CTD 215 Lecture 19: Textiles Chapter 19 Preparation and Printing

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Clothing, Textiles and Interior Design
CTD 215

Preparation and Printing Fabric Preparation • Finishes applied to textile products prior to dyeing or other finishes are classified as fabric preparation finishes. What is Finishing? • Changes or enhances the… • • • Performance • Adds cost and time Typical Fabric Preparation for a Woven Polyester/Cotton Blouse or Shirting Fabric • Desizing: warp size is removed with enzymes • Singeing: • Shearing: cutting fiber ends. Reduces pilling • Cleaning: scouring • Biopolishing: cellulose enzyme treatments to clean fuzz from cellulose and blend fabrics • Bleaching: • • Mercerizing: fabric is momentarily immersed in strong NaOH solution while under tension, then rinsed • Tentering: drying a fabric to specific width and length. Yarns straightened Other Fabric Preparation Finishes That Are Specific for Certain Fabrics • Carbonizing: for wool fabrics to remove any cellulosic impurities • Fulling • Degumming: for silk textiles, to remove silk gum • Following these finishes, fabrics are usually dyed or printed, then other finishes are applied. Colorants • Color is the first thing that attracts the consumer to a textile Color • Goal: produce appealing, level, fast color on a product at a reasonable price with good performance and minimal environmental impact • History and background • Complex area: difficult to get color on fabric in uniform appearance (level) that will not fade, bleed, or alter appearance. Color Theory • Complex phenomenon: physics of light, chemistry of colored objects, biology of the eye, behavioral sciences, and aesthetics. ➢ Metamerism: a color matches with one light source, but not with any other light source ➢ Bezold effect: when two or more colors merge into one new color, i.e., small scale print or yarn dyed fabric viewed from a distance. Color Measurement • Assign numerical values to a color • Used to match color and sort shades ➢ Color matching developing a formula to reproduce a color ➢ Shade sorting occurs when a manufacturer groups fabrics by color so that all fabric of one color match Colorants • Organic chemicals that selectively absorb or reflect wavelengths of light in the visible range • Dyeing is the application of color to a textile product in an overall sense, while printing is the application of color to selected portions of a textile product according to an established design. • Materials which are capable of providing color are called colorants; there are two types of colorants, dyes and pigments. • Dyes are colorants which enter the textile fiber at the molecular level • Pigments are large agglomerates of colorant molecules which are far too large to diffuse into the fiber and hence need to be physically attached to the fabric surface. • Dyes typically can be dissolved or dispersed in water • Pigments are insoluble color particles that are held on the surface of the fabric • Pigments are attached to the surface of textile substrates with glues or binders, and so may be used without regard to fiber type. • Textiles may be dyed at any stage of product production, but pigment application is usually done to textiles in fabric form Ingredients in Pigment Paste • Opacifiers: produce good covering power; variety of lusters • Thickeners: prevents migration of paste • Thinners: keeps paste semi-fluid • Antibleeding agents: eliminates halo effect • Pigments: colored compound • Softeners: maintain soft hand of fabric. • Easier to match colors with pigments than with dyes Dyes • There are two categories of dyes: Natural and synthetic • Materials used along with colorants to enhance the application of the colorants to the textile produce are called auxiliaries. • Not all dyes are appropriate for all fiber types. Fiber (referred to as substrate) and dye need to be carefully matched for proper results • Fastness varies with dye and dye class • Components: ➢ Chromophore: colored part of molecule ➢ Auxochrome: alters color and provides bonding and solubility sites Types of Dyeing • Dope dye, solution dye, producer dye ➢ For manufactured fibers only ➢ Dyes or pigments added to the polymer or solution prior to spinning ➢ Fibers emerge from spinneret already colored ➢ Commonly used for olefin and acetate • Gel dyeing: add dye to wet spun fiber while in the gel state • Fiber dyeing, or stock dyeing ➢ For any staple fiber ➢ Dyes are applied to fiber before it is spun ➢ Blending of different colored fibers gives heather yarns ➢ Wool fiber dyeing is also called top dyeing ➢ Fiber dyed wool needed for production of tweed fabrics • Yarn dyeing ➢ For any fiber type ➢ Dyes are applied to packages of yarns wound onto perforated dobbins in package dyeing machines, or skins of yarn, or entire beams of yarn are dyed ➢ Beam dyed yarn is used in denim manufacture ➢ Dyed yarns are necessary for the production of any woven or knit striped or plaid fabrics (unless the pattern is printed on) ➢ Spaced dyed yarns: different colors along the length, made by squirting dye onto packages • Piece dyeing ➢ For any fiber type ➢ Dyes are applied to fabrics after they have been woven or knit ➢ Piece dyeing may be done by either batch (usually up to 10,000 yards) or continuous processes (very large yardages) ➢ This is a very economical method of dyeing • Garment dyeing ➢ Best for cellulosic fibers or nylon ➢ Dyes are applied to garments after they are manufactured ➢ Typically done for hosiery and panty hose, also becoming popular for casual apparel for “just in time” buying Dyes-Fiber Combinations • Cellulosic fibers (cotton, flax, rayon, lyocell, etc.) may be dyed with a variety of dye types, depending upon the results desired. ➢ Vat dyes: inexpensive, fairly bright shades, some fastness problems. Indigo is a vat dye. ➢ Sulfur dyes: inexpensive, fairly dull shades. Used in work cloths, some dyes tender fabric. ➢ Direct dye: fairly expensive, bright clear shades, poor washfastness generally ➢ Reactives: expensive, bright clear shades, best washfastness of any of these. • Wool, silk, nylon are most commonly dyed with members of the acid dye family. Cationic dyes are used with some successes for wool and silk, but light fastness is not as good as that of acid dyes in wool. ➢ Acid dyes give bright, clear shades with good leveling and fairly good wash-fastness and light fastness ➢ Acid premetallized dyes give somewhat duller shades with better wash- fastness and light-fastness, but are also the hardest to level. ➢ Neutral premetallized dyes give the dullest shades of the three with the best overall fastness, but are also the hardest to level. Used for men’s worsted suit fabrics because of high light fastness. Polyester • Polyester is the most dyed with disperse dyes, although a small quantity is dyeable with cationic dyes. Blends of regular polyester, cationic dyeable polyester, and rayon can give three different colors in the same dyebath, producing heather effects fabrics. Disperse dyes • Acrylic fibers are mostly dyed with cationic dyes, but a small amount is manufactured as acid dyeable. Disperse dyes may also be used, but brightness and fastness if infer
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