weight as do also salts of lime and baryta. Alum, acetate of lead, and sulphate of lead are sometimes used. Adding large proportions of borax, ammonium phosphate, salts of magnesia, and sodium tungstate makes the fabric fireproof.

How the dressing is applied.-The dressing material is usually applied as a liquid paste to the back of the cloth and then run over hot rolls or cylinders in order to dry the paste quickly. Sometimes it is applied lightly to the surface, sometimes it is pressed in deeply by means of rollers. When both sides are dressed, the fabric is passed into and through the dressing material. When the cloth is dry, the sizing or dressing process is complete. If merely a dull, hard finish is desired, nothing further is necessary except to stretch and smooth out the cloth, measure, bolt, and press it. But if any kind of polish is demanded, then the cloth must be calendered, pressed, mangled, or ironed.

CALENDERING

Calendering is accomplished by passing the cloth between large rolls, from two to six, under heavy pressure. In the rolls the dressing is smoothed out, and the hard, dull finish becomes soft and glossy in appearance. Heated rolls give a better gloss. When the rolls are made to turn over each other at different rates, there is a heavy friction or ironing effect on the cloth. For the highest glosses not only starch but also fats and waxes are used, and all are ironed into the cloth under heavy pressure and at as great heat as the cloth will stand. When calendered the fabrics are usually dampened first, just as clothes are dampened by the housewife before she irons them. The dampening in a cloth-finishing plant is done by a special machine that sprays the cloth very evenly as it passes through.

The beetle finish.-There are several special finishes possible through variations in the calendering process. Beetling is one of these methods. The cloth is passed into a machine over wooden rollers and beaten by wooden hammers operated by the machine. The beetle finish gives to cotton or linen an appearance almost like satin and is very beautiful.

Watered effects.-Moire or watered effects are produced by pressing some parts of the threads in a fabric down flat while leaving the other parts of the threads in their natural or round condition. The effect is usually that of an indistinct pattern. It is obtained in different ways, sometimes by running the cloth through the calender double, or again by running the single fabric between rollers especially engraved with moire designs. Only soft fabrics are suited to this finish; hence, no dressing except fats is used for moire goods.

Embossing.-Soft fabrics are sometimes stamped with patterns in the manner of embossing by means of engraved calender rolls. This process is called stamping.

Schreiner finish.-Another special finish, known as “Schreiner finish,” is applied in the calendering operation by passing the cloth between rolls covered with great numbers of finely engraved lines. The number often runs as high as six hundred to the inch. Under a pressure of 4,500 pounds these lines are pressed into the fabric. The result is that the round threads are pressed flat, but the lines break up the flat surfaces into little planes that reflect the light much better than an ordinary flat surface would. This peculiar light reflection gives the cloth the quality of a very high luster. Heating the rolls makes this luster more lasting. The effect is very beautiful. Mercerized cotton finished in the Schreiner finish rivals silk in appearance.

Most of the finishes spoken of so far, the result of dressing and calendering, are easily destroyed. Wear destroys any of them in time. Washing destroys most of them. But as long as they last they are highly important elements in the appearance of the fabrics.

OTHER FINISHING PROCESSES

Dressings applied to the various textiles.-Dressings are usually applied in much greater quantity to cotton than to any other textile. Linen comes second, and the principal dressing substance used in linens is starch. Glue, gelatin, dextrin, albumen, and water glass are applied under certain conditions and for certain effects in woolen goods. The common weighting materials added to woolens are short hairs or short wool fibers, sometimes called flocks. Flocks are the ends of fibers sheared off from the surface of wool or worsted cloth. Woolen cloths are padded or impregnated with these in the fulling mills, sometimes adding from one-fourth to three-fourths to the weight of the wool. Such finishing processes as beetling, mangling, moireing, and stamping are never applied to woolens. Silk usually has very little dressing applied to it in the finishing process, and that little generally consists of gelatin, gum arabic, or tragacanth. The other finishing processes are very much the same for silk as they are for cotton.

Lisle finish.-Several other finishes, or modifications of the finishes just described, are used in cotton goods when it is desired to show special effects. The lisle finish is given yarns that are to be used in the manufacture of hosiery and underwear. The true lisle finish is obtained by using combed, long-stapled, sea-island or Egyptian cotton. The yarns made from these fibers are rapidly but repeatedly run through gas flames until they are entirely free from any projecting fiber ends or fuzz. The result is a very smooth, glossy thread. Another kind of lisle finish is obtainable in a finished fabric, as, for example, in hosiery, by treating with a weak solution of sulphuric or hydrochloric acid and then drying before washing out the acid. The goods are afterward tumbled around in a machine that exposes them to the air and heats them to about 100 degrees Fahrenheit. After a time the loose ends and fuzzy fibers become brittle and break off in the tumbling given the goods. When the goods present the proper lisle finish, they are cooled off and washed in an alkaline bath which stops the action of the dry acid and neutralizes it. After thorough washing in clean water, they are dried and are ready for dyeing or any other finishing process. Sometimes the acids are added to the dye bath to cause more speedily the same effect in the appearance of the goods. Some dyes are regularly made up with the acid mixture.

Wool finishing.-The finishing processes for woolens and worsteds are much more laborious and complex than those employed for cottons. A greater variety of machinery is required, and there are more steps in the process. The finishing of wool goods is divided into two main parts: the first is called the “wet finishing,” which includes washing, soaping, steaming, carbonizing, and the use of liquids; the second is called “dry finishing” and includes napping, shearing, polishing, measuring, and putting up in rolls or bolts.

Preparation of wool fabrics.-Woolen or worsted cloth, as it comes from the weave rooms to the finishers, is first inspected for flaws, broken threads, and weak places, and wherever these are found, chalk marks are made to assist the burlers and menders in finding the places. To aid in the inspection, the cloth is generally “perched” or thrown over a roller and drawn down in single thickness by the inspector as fast as he can look it over. A good light is desirable. Inspectors with practice attain great proficiency in finding weak places or imperfections in the cloth. After the bad spots in the fabric are repaired the goods are tacked together; that is, the pieces are fastened together in pairs with the faces of the cloth turned towards each other. The tacking is simply a stitching along the edge, done either by hand or machine. The purpose of tacking is to protect the faces of the cloth from becoming damaged in any way by the heavy operations to follow or from becoming impregnated with any foreign substance difficult to remove, such as short hairs or flocks.

Fulling.-The next step is the fulling. All kinds of clearfinished worsted dress goods for ladies and practically all wool cloths for men’s wear except worsteds are fulled. This is the most characteristic process in the wool industry; no other textile goes through any process like it. The wool fibers, it will be recalled, are jointed and have scales that cause the fibers to cling together readily. This, we have learned, is called the felting quality. By beating a mass of wool fibers, a very hard, compact mass can be obtained, because the fibers creep into closer and closer contact with each other, holding fast because of the scales. Fulling makes use of this principle. Wool cloth is shrunken and made heavier and closer in structure and consequently stronger. Fulled cloth may also take many more kinds of finish than unfulled fabrics. The fulling process is performed in machines that apply pressure, moisture, and heat to the goods. The cloths are soaked in hot, soapy water, pressed, rolled, and tumbled; as a result, the woolen fabrics contract and become closer in texture throughout.

Flocking.-Short wool fibers or flocks are frequently felted into wool fabrics in the fulling operation. A layer of these short fibers is spread over the back of the cloth and matted down by moistening. In the fulling operation these fibers sink into the fabric and therefore help to give the fabric weight and closeness. That this process is not always well done is evidenced by the fact that the flocks in the backs of suitings often wear loose, drop down, and collect at the bottom of garments, especially at points where the lining and the suiting are sewed together. Flocks must from most standpoints be considered as an adulteration of wool although their presence really helps some fabrics, such as kerseys. All crevices are filled up and the fabric is made solid. If the felting has been done well, the flocks perform a good service in the cloth, but otherwise the flocks come out easily and are a decided nuisance to the wearer of the goods. Flocks made from wool waste such as shoddy, mungo, and extract, when applied on shoddy wool cloth are bound to come out. But flocks cut from new wool, when applied to new wool cloth, produce an excellent effect if not too largely used. Adding 25 per cent in weight to the cloth by flocking is not unreasonable, but doubling the weight of the original fabric would be unjustifiable adulteration. Flocking adds little if any to the strength of the cloth.

Speck dyeing.-After fulling, the cloth is washed very carefully, and is usually given a light dye to cover up spots or imperfections due to foreign matter that could not be taken out before. If not so dyed, all the little specks in the cloth have to be removed by hand, a process called speck dyeing or burr dyeing.

