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Content Page
4.1 Materials for Clothing and Textiles 1 4.1.1 Textile Fibre Properties 2 4.1.2 Textile Fibre classification 2 4.1.3 Natural Fibres 3 4.1.4 Regenerated Fibres 15 4.1.5 Synthetic Fibres 19 4.1.6 Advanced Fibre Properties 26 4.1.7 Ways to Produce New Textile Materials 33 4.1.8 Other Materials Than Textile Fibres That Can Be Used 34 For Making Clothing
4.2 Fabric Construction 40 4.2.1 Types of Fabrics 40 4.2.2 Colouration 44 4.2.3 Finishing 48 4.2.4 Fabric Quality 52
2 4.1 Materials for Clothing and Textiles
Clothes and textiles can be made from different materials. Most of them are made from fabrics which are composed by a variety of fibres. People encounter different forms of fibres in their daily life, some are textiles fibres for making fabrics and textiles, others are non-textile fibres which include dietary fibre that can be found in our food, nerve and muscle fibre found in living organism, optical and reinforcement fibres for industrial uses.
Figure 4.1 Various kinds of fibre
Textile fibre is the basic unit of clothing and textiles and each type of fibre has its own properties and characteristics. Usually, they are spun into yarns, woven or knitted into fabrics and then made into clothing and textiles.
1 4.1.1 Textile Fibres Properties
Fibres are the basic substance building up fabrics. General properties of fibre are as follows:
Fibres are in line shape or thread-like substances.
Fibres are very fine with very small diameter.
There are two major types of fibre regarding to their length: short fibre and long fibre.
They are soft, flexible and can be bent easily.
Fibres are very light in terms of weight.
The surface of fibres can be either shiny like silk or dull like cotton.
Some are elastic.
Some possess natural colour or some are coloured later given that colouration is an important process in textile products.
4.1.2 Textile Fibre Classification
Generally, types of fibres are classified based on their sources. There are three main groups of fibres. They are namely natural, regenerated and man-made fibre.
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Figure 4.2 Common fibre classification
4.1.3 Natural Fibres
Those are fibres extracted from nature. They come from plants, animals and even minerals.
(A) Plants
Fibres can be obtained from different parts of plants, including seeds, basts (stem skin), leaves, etc.
(j) Cotton
Cotton is the most common textile fibre in the world with great economical value. Cotton plants are not just grown for fibre. Their seeds can be used for preparing cooking oil. Having high protein content, cotton seeds are also used as
3 supplementary diet for feeding livestock and poultry. From seed to cotton, it takes around 150 to 180 days. Cotton fibres are seeds hair. Sea-Island cotton is the longest cotton fibre with the length that ranges from 3.5 to 5 cm, Egyptian cotton ranges from 2.5 to 4.5 cm, and Asian cotton is the shortest that ranges from 1 to 1.8 cm.
z Fibre identification Burning Tests Other Tests - burns quickly with afterglow Tearing Test - smell like burnt paper - short fibres appear at the torn edges - pale grey residue and powdery ash Solubility Test - dissolves in sulphuric acid
z Properties Physical Mechanical Chemical - very fine fibre (1 – 4 - poor extensibility - damaged by dex) - good strength concentrated mineral - ranges from 20 – 40 - good abrasion acids (e.g. sulfuric acid) mm long resistance and and chlorine bleach - flattened tube like durability - strong alkalis improve thread with twist - poor elasticity / absorbency, luster and - creamy white or resilient strength yellowish in colour - creases easily - relatively low on luster - weight ranging from very light to heavy
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - usually cool to wear - absorbs up to 20% of - very comfortable next - can be warmer by water vapour and not to the skin because using different yarn feel wet cotton fibres are fine and fabric construction - absorbs moisture and soft rapidly and can retain up to 60% moisture of their own weight without dripping - dries slowly
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z Application and after care Typical fabric Application After Care calico, corduroy, denim, Apparel - easy to wash gningham, drill, terry - shirts, blouses, - can be boiled but toweling underwear, trousers, lower temperature for ** International Cotton jeans, nightwear coloured items Emblem** Accessories - white items can be - handkerchiefs, laces, bleached ribbons, trimmings, - iron at quite high umbrellas temperature up to Household Textiles 200°C - household linen, - can be dry cleaned by curtains, towels, normal solvent furniture coverings - can be tumble dried Technical Textiles - may shrink - workwear and protective clothing, tents, awnings, sewing thread, medical and sanitary supplies
(ii) Flax
Flax is another plant fibre that has a long history. Similar to cotton, flax is planted not just for fibre production. Its seed can be used for meal and producing oil, linseed oil, which some use as low temperature frying oil, to prepare salads and some for industrial use in painting and coating. Besides, various parts of flax plant are used for making dye, paper, medicines, fishing nets, soap, etc. Flax plants have even been recently used as fuel.
The extraction of fibre from the plants’ stalks passes through the following steps, which involves a lot of labour work. This accounts for linen being an expensive good. The steps are as follows:
(1) Retting
Cut stems will go through a process called retting which is to degrade of inner
5 straw and free outer fibres. There are several retting methods such as liquid retting (to rot straw with water), field retting (to rot straw in open field, this occupies a large space), enzyme retting (use specific enzyme to rot straw), etc. The former two processes are employing bacteria to break down the skin and inner straw while the latter process is using chemical.
(2) Dressing
Dressing is sub-divided into three separated processes, breaking, scutching and heckling. Breaking is to break the stalk into pieces without harming the fibre portion. Scutching is to scrap away the straw from the fibre. Heckling, just like combing, passes fibres through a series of heckles of different sizes to remove remaining straw.
(3) Cleansing
After further cleansing the extracted fibre, it is readily for yarn spinning. z Fibre identification Burning Tests Other Tests - burns quickly with afterglow Dry Tearing Test - smell like burnt paper - long fibers appear at the torn edges - pale grey residue with powdery ash - dissolved by sulphuric acid
z Properties Physical Mechanical Chemical - coarse fibre bundle - very strong fibre and - damaged by acids but - ranges from 45 – even stronger when not alkalis 90cm long wet - moderate yellow to - good abrasion gray in colour, the best resistance, durable grade is creamy white and long lasting in colour - brittle and poor in - subdued luster flexibility - cylindrical shape with - very poor extensibility nodes / joints and elasticity - straight and smooth - creases badly
6 z Clothing comfort Warmth Absorbency Next-to-skin Comfort - cool to wear as poor - absorbs water quickly - stiff and with a firm insulation properties - fast drying, releases handle absorbed water quickly
z Application and after care Typical fabric Application After Care Interlining, Holland (for Apparel - can be boiled but window blinds), mattress - summer and leisure lower temperature for ticking wear, blouses, shirts, coloured items ** Linen Seal** skirts, trousers, - white items can be jackets, suits, bleached interlinings - can be ironed up to Accessories 220°C - pockets, bags, shoes, - can be dry cleaned by luggage, handbag, normal solvent trimmings - can be tumble dried Household Textiles - may shrink - household linen, tablecloths, curtains, tea towels, drapes, furniture and wall coverings, mattress lining, upholstery fabrics Technical Textiles - tarpulins, ropes, sewing thread, geotextiles
(B) Animals
Animal fibres are protein fibres which come mainly from hair of animals such as sheep, goats, camels, horses, some are from insects, silk worms, etc. Leather and fur can also be made into garments and are considered as other textile materials rather than fibre.
