Essential Terms and Definition of Dyeing (Part-2)

Dyeing Glossary | Essential Terms and Definition of Dyeing (Part-2)
Rana Sohel
Production Officer (Dyeing)
Sunman Textile Mills Ltd. Chittagong
Cell: +8801912-420118
Email: rsohel07tex@gmail.com



Introduction:
In previous part of dyeing terms, we have discussed about importance of dyeing glossary and its application. In this part we will discuss on more dyeing terms and definition. Which are very usable in student and job life.
dyeing terms
Essential Terms and Definition of Dyeing:

Indigo: Originally a natural blue vat dye extracted from plants, especially the indigofera tinctoria plant. Most indigo dyes today are synthetic. They are frequently used on dungarees and denims.

Ingrain dye: A colorant, which is formed, in situ, in the substrate by the development and coupling of one more intermediate compounds. The term was originally used for colorants obtained from oxidation bases and by azoic techniques, but is now reserved for other types of colorant formed in situ.

Inhibitor: A substance that retards or prevents a chemical or physical change. In textiles, a chemical agent that is added to prevent fading, degradation, or other undesirable effects.

Isoelectric: Same charge in a certain condition. When positive and negative charges are equal. The isoelectric point is pH value at which the molecule carries no electrical charge or the negative and positive charges are equal.

Isotherm: Constant temperature line used on graphs of climatic conditions or thermodynamic relations, such as pressure-volume relations at constant temperature.

Jet dyeing machine: A high-temperature piecedyeing machine that circulates the dye liquor through a Venturi jet, thus imparting a driving force to move the fabric. The fabric, in rope form, is sewn together to form a loop.

Kier: A large metal tank, capable to being heated uniformly, used for wet processing.

Kier boiling: Process of boiling cellulosic materials in alkaline liquors in a kier at or above atmospheric pressure.

Laboratory sample: A portion of material taken to represent the lot sample, or the original material and used in the laboratory as a source of test specimens.

Leuco dye: A soluble, reduced form of a dye from which the original dye may be regenerated by oxidation.

Liquor ratio: In wet processing the ratio of the weight of liquid used to the weight of goods treated.

Lot: A unit of production or a group of other units or packages that is taken for sampling or statistical examination, having one or more common properties and being readily separable from other similar units.

Metal-complex dye: A dye having a coordinated metal atom in its molecule. Unless the term metal-complex dye is used in direct association with a particular application class of dye, e.g. metal-complex disperse dye or metal-complex reactive dye, its use is inexact and inadvisable.

Migration: Movement of an added substance (e.g. dye or alkali) from one area to textiles to another. Commonly used to express the movement of color from the dyed area to the undyed area of cloth.

Mock Dyeing: A heat stabilization process for yarns. The yarns are wound onto packages and subjected to package dyeing conditions (water, pressure, temperature) but without dye an chemicals in the bath.

Mordant: A chemical used in some textile fibers to provide affinity for dyes. Or a substance, usually a metallic compound, applied to a substrate to form with a dye a complex which is retained by the substrate more firmly than the dye itself.

Mordant dye: A dye that is fixed with a suitable mordant.

Natural Dyes: Dyes made from natural substances, usually from the bark, leaves, roots, flowers, or wood of a plant. There are also insects, notably cochineal and lac, that make dyes.

Optical Brightener: A colorless compounds that, when applied to fabric, absorbs the ultraviolet radiation in light but emits radiation in the visible spectrum.

Over Dye: When one dye is dyed over another. Indigo is often used as an over dye. This term is sometimes used for dyeing over naturally colored fibers.

OWB: On the weight of bath.

OWF: On the weight of fabric/fibre

OWG: On the weight of goods.

OWV: On the weight of value.

Pad: A machine for impregnating fabrics with chemicals. It consists essentially of a trough followed by two or more pairs of squeeze rolls.

pH: Value indicating the acidity or alkalinity of a material. It is the negative logarithm of the effective hydrogen ion concentration. A pH of 7.0 is neutral; less than 7.0 is acidic; and more than 7.0 is basic.

