Dying Printing Finishing
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Dying Printing Finishing

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a complete guide of dyeing and printing

a complete guide of dyeing and printing

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  • Thank You this is wonderful. Clean , albeit a b it longer than my textile students will appreciate but if I edit it , it is very informative. Thanks
    Prof. Hein Purdue Construction Dept.
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Dying Printing Finishing Dying Printing Finishing Presentation Transcript

  • Dyeing, Printing and Finishing VESTEX Srini Venkataraman Dr. Sandeep Khatua March 2006 Bureau Veritas Consumer Products Services For the benefit of business and people
  • Summary 1) Preparatory Process and Their Importance 2) Dyeing 3) Dyeing Techniques 4) Printing 5) Dyeing / Printing Problems and Remedies 6) Finishing 2
  • 1 Preparatory Process and Their Important 3
  • 1 Preparation Objectives 8 Remove impurities (both natural and/or those added during production) from the fibers. 8 Improve the ability of the fibers to absorb water solutions of dyes and chemicals. 8 Impart the proper brightness or whiteness to fibers according to need, especially when brilliant or certain pastel shades are desired, and 8 Impart dimensional stability to thermoplastic textile materials. Bureau Veritas Consumer Products Services 4
  • 1 Preparation Importance 8 The importance of adequate and uniform preparation prior to dyeing cannot be overemphasized. Improper removal of impurities can lead to unlevel dyeing, streakiness, and poor penetration. 8 It is estimated that more than 60% of faulty dyeing are the result of improper preparation. 8 Preparation procedures may vary greatly from one fiber type to another. While natural fiber usually require extensive scouring and bleaching, synthetic fibers may need only a mild scouring. Bureau Veritas Consumer Products Services 5
  • 1 Preparation 8 Important Preparatory Steps for Cotton Fabric • Singeing • Desizing • Scouring • Bleaching • Mercerizing Bureau Veritas Consumer Products Services 6
  • 1 Preparation Singeing 8 Removes superficial hairiness from yarns, lint, loose yarns, and surface dirt from the face of the fabric and therefore provides more even surface for dyeing. 8 It also reduces formation of pills, or balls of fiber, on the fabric. 8 After the surface of the fabric is raised by brushing, the protruding fiber ends are burned off by the singeing process. In this process the fabric is passed through the small gas flame. 8 Note: Consumers may detect increased pilling in improperly singed Cotton fabrics. When Cotton blends are singed, care must be taken to avoid overheating the thermoplastic fibers. Bureau Veritas Consumer Products Services 7
  • 1 Preparation Desizing 8 Prior to weaving, Cotton warp yarns are coated with sizing materials to provide them with additional strength, and resistance to abrasion. The most common sizing materials used are different kinds of starches, and various grades of partially hydrolyzed polyvinyl alcohol. 8 Enzymes are often used for the effective removal of starches. 8 The main advantage of enzyme desizing is that there is no risk of damaging the fibers. However, enzymatic desizing is relatively expensive since it can not be combined with other preparatory operations. Bureau Veritas Consumer Products Services 8
  • 1 Preparation Scouring 8 This cleaning treatment, often referred to as alkali boil- off, removes most of the Cotton’s impurities, which includes natural and other impurities as well as sizing residues that were not removed during desizing. 8 In scouring the fabric is treated with a strong alkali solutions, close to or above the boil, for 1-2hours. A hot rinse is needed to remove the emulsified impurities. The final rinse may include a small amount of acetic acid if the fabric has to be neutralized. 8 Manmade fibers, especially those that have been heavily treated with spinning oils, are occasionally scoured with solvents. Bureau Veritas Consumer Products Services 9
  • 1 Preparation Bleaching 8 The purpose of Bleaching is to provide a uniform white surface on a fabric. It is chemical oxidation that destroys the colored impurities present. 8 Control of whiteness of bleached fabric is important to wet processing that follow. 8 Hydrogen Peroxide is the chemical most commonly used today for bleaching Cotton compared to Sodium Chlorite 8 Open Width Method and Rope Method: Open width method is widely used method especially when bleaching blends of Cotton with heat-sensitive fibers in order to avoid crease marks and other defects caused by treating fabrics in the rope form. Bureau Veritas Consumer Products Services 10
  • 1 Preparation Bleaching Open Width Method Bureau Veritas Consumer Products Services 11
  • 1 Preparation Bleaching Rope Method Bureau Veritas Consumer Products Services 12
  • 1 Preparation Mercerization 8 Two Types: 1) Tension Mercerization » The purpose of mercerization is to increase luster of Cotton fibers » The fiber untwists and swells, lumen becomes rounder in cross-section and it gains luster. Dye affinity and chemical reactivity increase. Fabric becomes stronger and smoother. 2) Slack Mercerization » Not as lustrous as tension method » Elongation and recovery properties improve and thus have been used to produce comfort stretch garments and fabric bandages, which need to conform to body shapes. Bureau Veritas Consumer Products Services 13
  • 1 Preparation Mercerization Note: Fabric Mercerization is Cheaper than double Mercerization which provides a softer hand Bureau Veritas Consumer Products Services 14
  • 1 Preparation Knit Fabric 8 Knitted fabrics are pre-relaxed to minimize torque, puckering of seams, and shrinkage during dyeing and drying. Conveyor type relaxation dryers and / or compacting are used to minimize residual fabric shrinkage. 8 After knitting, the lubricants (added to improve “knitability”) must be removed with a water-based or solvent scouring process. Bureau Veritas Consumer Products Services 15
  • 1 Preparation Thermoplastic Fabrics 8 Heat-setting or thermosetting is a heat treatment applied to fabrics made of thermoplastic fibers such as polyester or Nylon to impart dimensional stability. 8 Heat-setting affects the dye-ability of the fiber. Usually it decreases its dye-ability, and therefore when performed before dyeing it is extremely important to apply the heat- setting uniformly. 8 Uneven temperatures in the oven may cause differences in the fabric from selvage to selvage and/or from selvage to center which will show later as unlevel dyeing. Bureau Veritas Consumer Products Services 16