7 (i) Wool
Wool is a kind of animal fibre taken from fleece of sheep and goats. The quality of wool fibres is assessed based on several characteristics including fibre length, fineness, colour, cleanliness, damage and surface scales. The finer the fibre, the softer it is. However, it is less durable and easier to pill. For garment purposes, fineness is expected to be smaller than 25 micron. Coarser fibres are usually used for making carpets and rugs as they are resistant to abrasion. The finest and softest wool comes from Merino sheep which is about 7.5 – 12.5cm long and 16.9 – 22.6 microns in diameter.
Fineness (micron) Grade < 24.5 Fine 24.5 – 31.4 Medium 31.5 – 35.4 Fine Crossbred >35.5 Coarse Crossbred
Figure 4.3 Fineness of various grades of wool fibres z Fibre identification Burning Tests Other Tests - small and sputtering flame, self Solubility Test extinguishing - cold and concentrated sulphuric acid - smell like burning hair has scarcely any effect - black residue with friable cinder - boiling 5% caustic soda and little lithium hypochlorite solutions or strong alkaline will dissolve wool
z Properties Physical Mechanical Chemical - 50 – over 150mm in - medium strength and - weakened by alkalis length not very durable - damaged by chlorine - fine (15~23um), - strength decreases bleaches medium (24~30um) when wet - acids does not damage and coarse (over - very good in wool unless of a high 30um) extensibility, even concentration - light weight better when wet - surface with - moderate abrasion overlapping scales and resistance
8 Physical Mechanical Chemical crimps - good elongation, - colour ranges from elastic recovery white to cream, beige, - excellent resilience tan and black - poor dimensional stability - felting occurred when affected by heat and moisture
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - excellent for insulation - high moisture - except for fine wool, as air is trapped by absorption next-to-skin comfort is scales (hydrophilic) can not so good - warm to wear absorb 1/3 of its weight in water without feeling set - water repellent (hydrophobic) can repels raindrops - absorbs moisture slowly and resists moisture
z Application and after care Typical fabric Application After Care felt, tweed, gabardine Apparel - wash with care ** Woolmark ** - suits, pullovers, - do not bleach with ** Woolmark Blend ** sweater, waistcoats, chlorine bleach, could overcoats, dresses, be cleaned using winter clothing Perchloroethylene Accessories - will shrink and felt - ties, scarves, hats, - steam iron at 150°C socks, stockings with a pressing cloth Household Textiles otherwise the fabric - carpets, upholstery goes shiny fabrics, blankets, - do not tumble dry
9 Typical fabric Application After Care draperies - do not dry in direct Technical Textiles sunlight or over direct - industrial felt, fire heat protection clothing, - dry cleaning agricultural blankets, recommended geotextiles
(ii) Hair Hair fibres possess similar structure and properties (physical, mechanical and chemical) as wool. But, they are much smoother, longer and with scales that are less prominent. The care of hair fibres is also very similar to that of wool. Hair fibres include camel hair, mohair, cashmere, alpaca, llama, vicuna and angora (rabbit hair).
Hair Fibre Properties Application Camel Hair - fine, heavy, soft, weak, - outerwear, interlining (undercoat of the lightly crimped camel) - warm, water-repellent, durable Mohair - long, soft, lightly curled, - outerwear (hair of the Angora - warm, smooth, slippery, goat) have a silky lustre - absorb dye evenly and permanently - good abrasion, crease-resistant - dust-repellent, fire-resistant Cashmere - - soft, light, lustrous - -expensive luxury (underhair of the - very warm and expensive fabrics for coats and Kashmir goat or - crease-resistant, dirt suits cashmere goat from repellent - luxury knitwear and India, Tibet, - non-static, fire-resistant interior textiles for cars, Mongolia and areas planes, yachts near Himalayan mountains)
Alpaca, llama, - fine, soft, strong, lightly - expensive knitted vicuna crimped, very warm fabrics, jacket,
10 (Alpaca and vicuna - high luster, durable overcoats, blankets are different kinds of - water repellent, high llama) insulative quality
Angora - long, fine, very light, silky - thermal underwear and (hair of Angora - good moisture absorbency ski underwear when rabbit) blended with wool
(iii) Silk
Silk is another kind of animal fibre obtained from cocoons of silkworm larvae. Silkworms can be obtained from cultivation (sericulture) or wild. Mulberry silkworm (Bombyx mori) is the species for sericulture. Same as wool, silk fibre is protein in nature. Silk has been popular in Eastern countries such as China for many decades. Initially, it was mainly for kings and it became luxury fabrics for the rich. z Fibre identification Burning Tests Other Tests - small flame, slowly self extinguishing Solubility Test - smell like burning hair or horn - dissolves in sulphuric acid - black residue with friable cinder - dissolves in lithium hypochlorite
Figure 4.4 Micrographs of both cultivated and Tussah (wild) silk fibres. (Source: American Association of Textile Colorists and Chemists)
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Figure 4.5 3D shape of silk fibres (Source: American Association of Textile Colorists and Chemists)
z Properties Physical Mechanical Chemical - filaments up to 1km in - strong, durable and - turns yellow and length light degrades when - triangular in - loses up to 20% of its exposed to alkaline cross-section with strength when wet detergent and chloride round corners - elastic, extensibility lies bleach - smooth and rod like between 10% to 30% - affected by surface with some - with stable dimensional perspiration, striations stability antiperspirant and - with natural shinness - fairly crease-resistant, perfume, may change - individual filament is creases drop out colour and becomes too fine to be wound - smooth and soft handle brittle separately, 7 – 10 of them are collected and wound together to form the raw or greige silk - cultivated silk is soft, smooth and lustrous - wild silk is coarse, irregular and thicker than cultivated silk, normally brown, but
12 Physical Mechanical Chemical maybe yellow, orange, or green in colour
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - both cool and warm - can absorb and hold - very good next-to-skin - fabrics made are very 1/3 of its weight in comfort for its softness fine and lie smoothly water without feeling and fineness on the skin, this allows wet very small amount of air enclosed between the skin and the fabric which provides a cooling effect - The compact and fine fabrics are also good insulator which enclose the warm air between the skin and the fabric
z Application and after care Typical fabric Application After Care Cultivated silk - Chiffon, Apparel - wash with gentle crepe, damask, satin, twill, - dresses, blouses, detergents with voile lingerie, ski underwear, minimum agitation and Wild silk - tussah silk, evening dress cool rinse doupion, Shantung Accessories - steam and water can ** Silk Seal** - scarves, squares, remove stains gloves, ties, hats, - do not bleached unless artificial flowers, non chlorine bleach is handbags, umbrellas used Household Textiles - do not tumble dry or - wall hangings, drapes, dry in direct sunlight wall coverings, carpets, - iron with dry iron at 120 lampshades, to 150°C on back of bedclothes fabric, do not press on Technical Textiles seam
13 Typical fabric Application After Care - sewing thread, - best to be dry cleaned embroidery threads, racing bicycle tyres
(C) Mineral Fibres
Beside plants and animals, fibres can also be obtained from minerals. Fibres from six type of minerals, chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite, are called asbestos. The main chemical composite of the asbestos is fibrous form of hydrated magnesium silicates. They are strong with high tensile strength, flame resistant and good insulator of electricity. Asbestos are widely used in cement, thermal insulation, electrical insulation, heat resistant garments, etc., in the past. The drawback of asbestos is health problem. As the fibre is very fine, its dust can trap in the small air sacs of the lung and cause diseases such as asbestosis, lung cancer, etc. Now, it is regulatory banned or controlled in many countries. Persons who handle asbestos material need to equip with self-sustain respirators to protect the lung.
