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Textile processing of many textile material

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Textile processing of many textile material

  1. 1. UNIT-1:Natural and added impurities in Textiles etc.
  2. 2. Natural Impurities • The impurities that present naturally in the plants/fibre (cotton, Wool, Silk etc) are called natural impurities in wet processing points of view as these impurities hinder the further processing of fibres. • Natural Impurities in cotton • Natural Impurities in wool • Natural impurities in silk
  3. 3. Natural Impurities in Cotton Cellulose 80-90% Water 6-8% Waxes and fats 0.5 - 1% Proteins 0 - 1.5% Hemicelluloses and pectin’s 4 - 6% Ash 1 - 1.8%
  4. 4. Structure of cotton fibre • Structure differentiated into concentric zones and a hollow central core known as lumen. • The outermost layer is known as the cuticle and is a thin film of fats, pectins and waxes • Beneath this is the primary wall, composed mainly of cellulose in which the fibrils are arranged in a criss-cross pattern. • Further toward centre is the secondary wall composed of cellulose which constitutes the bulk of the fibre. • The secondary wall is differentiated in to three zones S1, S2 and S3. • S1= Outermost, thin layer fibrils periodically reverse the direction of the spiral. • S2= Accounts for the bulk of the cellulosic content and in this case the fibrils are again in the form of helices with a somewhat lower pitch of 20o and 30o. • S3= Found in mature cotton and adjacent of the lumen and consists of the mineral salts and the proteins
  5. 5. Cellulose • It is an insoluble substance which is the main constituent of plant cell walls and of vegetable fibres such as cotton. It is a polysaccharide consisting of chains of glucose monomers • Cellulose is an organic compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units D-Glucose β(1→4) linked D-glucose units 1 4
  6. 6. (flavus = yellow) Molecular structure of the flavone
  7. 7. Natural Impurities-Wool Wool fibre contains 20- 50% impurities like: • Dirt, dust, vegetable matter, wool grease, dried sweat
  8. 8. Scouring of Wool • Wool is a protein fibre and sensitive to bases. Wool can be scoured by using detergent at pH up to 7 at 60oC • To remove vegetable material it is carbonised by using Dilute Sulphuric acid.
  9. 9. Detachment of Oil from wool by action of detergent
  10. 10. Natural Impurities-Silk • Silk contain 22 to 25% gum
  11. 11. Scouring of Silk De-gumming: • It is scoured by using Soap and soda ash • Treatment for 1 hour at 50oC (repeat this process three times) • Bleaching is carried out with hydrogen peroxide ( NaOH is not used) With sodium silicate
  12. 12. Added Impurities • Oil used during spinning, • Stains during spinning and fabric forming • Sizing material during weaving
  13. 13. To dye or print textile material it is needed to remove these impurities: Process Called Preparation
  14. 14. Preparation / Pretreatment • Processes used to remove impurities from fibres to make it dye able or printable. • Natural fibers and synthetic fibers contain primary impurities that are contained naturally, and secondary impurities that are added during spinning, knitting and weaving processes. • Textile pretreatment is the series of cleaning operations .All impurities which causes adverse effect during dyeing and printing is removed in pretreatment process.
  15. 15. Objective of Pretreatment: • To Convert fabric from hydrophobic to hydrophilic state. • To remove dust, dirt etc from the fabric. • To achieve the degree of desire whiteness.
  16. 16. Main steps of preparations • Singeing • Desizing • Scouring • Bleaching • mercerizing
  17. 17. Singeing • It is a process to remove protruding fibres from the surface of fabric using flame OR • Singeing is a process of burning protruding fibres from a textile structure
  18. 18. Desizing • This is a process of removing sizing chemical i.e added impurties (added during weaving process) from the fabric so the fabric can absorb water.
  19. 19. Scouring • It is the process to remove natural impurities present in the natural fibres (like cotton, wool, silk etc) such as wax, pectine, coloour, gum etc.