  • 2 Dyeing 17
  • 2 Dyeing 8 Dyeing is by far the most widely used means of applying color to textiles. 8 Dyes, by definition, are soluble in the medium in which they are applied, and the medium is almost always water. Bureau Veritas Consumer Products Services 18
  • 2 Dyeing Classification and Fibers 8 There are several different ways by which coloring materials are classified. 8 Classification of dyes by the method of application is the most common one, which are: • Acid dyes (Protein fibers, polyamides etc) • Basic dyes (Acrylics, Basic dye-able polyester, etc) • Direct dyes (Cellulosics, and some others) • Azoic dyes (Cellulosics) • Vat dyes (Cellulosics) • Reactive Dyes (Cellulosics) • Disperse Dyes (Polyester, Acetate, Polyamides, acrylics, and Other Hydrophobic fibers) Bureau Veritas Consumer Products Services 19
  • 2 Dyeing How Dyeing Takes Place Immerse Textile in Dye-bath All Dye is in Bath Apply Heat, Time, Chemicals Fabric Most of the Dye Now on Textiles to Drive Dye into Textiles Fabric Unfixed Surface Rinse to Remove Surface Dye Dye Removed Bureau Veritas Consumer Products Services 20
  • 2 Dyeing How Dyeing Takes Place Polymer Morphology Inside a Fiber Bureau Veritas Consumer Products Services 21
  • 2 Dyeing Typical Reactive Dyeing Process on Cotton Woven Bureau Veritas Consumer Products Services 22
  • 2 Dyeing 8 The Major System Variables • Textile substrate • Application method • Dye selection and formulation 8 Need to Control These Variables in Order to Achieve: • Target shade predictability • Required fastness • Efficiency in terms of cost of materials and plant occupancy Bureau Veritas Consumer Products Services 23
  • 2 Dyeing 8 General Principles and Terms Met in Dyeing 1) Dye Exhaustion – This describes how much of the total dye applied resides on the fiber rather than in the dye liquor 2) Equilibrium – This is when the final or equilibrium degree of exhaustion has been reached. If the dyeing is allowed to proceed under the same conditions for a longer time, the shade of the dyed goods will remain the same. 3) Levelness and Leveling Power - levelness depends on: » Liquor ratio – The leveling power increase as the LR increases as there is more dye in the bath » Substantivity – Low substantivity favors leveling » Temperature – Higher temperature give more level dyeing » Time – Longer times give more level dyeing Bureau Veritas Consumer Products Services 24
  • 2 Dyeing Stages 8 Dyeing Can Be Done at Different Stages: • Fiber Stage • Yarn Stage • Fabric Stage • Garment Stage Bureau Veritas Consumer Products Services 25
  • 2 Dyeing Stages Bureau Veritas Consumer Products Services 26
  • 2 Dyeing Fiber 8 Stock Dyeing • Masses of loose fibers are placed in large drums into which dye is pumped and circulated. • Tweed fabrics with a heather-like color effect such as Harris tweed is done using this method. Bureau Veritas Consumer Products Services 27
  • 2 Dyeing Fiber 8 Producer or Solution Dyeing • Colorant is added to the spinning solution before the polymer mix is extruded and formed into a manufactured fiber. • This method is very desirable when high colorfastness is desired such as automotive seating fabrics, carpeting etc. Bureau Veritas Consumer Products Services 28
  • 2 Dyeing Yarn 8 Yarn Dyeing • Yarns are immersed into a dyebath prior to being made into fabric. • Loosely wound hanks can be dyed (skein dyeing), • Yarns wound into small tubes called package can be dyed (package dyeing), or • The entire warp beam can be immersed into dyebath (beam dyeing). Bureau Veritas Consumer Products Services 29
  • 2 Dyeing Yarn / Fabric Dyeing 8 Beam Dyeing • Both yarn and fabric can be dyed by this process Bureau Veritas Consumer Products Services 30
  • 2 Dyeing Fabric 8 Piece Winch (or beck) Dyeing • Fabric pieces are sewn end to end and this rope-like form is dyed in a relaxed state. • It is most widely used on knitted, woolen and worsted fabrics. Bureau Veritas Consumer Products Services 31
  • 2 Dyeing Fabric 8 Piece Jet Dyeing • Dyeing is done in a closed, tube-like system in which the fabric passes through a fast moving stream of pressurized dye liquor. • It is primarily used for fabrics prone to felting. Bureau Veritas Consumer Products Services 32
  • 2 Dyeing Fabric 8 Piece Jig Dyeing • Fabric is treated in open width and is passed through the dye bath rather than immersed in to a dye bath and this is repeated. • There is a degree of tension on the fabric and is therefore used on woven fabrics and not knits. Bureau Veritas Consumer Products Services 33
  • 2 Dyeing Fabric 8 Piece Pad Dyeing • The dye solution is applied by means of a padder and the fabric in open form is run through an open vat. • The fabric is subject to tension, so only selected fabrics can be dyed. • Advantages: System can handle thousands of yards and dye can be added automatically to provide consistency of dye color Bureau Veritas Consumer Products Services 34
  • 2 Dyeing Garment • Dyeing is done on completed garments. • Garments are placed in a nylon bag and placed in large tubs containing dye bath. • Garments having differential shrinkage among various components may have difficulty being dyed by this method. Bureau Veritas Consumer Products Services 35
  • 3 Dyeing Techniques 36
  • 3 Dyeing Techniques Reactive 8 Reactive Dyeing • The reactive dyes are water-soluble anionic dyes, which react with hydroxyl groups of cellulose to become covalently bonded to the fiber • The chemical reaction between a reactive dye and a cellulose fiber takes place in the presence of a base and can be summarized as follows • Offers bright colors with very good colorfastness, (particularly good washfastness and excellent light fastness). • Susceptible to damage from chlorine bleaches Bureau Veritas Consumer Products Services 37
  • 3 Dyeing Techniques VAT 8 The Vat dyes are insoluble organic compounds that are not substantive to cellulose. The following steps are involved in dyeing: 1) Reduction (Vatting): Prior to dyeing they are converted to their soluble form (leuco soluble vat dye) by means of reduction in the presence of a strong base. 2) Dyeing: In this soluble form, they are substantive to cellulosic fibers, and can be applied to them. 3) Oxidation: Once inside the fibers, uniformly distributed, the Vat dyes are then oxidized and converted back to their original insoluble form. 4) Soaping: to achieve a stable shade. Bureau Veritas Consumer Products Services 38
  • 3 Dyeing Techniques VAT 8 The soft water throughout the dyeing stage is a must with Vat dyes, since the soluble Leuco salts form insoluble salts with Calcium or Magnesium ions as well as with transition metals. 8 A wide choice of colors with good to excellent colorfastness is available, although their lightfastness may be somewhat inferior. Bureau Veritas Consumer Products Services 39