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(A) Asbestos fibres on mineral (B) Electronic micrograph of asbestos fibre
Figure 4.6 Asbestos fibre (Source: (A) www.ehs.sfu.ca (B) erc.carleton.edu)
Another type of mineral fibre is glass fibres. They are mainly used as reinforcement fibre in the composite material and heat insulation products. Furthermore, metal fibres or yarns, such as silver, aluminum, etc., are frequently used for decorative purpose. As metal fibre are electrical conductive, they also employ for anti-static clothing for petroleum and electronic industry which can dissipate the accumulative charges to avoid explosion and electronic device damage.
4.1.4 Regenerated Fibres
Although there are a lot of advantages that cotton (or cellulosic) fibres possess, the sources of this kind of fibre are limited. People are looking for ways to produce fibres with similar properties. Regenerated fibres are mainly a group of cellulosic fibres that, through chemical methods, being regenerated from other cellulosic such as wood pulp, etc., that are not commonly used in the textile industry. Discovery of nitrocellulose is the milestone of the development of regenerated fibres. It can be dissolved in acetone (organic solvent). The basic principle of producing regenerated fibres is the dissolution of cellulose and the regeneration of fibres through fibre spinning. The process produces filament yarns which can be chopped into staple to imitate natural fibres. Recently, renewable resources such as bamboo are used for regenerated fibre production.
15 (A) Acetate
Acetate or cellulose acetate fibres are produced through the process of treating cellulose with acetic acid anhydride. z Fibre identification Burning Tests Other Tests - burns quickly and melts in a flame Solubility Test - with an acidic smell - soluble in acetone, dichloromethane, - with hard and black residue glacial acetic acid and formic acid - sensitive to both acids and alkalis
z Properties Physical Mechanical Chemical - filaments or cut into - low strength, even - thermoplastic staple weaker when wet - melts at temperature - white fibre with - poor abrasion over 135°C longitudinal resistance, elasticity - resistance in weak - variable fineness, can and resilience acids and alkalis be spun as microfibres - dimensionally unstable - striations and irregular - creases and shrink cross section easily - subdued luster, smooth - full handle and elegant drape
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - not very warm - low moisture - comfortable but prone absorption to static - fast drying
z Application and after care Typical fabric Application After Care brocade, satin, taffeta Apparel - thermoplastic and ** Arnel** - silk-type fabrics for sensitive to dry heat ** Tricel ** dresses, robes, - must be washed and lingerie, lining ironed carefully
16 Typical fabric Application After Care Accessories - do not bleach - trimmings - do not tumble dried Household Textiles - can be dry cleaned - embroidery yarns, ribbons, window treatment Technical Textiles - microfiber performance fabrics, cigarette filter
(B) Viscose Rayon
Viscose rayon is another kind of regenerated fibre from cellulose. It is produced by the ‘viscose process’ through wet spinning. This process is based on the dissolution of cellulose from wood pulp using carbon disulphide (CS2). z Fibre identification Burning Tests Other Tests - burns quickly with bright flame and Wet Tearing Test afterglow - tears straight through a wet spot - smell like burning paper Solubility Test - with pale grey powdery ash - dissolves in sulphuric acid - attacked by hydrochloric acid
z Properties Physical Mechanical Chemical - filaments or cut into - lower strength, - thermoplastic staples abrasion resistance - degraded by acids and - white, lustrous fibre and durability than alkalis with irregular cross cotton, can tear when section wet - variable fineness - wet strength is 40-70% - light weight lower than its dry strength - dimensionally unstable - poor elastic recovery, shrink and creases
17 Physical Mechanical Chemical easily - poor resiliency - good extensibility
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - low warmth as low - more absorbent than - fine and soft, very good ability to trap air cotton, absorbs next to the skin comfort - cool to the touch 11-14% of water vapour - high moisture absorption (hydrophilic), swells and absorbs 80 to 120% of water in liquid water - non-static
z Application and after care Typical fabric Application After Care Filament Can be used to resembles - wash in 60°C water - lustrous and crepe wool, silk, cotton or linen - do not bleach fabric - iron temperature in Apparel 60°C Staple - dresses, shirts, suits, - easy to iron - cotton, linen and lingerie, sportswear - can be dry cleaned wool-like fabric Accessories - do not tumble dried - trimmings Household Textiles - curtains, lining fabrics, blankets, tablecloths, bedspreads, slipcovers, upholstery fabrics, drappies Technical Textiles - medical and sanitary products where good
18 Typical fabric Application After Care absorbency is required
4.1.5 Synthetic Fibres
Synthetic fibres refer to fibres based on polymerisation of monomers. Monomers are mainly obtained from petroleum. Petroleum is a non-renewable resource and will use up in time. Scientists are continuously looking for substitutions, particularly renewable resources. New fibres have evolved based on chemicals extracted from corn, sugar beet, Soya bean, etc., e.g. Polylactic acid fibre.
