Dyes and Chemicals

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Dyes Definition:
A class of materials used to render color to inks. As opposed to pigments, dyes are normally completely dissolved in the chemical vehicle. Substances that is dissolved in water and is used to color hair, cloth, leather, or other material. Dyes are chemical compounds that can attach themselves to fabrics or surfaces to give them colour. Most dyes are complex organic molecules and need to be resistant to many things such as the weather and the action of detergents. Indigo, otained from plants was being used by the Egyptians 5000 years ago, and natural dyes obtained from plants and animal sources are stil used today. In 1856, Perkin developed the first synthetic dye based upon aniline. The product used in the process of colouring a material Dyes are used in coloring pile materials such as wool, silk and cotton. There are two types of dyes: Natural Dyes and Synthetic Dyes. Any type of colorant that transfers color by dissolving in a solution. There are natural dyes, from plants such as beet root or walnut husk, and synthetic dyes. Colorants with names like "FD&C Red" are dyes that are approved for use in Foods, Drugs and Cosmetics. There are a limited number of dyes approved for use in cosmetics; some are natural, although most are synthetic. Synthetic or natural organic chemicals that are soluble in most common solvents. Characterized by good transparency, high tinctorial strength and low specific gravity.

Types of Dyes:
Acid Dyes:
Acid (anionic) dyes are water-soluble dyes applied to wool, silk, nylon, modified rayon, certain modified acrylic, and polyester fibers. Fibers that will be damaged by acids, such as cellulosics, cannot be dyed with this family of dyes. The dyes in this class vary in their chemical composition but all use an acid bath. These dyes produce bright colors and have a complete color range but colorfastness varies.

Azoic Dyes:
Azoic (naphthol) dyes are produced within the fiber of cellulose fibers. The fiber is impregnated with one component of the dye, followed by treatment with another component, thus forming the dye. When the two components are joined under suitable conditions (a low temperature water bath is employed) a large, insoluble, colored molecule forms within the fiber. Because the color is within the fiber, colorfastness is excellent. Excess color on the outside of the fiber will rub off (crock) if not removed.

Basic Dyes:
Basic (cationic) dyes are very bright but have poor colorfastness; they have limited use on cellulosic and protein fibers. Wool and silk can be dyed by basic dyes in a dye bath containing acid. Cotton fibers can be dyed by basic dyes but only in the presence of a mordant, generally a metallic salt. The colored portion of the dye molecule carries a positive charge. Basic dyes are relatively colorfast on acrylic fibers. Nylon and polyester fibers that have been modified to accept basic dyes will exhibit excellent colorfastness. The first synthetic dye, mauveine, belongs in this class.

Direct Dyes:
Direct (substantive) dyes are soluble and have an affinity for cellulose fibers. An electrolyte, salt, is added to the dye bath to control the absorption rate of the dye by the fiber. The dye is absorbed by the fiber; colorfastness to light is good but colorfastness to laundering is not. Direct dyes are best used when wet cleaning is restricted. Developed direct dyes are those that are developed on the fabric after dyeing. They produce an insoluble dye that forms a chemical bond with the fiber molecules. Developed direct dyes have better wash fastness but poorer light fastness as compared with direct dyes. Both are used on lower-cost fabrics.

Disperse Dyes:
Disperse dyes were first developed to dye acetate fibers. Hydrophobic fibers have little affinity for water-soluble dyes. A method to dye hydrophobic fibers by dispersing colored organic substances in water with a surfactant was developed. The finely colored particles are applied in aqueous dispersion and the color dissolves in the hydrophobic fiber. Disperse dyes are the best method for dyeing acetate and polyester. Acrylic, aramid, modacrylic, nylon, olefin, and polyester are dyed by dispersed dyes; colorfastness is good to excellent.

Pigment Dyes:
Pigment dyes are not dyes but insoluble coloring particles. Pigments are added to the spinning solution (the liquid fiber before extrusion) of synthetic fibers and become an integral part of the fiber. Colorfastness is excellent. Pigments are also printed on fabric using resin binders. The adhesive attaches the color to the fabric. Colorfastness is dependent on the binder or adhesive used rather than the pigment. Pigment printing is an economical and simple means of adding color to fabrics.

Reactive Dyes:
Reactive (fiber-reactive) dyes combine with fiber molecules either by addition or substitution. The color cannot be removed if properly applied. Colors are bright with very good colorfastness but are susceptible to damage by chlorine bleaches. Reactive dyes color cellulosics (cotton, flax, and viscose rayon), silk, wool, and nylon. Reactive dyes are used in conjunction with disperse dyes to dye polyester and cellulosic fiber blends. They were introduced to the industry in 1956.

Sulfur Dyes:
Sulfur dyes are insoluble but become soluble in sodium polysulphide. They have excellent colorfastness to water. Another advantage is their low cost and ease of application. Dark shades-black, brown, navy blue-are typical of sulfur dyes. Newer sulfur dyes are available in brighter colors. They perform well if correctly applied. They are susceptible to damage by chlorine bleaches. Sulfur dyes color primarily cellulosics, such as heavyweight cotton and viscose rayon.

Vat Dyes:
Vat dyes are insoluble in water but become soluble when reduced in the presence of an alkali. Oxidizing the dyed fabric produces a water insoluble dye. The term vat dyes is derived from the large vessels used to apply the dye. The first synthetic indigo dye, introduced to the industry in 1896, belongs to this class. Vat dyes have an incomplete color range but good to excellent colorfastness. They are primarily used to dye cotton work clothes, sportswear, prints, drapery fabrics, and cotton polyester blends.

Chemicals Definition:
Substances which are used in factories, farms and homes for a variety of purposes such as cleaning, painting, killing pests, and helping maintain vehicles. MIN chemicals include chemical elements, as well as a large array of compounds such as acids, bases, catalysts, explosives, and fuels. Examples of included chemicals are: excess mercury, chlorine, and laboratory chemicals. Small quantities of chemicals (eg, 100 pounds or less), such as those found in laboratories, are included. Special MIN chemicals are MIN chemicals that the team believed to be of particular stakeholder concern, including cost of storage or disposition; environment, health, or safety concerns; and regulatory concern. Elements and compounds that do not meet the definition of a MIN material and those elements and compounds explicitly covered by Some studies have pointed to exposure to estrogen-like chemicals that are found in pesticides and other industrial products as a possible increased risk of breast cancer. Substances used in or found by a chemical process. Pesticides and other sprays used to eradicate unwanted plants and animals in cultivated areas. A substance (ie element or chemical compound) obtained by a chemical process.

Advantages of Natural Dyes:
Minimal Environmental Impact:
Because they come from natural sources, natural dyes are not harmful to the environment, which makes it so appealing for consumers. Natural dyes are biodegradable and disposing them don’t cause pollution.

Natural dyes are obtained from renewable sources that can be harnessed without imposing harm to the environment.

Color pay-off:
If you’re going for a soft hue or soothing shade, natural dyes can help you achieve that look.

Some natural dyes, such as carmine found in lipsticks, will not cause harm or health problems when ingested.

Dyes and Chemicals