  • 3 Dyeing Techniques Sulfur 8 Sulfur dyes are insoluble in water and their application to cellulosic fibers resembles that of the Vat dyes in principle. They are relatively low in cost. 8 Traditionally they were used for dark shades (browns, blacks and navy blues) but some of the newer dyes are available in bright colors . 8 Sulphur dyes (if applied incorrectly) on material stored at higher than normal room temperature and in presence of moisture tend to oxidize to form strong sulfuric acids. These acids will then cause tendering of cellulose fibers. To prevent tendering, the final rinse is carried out with mild alkali solutions. 8 Sulfur dyed fabrics have good colorfastness to washing but are sensitive to chlorine bleaching. Lightfastness is only fair but is adequate for most end uses not requiring prolonged sunlight exposure. Bureau Veritas Consumer Products Services 40
  • 3 Dyeing Techniques Direct 8 Direct dyes are soluble anionic dyes. 8 The Direct dyes are so called because they were the first dyes to dye cellulosic fibers directly without the need for a pre-treatment of the fibers with a mordant. 8 The mechanisms by which direct dyes become attached to cellulose is assumed to be through the formation of a large number of weak attractions between the dye and the fiber. 8 Direct dyes exhibit relatively good colorfastness to sunlight, and some are considered to have excellent lightfastness. However colorfastness to washing is poor and therefore not appropriate for frequently washed apparel. 8 The problem of poor washfastness can be improved to some degree by formaldehyde after treatment. Bureau Veritas Consumer Products Services 41
  • 3 Dyeing Techniques Disperse 8 The disperse dyes are non-ionic aromatic compounds with an extremely low solubility in water. 8 Disperse dyes require special fabric preparation for uniform application. • Dyeing procedure for Polyester fiber include; 1) Low temperature dyeing with dye-carrier 2) High Temperature/High Pressure Dyeing 3) Continuous dyeing by the thermosol process 8 Extremely colorfast to laundering. Good colorfastness to light and dry cleaning. But dyes may sublime( evaporates) when exposed to high temperature in pressing. 8 Fume fading is a problem with disperse dyes. It is not unusual to see acetate linings turn pink after storage in an area with gas heat. Bureau Veritas Consumer Products Services 42
  • 3 Dyeing Techniques Bureau Veritas Consumer Products Services 43
  • 3 Dyeing Techniques Dyestuff Properties Perspiratio Ease of Dyes Cost Washfastness Lightfastness Crockfastness n Application Fastness Average Acid Average Fair - Good Good Good Good - Average Average – Basic Poor – Good Poor – Good Fair – Good Fair – Good + Fairly Difficult Wet – Poor Poor – Direct Cheap Easy Poor – Good Fair – Good Dry – Good Good Disperse Average Fairly Hard Good Good Fair – Good Fair – Good Naphthol Average Hard Good Good Fair – Good Fair – Good Average Good – Average – Reactive Excellent Good Fair – Good Fair – Good + Fairly Difficult (if soaped) Sulfur Cheap Fairly Difficult Good Fair – Good Good Good Average Good – Good – Vat Fairly Difficult Good Good + Excellent Excellent Bureau Veritas Consumer Products Services 44
  • 3 Dyeing Techniques Blends 8 Union Dyeing • In union dyeing, the components of a blend are dyed with the same shade to obtain a solid color. • Dyes must be carefully selected and properly applied to ensure color uniformity. • Union dyeing can be applied by two methods: One- bath (single dye) and Two-bath (double dye) methods. • Polyester/Cotton intimate blends are often dyed with these methods. • Two-bath method offers better result on Polyester/Cotton blends compared to One-bath method. • One-bath method is cheaper than Two-bath method. Bureau Veritas Consumer Products Services 45
  • 3 Dyeing Techniques Blends 8 Cross Dyeing • The method of obtaining a multi-color effect on a blend is referred to as Cross-Dyeing. • In cross dyeing, a fabric containing two or more fiber types or fiber variants is purposely dyed so that each fiber type or variant accepts a different type of dye and becomes a different color. • The end product depends on the fiber arrangement in the fabric. It may be a check, a plaid, a tweed, a stripe, a muted color, a heather effect, or some other design. Bureau Veritas Consumer Products Services 46
  • 3 Dyeing Techniques Pigment Coloration 8 Advantages • Pigment coloration is economical because of limited number of processing steps. • Blends can be dyed a uniform shade with one operation applicable to all fibers. • Pigment coloration has an extensive color range and high light fastness. • Pigment coloration has satisfactory washfastness. 8 The possibility of combining dyeing and finishing exists with pigment coloration. Products must be selected so that finish and binder react under same conditions of pH and/or temperature. Bureau Veritas Consumer Products Services 47
  • 3 Dyeing Techniques Pigment Coloration 8 Disadvantages • Heavy shades crock badly. Light shades may wet crock. • Pigment coloration is normally applied by padding. • Pigment adversely affects hand. The large amount of binder required may stiffen fabric. This is most noticeable on very thin fabrics. • Pigment coloration may have sticking or buildup on pad rolls. • Migration (uneven coloration) may occur if drying is variable or pickup is high. Bureau Veritas Consumer Products Services 48
  • 3 Dyeing Techniques Optical Brighteners 8 Optical brighteners, also called Fluorescent Brighteners or Fluorescent Brightening Agents (FBA) are colorless dyes that work by emitting visible light when exposed to invisible ultra-violet light. 8 They are used to make white or light-colored fabrics appear brighter. Mostly bleached white fabrics are treated with these brighteners. 8 Fabrics and garments that are truly prepared for dyeing should not contain brighteners. Optical brighteners can interfere with some dyes by competing for the "dye sites" on the fibers. Bureau Veritas Consumer Products Services 49
  • 3 Dyeing Techniques Optical Brighteners 8 Optical brighteners have the property of absorbing ultra- violet (UV) light and re-emitting energy in the form of weaker energy, i.e. visible light (violet-blue light) so that the yellow color of the material will appear white. 8 The chemical structures of these agents contain an aliphatic carbon-carbon double bond, which is sensitive to sunlight, oxidation, weathering, etc. 8 Therefore, these compounds do not have good fastness properties, and tend to loose their ability to absorb UV light over short periods of time in use. 8 The presence of high concentrations or improper application or cheaper quality of fluorescent brighteners could lead to yellowing of the material instead of whitening. Bureau Veritas Consumer Products Services 50