(A) Polyester
Polyester fibres refer to polymer containing ester (—COO—) linkage which generated from an acid (R-COOH) and an alcohol (R’-OH). The most common polyester is polyethylene terephthalate (PET). z Fibre identification Burning Tests Other Tests - melts and shrinks from the flame Solubility Test - form a brownish mass - soluble in concentrated sulphuric - hard and uncrushable residue acid, concentrated potassium hydroxide, tetrachloroethane and phenols, dichlorobenzene
z Properties Physical Mechanical Chemical - filaments or cut into - good strength, lost - thermoplastic, heat staples strength with long sensitive, melts at - variable fineness from exposure to sunlight around 350°C microfibers to coarse - abrasion resistant, tear - resistant to acids, fibres resistance and durable alkalis, solvents - white fibre with - good extensibility (15 – different cross 50%) sections: round, - good elasticity, crease tri-and multilobal, oval resistant and hollow - dimensionally very - range from high luster stable
19 Physical Mechanical Chemical to matt depending on fibre cross-section and addition of delustrants
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - enclosed little air - little moisture - next-to-skin comfort is - good insulator if made absorption not very good into bulky fabric - fast drying - prone to static -
z Application and after care Typical fabric Application After Care Staple fibre fabrics, Apparel - wash in 60°C water textured filament fabrics, - underwear, causal and - do not bleach microfiber fabrics formal wear, uniforms, - iron temperature in outerwear, rainwear, 60°C lining, microfibre fleece - can be dry cleaned garments - can be tumble dried Accessories - ties, scarves, Household Textiles - furnishing, upholstery, carpets, pillows, hotel bedding, sewing threading Technical Textiles - transport textiles, ropes, sails, tents, tyre cord, geotextiles, medical textiles such as artificial ligaments
This is a fibre composed of linear polymer of amide linkage (—NHCO—) which is formed from reacting an acid (R-COOH) and an amine (R’-NH2). z Fibre identification Burning Tests Other Tests - shrinks and melts away from flame Solubility Test with fibre-forming drips - destroyed by 80% formic acid, - hard and uncrushable residue hydrochloric acid and concentrated mineral acids - slightly degraded by dilute organic acids z Properties Physical Mechanical Chemical - produced in filaments - very strong but lower - thermoplastic, can be or cut into staples modulus permanently shaped by - transparent and - excellent abrasion heat resembles a glass rod resistance and tear - resistant to alkalis and with round cross resistance, very many solvents but section durable affected by - variable fineness from - wet strength is 80 to concentrated acids microfibers to coarse 90% of the dry - becomes yellow and fibres - very high breaking lose strength when - may be dyed to many elongation (20 – 80%), exposed to sunlight for colours both wet or dry a long time - range from high luster - very resilient and to matt, depending on wrinkle resistant fibre cross section and - good elasticity, good addition of delustrants crease recovery - fabrics may be fine and soft or firm according to fibre fineness, fabric construction and finishing - light weight
21 z Clothing comfort Warmth Absorbency Next-to-skin Comfort - thermal insulation - small moisture - can be made into fine depends on whether it absorption (3.5 – 4.5%) and soft fibres is flat and textured - windproof, - prone to static filaments hydrophobic, water - uncomfortable in warm - flat filaments trap very repellent and humid weather little air therefore cool to wear - textured filaments trap air so warm to wear
z Application and after care Typical fabric Application After Care Staple fibre fabrics, Apparel - wash in 40°C water textured filament fabrics, - tights, underwear,, - iron without steam in microfiber fabrics nightwear, lining, active 40°C (e.g. Nylon 6, Nylon 6,6) sports wear, fleece - do not bleach garment - can be dry cleaned Accessories - tumbled dried with care - socks, ties Household Textiles - carpets, curtains, umbrellas, sewing yarns Technical Textiles - tents, ropes, sails, parachutes, tyre cords, seat belts
(C) Acrylic
Acrylic or polyacrylonitrile (PAN) fibre is an additional polymer. Acrylic fibre is polymer containing at least 85% acrylonitrile monomer (H2C=CH-CN). It is commonly used as wool substitute as its resilient resembles to that of wool but without felting and shrinkage tendency.
Modacrylic refers as modified acrylic. As per USA fibre regulation definition,
22 modacrylic is a copolymer containing less than 85% but at least 35% acrylonitrile monomer. z Fibre identification Burning Tests Other Tests - shrinks and burns with a sooty flame Solubility Test - with melting, dripping and forms black - dissolves in dimethylformamide, beads dimethylacetamide and nitric acid - pungent smell - hard and unbreakable residue
z Properties Physical Mechanical Chemical - produced as staples, - strong and durable - thermoplastics, burns crimp with striations when compare with and melts when and may be smooth or cotton and wool exposed to open flame twisted surface - good extensibility - crimp, pleats and - variable fineness, - good resistance to light creases can be heat ranges from microfiber and chemical, set to coarse fibres - moderate resiliency, - may shrink and - wet-spun acrylics are round and bean discolour with high round and bean shapes have greater temperature shaped resilience - resists acids except - dry-spun acrylics are - moderate tenacity nitric acid dog-boned shaped with - wrinkle resistant, - moderately resists increased softness and moderate elastic alkalis but degraded by luster recovery sodium hydroxide - wool-like handle - has pilling tendency - may be dyed to many - moderate dimensional colours stability - range from high luster - soft to matt depending on fibre cross section and addition of delustrants - low density
23 z Clothing comfort Warmth Absorbency Next-to-skin Comfort - warm, insulating - low absorbency - comfortable to wear qualities similar to wool - fast drying - prone to static
z Application and after care Typical fabric Application After Care Usually blended with other Apparel - wash in 40°C water fibres, such as cotton, - lightweight, - iron with low linen, viscose rayon, wool nonallergenic wool temperature around and silk substitutes, sweaters, 40°C fleece, knitted wear, - strong detergents and pile, fake-fur and fleece non-chloride bleach fabrics may be used Accessories - dry-cleaning solvents - socks may cause stiffening Household Textiles - blankets, curtains, upholstery, carpet, fluffy knitting yarns Technical Textiles - awnings, tarpaulins, tents, outdoor furniture, microfiber performance fabrics
(D) Spandex
Spandex is USA fibre generic name for elastic fibre and in the European market, it is called elastane. It is mainly composed of segmented polyurethane (PU). According to the USA fibre regulation definition, fibres that contain at 85% by weight of segmented PU are referred as Spandex. Spandex filament is usually incorporated in fabrics to produce elasticity. z Fibre identification Burning Tests Other Tests - burns and melts, continues to burn Solubility Test when the flame is removed - dissolves in cyclohexanone and
24 - drips but does not shrink from the dichlorobenzene flame - with a chemical odor - with hard and black residue
z Properties Physical Mechanical Chemical - cross sectional - excellent elastic - degraded by appearance: fibrillar recovery (can be concentrated chlorine - longitudinal stretched by from bleach and becomes appearance: smooth 400 – 700% and yellowish or striated recovers its original - thermoplastics and - white or gray and length) melts at 230°C delustered - good strength, - from 20 to 4300 denier resiliency and - monofilament or dimensional stability multifilament - very high crease resistant - poor abrasion resistance and tenacity when compared with other fibres
z Clothing comfort Warmth Absorbency Next-to-skin Comfort - Low warmth, always - absorbent and dyes - adds stretch to comfort used in blends well - soft or firm handle
z Application and after care Typical fabric Application After Care Need to be combined with Apparel - may be machine other fibres, natural or - body-hugging washed or dry cleaned synthetic to make into comfortable garments - can be tumble dried fabric, e.g. - sports wear, skiwear, and iron up to 150°C - swimwear lingerie, hosiery, - aged when subjected - hosiery leisurewear, fashion to extreme stretching - jersey fabrics products - woven fabrics Accessories
25 Typical fabric Application After Care - flat knits - shoes Technical Textiles -medical products such as bandages, nappies
4.1.6 Advanced Fibre Properties
(A) Polymers
Textile fibres are made from a class of chemical called polymer, natural or synthetic forming polymer. Polymer is a long chain shaped molecule made from a number of repeating chemical units called monomer. Polymer is also called macromolecule as its size is comparatively larger than that of usual chemical compounds. They are fundamental constituent of many materials ranging from plastics and rubbers to complicated biological substances such as carbohydrate and protein.