Carbonizing.-Carbonizing is usually performed before the wool is spun into yarn, but in some cases not until the cloth is woven. In this case it takes the place of speck dyeing. The process is the same for cloth as for loose wool. The vegetable matter is destroyed by soaking the cloth in weak acids and then heating in an oven.

Napping.-After washing, stretching, and drying, most goods are ready to receive the finish. In most cases this first involves raising a nap or fuzz evenly all over the surface, and for this purpose machines have been invented. The oldest of such machines use teasel or thistle burrs, whereas the later napping machines use little wire hooks. Some claim that the teasel burr has certain qualities for raising the wool nap that cannot be produced in any steel wire or spring hook or barb. The principle, however, is the same in all inventions for this purpose. The gigs or napping machines all stretch the cloth and then cause it to pass over many fine little hooks of teasel burrs or of steel wire which draw out a multitude of little ends of wool fiber all over the surface of the cloth. In some cases, the napping or gigging is performed on wet cloth; in others, the cloth is dry. Dry napping is in fact now the more common, although the wet methods are still employed for certain cloths and finishes.

The finish of wool cloth depends upon the degree o f napping and upon the variety of fiber. Meltons require only a little napping; kerseys, beavers, and doeskins, a very thorough one. Cloths that must wear exceedingly well must be napped as little as possible, since the process reduces the strength of the fabric. Cassimeres are given several kinds of finish, Saxony finish, for example, or velour finish. Other fabrics are each given their characteristic finish by slightly varying the amount of nap, or the treatment of the nap after it has been raised. Among such fabrics are cheviots, kerseys, meltons, beavers, chinchillas, outing flannels, doeskins, reversibles, thibets, satinets, blankets, and others.

Lustering.-After napping, such fabrics as kerseys, beavers, broadcloths, thibets, venetians, tricots, plushes, uniform cloths, and all worsteds, require another special operation known as steam lustering. Steam is forced through the cloth for about five minutes, followed by cold water. The steam brings out the luster which the cold water sets or fixes.

Stretching and clipping.-The dry finishing processes begin with stretching (or tentering) and then drying the cloth. Special machines accomplish this as well as all the other processes. The cloth now passes through a shearing machine which brushes the nap in the direction desired, afterward clipping it evenly over all the surfaces. The clippers operate like the revolving blades of a lawn mower. Goods that have not been napped are generally singed in much the same manner as cotton fabrics. Next, the sheared fabrics are brushed, and perhaps polished by means of pumice cloth or sandpaper, to make the cloth smooth and lustrous.

Final steps.-Finally the goods are pressed and thereby given a finished appearance. This is usually performed by means of heavy presses, either with dry heat or with steam. The most common present-day method of pressing cloth is by running it between heavy rollers heated by steam. Care must be taken not to get the rolls too hot or the wool will be damaged. The cloth is next inspected again, run through a measuring machine, doubled, rolled, and wrapped in paper, and packed into cases ready for the clothing manufacturer or the dry goods jobber and the retail store.

Worsted finishing.-Worsteds are not generally fulled as are woolens. After burling, worsteds are usually singed and then crabbed. The crabbing process sets the weave so that in the later operations it will not be obliterated. It consists in running the cloth tightly stretched over rollers through a trough containing hot water. After an hour or two of this the cloth is scoured and rinsed and then closely sheared. There are several varieties of worsted, each of which requires its own special finish or after-treatment. Innovations are constantly introduced to alter the appearance a little in one way or another. Among these are the fancy or yarn-dyed worsteds, serges, worsted dress goods, and worsted cheviots.

STANDARD COTTON FABRICS


TEXTILE TERMS & DEFINITIONS

Armure
Fibre : Cotton, silk, wool, rayon, synthetics, and blends.
Weave : Plain, twill, or rib, background often has a small design either jacquard or dobby made with warp floats on surface giving a raised effect.
Characteristics : Design is often in two colours and raised. The name was derived from original fabric which was woven with a small interlaced design of chain armor and used for military equipment during the Crusades.
Uses : a rich looking dress fabric, draperies, or upholstery.
Batiste
Fibre : Cotton, also rayon and wool.
Weave : Plain
Characteristics : Named after Jean Baptiste, a French linen weaver. Light weight, soft, semi-sheer fabric which resembles nainsook, but finer. It belongs to the lawn family; almost transparent. It is made of tightly twisted, combed yarns and mercerized finish. Sometimes it is printed or embroidered. In a heavier weight, it is used for foundation garments and linings in a plain, figured, striped, or flowered design. Considered similar to nainsook but finer and lighter in weight. Now usually made of 100% polyester distinguished by slubs in filling direction.

Birdseye
Fibre : In cotton and Linen or blend of rayon staple and cotton.
Weave : Usually dobby
Characteristics : Very soft, light weight, and absorbent. Woven with a loosely twisted filling to increase absorbency. Launders very well. No starch is applied because the absorption properties must be of the best. Material must be free from any foreign matter. It is also called “diaper cloth” and is used for that purpose as well as very good towelling. Also “novelty” birdseye effects used as summer dress fabrics.

Broadcloth
Fibre : Cotton and silk, and rayon. Very different than wool broadcloth.
Weave : Plain weave and in most cotton broadcloths made with a very fine crosswise rib weave.
Characteristics : Originally indicated a cloth woven on a wide loom. Very closely woven and in cotton, made from either carded or combed yarns. The filling is heavier and has less twist. It is finer than poplin when made with a crosswise rib and it is lustrous and soft with a good texture. Thread count ranges from high quality 144 x 6 count down to 80 x 60. Has a smooth finish. May be bleached, dyed, or printed; also is often mercerized. Wears very well. If not of a high quality or treated it wrinkles very badly. Finest quality made from Egyptain or combed pima cotton – also sea island.
Uses : Shirts, dresses, particularly the tailored type in plain colours, blouses, summer wear of all kinds.

Brocade
Fibre : Cotton brocade often has the ground of cotton and the pattern of rayon and silk. Pattern is in low relief.
Weave : Jacquard and dobby
Characteristics : Rich, heavy, elaborate design effect. Sometimes with coloured or metallic threads making the design usually against a satin weave background. This makes the figures stand out. The figures in brocade are rather loose, while in damask the figure threads are actually bound into the material. The pattern may be satin on a twill ground or twill on a satin ground. Often reversible. The motifs may be of flowers, foliage, Scrollwork, Pastoral scenes, or other designs. The price range is wide. Generally reputed to have been developed from the latin name “brocade” which means to figure.
Uses : All types of after 5 wear, church vestments, interior furnishings, and state robes.

Buckram
Fibre : Cotton, some in linen, synthetics.
Weave : Plain
Characteristics : Cheap, low-textured, loose weave, very heavily sized and stiff. Also, 2 fabrics are glued together; one is open weave and the other much finer. Some is also made in linen in a single fabric. Also called crinoline book muslin or book binding. Name from Bokhara in Southern Russia, where it was first made.
Uses : Used for interlinings and all kinds of stiffening in clothes, book binding, and for millinery (because it can be moistened and shaped). Used to give stiffness to leather garments not as stiff and often coloured is called “tarlatan”. Softens with heat. Can be shaped while warm.

Calico
Fibre : Cotton
Weave : Plain – usually a low count.
Characteristics : Originated in Calcutta, India, and is one of the oldest cottons. Rather coarse and light in weight. Pattern is printed on one side by discharge or resist printing. It is not always fast in colours. Sized for crispness but washes out and requires starch each time. Designs are often geometric in shape, but originally elaborate designs of birds, trees, and flowers. Inexpensive. Similar to percale. Very little on the market today, but the designs are still in use on other fabrics and sold as “calico print.”
Uses : Housedresses, aprons, patchwork quilts.

Cambric
Fibre : Cotton, also linen.
Weave : Plain
Characteristics : Soft, closely woven, light. Either bleached or piece dyed. Highly mercerized, lint free. Calendered on the right side with a slight gloss. Lower qualities have a smooth bright finish. Similar to batiste but is stiffer and fewer slubs. Launders very well. Has good body, sews and finishes well. Originally made in Cambria, France of linen and used for Church embroidery and table linens.
Uses : Handkerchiefs, underwear, slips, nightgowns, children’s dresses, aprons, shirts and blouses.

Candlewick Fabric
Fibre : Cotton – also wool.
Weave : Plain
Characteristics : An unbleached muslin bed sheeting (also called Kraft muslin) used as a base fabric on which a chenille effect is formed by application of candlewick (heavy plied yarn) loops, which are then cut to give the fuzzy effect and cut yarn appearance of true chenille yarn. May be uncut also. (True chenille is a cotton, wool, silk, or rayon yarn which has a pile protruding all around at slight angles and stimulates a caterpillar. Chenille is the French word for caterpillar.)
Uses : Bedspreads, drapes, housecoats, beach wear.