Pick-up: % or weight added per unit weight of fabric.

Pigment: A substance consisting of small particles that is insoluble in the applied medium & is used primarily for its coloring properties.

Pigment printing: In pigment printing insoluble pigments which have no affinity for the fibres are fixed on the textiles with binding agent in the pattern required.

Premetallized acid dye: An acid dye manufactured by reacting an equivalent of a suitable metal ion with one equivalent of a dye, or with two equivalents of the same or different dyes, capable of chelating the metal.

Preparation: In textile manufacturing, those processing operations performed on greige fabric, colored fabric, textile yarns or fibers to ready them for dyeing, printing or finishing. For example, typical greige cotton fabric preparation includes singeing, desizing, scouring, bleaching and (optionally) mercerizing.

Reactive dye: A dye that, under suitable conditions, is capable of reacting chemically with a substrate to form a covalent dye-substrate linkage.

Reduction clearing (RC): The removals of unabsorbed disperse dye from the surface of polyester at the end of the dyeing or printing process by treatment in a sodium hydroxide/sodium hydrosulfite bath. A surface-active agent may be employed in the process.

Retarder (Retardants): A chemical that, when added to the dyebath, decreases the rate of dyeing but does not affect the final exhaustion.

Saponification: Specifically in relation to manufactured fibers, saponification is the process of removing part or all of the groups from acetate or triacetate fiber, leaving regenerated cellulose.

Saturation: The maximum intensity or purity of a color. If the color is as brilliant as possible, it is at saturation; if the color is subdued or grayed, it is dull, weak, and low in intensity.

Scouring: In textile processing, treatment of textile materials in aqueous or other solutions to remove nature fats, waxes, proteins and other constituents as well as dirt, oil and other impurities.

Shade: A common term loosely used to describe broadly a particular color or depth, e.g. pale shade, 2% shade, mode shade, fashion shade.

Shading: In colored textile fabrics, gradual changes in hue, chroma and/or lightness lengthwise or widthwise. When unintended, shading is considered a defect; may be international for styling purposes.

Sizing: A generic term for compounds that are applied to warp yarn to bind the fiber together and stiffen the yarn to provide abrasion resistance during weaving, Starch, gelatin, oil, wax and manufactured polymers such as polyvinyl alcohol, polystyrene, polyacrylic acid, and polyacetates are employed.

Soap: Soap is a metallic salt of saturated or unsaturated higher fatty acid. There may be pb, Mg, Ca or other metallic salts.

Softener: 
  1. A product designed to impart a soft mellowness to the fabric. Examples are glucose, glycerine, tallow, or any one of a number of quaternary ammonium compounds.
  2. A substance that reduces the hardness of water by removing or sequestering the calcium and magnesium ions.
  3. A substance used to reduce friction during mixing and processing when dry powders are added to polymers.
Solubilized sulfur dye: A thiosulfuric acid derivative of a sulfur dye which during dyeing is converted to the substantive alkali-soluble thiol form.

Solubilized vat dye: A water-soluble salt of the sulfuric ester of a leuco vat dye. After application to the fiber the parent vat dye is regenerated by hydrolysis and oxidation.

Solvent dye: A dye which is soluble in organic solvents, but not in water, and is widely used in lacquers, inks, waxes, plastics, soaps, cosmetics, fuels and colored smokes.

Solvent Dyeing: The use of solvents as dye bath media instead of water becomes quite a popular concept, where solvent carries the dye molecules to the interior of fibre & then recovered. Introduction of Hydrophobic fibres like cellulose acetate has pronounced dyeing problem as no synthetic & natural dye at that time , are capable of dye it.

Souring: Any treatment of textile materials in dilute acid. Its purpose is the neutralization of any alkali that is present.

Space Dyeing: The process of applying multiple dyes to damp fiber then heat setting it, usually by steaming or baking. Brushes can be used, but tools for pouring or squirting are often more effective.

Substantivity: The attraction, under the precise conditions of test, between a substrate and a dye (or other substance) where the latter is selectively extracted from the application medium by the substrate.