  20. 20. Bleaching • It is the process to make textile fabric white. Various types of bleaching agents- Oxidising or reducing may be used
  21. 21. Mercerisation • In this process the cellulose material mostly cotton yarn or fabric is treated with high concentration of sodium hydroxide. With this process following effects are observed in the cotton: • Improved luster • Improve absorbency • Improve reactivity with chemicals • Improve stability of form • Improve smoothness • Improve hand
  22. 22. Decatising • It is a process of steaming woll or its blends to set the fabric and reduce shrinkage and creasing. It is a finishing process in which the fabric is wound tightly onto a perforated roller and either immersed in hot water, which is also circulated through the fabric (Wet decatising) or has steam blown through it (dry decatising). • It is used mainly to improve the handle and appearance or worsted fabrics.
  23. 23. PROCESS SEQUENCES OF CHEMICAL PROCESSING Grey fabric Inspection & Stitching Shearing & Cropping SingeingDesizingScouringBleachingDrying Mercerising Dyeing Printing Soaping & Drying Finishing Folding & Packing
  24. 24. Preparation • Following are the steps to be taken before going wet processing : Grey inspection Stitching Shearing and cropping Singeing
  25. 25. Preparation/Pretreatment 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 Singeing
  26. 26. STITCHING • Grey stage fabric usually 60-70 m in length so that several pieces are stitched together to make a processable length ( Lot size ). • Normally Polyester ( Sewing thread ) yarn is used for stitching
  27. 27. Precautions before stitching • Marked each piece properly for sort number, lot number etc. so that piec can be identify at any stage of the processing • Two pieces are arranged selvedge to selvedge and the ends are stiched on a special end to end stitching machine so that pieces are joined without overlapping
  28. 28. Stitches & Stitching threads • Cotton threads: 3/40s, 4/30s, 4/36s, 6/28s and 6/36s are popular • Polyester threads are also used when carbonising is required • Stitches per inches: 6 to 7 for coarse, 7 to 8 for poplin and 8 to 10 for cambric
  29. 29. STITCHING DEFECTS Protruding Selvedge • Due to difference in width of the pieces • Some time careless handling also lead to a protruding selvedge Causes: Fold or selvedge crease and the fold portion either less dyed or remain undyed
  30. 30. STITCHING DEFECTS Open End • Pieces are not locked in the stitch at and near the selvedge • Due to careless handling Causes: Such stitch will open out more and more every pull around guide roll during processing. It may induce Fold or crease formation at the selvedge, undyed/unprinted folds will result.
  31. 31. STITCHING DEFECTS Loose Thread • Due to careless handling Causes: It may cause thread mark in dyeing and printing, lead entanglement in machine parts, etc. The loose thread may pick up soil and damage long lengths
  32. 32. STITCHING DEFECTS Fold • If the large folds are inserted in the stitch to accommodate width difference of two pieces, it will surely lead to damage Causes: It may cause warp stripes in dyeing and creases in dyeing and printing
  33. 33. STITCHING DEFECTS Broken Stitch • It may be due to poor machine condition, poor quality of thread or poor method of operation Causes: It may cause damage in dyeing and printing
  34. 34. SHEARING & CROPPING • In shearing ,the fibres are cut in an angular manner on the surface of the fabric itself, resulting in a soft feel • Singeing and shearing are almost the same in effect. In singeing the fibres in the interlacement of the fabric are burnt by flames whereas in shearing the fibres are cut in an angular manner on the surface of the fabric itself, resulting in a soft feel.
  35. 35. Singeing Singeing is a process of burning protruding fibres from a textile structure
  36. 36. TypesOfSingeingMachines
  37. 37. Rotary (Roller)-cylinder singeing m/c In this type of singeing machine, the cloth passes over and in contact with a heated rotary cylinder made of copper or cast iron.  The rotary cylinder has internal firing and revolves slowly so that constantly a fresh surface of the roller comes in contact with the cloth. The direction of rotation of the cylinder is opposite to the direction of the fabric so that the protruding fibers or nap of the fabric is raised. This type of machine is particularly suitable for the singeing of velvets and other pile fabrics. If the singeing of both sides of the fabric is required, then two cylinder are employed, one for each side of the fabric.
