Tài liệu Stretchable denim - a review

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www.fibre2fashion.com www.fibre2fashion.com Stretchable denim: A review By: Manjunath Burji, P.V. Kadole & Sandip Patil Denim is one of the cotton fabrics used for manufacturing jeans. It has become an evergreen favourite of every individual worldwide irrespective of age, gender, season, occasion and fashion. The textile industry has produced more indigo denim than any other woven fabric. The denim fabric is bluer on the surface, being warp-face. The weft is left undyed which makes the fabric appear almost white on the reverse. The reasons for the unmatched success of denim are durability, comfort, feel, appearance and versatility. Now, denim trends are modified according to customer's requirements to improve the quality of the fabric. Stretchable denims are more popular than regular denim, because of their elasticity and fit. There are two categories of stretch denim, based on the degree of stretchability. They are, power or action stretch and comfort stretch. Power or action stretch provides a fabric with high degree of extensibility and quick recovery. The stretch factor generally ranges from at least 30-60 per cent or more with no greater than 5- 6 per cent recovery loss. Comfort stretch alludes to fabric with less than 30 per cent stretch factor and no greater than 2-5 per cent recovery loss. Raw material for denim The warp and weft most used is open-end (rotor spun). Now machine manufacturers install a new device to the OE machine which can produce a slub effect in yarn with predetermined thickness and spacing between two slubs. This yarn looks better than ring yarn. Elastane yarns meet customer requirements of comfort, stretchability and appearance, so that again new trends are developed in denims using elastane yarns in the weft. Poly-lycra air-covered yarn and cotton-lycra core-covered yarn are popularly used in denims. Spandex fibre The fibre-forming substance is a long-chain synthetic polymer comprised of at least 85 per cent of segmented polyurethane. Spandex is synthetic fibre known for its elasticity and stretchability. It is stronger and more durable than rubber. Spandex fibres are manufactured using solution dry spinning method and drawn out to produce a long fibre. The most commonly used methods are the solution dryspinning that produces over 90 per cent of the world's spandex fibre. Process involved in stretchable denims Manufacturing process of weft way stretch denim is: Figure 1 Value chain of stretchable denim www.fibre2fashion.com Production of core-spun and cover-cover elastic yarn Elastane yarn is produced on ring frame machine, rotor spinner and air vortex machine with special attachment for spandex feeding system. Using special control device to control spandex stretch, tenacity and drawing. In above techniques, spandex is put at the centre and surrounded by other fibers. Polyester, nylon, rayon and cotton are the more popular fibres used to cover spandex monofilament yarn. Winding Winding is the intermediate process between spinning and weaving. Lengths of yarn are wound on a cone or spool for weaving. These cones are used to make warp beam for weaving. The last phase of yarn production is the winding process. Here the cops produced by ring machines are spliced (joined) together and transformed into the bobbin format of specific length. Splicing is the important process to improve productivity. There are many types of splicing: thermos splicing, air splicing and knotting. The type of splicer used depends upon the fibre type and further application of yarn. The sensors monitor the yarn surface throughout the length of yarn and they remove faults in the yarn like unevenness. Yarn spinning is completed by winding. Warping process In general terms, warping is transferring many yarns from a creel of single-end packages forming a parallel sheet of yarns wound onto a beam or a section beam. The warp beam that is installed on the weaving machine is called the weaver's beam. A weaver's beam can contain several thousand ends and for different reasons it is rarely produced in one operation. There are four types of warping:  Direct Warping  Indirect or Sectional Warping  Ball Warping  Draw Warping Sucker Muller (hacoba) sectional warping type of machine is one of the most popular machines for warping. The section beam is tapered at one end. Warp yarn is wound on the beam in sections, starting with the tapered end of the beam. In each section, there are many threads that traverse together slowly throughout the length of each section. The last section of tapered threads on warping beam keeps threads stable. It is important that each layer on the beam contains the same number of yarns. Machine parameters are speed 700mpm, warping width 1500mm and warp beam pressure 2000N with creel capacity 432. The number of each section depends upon the creel capacity Dyeing of warp sheet Dye is applied on the weaver's beam before it gets to the loom. There are two ways of dyeing:  Rope dyeing  Dyeing and sizing www.fibre2fashion.com Rope dyeing is the most popular dyeing methods for denim fabric. This gives good results of dye shade on warp sheet. For most denim warps, there is no need to size after dyeing because of the heavy count, so there is less warp breakages on loom. Sucker Muller dyeing cum sizing machine is very efficient for count range between 10s Ne to 20s Ne. Both the dyeing and sizing operations are done in a single stage. Shade percentage depends upon the speed of machine and concentration of dye solution. According to requirement of shade percentage, for better shade percentage machine speed kept at 30mpm (0.63 shade percentage for indigo dye) with yarn through put 4.45 kg/min. After drying of warp sheet, the warp sheet is immersed in size-paste bath for adding additional strength to warps and coating to avoid the abrasion of threads on loom during weaving. Parameters are refractive index 10 (measurement of solid