Figure 4.8 A segment of linear polymer chain building up with monomers
Natural polymers exist as short fibres, which will be combed, lined up and twisted to make longer, usable lengths.
cellulose based fibres, such as cotton and flax, are composed of the glucose polymer cellulose
animal fibre, like wool, is composed of the protein polymer keratin
‘Regenerated’ fibres, e.g. viscose are fine continuous filaments of regenerated cellulose.
26 Synthetic fibres are made from petrochemicals using the process of polymerisation. Polymerisation refers to chemical reactions that link monomer(s) together to form synthetic polymer. There are two types of chemical reactions, addition and condensation. Additional polymers are made by adding identical monomers to each other to form long chains. The polymer produced is called homopolymer. Polyethylene (PE), plastic which is used for polybag, is an example of this type of polymer. Another example is polyacrylonitrile (PAN) or acrylic.
Figure 4.8 Polymerisation through addition reaction.
Condensation polymers are made by adding different monomers together to form long chains. Two or more types of monomers are used, the polymer is called heteropolymer. The name of the polymer is usually based on the chemical structure of linkage. For example, Polyester is a kind of polymer based on ester (—COO—) linkage. Nylon (or polyamide) is another example based on the amide (—NH-CO—) linkage.
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Figure 4.9 Condensation polymerisation of polyester.
Another type of polymer is called block copolymer. This is a kind of polymer with two different kinds of monomers linked together either in branch or block structure. Elastane is made by block polymerization.
28 (B) Shape (Morphology)
Shape is the one of the fundamental characteristics of textile fibres. The study of shape, appearance and form of a substance is called “morphology”. The fundamental substance of fibre is polymers. Basically, different kinds of polymeric substances in a fibre and the different arrangements of polymers (microstructures) within the fibre determine the shape. There are many factors affecting fibres’ shape. Take cotton as an example. It is the fibre extracted from cotton plants. The shape of cotton fibre is grown by natural. However, weather, soil condition, irrigation, etc, will affect the growth of cotton plants and also cotton fibres in terms of their yield, fibre length, etc. On the contrary, polyester is made from petroleum chemicals. Its shape is determined by the way how it is manufactured. The process is called fibre spinning. For fibres taken from nature, their shapes can be used as fibre identity. However, for man-made fibre shapes that are not definite, they can be made into different forms as one desires.
Figure 4.10 Micrographs of two different forms of acrylic fibres. The left-hand side fibre is oval shape (modified wet spun, 3.0 denier (0.33 tex) per filament, semi dull lustre) and the right-hand side fibre is bi-lobed and tri-lobed shape (solvent spun). (Source: American Association for Textile Colorists and Chemists)
Fibre shape determines many of the final properties of fabric such as smoothness,
29 shininess, shrinkage, easiness of yarn spinning, pilling resistance, etc.
Figure 4.11 Micrograph of various textile fibres
As shape relates to many properties, there are processes to modify fibre shapes to produce a particular effect. Mercerisation of cotton is an example. As natural cotton fibres are in ribbon shape and they look dull, mercerisation is a process using strong alkaline to swell cotton fibres. The inflated fibres give silky shininess to cotton fibres. Another advantage is strengthening of fibre.
Figure 4.12 Comparison of the shapes of natural cotton and mercerized cotton fibres. As the ribbon shape being inflated by strong alkaline, mercerised cotton has fuller shape and reflects light evenly. This is why mercerised cotton has silky shininess appearance.
30 (C) Arrangements of Polymer in Fibres
Polymers align along the fibre lengthwise dimension. Such arrangement not just gives rise to the thread-like shape of fibre, it also contributes to other properties such as strength of fibre, swelling behavior in water, absorbency, etc.
Although polymeric molecules align mainly along the fibre axis, the alignment of polymer will give rise to two microstructures, crystalline and amorphous region. Crystalline structure is a region where polymeric chains are orderly arranged and demonstrate crystal properties. This is the rigid section that renders the material stiffness and strength. Crystalline section is usually opaque. As polymer chains are orderly arranged, light can be reflected in definite pattern efficiently.
Figure 4.13 Crystalline and amorphous micro-structures of polymeric chains in fibres. Different polymer chains are illustrated in different colours. Polymer chains aligned orderly in particular axis in the crystalline region. Polymer chains being arranged randomly without any order in the amorphous region.
As polymeric chains are not orderly arranged, there are many intermolecular spaces in the region. Other molecules such as water, dye, etc can easily diffuse in and out. This region is important for water absorption and dyeing. Of course, another factor concerning water absorption is the presence of hydrophilic (water liking) groups in the polymeric chain.
The relative proportion of these two microstructures determines a lot of fibre properties such as strength, dyeability, absorbency, transparency, softness, etc. More proportion of crystalline structures renders fibres greater strength, e.g. nylon. Greater proportion of amorphous structures renders fibres greater water absorption ability, easy colouration and more soft, etc.
31 (D) Moisture Regain
Most of the textile fibres are hydroscopic. Hydroscopic substances all have the ability to attract water molecules from the moist surrounding and release water molecules to dry surrounding through desorption. The driving force behind is most textile fibres possess hydrophilic (water – loving) groups that can bond to water molecule through a weak link called hydrogen bonding. This is a property affecting a number of physical characteristics such as hand feel (i.e. comfortability), weight, strength, colour stability, pilling and abrasion resistance, etc of textile products.
Moisture regain of textile fibre is the percentage of the amount of water a fibre can hold in a particular environment, which is usually standardised at 21°C, 65% relative humidity, in respect to the dry weight of the fibre.
Amount of water Moisture Regain = X 100% Fibre Dry Weight
Material Moisture Regain (%) Acrylic hand knitting 1.5 yarn Cellulose acetate 6 Cotton 8.5 Flax and hemp 12 Nylon 4 Silk 11 Viscose rayon 11 Wool tops 18.5 Scoured wool 16
Figure 4.14 Moisture content of various textile fibres
As one can see, man-made fibres such as acrylic have low moisture regain. This is one of the reasons why some end users may feel uncomfortable with man-made fibre products. A majority of people agree that cotton is comfortable and one reason is its high moisture content. Furthermore, moisture regain of a fibre indicates the degree of hydroscopy of fibre. Low hydroscopic substances, such as acrylic, are hard to dye and usually carried out at high temperature.
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4.1.7 Ways to Produce New Textile Materials
(A) Blending
Blending is mix two or more fibres together. The advantage of fibre blending is that poor properties of one component can be compensated by good ones of the other component. For example, some natural fibres shrink and wrinkle after laundering. Blending with man-made fibres can reduce shrinkage and wrinkle of natural fibres.
Different fibres can blend in fibre, yarn or fabric stage. There are many combinations of blending materials. Blending ratio can also be tuned to control the blended fabric properties. All these make blended fibres a versatile group of textile materials for various kinds of applications.