Canton Flannel
Fibre : Cotton
Weave : Four harness warp-faced twill weave.
Characteristics : The filling yarn is a very loosely twisted and soft and later brushed to produced a soft nap on the back, the warp is medium in size. The face is a twill. Heavy, warm, strong and absorbent. Named for Canton, China where it was first made. Comes bleached, unbleached, dyed, and some is printed.
Uses : Interlinings, sleeping garments, linings, coverings, work gloves.

Chambray

Fibre : Cotton
Weave : Plain weave or dobby designs on a plain-weave ground.
Characteristics : Made with a dyed warp and a white or unbleached filling. Both carded and combed yarns used. Has a white selvedge. Some woven with alternating white and coloured warp. “Faded” look. Has very soft colouring. Some made with stripes, checks or embroidered. Smooth, strong, closely woven, soft and has a slight lustre. Wears very well, easy to sew, and launders well. If not crease resistant, it wrinkles easily. Originated in Cobrai, France it was first made for sunbonnets.
Uses : Children’s wear, dresses, shirts and blouses, aprons, all kinds of sportswear.

Chamois Cloth
Fibre : Cotton
Weave : Plain
Characteristics : Fabric is napped, sheared, and dyed to simulate chamois leather. It is stiffer than kasha and thicker, softer and more durable than flannelette. Must be designated as “cotton chamoise-colour cloth”.
Uses : Dusters, interlining, storage bags for articles to prevent scratching.

Chamoisette
Fibre : Cotton, also rayon and nylon.
Weave : Knitted, double knit construction.
Characteristics : A fine, firmly knit fabric. Has a vary short soft nap. Wears well. Nylon chamoisette is more often called “glove silk”.
Uses : Gloves.

Cheesecloth
Fibre : Cotton
Weave : Plain
Characteristics : Originally used as a wrapping material for pressing cheese. Loosely woven, thin, light in weight, open in construction, and soft. Carded yarns are always used. It is also called gauze weave. When woven in 36″ widths it is called tobacco cloth, When an applied finish is added, it is called buckram, crinoline, or bunting.
Uses : In the grey cloth, it is used for covering tobacco plants, tea bags and wiping cloths.
Finished cloth is used for curtains, bandages, dust cloths, cheap bunting, hat lining, surgical gauze, fly nets, food wrapping, e.g. meat and cheese, costumes and basket tops.

Chenille Fabric
Fibre : Cotton and any of the main textile fibres.
Weave : Mostly plain weave.
Characteristics : Warp yarn of any major textile fibre. Filling of chenille yarns (Has a pile protruding all around at right angles). The word is French for caterpillar and fabric looks hairy. Do not confuse with tufted effects obtained without the use of true Chenille filling.
Uses : Millinery, rugs, decorative fabrics, trimmings, upholstery.

Chinchilla
Fibre : Cotton or wool, and some manmade and synthetics.
Weave : Sateen or twill construction with extra fillings for long floats.
Characteristics : Does not resemble true chinchillas fur. Has small nubs on the surface of the fabric which are made by the chincilla machine. It attacks the face and causes the long floats to be worked into nubs and balls. Cotton warp is often used because it cannot show from either side. Made in medium and heavy weights. Very warm and cozy fabrics. Takes its name from Chinchilla Spain where it was invented.
Uses : In cotton, used for baby’s blankets and bunting bags.

Chino
Fibre : Cotton
Weave : Twill (left hand)
Characteristics : Combined two-ply warp and filling. Has a sheen that remains. Fabric was purchased in China (thus the name) by the U.S. Army for uniforms. Originally used for army cloth in England many years before and dyed olive-drab. Fabric is mercerized and sanforized. Washs and wears extremely well with a minimum of care.
Uses : Army uniforms, summer suits and dresses, sportswear.

Chintz
Fibre : Cotton
Weave : Plain
Characteristics : Has bright gay figures, large flower designs, birds and other designs. Also comes in plain colours. Several types of glaze. The wax and starch glaze produced by friction or glazing calendars will wash out. The resin glaze finish will not wash out and withstand drycleaning. Also comes semi-glazed. Unglazed chintz is called cretonne. Named from the Indian word “Chint” meaning ” broad, gaudily printed fabric”.
Uses : Draperies, slipcovers, dresses, sportwear.

Corduroy
Fibre : Cotton, rayon, and other textile fibres.
Weave : Filling Pile with both plain and twill back.
Characteristics : Made with an extra filling yarn. In the velvet family of fabrics. Has narrow medium and wide wales, also thick n’thin or checkerboard patterns. Wales have different widths and depths. Has to be cut all one way with pile running up. Most of it is washable and wears very well. Has a soft lustre.
Uses : Children’s clothes of all kinds, dresses, jackets, skirts, suits, slacks, sportswear, men’s trousers, jackets, bedspreads, draperies, and upholstery.

Crepe
Fibre : Worsted cotton, wool, silk, man-made synthetics.
Weave : Mostly plain, but various weaves.
Characteristics : Has a crinkled, puckered surface or soft mossy finish. Comes in different weights and degrees of sheerness. Dull with a harch dry feel. Woolen crepes are softer than worsted. If it is fine, it drapes well. Has very good wearing qualities. Has a very slimming effect.
Uses : Depending on weight, it is used for dresses of all types, including long dinner dresses, suits, and coats.

Crettone
Fibre : Cotton, linen, rayon
Weave : Plain or twill.
Characteristics : Finished in widths from 30 to 50 inches. Quality and price vary a great deal. The warp counts are finer than the filling counts which are spun rather loose. Strong substantial and gives good wear. Printed cretonne often has very bright colours and patterns. The fabric has no lustre (when glazed, it is called chintz). Some are warp printed and if they are, they are usually completely reversible. Designs run from the conservative to very wild and often completely cover the surface.
Uses : Bedspreads, chairs, draperies, pillows, slipcovers, coverings of all kinds, beach wear, sportwear.

Denim
Fibre : Cotton
Weave : Twill – right hand – may be L2/1 or L3/1.
Characteristics : Name derived from French “serge de Nimes”. Originally had dark blue, brown or dark grey warp with a white or gray filling giving a mottled look and used only for work clothes. Now woven in bright and pastel colours with stripes as well as plain. Long wearing, it resists snags and tears, Comes in heavy and lighter weights.
Uses : Work clothes, overalls, caps, uniforms, bedspreads, slipcovers, draperies, upholstery, sportswear, of all kinds, dresses and has even been used for evening wear.

Dimity
Fibre : Cotton
Weave : Plain weave with a crosswise or lengthwise spaced rib or crossbar effect.
Characteristics : A thin sheer with corded spaced stripes that could be single, double or triple grouping. Made of combed yarn and is 36” wide. Has a crisp texture which remains fairly well after washing. Resembles lawn in the white state. It is easy to sew and manipulate and launders well. Creases unless creaseresistant. May be bleached, dyed, or printed and often printed with a small rosebud design. It is mercerized and has a soft lustre.
Uses : Children’s dresses, women’s dresses, and blouses, infant’s wear, collar and cuff sets, basinettes, bedspreads, curtains, underwear. Has a very young look.

Domett Flannel
Fibre : Cotton
Weave : Plain and twill
Characteristics : Also spelled domet. Generally made in white. Has a longer nap than on flannelette. Soft filling yarns of medium or light weight are used to obtain the nap. The term domett is interchangeable with “outing flannel” but it is only made in a plain weave. Both are soft and fleecy and won’t irritate the skin. Any sizing or starching must be removed before using. Outing flannel is also piece-dyed and some printed and produced in a spun rayon also.
Uses : Mostly used for infants wear, interlinings, polished cloths.

Pique
Fibre: Cotton, rayon, synthetics.
Weave: Lengthwise rib, English crosswise rib or cord weave.
Characteristics: Originally was a crosswise rib but now mostly a lenghtwise rib and the same as bedford cord. Ribs are often filled to give a more pronounced wale (cord weave). Comes in medium to heavy weights. It is generally made of combed face yarns and carded stuffer yarns. It is durable and launders well. Wrinkles badly unless given a wrinkle-free finish. Various prices. Also comes in different patterns besides wales. The small figured motifs are called cloque. Some of the patterns are birdseye (small diamond), waffle (small squares). honeycomb (like the design on honeycomb honey). When the fabric begins to wear out it wears at the corded areas first.
Uses : Trims, collars, cuffs, millinery, infants wear, particularly coats, and bonnets, women’s and children’s summer dresses, skirts and blouses, shirts, playclothes, and evening gowns.