content), viscosity of 20, size pick-up 70-80 per cent and size add-on 7-8 per cent for better performance on loom during weaving. Dyes ● Sulphur dye Sulphur dyes are widely used on cotton because they are economical. They have good to excellent wash-fastness and good light-fastness in dark shades. Light fastness of pale shades is poor. ● Vat dye Vat dyes are mainly applied on cellulosic fibres, but some can be applied to protein fibres. Indigo is a special case in the vat dye class. Indigo is attractive for its pleasing blue colour and for the unique fading characteristics of garment dyed with it. Vat dyes are characterised by the presence of a ketone group. Vat dyes in ketone form are water-insoluble pigments. Fabric production There are many ways to produce elastane fabric by many fabric forming technologies. Popularly, it is produced by knitting and weaving technologies. Knitted fabric is more stretchable than woven fabric because of the loop structure. Elasticity of fabric is much lower in both the cases than that of the elastane yarn because of the restriction of the hard fibre structure. Stress and strain curve combined shows the elastic power of the fibre and the effect of the hard fibre assembly recovering from compression. Elastane yarns are more efficient in sports and comfort application. It gives sufficient elastic properties to the fabric even with 2-3 per cent of elastane. Interlacement between warp sheet and weft yarn is known as weaving. There is a wide range of looms being used, right from the simplest handloom to the most sophisticated loom. For denim fabric especially 1/2, 2/2, 3/1 types of twill weaves are used for fabric construction. It is easy to weave on shuttles loom with better weaving efficiency. Rapier is one of the best and popular machines for weaving of 10s Ne-20s Ne warps and elastane weft for weaving stretchable denim. Heat setting of fabric Heat setting is the more important stage to keep the fabric width constant throughout the fabric to avoid further shrinkage in finishing stage. At this stage, shrinkage of fabric width and length are in our hand. We have to keep it according to garment requirement. Recommended temperature of six chambers are 1750c and speed of around 40 meters/min, for stretchable denim fabric. www.fibre2fashion.com The Stenter is a gas-fired oven, with the fabric passing through on a chain drive, held in place by pins. Air is circulated above and below the fabric before being exhausted into the atmosphere. As well as for drying processes, the stenter is used for pulling the fabric to width, chemical finishing and heat setting and curing. It is versatile equipment. Modern stenters are designed with improved air circulation, which helps to improve drying, and with integrated heat recovery and environmental abatement systems. Finishing It is a process done to fibre, yarns and fabric causing them to change in appearance, texture and performance. The term 'finishing' covers all those treatments that serve to impart to the textile the desired end-use properties. These can include properties relating to visual effect, handle and special characteristics such as waterproofing and non-flammability. Finishing treatment is done to achieve the ultimate customer requirements. These are mostly value added processes. Type of finishing:  Mechanical finish  Chemical finish In case of stretchable fabric, normal finishing is suitable. Keep the temperature at 1000c-1100c and warp shrinkage approximately at 10 per cent. Testing Following are the tests carried for elastic fabric Table 1: Yarn testing Test ASTM standards Count ASTM D1059 Denier ASTM D1059 Tensile testing of normal yarn Elastic property (CRE type testing machine) ASTM D2256 & ASTM D2256M ASTM D2731 Shrinkage % ASTM D2259 Yarn slippage ASTM D434 Table 2: Fabric testing Test ASTM standards Breaking Strength (CRT type machine) ASTM D5034 Tear strength ASTM D1424 Moisture vapor transfer rate ASTM E96 Skewness ASTM D3882 www.fibre2fashion.com Warp elongation ASTM D3774 Width ASTM D3107 Weight ASTM D3776 Dimensional change AATCC test method 135 Air-permeability ASTM D737 Application Elastane fabric is more suitable for comfort than non-elastane fabric. Elastane fabric is used in athletics and sports and may improve performance in sports like cycling and swimming. They are also important for inner wear. This type of fabric enables freedom of body movement by reducing the fabric resistance to body stretch. Drastic differences between skin and fabric movements result in restrictions of movements to the wearer. Conclusion Elastic property of fabric gives it outstanding performance welcomed by consumers. From a debut in sports and leisure garments it is now becoming the standard for working apparel and in denim, the universal clothing fabric. Elastic fabric gives much better properties like wear comfort, crease resistance, durability, drape and handle than regular fabric. References 1. Dr. Mrs. Shailaja D. Naik, "Manufacturing of Denim Jeans at Trouser Town." The Textile Industry & Trade Journal January-February 1999 pages 43-47. 2. Ashwin Thakkar, "Some aspects of producing stretch denim fabric," Indian Textile Journal, November 2012 pages 32-37. 3. Scott c. Wagner, Technical bulletin on denim fabric manufacturing, pages 42 and 43. 4. A Merrow Monograph, Elastomeric Fibers by R. Meredith, Book, pages 9-36 5. Dorlastan.com (20-08-2008). 6. Gajanan Bhat, Subhash Chanda & Simon Yakopson, "Thermal Properties of Elastic Faibres," Thermochimica Acta, 2001 page 367. 7. Preston University Report On Denim Manufacturing. 8. "Annual book of ASTM standards" section 7 vol. 7.2, year 2011. 9. M. Senthilkumar, N.Anbumani, J Hayavadana, "Elastane Fabric - A Tool for Stretch Application in Sports," Indian Journal of Fibre & Textile Research, September 2011 Vol 36 page 300-307. 10. Voyce J, Dafniotis P, & Towlson S, Textile in Sports, edition 1 (Wood Head Publication, Cambridge UK), 2005 Chapter 10 pages 205-230.
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