Blending combination Example Natural - natural Cotton - Ramie Natural - regenerated Cotton - Rayon Natural - synthetic Wool - Polyester Synthetic – regenerated Polyester - Rayon Synthetic - synthetic Nylon - Spandex
Figure 4.15 Various kinds of blending of different textile materials
(B) New Textile Fibres Development
Polymer research has started from the 19th century and was well developed throughout the period from the 60s to the 80s. Nowadays, new advancement of synthetic textile materials is not too much. The new direction of synthetic textile fibre production leans more towards environmental protection. The major supply of chemicals is based on the petroleum industry. Petroleum is a fossil fuel and non-renewable. As the volume of petroleum content is decreasing in the world, researchers are looking for new sources for chemicals production. Recently, fibre scientists start using chemicals from fast growing plants such as corn, soya bean, sugar cane, etc.
33 Polylactic Acid (PLA) Fibres
PLA fibre is a newly developed textile fibre which is generated based on corn rather than petroleum chemicals. This fibre is manufactured from the lactic acid obtained from the fermentation of sugar extracted from corn. Some call it “corn” fibre. The fibre has low moisture regain and good wicking, which makes it good for sportswear. It demonstrates low flammability with less smoke generated during its production process. It is very light and resistant to ultraviolet radiation. The merit of the fibre is that it is an environmentally friendly fibre as it is generated from renewable resources.
4.1.8 Materials Other Than Textile Fibres that Can be Used for Making Clothing
Apart from textile fibres, there are many other types of materials that can be used for making garments. Some of them have a longer history than that of textile fibres.
(A) Leather and Fur
Leather and fur have had a very long history. Ancient people used them for clothing long before the use of textile. They hunted animals for food and cut the skin of animals for making clothing that kept them warm. Nowadays, leather usually comes from cows, sheep, pigs, etc. Fur is also skin from animals but with hair. Fur keeps warm much better than leather and is used for winter clothing. Nowadays, fur is usually taken from precious animals such as arctic fox. To avoid the extinction of the species, many countries have restriction on the hunting of those animals. Fur garments are expensive because of the limited supply of fur and they are usually handmade.
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(A) red leather jacket (B) fox fur clothing Figure 4.16 Typical leather and fur clothing
35 Leather is also called ‘hide’, which is a part of animal skin. Leather is:
Flexible
Durable
Strong
Dimensional stable
Abrasion resistant
Flame resistant
Water resistant
Leather from different animals and body parts has its unique texture and different properties. Leather along the backbone is with more strength than that across the backbone direction. Yet, leather cross the backbone is more stretchable.
Figure 4.17 Leather structure
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Figure 4.18 Anisotropy of leather
(B) Metal
Metals are heavy, inflexible, hard, no water absorption, etc. It is seldom used for making modern garments. However, metal armors were one of the important military and warfare necessity in the past. They provide maximum protection to the body from attacks of all sorts of sharp weapons. The major drawbacks are its heavy weight and inflexibility. Nowadays, metal can be used as decoration and accessories. It can also be incorporated in garment in the form of yarn or foil.
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Figure 4.19 Modern made metallic armor for collection. The armor is built from forged and hammered mild steel plates. (Source: © 2006 Kropserkel Inc.)
(C) Paper
Paper (or non-woven) fabrics are commonly used as disposable or one time use items such as disposable underwear, diaper, lab coat, etc. The costing is comparatively lower than that of usual textiles. Unlike textile fabrics, the production of non-woven fabrics needs no yarn. It is a direct process done with fibres. Fibres are laid randomly and interlocked with other fibre strands through entanglement, adhesive or fusion. As the production steps are simple, its cost is greatly reduced.
(D) Plastics
Plastics are developed in parallel with synthetic fibres. It can be applied to clothing, particularly to raincoats. Polyvinyl chloride (PVC) and polyethylene (PE) are the common plastics employed. The difference between plastics and textile fibres are their different forms. Plastic are extruded in sheet form for clothing while textile fibres
38 are extruded in thread form. Plastic are a kind of versatile material and provide a wide varieties of surface texture such as smooth, embossed, imitate leather, etc. Imitated leather is usually composed of a thick layer of polyurethane (PU) foam and coated with a thin layer of PVC that is molded to give the leather a look texture. For increasing strength, a layer of textile cloth is bonded underneath as backing. There is another kind of clothing plastic called “pleather” which refers to plastic leather or synthetic leather. Pleather is a thick layer of plastic with moulded leather texture on the face or its smooth surface. The back side is usually bonded with a layer of textile cloth for improving strength and making wearers feel comfortable.
(A) Leather jacket (B) PVC raincoat
Figure 4.20 Plastic clothing
39 4.2 Fabric Construction
Fabric is constructed from yarns. Yarns are threads which are made from smaller threads. Fabrics are readily made materials for the production of various kinds of textile products.
Figure 4.21 Different stages of textile production
There are two basic types of textile fibres, staples (short fibres) and filaments (long fibres). Staples are short and need to be twisted together to form yarns. Filaments are very long and require very few twisting to form yarns.
Figure 4.22 Basic types of yarn
4.2.1 Types of Fabrics
Fabrics are constructed from yarns. Basically, there are two main types of fabrics, woven and knit fabric. They are produced completely differently and they certainly possess different properties.
40 (A) Woven Fabrics
Woven fabrics are made from interlacing two sets of yarns at a right angle. The process is called weaving. Yarns parallel to length are called warps or ends. Yarns parallel to width are called wefts or fills. Warp yarns require under tension during the weaving process. They usually have greater strength than wefts. Warp yarns pass over and under the wefts alternatively. Weft yarns run in similar pattern. By changing such interweaving pattern, different types of woven fabrics can be produced. Woven fabrics are strong fabrics with greater stability in terms of the maintenance of their shape. They will not shrink much after laundering.
Figure 4.23 Basic construction of a woven fabric. The purple yarns are warps and the yellow yarns are wefts.
(B) Knit Fabrics
The construction of knit fabrics is completely different from that of woven fabrics. They are formed by interlocking yarn loops. The process is called knitting. Hand knitting garments are produced based on such technique. Yarns are running across the width of fabrics. The direction is called course. The direction parallel to length is called wale.
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Figure 4.24 Basic construction of a knit fabric. Alternate courses are illustrated in blue and green. For circular knit fabric, they can be the same yarn.
Knit fabrics formed from yarn loops can be extended widthwise more easily. They are soft and can be draped easily. However, they are a form of weaker fabric that is more stretchable and less dimensionally stable. Knit garments are advised to be washed by hand or washing machine with gentle cycle to minimise shrinkage.
The two basic loops structures are called purl and knit stitches. By arranging these two basic structures, various kinds of knit fabrics can be produced.
Figure 4.25 Two types of yarn loops present in knit fabric
Furthermore, the appearance of the face and the back of knit fabrics are different. The face side of a knit fabric has the “V” shape of yarn segments. The back side of the fabric looks differently.