Plisse
Fibre : Cotton, rayon, and others.
Weave : Plain
Characteristics : Could be made from any fine material, e.g. organdy, lawn, etc. Treated with caustic soda solution which shrinks parts of the goods either all
over or in stripes giving a blistered effect. Similar to seersucker in appearance. This crinkle may or may not be removed after washing. This depends on the quality of the fabric. It does not need to be ironed, but if a double thickness, such as a hem needs a little, it should be done after the fabric is thoroughly dry.
Uses : Sleepwear, housecoats, dresses, blouses for women and children, curtains, bedspreads, and bassinettes. Often it is called wrinkle crepe and may be made with a wax/shrink process (the waxed parts remain free of shrinkage and cause the ripples).

Point d’esprit
Fibre : Cotton – some in silk.
Weave : Leno, gauze, knotted, or mesh.
Characteristics : First made in France in 1834. Dull surfaced net with various sized holes. Has white or coloured dots individually spaced or in groups.
Uses : Curtains, bassinettes, evening gowns

Poplin
Fibre : Cotton, wool, and other textile fibres.
Weave : Crosswise rib. The filling is cylindrical. Two or three times as many warp as weft per inch.
Characteristics : Has a more pronounced filling effect than broadcloth. It is mercerized and has quite a high lustre. It may be bleached, or dyed (usually vat dyes are used) or printed. Heavy poplin is given a water-repellent finish for outdoor use. Originally made with silk warp and a heavier wool filling. Some also mildew-proof, fire-retardant, and some given a suede finish. American cotton broadcloth shirting is known as poplin in Great Britain.
Uses : Sportswear of all kinds, shirts, boy’s suits, uniforms, draperies, blouses, dresses.

Sailcloth
Fibre : Cotton, linen, nylon.
Weave : Plain, some made with a crosswise rib.
Characteristics : A strong canvas or duck. The weights vary, but most often the count is around 148×60. Able to withstand the elements (rain, wind and snow). Sailcloth for clothing is sold frequently and is much lighter weight than used for sails.
Uses : Sails, awnings, and all kinds of sportswear for men, women, and children.

Sateen
Fibre : Cotton, some also made in rayon.
Weave : Sateen, 5-harness, filling-face weave.
Characteristics : Lustrous and smooth with the sheen in a filling direction. Carded or combed yarns are used. Better qualities are mercerized to give a higher sheen. Some are only calendered to produce the sheen but this disappears with washing and is not considered genuine sateen. May be bleached, dyed, or printed. Difficult to make good bound buttonholes on it as it has a tendency to slip at the seams.
Uses : Dresses, sportswear, blouses, robes, pyjamas, linings for draperies, bedspreads, slip covers.

Seersucker
Fibre : Cotton, rayon, synthetics.
Weave : Plain, slack tension weave.
Characteristics : Term derived from the Persian “shirushaker”, a kind of cloth, literally “milk and sugar”. Crepe-stripe effect. Coloured stripes are often used. Dull surface. Comes in medium to heavy weights. the woven crinkle is produced by alternating slack and tight yarns in the warp. This is permanent. Some may be produced by pressing or chemicals, which is not likely to be permanent – called plisse. Durable, gives good service and wear. May be laundered without ironing. Can be bleached, yarn dyed, or printed. Some comes in a check effect.
Uses : Summer suits for men, women, and children, coats, uniforms, trims, nightwear, all kinds of sportswear, dresses, blouses, children’s wear of all kinds, curtains, bedspreads, slipcovers.

Shantung
Fibre : Cotton, silk, rayon, synthetics.
Weave : Plain.
Characteristics : It is a raw silk made from Tussah silk or silk waste, depending on the quality. It is quite similar to pongee, but has a more irregular surface, heavier, and rougher. Most of the slubs are in the filling direction. Wrinkles quite a bit. Underlining helps to prevent this as well as slipping at the seams. Do not fit too tightly, if long wear is expected. Comes in various weights, colours and also printed.
Uses : Dresses, suits, and coats.

Terry cloth
Fibre : Cotton and some linen.
Weave : Pile, also jacquard and dobby combined with pile.
Characteristics : Either all over loops on both sides of the fabric or patterned loops on both sides. Formed with an extra warp yarn. long wearing, easy to launder and requires no ironing. May be bleached, dyed, or printed. Better qualities have a close, firm, underweave, with very close loops. Very absorbent, and the longer the loop, the greater the absorbency. When the pile is only on one side, it is called “Turkish towelling.”
Uses : Towels, beachwear, bathrobes, all kinds of sportswear, children’s wear, slip covers, and draperies.

Tiking
Fibre : Cotton
Weave : Usually twill (L2/1 or L3/1), some jacquard, satin, and dobby.
Characteristics : Very tightly woven with more warp than filling yarns. Very sturdy and strong, smooth and lustrous. Usually has white and coloured stripes, but some patterned (floral). Can be made water-repellent, germ resistant, and feather-proof.
Uses : Pillow covers, mattress coverings, upholstering and some sportswear. `Bohemian ticking” has a plain weave, a very high texture, and is featherproof. Lighter weight than regular ticking. Patterned with narrow coloured striped on a white background or may have a chambray effect by using a white or unbleached warp with a blue or red filling.

Health effects of Man-made fibers


Clara S. Ross, James E. Lockey

The industrial use of various types of man-made fibres has been increasing, particularly since restrictions were placed on the use of asbestos in view of its known health hazards. The potential for adverse health effects related to the production and use of man-made fibres is still being studied. This article will provide an overview of the general principles regarding the potential for toxicity related to such fibres, an overview of the various types of fibres in production (as listed in table 1) and an update regarding existing and ongoing studies of their potential health effects.

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Table 1    Synthetic fibres

image

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Toxicity Determinants

The primary factors related to potential for toxicity due to exposure to fibres are:

1. fibre dimension

2. fibre durability and

3. dose to the target organ.

Generally, fibres that are long and thin (but of a respirable size) and are durable have the greatest potential for causing adverse effects if delivered to the lungs in sufficient concentration. Fibre toxicity has been correlated in short-term animal inhalation studies with inflammation, cytotoxicity, altered macrocyte function and biopersistence. Carcinogenic potential is most likely related to cellular DNA damage via formation of oxygen-free radicals, formation of clastogenic factors, or missegregation of chromosomes in cells in mitosis-alone or in combination. Fibres of a respirable size are those less than 3.0 to 3.5 in diameter and less than 200 in length. According to the “Stanton hypothesis,” the carcinogenic potential of fibres (as determined by animal pleural implantation studies) is related to their dimension (the greatest risk is associated with fibres less than 0.25 in diameter and greater than 8 in length) and durability (Stanton et al. 1981). Naturally occurring mineral fibres, such as asbestos, exist in a polycrystalline structure that has the propensity to cleave along longitudinal planes, creating thinner fibres with higher length-to-width ratios, which have a greater potential for toxicity. The vast majority of man-made fibres are non-crystalline or amorphous and will fracture perpendicularly to their longitudinal plane into shorter fibres. This is an important difference between asbestos and non-asbestos fibrous silicates and man-made fibres. The durability of fibres deposited in the lung is dependent upon the lung’s ability to clear the fibres, as well as the fibres’ physical and chemical properties. The durability of man-made fibres can be altered in the production process, according to end-use requirements, through the addition of certain stabilizers such as . Because of this variability in the chemical constituents and size of man-made fibres, their potential toxicity has to be evaluated on a fibre-type by fibre-type basis.

Man-made Fibres

Aluminium oxide fibres

Crystalline aluminium oxide fibre toxicity has been suggested by a case report of pulmonary fibrosis in a worker employed in aluminium smelting for 19 years (Jederlinic et al. 1990). His chest radiograph revealed interstitial fibrosis. Analysis of the lung tissue by electron microscopy techniques demonstrated crystalline fibres per gram of dry lung tissue, or ten times more fibres than the number of asbestos fibres found in lung tissue from chrysotile asbestos miners with asbestosis. Further study is needed to determine the role of crystalline aluminium oxide fibres (figure 1) and pulmonary fibrosis.

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Figure 1    Scanning electron micrograph (SEM) of aluminium oxide fibres

Courtesy of T. Hesterberg.

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This case report, however, suggests a potential for fibrization to take place when proper environmental conditions coexist, such as increased air flow across molten materials. Both phase-contrast light microscopy and electron microscopy with energy dispersion x-ray analysis should be used to identify potential airborne fibres in the work environment and in lung tissue samples in cases where there are clinical findings consistent with fibre-induced pneumoconiosis.