  38. 38. Rotary cylinder singeing
  39. 39. Plate singeing In this type of singeing machine, the cloth passes over and in contact with one or two heated curved copper plates. The thickness of the plates ranges from 1 to 2 inches. The heating of the plates is done by a suitable burning arrangement of gas mixed with air. The plates are heated to bright redness and the cloth passes over and in contact with these plates at a speed ranging from 150 to 250 yards per minute, the protruding fiber are burnt during the passage. The fiber end present in the interstices of warp and weft are not singed, since they are not made accessible Due to contact between the cloth and a hard and hot surface of metal a certain amount of luster in the cloth is produced.
  40. 40. Plate singeing Disadvantage: It may be not possible to maintain the plates at uniform temperature and this cause uneven singeing.
  41. 41. Gas singeing machine In this type of singeing machine, the fabric passes over a burning gas flame at such a speed that only the protruding fibres burn and the main body of the fabric is not damaged by the flame. This is the most common type of machine used for singeing fabrics as well yarns
  42. 42. Gas singeing machine
  43. 43. Important GAS singeing parameters Following are the important gas singeing parameters: Flame intensity Fabric speed Singeing position Distance between flame burner and fabric Flame Width
  44. 44. Flame intensity The flame intensity of the singeing burners is based on the amount and the outlet speed of the gas-air mixture leaving the burner slots. Besides having high thermal energy, flame also has considerable mechanical energy. All the thermal and mechanical energy of the flame is directed onto the fabric during singeing. The temperature of the flame at the mouth of the burner is in the range of 1250 to 1300oC. The speed of the flame at the burner outlet may be between 15 and 35 meter per second. The flame intensity usually lies between 5 and 20 mbars.
  45. 45. Fabric Speed The fabric speed in the singeing machine is usually in the range of 50-160 m/min depending on fabric (gram per square meter) weight and fibre blend. For heavier fabrics, the speed is kept slower as compared to lighter weight fabrics.
  46. 46. Singeing Position This is the most intensive singeing position with highest efficiency.  In this position, the flame bounces onto the free-guided fabric at right angles. This position is usually recommended for singeing of fabrics with all natural fibres (e.g. cotton), regenerated fibres and blended fabrics, which have been tightly woven and have weights over 125 g/m2 Flame 1. Singeing onto free-guided fabricWatercooledroller
  47. 47. 2. Singeing onto water-cooled roller In this position, the flame bounces at right angles onto the fabric while the fabric passes onto water-cooled guide roller.  This position avoids the penetration of the flame into the fabric. The flame does not pass through the fabric, and because of the fabric passing onto water-cooled roller, any thermal damage of temperature-sensitive synthetic fabrics is avoided.  This position is usually recommended for all blended and synthetic fabrics as well as for fabrics having weights less than 125 g/m2 and fabrics with open structure. Watercooledroller
  48. 48. 3. Tangential Singeing In this position, the singeing flame falls on the fabric tangentially.  The flame touches only the protruding fibres without having any significant contact with the main fabric body. This position is usually recommended for very light weight and sensitive fabrics as well as fabrics with broken filaments. Watercooledroller
  49. 49. Distance between Flame Burner and Fabric As the energy content of the flame is lower the farther it is from the burner, the singeing efficiency is consequently decreased by increasing the burner-fabric distance. The distance between the burner and the fabric is usually in the range of 6-8mm but it can be adjusted in a range from 6-20mm.