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Figure 4.26 Back side of a knit fabric
(C) Non-Woven Fabrics
Non-woven fabrics are constructed differently from the above two types of fabrics. They are directly produced from fibres without yarn. This minimises the cost of production and non-woven fabrics are cheaper and usually applied to garments of one-time use. One of the examples is the protective clothing used in hospitals. This kind of clothing is expected to be disposed immediately after use to avoid bacterial infection.
The formation of non-woven fabrics is by compressing fibres together through:
Mechanical bonding
Glue
Heat fusion
Common materials used to produce non-woven fabrics are synthetic fibres such as polypropylene (PP), polyester, etc. Non-woven fabrics are popular nowadays in terms of the application of many products other than clothing. Some examples of all these different applications are dust filter and environmental shopping bag.
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Figure 4.27 Non-woven fabrics
4.2.2 Colouration
Colouration is an important process in terms of textile production. Textile colours are achieved through two processes, dyeing and printing. Dyeing gives solid colours to fabrics and printing gives colour patterns to fabrics.
(A) Colour Basics
The colours are light radiation which may come directly from the light source that are transmitted or reflected by objects. Lights can be considered as waves with different wavelengths. Human eyes can only see a certain part of the light spectrum. These lights that fall into this part of the colour spectrum visible to human eyes are called visible lights, ranging from wavelength 400 nm to 700 nm. Blue light is a short wavelength, around 400 nm and carries higher energy. Red light is a longer wavelength, around 700 nm, and carries lower energy. There are three elements that help to percept the colour(s) of an object. They are light, the object and the eyes. Without one of them, one will not be able to see the object’s colour.
Figure 4.28 Red and blue light radiation
(B) Dyeing
44 Dyeing is the colouration of textiles by the application of dyes. Dyes are a group of colour molecules (colourants) with the following characteristics:
Water soluble
Affinity to textile fibres
There is another type of colourants called pigment which are:
Water insoluble
No affinity to textile fibres
Combined to fibres through binders
Dyeing is carried out in water and the water is called the dye liquor. Dye molecules migrate from the dye liquor to the textile fibres. Dyes are then absorbed by fibres. From that point onward, the dyes are exhausted. However, this is not the final destination of dyes. They will further diffuse into the fibres and finally combine with a particular fibre structure called dyesite. This process is called fixation. Fixed dyes do not easily migrate back to the dye liquor. The amount of dye exhausted is equal to the amount of dye absorbed and fixed. Of course, absorbed dyes may diffuse back to the dye liquor before they are fixed. The fixing process is called desorption. In the situation when exhaustion rate is equal to desorption rate, the dyeing process attains equilibrium and any further dyeing will not result in any further increase in colour depth. The amount of dye exhausted at this stage is called equilibrium exhaustion.
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Figure 4.29 Dyeing process
(C) Printing
Printing can be considered as a local colouration process. Colour will only apply to the printed area and the unprinted area will not be coloured. Printing is carried out with print paste which consists of a high concentration of colourant together with thickener. The purpose of the thickener used in this process is to limit the side migration of colourants (or sometimes called bleeding). Dye and pigment can be applied. For pigment print, binders are mixed into the print paste.
Printing patterns are usually transferred to rotary screens or flatbed screens. The unprinted area is blocked by photosensitive resist and left the printed area open. Print paste is squeezed through the printed area and transferred onto fabrics.
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(A) Flatbed screen printing
(B) Rotary screen printing
Figure 30 Principle of textile printing
(D) Colour Fastness
The resistance of colour of a dyed or printed textile is called colour fastness. The resistance can be measured in two aspects. They are namely, colour change and staining.
Colour change generally refers to the fading of colour in respect to various processing and daily actions such as washing. Staining refers to the colour migration from the item to its adjacent item. For the sake of measurement, white fabrics are usually selected to be the adjacent material.
Colour fastness is affected by the types of dye applied and the dyeing operation. It is also measured in terms of various factors. Common colour fastness properties are:
Washing
Light
Rubbing
47 4.2.3 Finishing
Finishing is commonly referring to treatments applied to textiles for the modification or addition of the textile properties. There are many types of finishing that may change surface appearance, absorption properties, etc. Finishing can be applied through mechanical or chemical process.
(A) Mechanical Finishing
Mechanical finishing refers to the finishing achieved through mechanical actions. They usually modify the surface appearance and hand feel of fabrics.
(i) Raising
This is a process to produce raised surface on the fabric through brushing. Short fibres are uplifted from yarns by brushing rollers. The brushed surface is soft and comfortable. The brushed side is usually facing the skin and one of the major applications of brushed fabrics is sleepwear. Brushing can also be applied to both sides of fabrics. However, brushed fabrics have weaker strength as yarns are damaged. The more the brushing, the weaker the fabric becomes. Apart from brushing rollers, sanding can also produce raised surface which produces suede effect. By decreasing the sand size, peach surface can be produced on fabrics.
Figure 4.31 Brushing
48 (ii) Calendaring
This process applies a heavy and usually heated metal calendar on either one side or both sides of fabrics, which is similar to ironing. This will produce a smooth surface and increase the luster of fabrics.
Figure 4.32 Calendaring
(iii) Embossing
This process applies an embossing calendar to fabrics. The embossment is usually patterned to produce an embossed pattern on fabrics. The calendars of either of both sides can be heated for synthetic fabric to enhance the embossing effect.
Figure 4.33 Embossing
(iv) Fulling
This is a specific finishing process for woolen fabric. The fabrics are subject to moisture, heat, friction and pressure control, which are main reasons that cause shrinkage. The treated fabrics become much compact and dense. This produces a fulling hand feel.
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Figure 4.34 Schematic diagram of an fulling equipment
(B) Chemical Finishing
These kinds of finishing produce wide varieties of effects on fabrics through chemical treatments. They can enhance the dimensional stability, induce water resistance, improve softness, etc. Some of these different kinds of finishing are as follows:-.
(i) Water Repellency
Most of the untreated textile materials absorb water or moisture to a certain degree. Water repellency finish aims to render fabric resistance to wetting. The finish is based on the application of water repelling agents such as wax, olefin, fluoropolymer, etc. For fabrics with water repelling finish, water will form spherical or hemispherical droplets on the surface of fabrics.
(ii) Water Proofing
Water proofing finish renders the fabrics’ impermeability to water. This is usually done by coating textiles with plastic such as PVC, olefin, silicone rubber, etc. Such kind of finish can prevent water from passing through the fabrics but it also blocks air diffusion. This makes the wearers feel uncomfortable when wearing clothing of this sort. Modern water proof textiles can combine water resistance and air permeability together. An example of this kind of modern water proof textile would be Gore-tex.
50 (iii) Stain Resistance
This finishing shares similar principles of that of water repellency finish. Low surface tension substances are applied to fabric surface. Dirt cannot attach firmly or even without any attachment to fabric surface. Contemporary stain resistance agents are mainly based on fluoropolymer such as Teflon. This group of polymers is well known to have low surface tension.
(iv) Antibacterial Finishing
This finishing applies germicides to fabrics to kill or stop the growth of bacteria. Several major applications of this finishing are:
y Sportswear, underwear and socks to prevent bacterial decomposition of sweat from causing irritating and unpleasant odor.
y Medical uniform to prevent bacterial infection.
y General products to prevent bacterial degradation of textile material.
