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Wet Processing - Introduction (WPE-1)

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Wet Processing - Introduction (WPE-1)

  1. 1. Textile Engineering
  2. 2. 2 Presented by: Mazharul Islam. B.Sc. in Textile Engineering. Dept. of Wet Process Engineering (WPE). PTEC _ Session 2015-16 (10th Batch). Email: tex.mazharul@gmail.com
  3. 3. INTRODUCTION Wet processing and its main Divisions: The process by which the textile mtls are treated associated with water is called wet processing. There are mainly 3 divisions of wet processing- a) Pretreatment (or preparation) b) Coloration (dyeing or printing) c) Finishing i) Pretreatment: The process, which are done to make the textile mtl suitable for dyeing & printing are called pre-treatment. To ensure that the textile has the right physical and chemical properties to enable it to be colored or finish. Such as desizing, scouring, bleaching etc. Purpose: • To remove added and natural impurities from textile material • Removal impurities to the maximum extent possible with minimum effect on fibrestrength. • To impart desirable properties to textile material 3
  4. 4. ii) Dyeing & printing: The process by which the textile mtl are coloured by different types of dye or pigments, related chemicals required water is called dyeing. Other definition: Dyeing is a chemical process which involves the migration of the dye from the dye solution to the surface of the fibresin the fabric being coloured, the diffusion of the dye through the fibresand the fixing of the dye by chemical bonding. And Localized application of dyestuff or pigments on fabric according to the predetermined design is called printing. iii) Finishing: The process by which the textile mtls are made suitable for marketing to satisfaction/attraction of buyer are called finishing i.e. calendaring, Flame retardant finish leveling, anti-creasing, mercerizing, packaging etc. 4
  5. 5. Sewing / Stitching ↓ Shearing & Cropping ↓ Singeing ↓ Desizing ↓ Scouring ↓ Bleaching ↓ Mercerization ↓ Coloration (Dyeing and Printing) ↓ Washing ↓ Finishing ↓ Folding & Packaging ↓ Delivery SEQUENCES OF WET PROCESSING Singeing ↓ Desizing ↓ Scouring ↓ Bleaching ↓ Mercerization Typically a woven Cotton fabric would be prepared by sequence of process as shown In case of knitting Sizing step is not Involved so desizing is not required, and mercerization is done only for cotton. Preparation/Pretreatment 5
  6. 6. Definition of some important terms: 1) Greyfabric: It’s the fabric coming from the loom state, no chemical processing is applied on it. 2) Grey Checking & GreyTesting: Here the fabric is checked carefully that is there any deformities or not. Here the yarn density, number of ends & number of picks per unit length, yarn strength is also examined. Proper repairing of the fabric is also done here. 6
  7. 7. (3) Stitching: To increase the length of the fabric for making suitable for processing is called stitching. It is done by plain sewing m/c. (4) Brushing: To remove the loose fibre & loose ends of the warp & weft threads is known as brushing. (5) Shearing / Cropping: The process by which the attached ends of the warp & weft thread is removed by cutting by the knives or blades is called shearing. Shearing is done for cotton & cropping for jute. 7
  8. 8. (6) Sinzing: The process by which the protruding/projecting fibres are removed from the fabrics by burning or heat to increase the smoothness of the fabric is called sinzing. This process is mainly done by gas flame. (7) Desizing: The process by which the sizing mtls (starch) are removed from the fabric is known as desizing. The sizing mtls was applied at the warp yarns of the fabric at the time of weaving. 8
  9. 9. 8) Scouring: The process by which the natural impurities (oil, wax, fat etc.) & added/external/advantatious impurities (dirt, dust etc.) are removed from the fabric is called scouring. It is done by strong NaOH. 9) Souring: The process by which the alkali are removed from the scoured fabric with dilute acid solution is known as souring. 10)Bleaching: The process by which the natural colours (nitrogeneous substance) are removed from the fabric to make the fabric pure & permanent white is known as bleaching. It is done by bleaching agent. 9
  10. 10. (11) Mercerizing: The process by which the cellulosic mtls / substance are treated with highly conc. NaOH to impart some properties such as strength, absorbency capacity, lusture is known as mercerizing. It is optional. If the fabrics are 100% export oriented then it is done by highly conc. NaOH (48-52° Tw). (12) Coloration: Coloration is the process of providing the fabric with color. 10
  11. 11. (13) Washing: Washing is done by firstly cold wash, then hot wash (80°C) & finally normal wash. (14) Finishing: Finishing is the process of providing the properties that customer will value. (15) Delivery: After packing the fabroc is delivered to the respective buyer (16) Heat setting: The process by which the width of the fabrics are adjusted by heat is called heat setting. 11
  12. 12. (17) After treatment: The process by which the loose dyes are removed from the dyed fabrics to increase the lusture & fastness property of the fabric is known as after treatment. (18) Calendaring: It is done to remove the undesirable creese & crinkle. (19) Steaming / Curing: To fix up the dyestuff / pigment with the fabric. Steaming is used for dyestuff & it is done in 100-105°C. curing is used for pigments & it is done in 120-180°C. (20) Stentering: It is done to increase/adjust the width of the fabric. 12
  13. 13. Pdf download link: Edu-Expert YouTube channel. References: 1. Chemical Technology in the pretreatment Processes of Textiles (S.R. KARMAKAR) 2. Textile Preparation & Dyeing (A.K. Roy Choudhury) 3. Chemistry & Technology of fabric preparation & finishing (C. Tomasino) 4. www.bdtextileinfo.blogspot.com 5. Wet Processing-I slide. (MD. MH Tomal, Lecturer, BUTex) 13
  14. 14. Thank You ! 14

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