Carbon/Graphite Fibres

Carbonaceous pitch, rayon or polyacrylonitrile fibres heated to 1,200 form amorphous carbon fibres, and when heated above 2,200 form crystalline graphite fibres (figure 2). Resin binders can be added to increase the strength and to allow moulding and machining of the material. Generally, these fibres have a diameter of 7 to 10 , but variations in size occur due to the manufacturing process and mechanical manipulation. Carbon/graphite composites are used in the aircraft, automobile and sporting goods industries. Exposure to respirable-sized carbon/graphite particles can occur during the manufacturing process and with mechanical manipulation. Furthermore, small quantities of respirable-sized fibres can be produced when composites are heated to 900 to 1,100 . The existing knowledge regarding these fibres is inadequate to provide definite answers as to their potential for causing adverse health effects. Studies involving intratracheal injection of different graphite fibre composite dusts in rats produced heterogeneous results. Three of the dust samples tested produced minimal toxicity, and two of the samples produced consistent toxicity as manifested by cytotoxicity for alveolar macrophages and differences in the total number of cells recovered from the lung (Martin, Meyer and Luchtel 1989). Clastogenic effects have been observed in mutagenicity studies of pitch-based fibres, but not of polyacrylonitrile-based carbon fibres. A ten-year study of carbon fibre production workers, manufacturing fibres 8 to 10 mm in diameter, did not reveal any abnormalities (Jones, Jones and Lyle 1982). Until further studies are available, it is recommended that exposure to respirable-sized carbon/graphite fibres be 1 fibre/ml (f/ml) or lower, and that exposure to respirable-sized composite particulates be maintained below the current respirable dust standard for nuisance dust.

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Figure 2   SEM of carbon fibres

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Kevlar para-aramid fibres

Kevlar para-aramid fibres are approximately 12 in diameter and the curved ribbon-like fibrils on the surface of the fibres are less than 1 in width (figure 3). The fibrils partially peel off the fibres and interlock with other fibrils to form clumps which are non-respirable in size. The physical properties of Kevlar fibres include substantial heat resistance and tensile strength. They have many different uses, serving as a reinforcing agent in plastics, fabrics and rubber, and as an automobile brake friction material. The eight-hour time-weighted average (TWA) of fibril levels during manufacturing and end-use applications ranges from 0.01 to 0.4 f/ml (Merriman 1989). Very low levels of Kevlar aramid fibres are generated in dust when used in friction materials. The only available health effects data is from animal studies. Rat inhalation studies involving one- to two-year time periods and exposures to fibrils at 25, 100 and 400 f/ml revealed alveolar bronchiolarization which was dose-related. Slight fibrosis and alveolar duct fibrotic changes also were noted at the higher exposure levels. The fibrosis may have been related to overloading of pulmonary clearance mechanisms. A tumour type unique to rats, cystic keratinizing squamous cell tumour, developed in a few of the study animals (Lee et al. 1988). Short-term rat inhalation studies indicate that the fibrils have low durability in lung tissue and are rapidly cleared (Warheit et al. 1992). There are no studies available regarding the human health effects of exposure to Kevlar para-aramid fibre. However, in view of the evidence of decreased biopersistence and given the physical structure of Kevlar, the health risks should be minimal if exposures to fibrils are maintained at 0.5 f/ml or less, as is now the case in commercial applications.

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Figure 3    SEM of Kevlar para-aramid fibres

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Silicon carbide fibres and whiskers

Silicon carbide (carborundum) is a widely used abrasive and refractory material that is manufactured by combining silica and carbon at 2,400 . Silicon carbide fibres and whiskers-figure 4 (Harper et al. 1995)-can be generated as by-products of the manufacture of silicon carbide crystals or can be purposely produced as polycrystalline fibres or monocrystalline whiskers. The fibres generally are less than 1 to 2  in diameter and range from 3 to 30 in length. The whiskers average 0.5 in diameter and 10 in length. Incorporation of silicon carbide fibres and whiskers adds strength to products such as metal matrix composites, ceramics and ceramic components. Exposure to fibres and whiskers can occur during the production and manufacturing processes and potentially during the machining and finishing processes. For example, short-term exposure during handling of recycled materials has been shown to reach levels up to 5 f/ml. Machining of metal and ceramic matrix composites have resulted in eight-hour TWA exposure concentrations of 0.031 f/ml and up to 0.76 f/ml, respectively (Scansetti, Piolatto and Botta 1992; Bye 1985).

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Figure 4    SEMs of silicon carbide fibres (A) and whiskers (B)

A

B

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Existing data from animal and human studies indicate a definite fibrogenic and possible carcinogenic potential. In vitro mouse cell culture studies involving silicon carbide whiskers revealed cytotoxicity equal to or greater than that resulting from crocidolite asbestos (Johnson et al. 1992; Vaughan et al. 1991). Persistent adenomatous hyperplasia of rat lungs was demonstrated in a subacute inhalation study (Lapin et al. 1991). Sheep inhalation studies involving silicon carbide dust revealed that the particles were inert. However, exposure to silicon carbide fibres resulted in fibrosing alveolitis and increased fibroblast growth activity (Bйgin et al. 1989). Studies of lung tissue samples from silicon carbide manufacturing workers revealed silicotic nodules and ferruginous bodies and indicated that silicon carbide fibres are durable and can exist in high concentrations in lung parenchyma. Chest radiographs also have been consistent with nodular and irregular interstitial changes and pleural plaques.

Silicon carbide fibres and whiskers are respirable in size, durable, and have definite fibrogenic potential in lung tissue. A manufacturer of silicon carbide whiskers has set an internal standard at 0.2 f/ml as an eight-hour TWA (Beaumont 1991). This is a prudent recommendation based on currently available health information.

Man-made Vitreous Fibres

Man-made vitreous fibres (MMVFs) generally are classified as:

1. glass fibre (glass wool or fibreglass, continuous glass filament and special-purpose glass fibre)

2. mineral wool (rock wool and slag wool) and

3. ceramic fibre (ceramic textile fibre and refractory ceramic fibre).

The manufacturing process begins with melting raw materials with subsequent rapid cooling, resulting in the production of non-crystalline (or vitreous) fibres. Some manufacturing processes allow for large variations in terms of fibre size, the lower limit being 1 or less in diameter (figure 5). Stabilizers (such as , and ZnO) and modifiers (such as MgO,  , BaO, CaO, and ) can be added to alter the physical and chemical properties such as tensile strength, elasticity, durability and thermal non-transference.

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Figure 5    SEM of slag wool

Rock wool, glass fibres and refractory ceramic fibres are identical in appearance

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Glass fibre is manufactured from silicon dioxide and various concentrations of stabilizers and modifiers. Most glass wool is produced through use of a rotary process resulting in 3 to 15 average diameter discontinuous fibres with variations to 1 or less in diameter. The glass wool fibres are bound together, most commonly with phenolic formaldehyde resins, and then put through a heat-curing polymerization process. Other agents, including lubricants and wetting agents, may also be added, depending on the production process. The continuous glass filament production process results in less variation from the average fibre diameter in comparison to glass wool and special-purpose glass fibre. Continuous glass filament fibres range from 3 to 25 in diameter. Special-purpose glass fibre production involves a flame attenuation fibrization process that produces fibres with an average diameter of less than 3 .

Slag wool and rock wool production involves melting and fibrizing slag from metallic ore and igneous rock, respectively. The production process includes a dish shaped wheel and wheel centrifuge process. It produces 3.5 to 7 average diameter discontinuous fibres whose size may range well into the respirable range. Mineral wool can be manufactured with or without binder, depending on end-use applications.

Refractory ceramic fibre is manufactured through a wheel centrifuge or steam jet fibrization process using melted kaolin clay, alumina/silica, or alumina/silica/zirconia. Average fibre diameters range from 1 to 5 . When heated to temperatures above 1,000 , refractory ceramic fibres can undergo conversion to cristobalite (a crystalline silica).

MMVFs with different fibre diameters and chemical composition are used in over 35,000 applications. Glass wool is used in residential and commercial acoustical and thermal insulation applications, as well as in air handling systems. Continuous glass filament is used in fabrics and as reinforcing agents in plastics such as are employed in automobile parts. Special-purpose glass fibre is used in specialty applications, for instance in aircraft, that require high heat and acoustical insulation properties. Rock and slag wool without binder is used as blown insulation and in ceiling tiles. Rock and slag wool with a phenolic resin binder is used in insulation materials, such as insulation blankets and batts. Refractory ceramic fibre constitutes 1 to 2% of the worldwide production of MMVF. Refractory ceramic fibre is used in specialized high-temperature industrial applications, such as furnaces and kilns. Glass wool, continuous glass filament and mineral wool are manufactured in the greatest amounts.

MMVFs are thought to have less potential than naturally occurring fibrous silicates (such as asbestos) for producing adverse health effects because of their non-crystalline state and their propensity to fracture into shorter fibres. Existing data suggests that the most commonly utilized MMVF, glass wool, has the lowest risk of producing adverse health effects, followed by rock and slag wool, and then both special-purpose glass fibre with increased durability and refractory ceramic fibre. Special-purpose glass fibre and refractory ceramic fibre have the greatest potential for existing as respirable-sized fibres as they are generally less than 3 in diameter. Special-purpose glass fibre (with increased concentration of stabilizers such as ) and refractory ceramic fibre are also durable in physiologic fluids. Continuous glass filaments are non-respirable in size and therefore do not represent a potential pulmonary health risk.