  • 4 Printing 51
  • 4 Printing 8 The application of colorant in definite, repeated patterns to fabric, yarn or sliver. 8 The different methods of printing include hand screen, automatic screen, rotary screen, roller and heat transfer. 8 Each method can be used to print one or more print types. 8 These include direct, discharge and resist prints. Bureau Veritas Consumer Products Services 52
  • 4 Printing 8 There are Three Methods of Printing: • Screen Printing • Roller Printing • Heat-Transfer Printing Bureau Veritas Consumer Products Services 53
  • 4 Printing Methods 8 Screen Printing • This printing involves coating of a screen fabric (made of nylon, polyester, or metal tightly mounted on a wooden or metal frame) with an opaque nonporous film with the design areas cut out of it. • The screen is placed on top of the fabric, print paste is poured into the frame and forced through the mesh. • The dye can then pass through the fine mesh and coat the fabric only in the areas of the design. • Each color requires its own screen and separate application of color. Also each color of the design must be precisely located on the screen so that it becomes properly placed and printed. Bureau Veritas Consumer Products Services 54
  • 4 Printing Methods 8 Screen Printing • Types of Screen Printing Include: » Flatbed Screen - Hand or Automatic » Rotary Screen Bureau Veritas Consumer Products Services 55
  • 4 Printing Flatbed Screen 8 They are used primarily to print on flat substrates 8 Consists of a bed or vacuum table that holds the substrate in place during printing, a carriage that holds the printing screen, and a squeegee. 8 Printing takes place in three steps. First, ink is poured on the screen, and the screen is moved into position over the substrate. Then the squeegee is pressed against the mesh and drawn over the image area to push ink through the open areas of the screen onto the substrate. Finally, the screen is lifted away from the substrate. Bureau Veritas Consumer Products Services 56
  • 4 Printing Rotary Screen Printing Process Bureau Veritas Consumer Products Services 57
  • 4 Printing Rotary vs Flatbed Screen 8 The equipment costs for Flatbed screen printing are lower than other printing processes, but the rate of production is usually slower. 8 Rotary printing is a continuous, stepless image transfer method whereas flatbed printing is a two step process. 8 Flatbed screen printing is good for small repeat units or rigid stock printing (impossible to support on rotary machine). 8 Rotary screen is best choice for coarse halftones and specialty inks. Bureau Veritas Consumer Products Services 58
  • 4 Printing Methods 8 Roller Printing • In this printing method, the design is put onto fabric by copper engraved rollers or cylinders. • A separate engraved roller is required for each color. • Copper rollers can be engraved with very fine delicate designs. • The size of engraved cylinders is governed by the printing machine and the design. Bureau Veritas Consumer Products Services 59
  • 4 Printing Roller Printing Process Bureau Veritas Consumer Products Services 60
  • 4 Printing Print Inks 8 Two Types of Ink are Used in the Textile Industry: 1) Water-based Ink 2) Plastisol Ink » Plastisol is the choice for printing of finished goods such as T-shirts, sweatshirts, jackets, and tote bags. » Water-based ink is the ink of choice for the printing of yard goods; either in piece form or on the roll. Bureau Veritas Consumer Products Services 61
  • 4 Printing Plastisol Printing 8 Plastisol ink is a PVC based system that contains no solvent. 8 It is thermoplastic that requires specific heat and time for complete curing. Failure to follow proper curing guidelines will result in an “under Cure” of the print and therefore will cause poor washfastness, and/or a resistance to abrasion. 8 The performance of plastisol can be affected by addition of additives such as Extenders, plasticizers, reducers and resins. 8 Problems such as fading, pulling away and/or cracking can occur if additives are used properly. 8 If not cured properly, phthalates (a commonly used plasticizer) could cause skin irritation. Bureau Veritas Consumer Products Services 62
  • 4 Printing Plastisol Inks 8 Advantages of Plastisol Inks • User-friendly, very easy to manage • Can be left in the screen for extended periods of time without clogging the mesh • It is ready to use right out of the container more than 90% of the time • Can be printed wet-on-wet, which allows for increased production speeds • Can be printed on light and dark fabrics • Disposal of waste plastisol is a simple process Bureau Veritas Consumer Products Services 63
  • 4 Printing Water-based Links 8 Advantages of Water-based Inks • Good choice when soft hand is desirable • Excellent for high speed roll-to-roll yardage printing • Such printing is done on large sophisticated equipment that has very large drying (curing) capacity. • Good choice where ink penetration is desirable such as in towel printing Bureau Veritas Consumer Products Services 64
  • 4 Printing Plastisol vs. Water-based Links Ease Waste Curing of Opacity Hand Cost Ink Printing Recovery Low- Medium - Moderate - Plastisol Easy Fair Excellent High Heavy High Low - Low - Water-based Hard Easy Soft Fair Medium Moderate Plastisol Water-based T-shirts, light colored Excellent Excellent T-shirts, dark colored Good Poor Nylon Jackets Good Fair Towels Poor Excellent Yardage Poor Excellent Bureau Veritas Consumer Products Services 65
  • 4 Printing Metallic Prints 8 Metallic inks are simply finely ground metal and/or plastic flakes that are suspended in a clear plastisol base. 8 can be used as accents in a design or as the entire print. 8 One of the biggest problems with metallics is that some brands that use metal flakes dull and tarnish badly after the first washing but small plastic flake that doesn't tarnish 8 A popular technique to improve the washability and brightness of metallic prints is to add 5% nylon jacket bonding agent to the mixture. This helps seal the metal particles and minimize the tarnishing. Bureau Veritas Consumer Products Services 66
