printing Dyeing method (2)textile science.pptx

textile science

1. Dyeing Department of Fabric & Apparel Science Institute of Home Economics University of Delhi

2. Colour Colour is a visual sensation. It results from the reflection of certain visible light rays that strike the retina of the eye and stimulate the nerve cells of the eyes - nerves send a message to the brain, which in turn, produces the sensation of a specific colour . When all the visible light rays are reflected we see white . When all the visible light rays are absorbed we see black .

3. Dye Colour can be added to textile objects by application of dyes. These dye molecules absorb light rays of selected wavelengths causing the fabric surface to reflect light rays which are not absorbed . Dye is an organic compound composed of 2 components: Dyes must be small particles that can be thoroughly dissolved in water or any other carrier in order to penetrate the fiber .

4. Theory of Dyeing: It involves the following steps :

5. Theory of dyeing Migration means movement of dyes from solution form to the fabric surface. Adsorption is the process by which a solid holds molecules of a gas or liquid or solute as a thin film. Absorption is the diffusion of dye from surface towards the centre of the fiber . Fixation is anchoring of the dye molecules by covalent or hydrogen bonds or other physical forces of a physical nature.

6. Classification of Fiber Dyes

7. Dyes for cotton/cellulosic: Direct dyes When a dye is applied directly to the fabric without the aid of an affixing agent, it is called direct dyeing. Most commercially significant dye class, complete colour range Good colour fastness to light Wash fastness is poor to moderate Easiest to produce, simplest to apply Also known as substantive dyes

8. Dyes for cotton/cellulosic: Vat dyes: Insoluble in water Require reduction to apply Reduced(hydrosulphite dissolved in alkali - NaOH )^ solubilised applied oxidised Incomplete colour range Good to excellent light and wash fastness Indigo - natural vat dye Primarily for cotton

9. Dyes for cotton/cellulosic: Sulphur dyes Insoluble in water, made soluble with the acid of caustic soda and sodium sulphide Application similar to vat dye Complete colour range except for red Dull colours used mainly for dark colours - browns, blacks and navy blues

10. Used for heavy work clothes Black sulphur dye is most widely used black dye Stored goods may become tender Sensitive to chlorine bleach Poor to excellent light and wash fastness Poor to good - yellows and browns Good to excellent - darker shades

11. Dyes for cotton/cellulosic: Azoics / Naphthol dyes/Ice colours : Used for batiks Colour developed on the fabric Good to excellent light and wash fastness Some sensitive to chlorine and peroxide bleach Bright shades particularly reds violets, yellows and burgundy Primarily for cotton Poor fastness to crocking Low in cost

12. Dyes for protein fibers : Acid dyes Protein , acrylic, nylon Bright colours Most are not fats to washing Vary from poor to good in fastness to light and perspiration Excellent fastness to dry cleaning Dyes applied from acid bath rather than water bath

13. Dyes for protein fibers : Metal complex dyes Less bright than acid dyes Have better fastness to laundry, perspiration and light

14. Dyes for Protein fibres: Chrome dyes/Mordant dyes: Dull colours but excellent fastness to light, washing, perspiration Widely used on wool floor coverings

15. Dyes for acrylic, modacrylic , some cellulosic and protein fibers : Basic dyes: (cationic dyes) Bright shades of excellent fastness to light, washing, perspiration, crocking on fibers Very poor fastness to washing and light on cellulosic and protein fibers

16. Dyes for acrylic, modacrylic , some cellulosic and protein fibers : Reactive dyes: Mostly for cellulosic but also used on protein fibers and nylon Bright shades Generally good to excellent fastness to light, washing, perspiration and crocking Poor fastness to chlorine Difficult dye for colour matching

17. Dyes for acetate,tri -acetate, acrylic, modacrylic , nylon and polyester: DISPERSE DYES Wash fastness varies with fiber Poor on acetate, excellent on polyester Fastness to perspiration, crocking and dry cleaning good to excellent Light fastness fair to good Gas fading(loss of colour or change in colour on exposure to nitrous oxide- a pollutant in air) on acetate, especially blues and violets

18. Pigments: These are not true dyes and can be used on all fibers . Pigments do not combine with the fiber molecules as dyes do. They physically hold on to the textile material with resin binders like glue etc. Heavy shades tend to stiffen fabric Excellent fastness to light Poor fastness to crocking in heavy shades Fair to good fastness to hand laundering

19. APPLICATION OF COLOUR Dyeing can be done during any stage in the manufacture of a textile. They may be dyed as fibre, as yarn or as a fabric or as garment; depending on the type of fabric or garment being produced.

20. Fiber stage dyeing: Stock dyeing: Dyeing of fibers or stock, before it is spun into yarn. It is done by putting loose, un-spun fibers into large vats containing the dye solution, which are then heated to proper temperature. 500 to 3000lbs of fiber can be dyed at one time. Features: Most costly method therefore production is low. It gives excellent dye penetration and evenness of colour throughout the fabric. Strong element of fashion risk; a decision of colour is made at very early stage of manufacture. Used mostly for woollen materials. It's advantage being that Different colour fibres can be spun together to create mixed colors yarns with ombre ' effects .

21. Fiber stage dyeing: Top dyeing Slivers known as top dyed in the stage of manufacture between fiber and worsted yarn. Results are similar to stock dyeing in terms of evenness and colour penetration.

22. Yarn stage dyeing It is dyeing of yarn before they are woven or knitted into fabrics. It is dyed in different forms- skeins, packages or beams.

23. Yarn stage dyeing Hanks/skeins: They are loosely wound are immersed in dye vats which are designed for the purpose. Knitted yarns are dyed as skeins – most costly yarn dyeing method.