Available health data is gathered from inhalation studies in animals and morbidity and mortality studies of workers involved with MMVF manufacturing. Inhalation studies involving exposure of rats to two commercial glass wool insulation materials averaging 1 in diameter and 20 in length revealed a mild pulmonary cellular response which partly reversed following discontinuation of exposure. Similar findings resulted from an animal inhalation study of a type of slag wool. Minimal fibrosis has been demonstrated with animal inhalation exposure to rock wool. Refractory ceramic fibre inhalation studies resulted in lung cancer, mesothelioma and pleural and pulmonary fibrosis in rats and in mesothelioma and pleural and pulmonary fibrosis in hamsters at a maximum tolerated dose of 250 f/ml. At 75 f/ml and 120 f/ml, one mesothelioma and minimal fibrosis was demonstrated in rats, and at 25 f/ml, there was a pulmonary cellular response (Bunn et al. 1993).

Skin, eye, and upper and lower respiratory tract irritation can occur and depends on exposure levels and job duties. Skin irritation has been the most common health effect noted and can cause up to 5% of new MMVF manufacturing plant workers to leave their employment within a few weeks. It is caused by mechanical trauma to the skin from fibres greater than 4 to 5 in diameter. It can be prevented with appropriate environmental control measures including avoiding direct skin contact with the fibres, wearing loose fitting, long-sleeved clothing, and washing work clothing separately. Upper and lower respiratory symptoms can occur in unusually dusty situations, particularly in MMVF product fabrication and end-use applications and in residential settings when MMVFs are not handled, installed or repaired correctly.

Studies of respiratory morbidity, as measured by symptoms, chest radiographs and pulmonary function tests among manufacturing plant workers generally have not found any adverse effects. However, an ongoing study of refractory ceramic fibre manufacturing plant workers has revealed an increased prevalence of pleural plaques (Lemasters et al. 1994). Studies in secondary production workers and end-users of MMVF are limited and have been hampered by the likelihood of the confounding factor of previous asbestos exposures.

Mortality studies of workers in glass fibre and mineral wool manufacturing plants are continuing in Europe and the United States. The data from the study in Europe revealed an overall increase in lung cancer mortality based upon national, but not local, mortality rates. There was an increasing trend of lung cancer in the glass and mineral wool cohorts with time since first employment but not with duration of employment. Using local mortality rates, there was an increase in lung cancer mortality for the earliest phase of mineral wool production (Simonato, Fletcher and Cherrie 1987; Boffetta et al. 1992). The data from the study in the United States demonstrated a statistically significant increased risk of respiratory cancer but failed to find an association between the development of cancer and various fibre exposure indices (Marsh et al. 1990). This is in accord with other case-control studies of slag wool and glass fibre manufacturing plant workers which have revealed an increased risk of lung cancer associated with cigarette smoking but not to the extent of MMVF exposure (Wong, Foliart and Trent 1991; Chiazze, Watkins and Fryar 1992). A mortality study of continuous glass filament manufacturing workers did not reveal an increased risk of mortality (Shannon et al. 1990). A mortality study involving refractory ceramic fibre workers is under way in the United States. Mortality studies of workers involved with product fabrication and end-users of MMVF are very limited.

In 1987, the International Agency for Research on Cancer (IARC) classified glass wool, rock wool, slag wool, and ceramic fibres as possible human carcinogens (group 2B). Ongoing animal studies and morbidity and mortality studies of workers involved with MMVF will help to further define any potential human health risk. Based on available data, the health risk from exposure to MMVF is substantially lower than what has been associated with asbestos exposure both from a morbidity and mortality perspective. The vast majority of the human studies, however, are from MMVF manufacturing facilities where exposure levels have generally been maintained below a 0.5 to 1 f/ml level over an eight-hour work day. The lack of morbidity and mortality data on secondary and end-users of MMVF makes it prudent to control respirable fibre exposure at or below these levels through environmental control measures, work practices, worker training and respiratory protection programmes. This is especially applicable with exposure to durable refractory ceramic and special purpose glass MMVF and any other type of respirable man-made fibre that is durable in biological media and that can therefore be deposited and retained in the pulmonary parenchyma.

Ref:-http://www.ilo.org/safework_bookshelf/english?content&nd=857170112

END PACKAGES PRODUCED ON WINDING M/CS


Most of the common packages on which the yarns are wound can be divided in to two groups.

(1)Parellal wound packages

(2)Cross wound packages.

(1)Parellal wound packages:-

These are double flanged bobbins,also known as warper’s bobbins on which yarn is wound in such a way that the coils of yarn are laid parellel sided or barrel shaped,Flanges are needed on either sides to support parellely laid coils.If flanges are not provided then coils at the two ends will COLLAPSE.  To withdraw the yarn from these packages,package has to be rotated by pull of yarn.Hence high unwinding speed will lead to excessive unwinding tension & yarn will break.Also as the unwinding is stopped the package continues to rotate due to its inertia,hence yarn may continue to come out from package.So this package is not suitable for the process taking place at high speed.

(2)Cross wound packages:-

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In this case the yarn is wound on cylindrical tubes or conical tubes.The yarn is laid on this in form of helices at the two extremes. In this type of winding the yarn wraps cross one another hence these packages are called cross wound packages.Because of laying in cross fashion there is no possibility of yarn coils collapsing at the two extremes.Hence these packages do not need flanges. The cylindrical cross wound package is known as CHEESE & the conical one as CONE. The yarn can be withdrawn from cone & cheese overend (& side ways unrolling also).The over end withdrawal allows unwinding at high speed without extreme increase  in tension.Rotation of package for unwinding is not essential hence the unwinding from package stops almost at the same instant when withdrawal is stopped. For some special cases yarn is required to be withdrawn side ways also.

Bobbins may be made of card or plastic, the latter being perforated if the yarn is to be package dyed. Parallel-sided cheeses have tubular bobbins. For cones, the bobbin is of a conical form, i.e., a truncated cone; the angle of taper — the semivertical angle — depends on the end use for the resulting package. Table 1 lists four common tapers. The wound cone package may have a fixed taper, which gives it flat ends, in which case the package is referred to as straight-ended. Cones may also have an accelerated taper, where the taper of the package is greater than the bobbin, resulting in a concave end at the top (the nose) and a convex end at the bottom (the base) of the package. These are called dished ends.

Table :- Common Tapers for Random-Wound Cones

Cone taper
(semivertical angle)
End uses
3°30′ General purposes
4°2′ Wet processing (e.g., dyeing)
5°5′ Weft knitting: at final diameter taper may increase to 10°
9°1′ Weft knitting: at final diameter taper may be 14° to 18°

Comparison of cross and parallel wound package

Sr no. Cross wound Package Parallel wound package
1 Self supporting Package Flanges are required to support the yarn
2 Overhead Unwinding Side-end Unwinding
3 Package is Stationary during unwinding Package rotates during Unwinding
4 The yarn stops immideatly the unwinding Stops The yarn doesnot stop unwinding as the  package continues to rotating due to inertia
5 Suitable for High speed unwinding Not suitable for high speed unwinding
6 yarn is laid at an angle to each other The yarn is laid parallel to one another
7 eg., Warper’s Bobbin Eg, Cone, Cheese & Spool

Sampling


It is not possible or desirable to test all the raw material or all the final output from a production process because of time and cost constraints. Also many tests are destructive so that there would not be any material left after it had been tested. Because of this, representative samples of the material are tested. The amount of material that is actually tested can represent a very small proportion of the total output. It is therefore important that this small sample should be truly representative of the whole of the material. For instance if the test for cotton fibre length is considered, this requires a 20 mg sample which may have been taken from a bale weighing 250kg. The sample represents only about one eleven-millionth of the bulk but the quality of the whole bale is judged on the results from it.

The aim of sampling is to produce an unbiased sample in which the proportions of, for instance, the different fibre lengths in the sample are the same as those in the bulk. Or to put it another way, each fibre in the bale should have an equal chance of being chosen for the sample methods from the test lot.

• Test specimen: this is the one that is actually used for the individual measurement and is derived from the laboratory sample. Normally, measurements are made from several test specimens.

• Package: elementary units (which can be unwound) within each container in the consignment. They might be bump top, hanks, skeins, bobbins, cones or other support on to which have been wound tow, top, sliver, roving or yarn.

• Container or case: a shipping unit identified on the dispatch note, usually a carton, box, bale or other container which may or may not contain packages.