  • 4 Printing Glitter 8 Glitter ink is made up of small mylar flakes that are suspended in a clear plastisol base. 8 Comes in wide variety of colors ranging from your basic silver and gold, to more vivid green, purple, cherry and more. 8 Because of the size of the glitter particle, this ink is not designed for detailed prints. It works best as a highlight ink for a design that need a little glitz. It works well on both light and dark shirts because the glitter flake makes the ink very opaque. 8 The clear base of the glitter mixture will need to be cured just like a normal plastisol except the ink deposit is so thick that a longer tunnel time is very important. 8 Glitter washes very good and will flake just a little. Unlike metallic ink that will dull, glitter retains it's brilliance because the flake is mylar and does not tarnish like some metallics. Bureau Veritas Consumer Products Services 67
  • 4 Printing Methods 8 Heat-Transfer Printing • This is also called thermal transfer printing. In this method the design is first printed on paper with printing inks containing disperse dyes. • The printed paper (called transfer paper) is placed on the fabric and passed through heat-transfer printing machine at about 400°F. Under this temperature, the dye on the paper sublimates and is transferred onto the fabric. • Disperse dyes is the only class of dyes that can be sublimated and used for this method of printing. Bureau Veritas Consumer Products Services 68
  • 4 Printing 8 Heat transfer is ideal for printing small runs of many products, especially where full color is required. 8 Heat transfer minimizes the need for large inventories of printed garments. 8 Adaptable when it comes to garments that are difficult to print, such as those with buttons and zippers. 8 Heat transfers allow a halftone print to be moire- free and have minimum fibrillation. Bureau Veritas Consumer Products Services 69
  • 4 Printing Types 8 There are Different Types of Prints Including: • Direct or Application Print • Discharge Print • Resist Print • Blotch Print • Warp Print • Flock Print • Burn-out Print • Duplex Print • Pigment Print • Engineered Print Bureau Veritas Consumer Products Services 70
  • 4 Printing Types 8 Direct Print • Also called application print. Design is printed directly onto a white cloth or a previously dyed fabric. They are the most popular print types. Bureau Veritas Consumer Products Services 71
  • 4 Printing Types 8 Discharge Print • Fabrics are dyed a solid color prior to printing. When printing is done, the design is applied by screen or roller with a chemical which removes the color of the originally dyed fabric. Discharge prints can be made with rollers and screen methods. They are not widely used because production costs are high. Bureau Veritas Consumer Products Services 72
  • 4 Printing Types 8 Resist Print • It involves a two step procedure: (1) printing a pattern design on a white fabric with a chemical that will prevent penetration of dyes; and (2) piece dyeing the fabric. The result is a dyed background with a white patterned area. Bureau Veritas Consumer Products Services 73
  • 4 Printing Types 8 Blotch Prints • It is one in which the background color is created by printing rather than dyeing. The ground and pattern design colors are printed onto a white cloth. One of the problems with blotch prints is that large background color areas of the print are not covered with the full depth of color. Bureau Veritas Consumer Products Services 74
  • 4 Printing Types 8 Warp Prints • This involves printing the warp yarns of a fabric before weaving. The fabric is woven with a solid color filling, usually white. The result is a soft, shadowed, blurred design on the fabric. These prints are found on high quality, costly fabrics because it requires careful, meticulous labor. Bureau Veritas Consumer Products Services 75
  • 4 Printing Types 8 Flock Prints • Tiny particles of fiber are made to adhere to a fabric surface in conformance to a particular design. Rayon and nylon fibers are typically used for flocking. The ability of flocked fibers to withstand dry cleaning and/or laundry depends on the adhesive. Adhesives with excellent fastness to cleaning processes are used. Bureau Veritas Consumer Products Services 76
  • 4 Printing Types 8 Burn-out Prints • This involves printing with a chemical that will destroy the fiber in the patterned design print area. In fabrics that are made with blended yarns, the burn-out chemical will destroy one fiber and leave the other undamaged. Unusual and interesting fabrics can be created by this method. Bureau Veritas Consumer Products Services 77
  • 4 Printing Types 8 Duplex Prints • These are fabrics in which both sides of the fabric are printed. They are made to imitate more costly woven yarn-dyed design effects such as stripes, checks and plaids. They are rarely used because of the high cost of printing both sides of a fabric. Bureau Veritas Consumer Products Services 78
  • 4 Printing Types 8 Pigment Print • They are direct prints made with pigments. The process is called dry printing as distinguished from wet (dye) printing. The pigment print area will be slightly stiffer and bit thicker than the non-print area. They are the least costly type of print to produce. Bureau Veritas Consumer Products Services 79
  • 4 Printing TYPES 8 Engineered Prints • These are prints that have two or more distinct designs, each located in separate areas of the fabric and each designed to become a specific part of a garment. Engineered prints include fabrics whose designs are especially pre-established topermit making a garment in a particular stylized effect. Bureau Veritas Consumer Products Services 80
  • 5 Dyeing / Printing Problems and Remedies 81
  • 5 Dyeing and Printing Problems A horizontal off-shade band across the fabric. Usually found in knit fabrics, the problem is caused by a defect in Barré the yarn, uneven tension in knitting, or other factors that produce a color band when the fabric is dyed. Color Color is discharged into a liquid medium and transfers to Bleeding another fabric. The transference of color from one fabric to another by Crocking rubbing. The loss of color brilliance through exposure to factors Fading such as sunlight or cleaning agents. A change of fabric color caused by localized abrasive Frosting wear, such as that occurring at collar points or garment creases. A change of shade in dyed fabric caused by the chemical Fume Fading reaction of certain disperse dyes with atmospheric contaminants such as burnt gas fumes and ozone. Design lines in printed fabrics that are meant to be sharp Fuzzy Pattern demarcations of color but that are muted or blurred. Bureau Veritas Consumer Products Services 82