  50. 50. Flame Width All good singeing machines come with a provision of flame width adjustment according to the width of the fabric. This is essential to optimize the gas economy
  51. 51. Essential conditions for good GAS singeing Following are three essential conditions for good singeing: A flame with high mechanical & thermal energy quickly burn thermoplastic protruding fibres (e.g. polyester) without any molten beads formation A homogeneous flame with uniform mechanical & thermal energy to result in uniform singeing An optimal flame/fabric contact time to neither result in incomplete not over-singeing
  52. 52. Testing singeing effectiveness The effectiveness of singeing process can be checked by one or more of the following: By looking at the singed fabric with magnifying glass and comparing its hairiness with that of the un-singed fabric. A well-singed fabric shows less hairiness. By testing the singed fabric for pilling performance and comparing it with that of the un-singed fabric. A well-singed fabric gives less pilling. By sticking and removing a sticking tape on the singed fabric and observing the number of fibres attached to the sticking side of the tape. A well-singed fabric results in less number of fibres sticking on the tape. Noticing the feel or handle of the singed fabric. An over- singed fabric may give a harsher feeling.
  53. 53. Bio polishing It is an enzyme treatment designed to improve fabric quality and provide following advantages: • Improve pilling resistance • A clear, lint and fuzz-free surface structure • Improved drape and softness • The effect are durable
  54. 54. Process • Cellulase enzyme is used • Enzyme dosage 1-2% owf • pH 4.5-5.5 • Temperature 40-55oC • Time 30-60 min. It is similar to singeing as it also provide similar effect on the fabric.
  55. 55. Fig. 7. Carbomatic® Singeing Line by Bejimac Fig. 8. DORNIER singeing machine for circular knitted fabrics
  56. 56. What should control during singeing operation? • Intensity and uniformity of flame • Working speed of the fabric to be singed • Effectiveness of singeing : should not add harshness in the fabric • Should not damage the synthetic filament yarn in the fabric
  57. 57. 1. Wool grease can be removed by scouring. These Grease/waxes are comprised of a variety of monocarboxylic, dicarboxylic and hydrocarboxylic acids as well as steroidal alcohols. It has been determined that unscoured wool contains an unoxidized fraction of wool grease and other contaminants that is easily removed and readily recoverable 2. Suint is usually considered to be a variable composition of water-soluble materials that is readily removed by scouring. 3. The dirt that is removed from the scoured wool consist of both inorganic and organic materials
  58. 58. • Suint: It is dried perspiration and soluble in water. Simple washing in detergent removes suint. • Wool fat or wool wax: It is complex mixture of esters, diesters and hydroxyesters fatty alcohol like lanoline and fatty acid. It is hydrolysed in the presence of mild alkali like ammonia at moderate temperature. Wool wax can be isolated and used in preparation of good quality soap and cosmetics.
  59. 59. • Dirt: It is held by adhesive action of suint and wool fat. It removed during the scouring and washing processes. Burrs: It is vegetable fragments consisting of dried grass, straw, sticks etc. These vegetable fragment come on the body of sheep during grazing and scratching the body against bush or tree to relive itching.
  60. 60. Removal of Vegetable matter (Carbonization of wool) • Wool is resistant to acid. Burr being a vegetable matter is not resistant to acid. • This property is used for the removal of burr. • In this case wool is treated with 5-7% Sulphuric acid for 2 hours followed by hydro- extraction and then drying at 80-90oC for 20- 30 minutes • Carbonized burr is removed by washing with mechanical agitation.
  61. 61. Decatising • Decatising or decatizing, also known as crabbing, blowing, and decating, is the process of making permanent a textile finish on a cloth, so that it does not shrink during garment making. • The word comes from the French décatir, which means to remove the cati or finish of the wool. • Though used mainly for wool, the term is also applied to processes performed on fabrics of other fibers, such as cotton, linen or polyester. Decatising A finishing process in which the fabric is wound tightly onto a perforated roller and either immersed in hot water, which is also circulated through the fabric (wet decatising) or has steam blown through it (drydecatising).
  62. 62. •Decatized wool fabric is interleaved with a cotton, polyester/cotton or polyester fabric and rolled up onto a perforated decatizing drum under controlled tension. The fabric is steamed for up to ten minutes and then cooled down by drawing ambient air through the fabric roll. The piece is then reversed and steamed again in order to ensure that an even treatment is achieved. •There are several quite different types of wool decatizing machines including batch decatizing machines, continuous decatizing machines, wet decatising machines and dry decatizing machines.