Fibre sampling from bulk

Zoning
Zoning is a method that is used for selecting samples from raw cotton or wool or other loose fibre where the properties may vary considerably from place to place. A handful of fibres is taken at random from each of at least 40 widely spaced places (zones) throughout the bulk of the consignment and is treated as follows. Each handful is divided into two parts and one half of it is discarded at random; the retained half is again divided into two and half of that discarded. This process is repeated until about nix fibres remain in the handful (where n is the total number of fibres required in the sample and x is the number of original handfuls). Each handful is treated in a similar manner and the fibres that remain are placed together to give a correctly sized test sample containing n fibres. The method is shown diagrammatically in Fig. 1. It is important that the whole of the final sample is tested.

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Fig:- Sampling by zoneing

Core sampling
Core sampling is a technique that is used for assessing the proportion of grease, vegetable matter and moisture in samples taken from unopened bales of raw wool. A tube with a sharpened tip is forced into the bale and a core of wool is withdrawn. The technique was first developed as core boring in which the tube was rotated by a portable electric drill. The method was then developed further to enable the cores to be cut by pressing the tube into the bale manually. This enables samples to be taken in areas remote from sources of power. The tubes for manual coring are 600mm long so that they can penetrate halfway into the bale, the whole bale being sampled by coring from both ends. A detachable cutting tip is used whose internal diameter is slightly smaller than that of the tube so that the cores will slide easily up the inside of the tube. The difference in diameter also helps retain the cores in the tube as it is withdrawn. To collect the sample the tube is entered in the direction of compression of the bale so that it is perpendicular to the layers of fleeces. A number of different sizes of nominal tube diameter are in use, 14, 15 and 18mm being the most common the weight of core extracted varying accordingly. The number of cores extracted is determined according to a sampling schedule and the cores are combined to give the required weight of sample. As the cores are removed they are placed immediately in an air-tight container to prevent any loss of moisture from them. The weight of the bale at the time of coring is recorded in order to calculate its total moisture content.

The method has been further developed to allow hydraulic coring by machine in warehouses where large numbers of bales are dealt with. Such machines compress the bale to 60% of its original length so as to allow the use of a tube which is long enough to core the full length of the bale.

Fibre sampling from combed slivers, rovings and yarn

One of the main difficulties in sampling fibres is that of obtaining a sample that is not biased. This is because unless special precautions are taken, the longer fibres in the material being sampled are more likely to be selected by the sampling procedures, leading to a length-biased sample. This is particularly likely to happen in sampling material such as sliver or yarn where the fibres are approximately parallel. Strictly speaking, it is the fibre extent as defined in Fig. 1.2 rather than the fibre length as such which determines the likelihood of selection. The obvious area where length bias must be avoided is in the measurement of fibre length, but any bias can also have effects when other properties such as fineness and strength are being measured since these properties often vary with the fibre length.

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Fig 2.:- The meaning of extenet

There are two ways of dealing with this problem:
1 Prepare a numerical sample (unbiased sample).
2 Prepare a length-biased sample in such a way that the bias can be allowed for in any calculation.

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Fig 3:- Selection of numerical sample

Numerical sample
In a numerical sample the percentage by number of fibres in each length group should be the same in the sample as it is in the bulk. In Fig.3, A and B represent two planes separated by a short distance in a sample consisting of parallel fibres. If all the fibres whose left-hand ends (shown as solid circles) lay between A and B were selected by some means they would constitute a numerical sample. The truth of this can be seen from the fact that if all the fibres that start to the left of A were removed then it would not alter the marked fibres. Similarly another pair of planes could be imagined to the right of B whose composition would be unaffected by the removal of the fibres starting between A and B. Therefore the whole length of the sample could be divided into such short lengths and there would be no means of distinguishing one length from another, provided the fibres
are uniformly distributed along the sliver. If the removal of one sample does not affect the composition of the remaining samples, then it can be considered to be a numerical sample and each segment is representative of the whole.

Length-biased sample
In a length-biased sample the percentage of fibres in any length group is proportional to the product of the length and the percentage of fibres of that length in the bulk. The removal of a length-biased sample changes the composition of the remaining material as a higher proportion of the longer fibres are removed from it.

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Fig4 :- selection of tuft sample

If the lines A and B in Fig. 3 represent planes through the sliver then the chance of a fibre crossing these lines is proportional to its length. If, therefore, the fibres crossing this area are selected in some way then the longer fibres will be preferentially selected. This can be achieved by gripping the sample along a narrow line of contact and then combing away any loose fibres from either side of the grips, so leaving a sample as depicted in Fig. 4 which is length-biased. This type of sample is also known as a tuft sample and a similar method is used to prepare cotton fibres for length measurement by the fibrograph. Figure  5 shows the fibre length histogram and mean fibre length from both a numerical sample and a length-biased sample prepared from the same material.

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Fig:5 Histogram of length based and numerical samples

By a similar line of reasoning if the sample is cut at the planes A and B the section between the planes will contain more pieces of the longer fibres because they are more likely to cross that section. If there are equal numbers of fibres in each length group, the total length of the group with the longest fibres will be greater than that of the other groups so that there will be a greater number of those fibres in the sample. Samples for the measurement of fibre diameter using the projection microscope are prepared in this manner by sectioning a bundle of fibres, thus giving a length-biased sample. The use of a length-biased sample is deliberate in this case so that the measured mean fibre diameter is then that of the total fibre length of the whole sample. If all the fibres in the sample are considered as being joined end to end the mean fibre diameter is then the average thickness of that fibre.

Random draw method
This method is used for sampling card sliver, ball sliver and top. The sliver to be sampled is parted carefully by hand so that the end to be used has no broken or cut fibres. The sliver is placed over two velvet boards with the parted end near the front of the first board. The opposite end of the sliver is weighed down with a glass plate to stop it moving as shown in Fig. 1.6. A wide grip which is capable of holding individual fibres is then used to remove and discard a 2mm fringe of fibres from the parted end. This procedure is repeated, removing and discarding 2mm draws of fibre until a distance equal to that of the longest fibre in the sliver has been removed. The sliver end has now been ‘normalised’ and any of the succeeding draws can be used to make up a sample as they will be representative of all fibre lengths. This is because they represent a numerical sample as described
above where all the fibres with ends between two lines are taken as the sample. When any measurements are made on such a sample all the fibres must be measured.

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Fig 6:- The random Draw method

Cut square method
This method is used for sampling the fibres in a yarn. A length of the yarn being tested is cut off and the end untwisted by hand. The end is laid on a small velvet board and covered with a glass plate. The untwisted end of the yarn is then cut about 5mm from the edge of the plate as shown in Fig. 7. All the fibres that project in front of the glass plate are removed one by one with a pair of forceps and discarded. By doing this all the cut fibres are removed, leaving only fibres with their natural length. The glass plate is then moved back a few millimetres, exposing more fibre ends. These are then removed one by one and measured. When these have all been measured the plate is moved back again until a total of 50 fibres have been measured. In each case once the plate has been moved all projecting fibre ends must be removed and measured. The whole process is then repeated on fresh lengths of yarn chosen at random from the bulk, until sufficient fibres have been measured.

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Fig7 :- The cut square method

Yarn sampling

When selecting yarn for testing it is suggested that ten packages are selected at random from the consignment. If the consignment contains more than five cases, five cases are selected at random from it. The test sample then consists of two packages selected at random from each case. If the consignment contains less than five cases, ten packages are selected at random from all the cases with approximately equal numbers from each case. The appropriate number of tests are then carried out on each package.

Fabric sampling

When taking fabric samples from a roll of fabric certain rules must be observed. Fabric samples are always taken from the warp and weft separately as the properties in each direction generally differ. The warp direction should be marked on each sample before it is cut out. No two specimens should contain the same set of warp or weft threads. This is shown diagrammatically in Fig. 8 where the incorrect layout shows two warp samples which contain the same set of warp threads so that their properties will be very similar. In the correct layout each sample contains a different set of warp threads so that their properties are potentially different depending on the degree of uniformity of the fabric. As it is the warp direction in this case that is being tested the use of the same weft threads is not important. Samples should not be taken from within 50mm of the selvedge as the fabric properties can change at the edge and they are no longer representative of the bulk.

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Fig 8:- Fabric Sampling

Soy Fibers


Soybean protein fiber is a new type of textile material. It has been praised by industry expert as the Healthy and Comfortable Fiber of 21 Century.

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Properties of this fiber are excellent. It has many merits of natural fiber and chemical fiber: thinness, lightness, high strength (tenacity), good resistance to acid and alkali, excellent moisture-absorption and wet-transference etc.

It can be used to produce knitting fabric or weaving fabric which are suitable for underskirt and garment.