  • 5 Dyeing and Printing Problems A phenomenon, also known as flare, that is observed when materials are viewed under different light sources. The Metamerism spectral reflectance curves are not identical, so the viewer sees one color under one light source (incandescent) and a different color under another light source (fluorescent). Migration The transfer of color from one area of the fabric to another. Lacking trueness. In printing, the design is transferred to Off Grain the fabric so the design of the fabric is not aligned with the yarns. Lacking color alignment. In printing fabrics, the color Off Register separation is imperfect, producing a situation in which the different color components of the design are not aligned. The unintentional variation in color within a piece of fabric Shading or a garment. Weak areas in fabric resulting from chemical damage, which Tender Spots may be produced by improper bleaching, chemical spills, or improperly applied coloring or finishing agents. Bureau Veritas Consumer Products Services 83
  • 6 Finishing 84
  • 6 Finishing 8 Finishing is a general term for a magnitude of processes and treatments that a fabric may undergo after it has been made (woven or knitted) and colored (dyed or printed). 8 It is the final processing of the cloth. Its purpose is to make the fabric more suitable for its intended end use. 8 Textile finishes can be classified as aesthetic finishes and functional finishes. 8 They are also categorized as chemical finishes and mechanical finishes. Bureau Veritas Consumer Products Services 85
  • 6 Finishing Aesthetic Finishes 8 These are finishes which change the appearance, drapability and hand (feel) of fabrics including parchmentizing, softeners, and stiffening finishes. 8 Finishes that alter or create texture include burn- out designs, embossing, plissé, raised fiber surfaces (brushing, gigging, napping, sueding, and flocking). 8 Finishes that alter fabric luster include beetling, calendering (simple, glazed, moiré, schreinering), optical finishes (delusterants, and optical brighteners). Bureau Veritas Consumer Products Services 86
  • 6 Finishing Functional Finishes 8 These are finishes which improve the performance properties of fabrics. 8 Finishes that enhance care properties include durable press, soil-release, stain- and soil-resistant finishes. 8 Finishes that provide comfort and safety include antistatic, chemical-protective, absorbent, flame resistance, water-repellent and waterproof finishes. 8 Finishes that alter durability include abrasion- resistant, slip resistant, and shrinkage control. 8 Finishes that provide environmental protection include antimicrobial finishes, fume fading inhibitors, metallic and plastic coatings, and mothproofing. Bureau Veritas Consumer Products Services 87
  • 6 Finishing Aesthetic Finishes 8 Finishing that Changes Appearance, Drapability and Hand • Parchmentizing » A finishing process to give cellulosic fabrics such characteristics as transparency, linen-like hand, and texture. The fabric is immersed briefly in an acid bath under controlled conditions and then quickly neutralized. This finish is most effective on mercerized cotton. • Softening » Softening agents are frequently used to improve the hand and drape of fabric. The most commonly used softeners are oils, fats, wax emulsions, soaps and synthetic detergents, and silicone compounds. Silicone compounds produce relatively durable softening. • Stiffening » Some fabrics need to be made stiffer and more crisp than they would otherwise be in order to meet an intended end use. Stiffening may be done by any of several chemical finishes, all applied by pad and either dried or cured. Starch is widely used but starch finishes are temporary. Bureau Veritas Consumer Products Services 88
  • 6 Finishing Aesthetic Finishes 8 Finishes that Alter or Create Texture • Plissé » This is a permanent finish, produced on cotton by the treatment of sodium hydroxide to produce a puckered or crinkled fabric. Sodium hydroxide is printed on the fabric in the form of paste and the fabric shrinks only where the paste is applied. Acetate, rayon, and manufactured fabrics with a puckered effect can be produced by chemical treatment or heat setting. • Embossing » This is a process to produce a raised design or pattern in relief on fabrics by passing the cloth between hot engraved rollers that press the design into the fabric. In thermoplastic fabrics (polyester, nylon) embossing is permanent. In other fabrics, resin finishes are used to create a durable effect. Bureau Veritas Consumer Products Services 89
  • 6 Finishing Aesthetic Finishes 8 Finishes that Alter or Create Texture • Diagram of Embossing Rolls Bureau Veritas Consumer Products Services 90
  • 6 Finishing Aesthetic Finishes 8 Finishes that Alter or Create Texture • Raised Fiber Surface » Fabric surfaces can be raised by brushing, gigging, napping, and sueding. Fabrics must be made of staple-fiber yarns with low twist and lubricated to ease the extraction of fiber ends from the cloth. Bureau Veritas Consumer Products Services 91
  • 6 Finishing Aesthetic Finishes 8 Finishes that Alter or Create Texture • Napping » Napping uses a series of 24-30 cylinders covered with fine metal wires bent into small hooks, to produce a thick, raised fiber surface on fabrics produced from loosely twisted staple-fiber yarns. A fabric can be napped on a single side or both. The nap maybe brushed and/or sheared to make it even. Napping is used on broadcloth, flannel, and blankets • Sueding » A process similar to napping, it is a mechanical finish that produces a soft, suede-like surface on the fabric. Instead of rotating, bristled wire covered brushes used in napping, the rotating cylinders used for sueding consist of a sandpaper-like material. Bureau Veritas Consumer Products Services 92
  • 6 Finishing Aesthetic Finishes 8 Finishes that Alter or Create Texture • Diagram of Napping Process Bureau Veritas Consumer Products Services 93
  • 6 Finishing Aesthetic Finishes 8 Finishing that Alter Fabric Luster • Calendering » A finishing process producing a flat, glossy, and smooth surface by passing the fabric under pressure between cylinders. The greater the heat and pressure, the higher the luster. Calender finishes include ciré, glazing, moiré, and schreinering. • Ciré » Ciré is a highly polished fabric produced by impregnating the fabric with wax or a thermoplastic material and then passing it through friction rollers. The resultant fabric is highly lustrous and takes on a popular “wet look.” When thermoplastic fiber fabrics are ciré finished, the fabric becomes moderately water repellent due to flattening and partial fusing of fibers. Bureau Veritas Consumer Products Services 94