Below are several newly developments of antibacterial finishing:
y Incorporation of nano-sized silver in yarn.
y Plasma induced germicide attachment to textile fibres to produce permanent antibacterial properties.
y Coating that contains microcapsule of antibacterial agent that can be released gradually upon daily usage.
Apart from bacterial attack, textile materials are also subject to fungal attack such as mildew. Sometimes white cotton towel in the bathroom is stained with dark purple spots. They are fungus. Fungus can also degrade cellulose to form slippery gel and fabrics can be rotten and break very easily. There are also different kinds of antifungal finishing to prevent these situations.
(v) Antistatic Finishing
Static electricity refers to the transfer of charges, particularly electrons, from one substance to another through rubbing. As textiles are dielectric (non-electrical conducting) materials, extra charges cumulate and cannot conduct away. When the cumulated charges build up to a certain level, they may discharge through air when some other objects approach. Static electricity builds up much more easily in dry season. Most of us may experience sparking when we take off clothes in winter.
51 Antistatic finishing can be achieved by incorporating conducting threads or yarns in fabrics so that extra charges can be conducted away without excessively accumulating on clothing. Antistatic clothing is particularly important in certain industries such as electronic and petroleum industries.
(vi) Nanotechnology
The term “nanotechnology” is very popular nowadays. You can see this term on a lot of commercial products such as cosmetics and electric appliance. “Nano” is a SI (International System of Units) prefix for describing numerical value. “Nano” stands for 10-9 only and nanotechnology refers to a length with its nanometre equal to10-9 m. Nanotechnology refers to the manufacturing or handling of materials in nanometre scale. Chemically speaking, an atom sizes in the range of 10-10 m. Nano scale is 10 times bigger than an atom. In other words, this technology refers to the manufacturing of products in molecular scale.
The main difference between nanotechnology and the traditional manufacturing process is the surface of products. For example, traditional techniques cannot produce a very uniform surface but nanotechnology can produce a very fine uniform surface that renders extra properties.
Below are some of the examples for the application of nanotechnology in textiles.
y Stain proof finishing.
y Antimicrobial finishing.
y Odorless textile.
y Fragrance release finishing.
y Skin care finishing.
4.2.4 Fabric Quality
Fabric quality can be measured in many aspects. Some of the aspects are as follows:-.
(A) Strength
Fabric strength is one of the important properties that determines the different application of fabrics. For example, work wear may require carrying heavy tools around as oppose to casual wear. The fabrics used in work wear must be strong
52 enough.
Fabric strength is usually expressed in term of tensile strength. “Tensile” refers to the tension created by pulling force. Tensile strength is measured by pulling the textile until it break and is defined as the unit breaking force per specimen width.
Figure 4.35 Tensile strength
(B) Elongation
Elongation measures the stretchability of textile. Generally speaking, woven fabrics are less stretchable than knit fabrics. Knit fabrics are more stretchable along the width rather than along the wale as yarn loops can straighten and extend. For woven fabrics, weftwise (widthwise) direction is more stretchable than warpwise (lengthwise) direction. Warp yarns are already straightened during weaving and they are not extended easily.
(C) Elasticity
Elasticity is similar to stretchability but it also measures the recovery power of the fabric. Although knit fabrics demonstrate slightly elastic along the course direction, normal fabrics are generally considered as non-elastic. A true elastic fabric contains elastic fibre. The common kind of elastic fibre is called spandex or elastane, which is mainly composed of polyurethane polymer. The famous brand of such kind of elastic fibre is “Lycra”, which was formerly owned by Du Pont, from Invista. There is another type of elastic fibre called elastoester. Swimwear requires good abrasion resistance and elasticity. Most of them are made with fabrics of nylon/spandex blend. It is important to note that spandex can be extended five time of its original length without
53 breakage and it returns back to its original length upon the release of loading.
(D) Abrasion Resistance
Abrasion means rubbing. Abrasion resistance is one of the properties of textiles as most of the textile products always rub against different surfaces during their daily application. Abrasion resistance refers to the number of cycles of rubbing will render defects on fabric. These defects include rupture, yarn breakage, surface coating chip off, colour loss, etc. Some textile products require good abrasion resistance. For example, textile furniture covers require very high abrasion resistance.
(E) Pilling Resistance
Pilling refers to the entanglement of short fibres forming small balls of fibre. The formation of pill is also through rubbing. Fuzz or short fibres may rise from the yarn surface. Further rubbing may entangle the fuzz to form pilling. Pilling resistance is affected by many factors such as yarn twisting, fibre stiffness, impurities, etc. The more the yarn twisting, the more the fibres bound tightly and harder together and this prevents the fibres from being rubbed off the surface. Stiffer fibres are more resistant to pilling formation as they require a longer length to turn around. Flexible fibres form pilling more easily as they turn around at shorter length.
Figure 4.36 A photo that shows pilling on a piece of fabric
54 (F) Dimensional Stability
After laundering, it is common to find that the clothes have shrunk. This relates to the dimensional stability of fabrics. Fabrics usually shrink after laundering. This phenomenon is due to the relaxation of stress that has been imposed on yarns during weaving. Woven fabrics are much compact than knit fabrics. Woven fabrics have a greater resistance to shrinkage. Dimensional change is not limited to just shrinkage. Over agitation during washing may result growth in fabrics. The commercial acceptance of fabric growth is stricter than shrinkage as fabric growth produce poor looking puckering on fabrics.
(G) Wrinkle Resistance
Wrinkle resistance is an appearance property of fabrics after wash or daily use. Cellulosic fibres are well known as a kind of poor wrinkle resistant material. They form wrinkles easily. Cellulosic clothing requires ironing after washing because wrinkles can be removed by ironing. Cellulosic fibres that are blended with synthetic fibres such as polyester, polyamide render better wrinkle resistance. Another way to enhance wrinkle resistance is resin (wrinkle free) finishing. Resin fixes the fabric construction and maintains fabric dimension and appearance. The drawbacks of wrinkle free finishing are lower fabric strength and present of formaldehyde. Depending on amount, formaldehyde may cause unpleasant “fishy” smell, skin irradiation and induce cancer.
(H) Absorbency
Water absorbency refers to the ability of fabrics to pick up water and is particularly important to the following products.
Sportswear
Underwear
Bathroom towels
Kitchen towels
Good water absorbency does not refer to just the quick uptake of water but also the fabrics’ ability to hold water in greater amount. Cellulosic fibres are a good example. Synthetic fibres are usually not good at absorbing water and they are rarely used to produce towels. Water absorbency may be hindered by surface finishing and industrial impurities. For example, yarns may come with lubricants that are oily based
55 substances. This may prevent water uptake. This is the reason why new towels are recommended to be washed once before use.
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Not for Sale
The copyright of the materials in this booklet belongs to the Education Bureau. The materials can be used by schools only for educational purpose. Prior written permission of the Education Bureau must be sought for other commercial uses.
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