Substrate:
  1. In textiles, a fiber, fiber assembly, yarn, fabric or garment to which another material is applied.
  2. Fabric to which coatings or other fabrics are applied. It can be of woven, knit, nonwovens, or weft-insertion construction. Generally, substrate properties are dependent both on fiber type and fabric construction. Usually the fabric is scoured, heat-set and otherwise finished prior to coating or bonding. Many smooth-surfaced manufactured fiber fabrics require impregnation with a latex prior to coating to ensure adequate adhesion.
Sulfur dye: A dye, containing sulfur both as an integral part of the chromophore and in attached polysulfide chains, normally applied in the alkali-soluble reduced (leuco) form from a sodium sulfide solution and subsequently oxidized to the insoluble form in the fiber.

Surfactant: An agent, soluble or dispersible in a liquid, which decreases the surface tension of the liquid contraction of “surface active agent”

Thickener: Thickener is a thick mass which impart stickiness & plasticity to the printing paste so that it may be applied on the fabric surface without bleeding or spreading & be capable of maintaining the design outline.

Uneven dyeing: A fabric dyeing that shows variations in shade resulting from incorrect processing or dyeing methods or from use of faulty materials.

Union dyeing: A process of dyeing textiles containing fibers having different dye affinities to achieve the appearance of a uniform, homogenous color.

Unlevelness: In textile dyeing and finishing, non-uniform distribution of a dye or chemical in or on a substrate.

Vat dyes: A water-insoluble dye, usually containing keto groups, which is normally, applied to the fiber from an alkaline aqueous solution of the reduced enol (Leuco) form which is subsequently oxidized in the fiber to the insoluble form.

Wash fastness: A measure of resistance to fading by laundering. Different dye types are measured at different temperatures. Wash Fast/Jacquard brand dyes are rated at 105F°, while more washfast dyes types like Lanaset/Sabraset are rated at 140F°.

Wet pick-up: In textile processing, the amount of liquid, and material carried by the liquid, applied to a textile. Wet pick-up is usually determined as a percentage of either the dry or conditioned weight of the textile prior to processing.

Wetting agent: It is a chemical substance that increases the spreading & penetrating properties of a liquid by lowering its surface tension that is the tendency of its molecules to adhere to each other.

What is stain resistance finish: It is the finish to prevent water & or oils from penetrating the fabric using potential aqueous & oily stain to bead up & roll off.

What is soil release finish: Soil release is the term used to describe clean ability of fabrics by the laundering process.

What is antimicrobial finished: Antimicrobial finish is one kind of chemical finish which is improve fabric durability on various substrates, impact on people & their environment, they interact with good & bad microorganism.

What is textile finishing: Finishing has been defined by textile instate as “Descriptive of processes, physical or chemical, applied to a substrate to produce a desired effect”. It is chemical or mechanical treatments performed on fibre, yarn or fabric to improve appearance, texture, or performance.

What is Calender: A machine in which heavy roller rotates in contact under presser, used to smooth & flatten fabric to close the intersections between the yarns & to confer a surface glaze.

What do you mean by DP & Curing: DP means Durable Press OR Permanent press, it is a finishing treatment designed to impart to a textile material or garments the retention of specific contours including defined creases & pleats resistant to normal usage, washing or dry.

Curing is a process following application of a finish to textile fabrics in which appropriate conditions are used to effect a chemical reaction.

Why foam is used?: In wet processing technology cost is very high mainly due to high consumption of energy which itself is the result of high consumption of water. The idea of replacing water in the use of foam reduces the total processing cost by reducing these costs- 1. Heating cost. 2. Effluent treatment cost. 3. Chemical & dye stuff cost

Wet pick-up: The weight of liquor taken up by a given weight of the fabric after impregnation, spraying, or coating element.

Wicking: The passage of liquids along or through a textile material or along the interstices formed by textile element & coating polymer of a coated fabrics.

Wrinkle recovery/resistance: A laboratory test to measure angle (degrees) of recovery from wrinkling or creasing. 
 
 
 

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