  • 6 Finishing Aesthetic Finishes 8 Finishing that Alter Fabric Luster • Glazing » A process that produces a smooth, high polish on the surface of the fabric. The material is treated with various materials including starch, paraffin, and shellac. Three rollers are used; the center roll is cotton-padded or paper, and the other two are metal. The metal rolls operate at a very high speed, and the other roll turns more slowly. The polish is created by the friction of the rolls. • Moiré » A moiré finish is characterized by a soft luster and an optical effect, which is created by interference between light rays reflected from the crushed and uncrushed parts of the fabric. Two layers of identical fabric are placed face to face and then subjected to heat and pressure whereby a pattern of parallel lines formed by the weft yarns of each fabric is impressed upon the weft yarns of the opposing fabric. Bureau Veritas Consumer Products Services 95
  • 6 Finishing Aesthetic Finishes 8 Finishing that Alter Fabric Luster • Schreinering » A finishing process where the fabric is passed under pressure between an engraved steel calender roller and a smooth roller. The engraved roller has 180- 360 fine lines embossed. This process flattens the fabric and produces fine lines on the surface which increases the light reflection to create a soft silk-like luster. Bureau Veritas Consumer Products Services 96
  • 6 Finishing Aesthetic Finishes 8 Finishing that Alter Fabric Luster ― Optical Finishes • Delusterants » A process of dulling the luster of manufactured fibers, yarns, or fabrics with pigments or chemical treatment. In most manufactured fibers, pigment is introduced in the spinning solution to reduce luster. Delusterants such as barium salts, zinc oxide, aluminum oxide and china clay can also be applied to yarns and fabrics. • Optical Brighteners » Optical brighteners are used in finishing to maintain white and bright fabrics. They adhere to the fabric and create an appearance of whiteness or brightness by the way they reflect light; they absorb ultraviolet light and reflect it as visible blue light. Bureau Veritas Consumer Products Services 97
  • 6 Finishing Functional Finishes 8 Finishing that Enhance Care Properties • Durable Press » This finish provides garments with shape retention, durable pleats and pressed creases, durably smooth seams, and wrinkle resistance. » There are two methods: 1) post-cure technique in which the garment rather than the fabric is cured and heat-set after construction or 2) flat or precured technique in which the piece goods are finished and cured. Almost all fabrics for durable press are blends of cellulosic fibers and polyester. Bureau Veritas Consumer Products Services 98
  • 6 Finishing Functional Finishes 8 Finishing that Enhance Care Properties • Soil Release » A finish that increases the absorbency of a fabric, and which makes it easier to remove soil and stains in washing. This finish (1) allows the stain to leave the fabric faster; (2) increases wicking action for greater comfort; (3) makes fabric dry-cleanable; and (4) maintains brightness after repeated laundering. • Stain- and Soil-resistant Finishes » Stain- and soil-resistant finishes resist staining. Stain- and soil-resistant finishes reduce the rate of soil deposition on a fabric either by creating an electric charge that repels the soil or by producing a smooth surface to which soil will not adhere. Fabrics treated with such finishes are therefore easily cleaned. Bureau Veritas Consumer Products Services 99
  • 6 Finishing Functional Finishes 8 Finishing that Alter Durability • Abrasion-resistant Finish » Abrasion resistance can be imparted by an acrylic resin; however, some resins are too soft to be effective and some are too hard and introduce brittleness to the fabric. These resins bind the fibers more firmly to the yarns. Some fiber such as nylon have inherent resistance to abrasion. Abrasion-resistant finishes are used on fabrics subject to prolonged abrasive wear such as pockets, waistband lining, and hatbands. • Slip-resistant Finishes » Finishes applied to a fabric to reduce or eliminate yarn slippage and reduce seam fraying are called antislip, slip- resistant, or nonslip finishes. Products such as rosins (they have poor washfastness), colloidal dispersions of silica (they reduce surface smoothness but are not durable), and formaldehyde resins (they are durable) are commonly used. Bureau Veritas Consumer Products Services 100
  • 6 Finishing Functional Finishes 8 Finishing that Alter Durability ― Shrinkage Control • There are Two Kinds of Fabric Shrinkage: » Relaxation Shrinkage This occurs because the fibers and yarns are under tension when the fabrics are made. Later when the fabric is wet in a tensionless condition, relaxation occurs. » Progressive Shrinkage This occurs each time a fabric is laundered. Unlike relaxation shrinkage which occurs only once, progressive shrinkage continues and the fabric shrinks a bit more with each laundering. Of the major fibers, only wool and viscose rayon are subject to progressive shrinkage. Bureau Veritas Consumer Products Services 101
  • ? ? Shrinkage Control 8 The factors that control shrinkage in fabrics or garments are: • Construction: A tighter fabric construction reduces potential shrinkage • Yarn twist: Optimum twist (based on yarn size) is very important for controlling shrinkage and torque. • Type of Weave or Knit: Pain weave of Jersey knit show more resistance to shrinkage than other types. • Tension During Sewing of Garments: Uneven or too much sewing tension can lead to differential shrinkage causing puckering in the seam areas. • Stability of Fiber and Yarns: Improper stabilization could lead to excessive shrinkage especially in blends where synthetic fiber shrinks differentially than the cellulosic fibers. Bureau Veritas Consumer Products Services 102
  • ? ? Shrinkage Control Illustration of Shrinkage on Woven Fabric Caused by Fiber and Yarn Swelling Loomstate Fabrics Fabric After Washing Bureau Veritas Consumer Products Services 103
  • 6 Finishing Functional Finishes 8 Finishing that Alter Durability ― Shrinkage Control • Compressive Shrinkage (Relaxation Method) » Used for woven cotton, tubular knit cotton, linen and rayon; the method consists of mechanically compressing the fabric lengthwise by overfeeding onto a large roller with damp blankets. Sanforized is a well known trade mark for fabrics treated by this method. • Heat Set (Relaxation Method) » Used for fabrics from thermoplastic fibers such as nylon, polyester and acrylic; it is based on the principle that thermoplastic materials will become stabilized in their configuration in which they happen to be when heated to their softening temperature. Bureau Veritas Consumer Products Services 104