24. Yarn stage dyeing: Package dyeing Yarn wound on a spool or tube called package. Many such spools fit into the machine. Dye flows from center to outside and then from outside to inside of the package. Package dyed yarns do not certain softness and loftiness that skein dyed yarns do. Widely used method for both knitted and woven fabrics.

25. Yarn stage dyeing: Beam dyeing Much larger version of package dyeing. An entire warp beam is wound onto to perforated cylinder which is then placed in the dyeing machine. Flow of dye bath alternates like package dyeing. Most economical method of yarn dyeing.

26. Features yarn dyeing Yarn dyeing is less costly than stock or top therefore processes are more productive Permits excellent penetration of dye into the fiber and thus produces a great clarity of colour.

27. Use of yarn dyeing For manufacturer of plaids, stripes, checks and other multicolour designs

28. Use of yarn dyeing Yarn dyeing is used as a technique to create Ikat fabrics. Ikat is a method of creating designs in fabric by the use of resist dyeing. The pattern isn’t created by painting or printing, but by protecting parts of the yarn with a resist by binding it before the dyeing process, removing the resist after dyeing, possibly repeating this process multiple times, and then using this yarn in the warp, weft, or both. Warp ikat is commonly found, weft ikat less so, and double or compound ikat the most complicated of all. It’s slow, laborious work that takes a skilled artisan to master.

29. YARN DYEING: IKAT

30. Fabric stage dyeing/Piece dyeing The dyeing of cloth after it has been woven or knitted, is known as piece dyeing. It is the most common method of dyeing use. Various methods used for this include: Beck/Box/Winch dyeing Jig dyeing Pas dyeing Beam dyeing

31. Fabric dyeing: Beck/Winch dyeing oldest type of dyeing method. The fabric piece is sewn end to end and is dyed in a rope like form in relaxed condition. Fabric moves on a reel and is kept immersed in the dye bath except for few yards around the reel. Advantages: it retains softness of hand and fabric fullness. It is used for light weight fabrics like knits and also wavy fabrics like woollens.

32. Fabric dyeing: Beck/Winch dyeing

33. Fabric dyeing: JIG dyeing Consists of a stationary dye bath with 2 rolls above the bath. The cloth is carried around the rolls in open width and is rolled back and forth through the dye bath once in every 20 minutes or so and is on rollers the remaining time. There are some problems of level dyeing.

34. Fabric dyeing: JIG dyeing

35. Fabric Stage dyeing: Pad dyeing In this, fabric runs through the dye bath in open width and then between squeeze rollers that force the dye into the fabric. Most pad dyeing part of continuous system or range where fabric continuously runs between pad and then into other chambers – steam, washer, rinse, dryer.

36. Fabric stage dyeing: Beam dyeing Similar to yarn beam dyeing. Here fabric beams are used instead of warp beam. Used for light weight fabrics, open constructions since dye bath cannot circulate through densely constructed fabric. Advantages: rapid and economical method for light weight and open fabrics. No stresses and tensions like in jig and pad method. Involves less fashion risk as compared to other methods.

37. Fabric stage dyeing: Beam dyeing

38. Design produced by piece dyeing Piece dyeing generally produces solid colours Tie and dye and Batik are the resist-dyeing processes for creating attractive coloured designs on fabrics. However, while in Batik, resistance to dye penetration is provided by a coated layer of wax, in the case of tie and dye, this is achieved by knotting, binding, folding or sewing certain parts of the cloth in such a way that the dye cannot penetrate into these areas when the cloth is dyed.

39. Tie and Dye This is also a hand process in which the colour penetration is resisted by using tightly tied cotton threads . It is a laborious process producing beautiful results in a number of colours. In tie and dye , the yarn or fabric to be dyed is first tied with threads to resist colour penetration in areas as required by the design and then dyed in the first colour, which is lightest of all. This process of tying and dyeing continuous till the product is coloured in its final colour.

40. Special dyeing effects: Cross dyeing A method of coloring fabrics made from more than one kind of fiber , for example, a wool and cotton blend. Each fiber in a fabric designed for cross-dyeing takes a specific dye in a different color or in variations of a color . A fabric that is crossdyed is more than one color . Cross-dyeing is often used to create heather effects (soft, misty colorings ), but strongly patterned fabrics can also be achieved, depending on the fibers used in the fabric.

41. Example- a shot effect can be created in the polyester cotton blend, by dyeing polyester component with red disperse dye and cotton component with yellow reactive dye. The produced fabric will give reddish orange yellowish effect ( Heathered effect).

42. Special dyeing effects: Union dyeing Union dyeing is “a method of dyeing a fabric containing two or more types of fibers or yarns to the same shade so as to achieve the appearance of a solid colored fabric”. Fabrics can be dyed using a single or multiple step process. Example: fabric of polyester and cotton can be dyed in solid green by using disperse dye for polyester and reactive dye for cotton.

43. Garment dyeing It is dyeing of completed garments. These include only non-tailored categories like sweaters, hosiery and pantyhose. Tailored garments like suits and dresses cannot be dyed as garments because the differences in shrinkage of the various components distort and misshape the article.

44. Garments are loosely packed in large nylon net bags. 10 to 50 of such bags are placed in large tubs containing dye bath and are kept agitated by a motor driven paddle in the dye bath. Machine is called paddle dyer. It is inexpensive method. t can dye garment as per buyer orders. It decreases the element of fashion risk.

45. Design produced by garment dyeing Tie and dye, batik process can be used to create designs on garments Ombré effect created using dip dyeing, color bleeding, or gradated dyeing technique can be achieved. It is an effect usually achieved by hand dipping fabric in dye so that it gradually goes from light to dark, or sometimes from one color to another.

46. Design produced by garment dyeing

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