01 preparation english (1)


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01 preparation english (1)

  1. 1. Introduction to Textile Preparation Assistant Professor Dr. Apichart Sonthisombat, Rajamangala Institute of TechnologyCopyright © 2004 Assist. Prof. Dr. A.Sonthisombat All rights reserved. 1
  2. 2. Basic Textile DefinitionsFibers = A smallest unit of textile materials.Usually classified by flexibility, fineness, anda ratio between length and diameter (L/Dratio)Natural Fibers = Fibers that come fromanimals (wool, silk etc.), plants (cotton, flax,hemp, jute etc.) or mineral material(asbestos).Synthetic Fibers = Man-made fibers orartificial fibers which is usually comes fromchemical agents. 2
  3. 3. Semi-synthetic Fibers = Fibers that comesfrom solutions of natural polymer orderivatives from the natural polymer(cellulose, protein etc.)Polymer = Macro molecules containingsmall chemical units (named “Monomer”) 3
  4. 4. Staple Fibers = Fibers from natural orsynthetic fibers which were cut into shortfibers. Normally, natural fibers are staplefibers (expected silk fibers). These fibershave 5-500 millimeters long.Filament Fibers = Fibers from natural orsynthetic fibers which have infinite length.Silk Fibers are the only one natural fibersclassified in this definition since their lengthbetween 700-1500 meters depending to theirraces. 4
  5. 5. Yarns = The combinations of fibers usingsome twisting (Z and S twists) in order tomake strong and stable yarns.Spun Yarns = The yarns that come formstaple fibers.Filament Yarns = The yarns that come fromfilament fibers (mono-filaments and multi-filaments)Fabrics = The products of weaving, knittingor non-woven processes. Normally, fabricshave a certain thickness and can withstandtear and tensile forces. 5
  6. 6. Textile Preparation is the heart of the textiledyeing, printing and finishing processes because fibers, yarns or fabrics have many impurities (i.e. cotton wax, starch, lubricant, silk sericin, wool oil etc.) as a proverb “Well begin is half done”. From the experience, more than60% of the faults from these factories come from preparation. 6
  7. 7. The Examples of preparation processes ofcotton and its blends fabrics100% Cotton fabrics1. Singeing2. Desizing (only for woven fabrics)3. Scouring4. Bleaching (only for pale or bright shades)5. Mercerizing6. Adding of Optical Brightening Agent 7
  8. 8. 100% Silk Fibers1. Degumming (to get rid of non-fibrousmaterials (sericin))2. Bleaching (to make the goods whiter) 8
  9. 9. 100% Wool Fibers1. Carbonising (to remove leave, bark andother parts of the plants from the wool fibers)2. Scouring (to get rid of fat and oil from thefibers)3. Bleaching (to make the fibers whiter) 9
  10. 10. Morphology of Textile Fibers1. Crystalline Regions are the regions thatcannot absorb water, humidity and dyestuffsolutions but they are the part for fiberstrength.2. Non-Crystalline Regions or Amorphousregions are the regions that can absorb water,humidity and dyestuff therefore they can bedyed but they are a very weak part of thefibers. 10
  11. 11. 3. Orientation of the Crystalline Regionsalongside the fiber axisThis property is very important in that it willincrease the tensile strength of the fiber if itpresents in the optimal quantity. Crystalline Amorphous Void space 11
  12. 12. Singeing ProcessSingeing is a process that uses gas flame orhot plate in order to get rid of small fibersprotruding (hairs) on the fabrics (thesefibers normally come from spun yarns).Objectives:1. To get rid of the small fibers2. To make the fabrics smoother than before3. To help the printing ink or dyestuff tomake clearer marks on the fabrics4. To improve rubbing fastness and washingfastness of the dyed or printed fabrics 12
  13. 13. Where does starch come from?Starch or Size is a material that help theweavers to ensure that their warp yarns arenot broken or struggle with the reeds.Therefore these will leading to lowproductivity and high machine break-downrate. Desizing processThis will get rid of the starch or size coveringthe warp yarns using enzymes, oxidizing agent, or other chemicals. 13
  14. 14. As the starch or size covering the warp yarns,it will lead to uneven dyeing, printing orfinishing. No need for this material on our fabrics. (Note this will effect only weaving process. For knitting process, no starch or size on the fabrics thus no need to desizing.)Objectives1. To get rid of starch from sizing of the warpyarns2. To ensure levelness of the dyestuff orprinting ink. If not taken out completely, it will affect washing and rubbing fastness of thefabrics. 14
  15. 15. Scouring ProcessScouring process is a process designed toremove natural fat, wax, oil from the cottonfabrics using sodium hydroxide and detergentat boil for 20-30 minutes. Synthetic fabricsand other protein fabrics may use onlysodium carbonate (weaker alkali) instead. 15
  16. 16. Objectives1. To remove natural fat, wax, and oilmaterials containing in the fabrics withoutdamaging the fibers2. To accelerate dye and chemical absorptionof the fabrics3. To improve the handle of the goods(softer) 16
  17. 17. Bleaching ProcessThe process is to make the goods whiter thanbefore. This will help the goods to absorbmore dyes and chemical and also make the dyeon the goods brighter. Normally, for cottonfabrics, hydrogen peroxide in alkali solution atboil are the most popular bleaching agent.Objectives1. To whiten the goods2. To make the goods to be suitable for dyeingand printing with pale or bright shade3. To be follow with adding optical brighteningagent process (super white) 17
  18. 18. Mercerizing ProcessThe is to make the cotton goods more lusterthan before using sodium hydroxide solutionin cold condition and tension. This will lead the cotton fibers to be swollen and increased strength. Also this will improve dye absorption of the fibers. John Mercer was the first chemist in the world who found this phenomenon in 1844. Therefore, the process was called“Mercerizing”Caustizing is the process nearly the same asmercerizing but it uses lower concentration ofthe hydroxide solution and without tension. 18
  19. 19. Objectives1. To make the goods more luster becauseraw cotton fibers are ribbon-like. After thisprocess, the fibers change to cylindrical shaperesulting more evenness reflected light fromthe goods. Before After2. To improve dyeability of the goods about5-10%. 19
  20. 20. Adding Optical Brightening AgentThe process is to add special dyestuff intotextile or paper to make them brighter when looking at black-light light bulb or natural sunlight. As the dyestuffs are colorless but using UV light to excite these dyes. They will reflect the light at the wavelength that human can see (i.e. blue, violet). So the goods look brighter and whiter. ----------------------- 20