COLORFASTNESS OF COTTON TEXTILES


INTRODUCTION

Today’s consumer is more sophisticated than ever. They are conscious not only of style and comfort, but also of care and durability. They demand a quality product. Market studies show that consumers make many purchase choices based on color. Therefore, a fabric’s ability to retain its original color is one of the most important properties of a textile product.

The colorfastness or color retention of cotton textiles is influenced by a number of variables that occur both pre-consumer and post-consumer. This report summarizes how variations in raw materials, chemicals, manufacturing processes and consumer practices all have an effect on the performance characteristics of a fabric. Manufacturers must understand how the many variables affect colorfastness to achieve the ultimate goal of consumer satisfaction.

COLORFASTNESS AND TEST METHODS

Colorfastness is defined by the American Association of Textile Chemists and Colorists as “the resistance of a material to change in any of its color characteristics, to transfer its colorant(s) to adjacent materials, or both, as a result of the exposure of the material to any environment that might be encountered during the processing, testing, storage, or use of the material.” In other words, it is a fabric’s ability to retain its color throughout its intended life cycle. There are many types of colorfastness properties that must be considered to provide the consumer with an acceptable product. The American Association of Textile Chemists and Colorists has over thirty test methods that evaluate different colorfastness properties. These include, but are not limited to wash, light, crock, dry cleaning, perspiration, abrasion and heat. The type of product being manufactured determines which types of colorfastness are important and therefore which test methods are relevant. For example, upholstery fabrics must have excellent lightfastness and crockfastness properties, whereas washfastness is important for clothing fabrics. Manufacturers must know a fabric’s intended end use in order to make processing decisions that will produce a product of acceptable performance.

TEXTILE MANUFACTURING PROCESSES AFFECTING COLORFASTNESS

1. Preparation

Many aspects in the textile manufacturing process of taking a loom state fabric to a finished product have an effect on the colorfastness properties. Preparation is the first stage of textile wet processing. Cotton fibers are approximately 95% cellulose. The non-cellulosic portion consists of natural products such as waxes, sugars, metals, and man-made products such as processing aids, grease, plastic, and rubber. To achieve optimum dyeing and finishing conditions, it is important that these impurities are thoroughly removed with minimal damage to the cotton fiber.

2.Dye Selection

Dyeing is the crucial step in determining the colorfastness performance of a fabric. The American Association of Textile Chemists and Colorists define a dye as “a colorant applied to or formed in a substrate, via the molecularly dispersed state, which exhibits some degree of permanence.” Dyeing is accomplished by immersing the textile in a dye bath, applying heat and chemicals to drive the dye onto the textile, and then rinsing the substrate to remove the surface dye. These principles are illustrated below.

Different dye classes are used for each fiber type. The table below shows which dyes can be used for which fibers.

Dye Classes Available for Different Fibers

Fiber Dyestuffs
Cotton & manmade cellulosics Direct, Vat, Sulfur, Naphthol, Reactive, Pigment
Polyester Disperse, Basic
Nylon Disperse, Acid, Premetallized
Acetate Disperse
Wool & Silk Acid, Premetallized
Acrylic Dispersed, Basic

Dye selection must be based on desired performance criteria, manufacturing restrictions and the costs a market can bear for each end product. Every dye has unique colorfastness properties. Some dyes are known for their excellent washfastness characteristics and others are known for their lightfastness properties. The structure of the dye, the amount of dye, its method of bonding to the fabric and dyeing procedures all contribute to a dye’s performance characteristics. Dye combinations in a specific formulation must also be evaluated for their effect on colorfastness. Heavy shades often have reduced fastness properties. When high concentrations of dye are required, proper rinsing and washing off procedures are essential. However, due to entrapped dye particles within the cellulose structure, some unbound dye molecules can still remain and contribute to color loss and dye transfer

DYES FOR COTTON

Dyes can be categorized based on the mechanism by which they become fixed to a fiber. Dyes used for cotton fibers can be categorized into the surface bonding, adhesion, or covalent bonding mechanisms.

Pigments are sometimes used to color cotton fabrics, however they are not considered dyes. They are completely insoluble in water and have no affinity for cotton fibers. Some type of resin, adhesive, or bonding agent must be used to fix them to the cotton fiber. Typically, they exhibit good colorfastness to light and poor colorfastness to washing.

Direct dyes are water soluble and categorized into the surface bonding type dye because they are absorbed by the cellulose. There is no chemical reaction, but rather a chemical attraction. The affinity is a result of hydrogen bonding of the dye molecule to the hydroxyl groups in the cellulose. After the dyestuff is dissolved in the water, a salt is added to control the absorption rate of the dye into the fiber. Direct dyes are fairly inexpensive and available in a wide range of shades. Typically, they exhibit good lightfastness and poor washfastness. However, by applying a fixing agent after dyeing the washfastness can be improved dramatically.

Vat, sulfur, and naphthol dyes are fine suspensions of water insoluble pigments, which adhere to the cotton fiber by undergoing an intermediate chemical state in which they become water-soluble and have an affinity for the fiber. Typically, vat dyes exhibit very good colorfastness properties. Sulfur dyes are used to achieve a low cost deep black. They exhibit fair colorfastness properties, although the lighter shades tend to have poor lightfastness. Naphthol dyes are available in brilliant colors at low cost, but application requirements limit their use. They exhibit good lightfastness and washfastness, but poor crockfastness.

Reactive dyes attach to the cellulose fiber by forming a strong covalent (molecular) chemical bond. These dyes were developed in the 1950’s as an economical process for achieving acceptable colorfastness in cellulosic fibers. Bright shades and excellent washfastness properties are the trademark of reactive dyes. One concern regarding reactive dyes is their susceptibility to damage from chlorine. Another is that lighter shades tend to have reduced lightfastness properties.

The following table summarizes the fastness properties of the dye categories or classes available for dyeing cotton fabrics. Keep in mind that these are generalizations. Every dye is unique and some dyes within a particular class may behave differently.

Finishing

Finishing is the final stage of textile wet processing. Different types of finishes can be utilized depending on the desired performance characteristics of the end product. Resin and enzyme treatments are common finishing techniques that can influence the colorfastness of textile fabrics. Crosslinking resins are used to improve the durable press or wrinkle resistance of a fabric. Generally, resin treated fabrics demonstrate improved color retention to laundering. However, this increase in color retention comes at the expense of reduced physical properties of the fabric. Silicone softeners incorporated into the resin finish bath may further improve color retention for some fabrics. Softeners and resins play a key role in reducing surface abrasion and therefore improved overall wash performance. Cellulase enzymes are used to remove surface fibers that can create a fuzzy appearance on the surface of a fabric. Generally, enzyme treated fabrics show improved ability to maintain their original color and appearance after multiple home launderings. The degree of improvement from any of these finishing techniques is highly dependent on the individual dyes used in a particular formulation to achieve a given shade

CONSUMER PRACTICES

Manufacturers can follow every recommendation and precaution to produce a fabric with optimum performance characteristics. However, colorfastness properties are also influenced by consumer practices. These include laundry detergent selection and wash procedures. Therefore, when evaluating colorfastness properties of a product it is important to use the appropriate test method that accurately reflects the consumer laundry practices. Due to higher energy costs consumers are laundering clothes at lower temperatures. For this reason detergent with “color safe” or activated peroxy bleaching agents, which improve cleaning efficacy at lower wash temperatures, are one of the fastest growing segments of the home laundry market. Some fabrics may fade a little when home laundered with standard detergent, but fabrics laundered with detergents containing activated bleach can show significant losses in color strength as determined by the sensitivity of the dye to those detergents. Another type of detergent available to consumers is those containing enzymes, which remove surface cellulosic fibers from the fabric. Many times the loss or apparent loss of color can be attributed to surface changes in the fabric caused by abrasion during laundering. Detergents containing enzymes generally reduce the color change associated with home laundering by decreasing the fuzziness of a fabric’s surface. Wash procedures also influence a fabric’s ability to retain its color. Consumer practices such as washing clothes inverted, reducing the wash load size, adding softener to the final rinse and reducing the tumble dry time minimize color loss.

CONCLUSIONS

The colorfastness of cotton textiles can be a complicated subject. Fiber quality, yarn formation, fabric construction, textile wet processes and consumer practices can all have an influence on the performance characteristics of a fabric. Of these variables, the choices made during textile wet processing have the most significant effect on the colorfastness properties. Dye selection is of the utmost importance. Consumer practices such as detergent selection and laundering techniques also play a major role in the color retention of a fabric. Customer satisfaction should improve as manufacturers gain experience and knowledge in understanding and controlling the many aspects that influence colorfastness.

REf. TECHNICAL BULLETIN( www.cottoninc.com)