  • 6 Finishing Functional Finishes 8 Finishing that Alter Durability ― Shrinkage Control • Sponging (Relaxation Method) » Used for woolen and worsted fabrics; it consists of thoroughly wetting the fabric with water or steam and allowing the material to dry slowly in a relaxed tensionless state. This does not make wool washable or shrink-proof; it permits wool to be steam pressed or caught in rain without severe shrinking. • Resin Treatments (Relaxation Method) » Used for fabrics of rayon and cotton; it involves impregnating rayon and cotton with resins and then curing which stabilizes the fabric and thus reduces its tendency to distort. Resins also provide crease resistance. It is preferable to hand wash resin treated rayon fabrics. Bureau Veritas Consumer Products Services 105
  • 6 Finishing Compressive Shrinkage Illustration of the Felt Blanket Machine Principle Felt Blanket Principle Bureau Veritas Consumer Products Services 106
  • 6 Finishing Compressive Shrinkage Diagram of the Rubber Belt Principle Rubber Belt Principle Bureau Veritas Consumer Products Services 107
  • Shrinkage Control 6 Finishing of Knit Fabrics Belt Principle for Imparting Mechanical Shrinkage for Knits Bureau Veritas Consumer Products Services 108
  • Shrinkage Control 6 Finishing of Knit Fabrics The Micrex Process 8 For open-width knit fabrics based on cavity type overfeeding Bureau Veritas Consumer Products Services 109
  • 6 Finishing Functional Finishes 8 Finishing that Provide Comfort and Safety • Antistatic » A finish that helps reduce or eliminate static buildup in fabrics. They are chemical compounds that, when applied to a fabric, reduces or eliminates the accumulation of static electricity. This may be added to the fiber lubricant or to yarn during spinning, by spraying, or in a final rinse, or in pad dyeing. Fabric softeners used in home laundering also reduce static. • Chemical-protective Finishes » These are finishes that prevent penetration of herbicide or pesticide through clothing and prevent easy removal by laundering of any pesticide on the surface of clothing. All cotton fabrics are better than polyester because pesticides are absorbed by polyester but not cotton. Bureau Veritas Consumer Products Services 110
  • 6 Finishing Functional Finishes 8 Finishing that Provide Comfort and Safety • Flame Retardant Finish » For most part, fabrics treated with these finishes burn in the direct path of flame but self-extinguish when the source of flame is removed. » Unfortunately, use of these finishes result in stiffening and loss of fabric drapability, strength loss, loss of finish in laundering (nondurable), and ineffectiveness when laundered in household bleach, soaps, or water softeners. » Some of the commonly used flame-retardant treatments include Pyrovatex CP (for cellulose and its blends), THPC (used extensively for children’s sleepwear), Firestop (trademarked by Cotton Incorporated; used in cellulose and its blends), Fyrol 76, TM-DABT (for 100% cotton and poly- cotton blends), Proban (cellulose blends), Spartan, Flamegard, Glotard, Fireway, Caliban, and Protogard. Bureau Veritas Consumer Products Services 111
  • 6 Finishing Functional Finishes 8 Finishing that Provide Comfort and Safety • Water and Stain Repellent Finishes » They are chemical finishes that resist the penetration of water through the fabric but permit the passage of air or moisture. The principle behind this ability is that yarns rather than fabric are coated with repellent chemicals. Water repellent finishes can be non-durable, durable, and renewable.The principle types include wax emulsions, resins (renewable), silicone compounds (durable), and zirconium compounds (non-durable). • Waterproof Finishes » These are finishes that resist wetting and the penetration of water. Waterproof fabrics are generally woven tightly and coated with rubber, plastic (usually vinyl), linseed oil, cellulose esters, or other compounds. Fabrics are non-permeable to air, possess a firm non-drapable hand and are not comfortable as wearing apparel. Bureau Veritas Consumer Products Services 112
  • 6 Finishing Functional Finishes 8 Finishing that Provide Environmental Protection • Antimicrobial Finish » They are applied to fabrics to prevent growth of microorganisms. They thereby control the spread of disease and reduce the danger of infection; help to inhibit the development of unpleasant odors from perspiration and other soils; and reduce damage to fabrics from mildew- producing fungi and rot-producing bacteria. These finishes may be durable or renewable. Pacificate and Sanitized are two well known trademarks for this finish. • Fume Fading Inhibitors » Some colors fade, particularly disperse dyes on acetate, caused by exposure to oxides of nitrogen in the atmosphere. Simple alkaline substances such as borax are sometimes used as after-treatments, but they are not permanent. Bureau Veritas Consumer Products Services 113
  • 6 Finishing Functional Finishes 8 Finishing that Provide Environmental Protection • Metallic and Plastic Coatings » Metallic and plastic coatings are applied to the back of fabrics. Aluminum coatings, modify the warmth and coolness of fabrics, are used for drapery lining. Plastic coatings help reduce the amount of soil that penetrates the fabric and delay the passage of heat through the fabric. One problem with coatings are they may peel or crack off the substrate. • Mothproofing Finish » Moth larvae and carpet beetles are known to attack animal-fiber fabrics. Mothproofing is a chemical that is added to the dyebath during dyeing of wool fabrics. Treated wool fabrics and silk fabrics are less susceptible to damage by moths and other insects. Finishes based on pyrethroids and pyrimidines are among the most successful products used for mothproofing. Bureau Veritas Consumer Products Services 114
  • 6 Finishing Nano-Care 8 The principles of nanotechnology are utilized to create exceptional performance in everyday items: apparel, home furnishings, commercial interiors, industrial fabrics. 8 Nanotechnology provides the ability to work on a nano or submicron scale to create intelligent structures that are stronger and have fundamentally different, performance-enhancing molecular organizations. 8 NANO-CARE® fabric protection imparts a revolutionary, carefree quality to wrinkle resistant fabric that minimizes stains, offers superior liquid repellency and maintains wrinkle resistance. NANO- CARE® enhanced fabrics cause water and oil spills to bead up and roll off fabric without penetrating the fibers. Bureau Veritas Consumer Products Services 115
  • 6 Finishing Nano-Care 8 Key Features • Superior Stain, Water, And Oil Repellency • Resists Wrinkles • Breathable Fabric • Preserves Original Hand • Easy Care • Durable Performance Bureau Veritas Consumer Products Services 116
  • QUESTIONS ? 117