Dyes are colored organic compounds that can color fibers and other materials. However, not all colored organic compounds can be used as dyes. Generally, to be used as a dye, the organic compounds need to have the following four conditions: (1) it must be able to dye a certain concentration of color; (2) It needs to have a certain binding force with the substrate; (3) It must be able to dissolve directly in water or to dissolve in water by chemical action; (4) The color it dyes on the substrate needs to have a certain durability and is not easy to fade or discolor. Dyes can be divided into two categories of natural dyes and synthetic dyes. The most natural dyes are derived from roots, berries, bark, leaves, wood, fungi and lichens. Synthetic dyes are produced from various chemicals and the great majority of dyes are obtained in this way because of their superior cost, optical properties, and resilience. And since 1856, the first synthetic dye, mauve, was discovered, many thousands of synthetic dyes have been prepared. At present, there are more than 7000 kinds of dyes produced in the world, and there are more than 2000 kinds of commonly used dyes. They are widely used in people's daily life, making the world colorful.

Classification and Applications

In addition to the division by source (natural and synthetic dyes), dyes can be divided into azo dyes, anthraquinone dyes, arylmethane dyes, indigo dyes, sulfur dyes, phthalocyanine dyes, nitro and nitroso dyes, stilbene dyes, heterocyclic dyes and many others, according to their chemical structure. However, the most common way of classification is according to their solubility and chemical properties, and dyes can be divided into direct dyes, acid dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, sulfur dyes, mordant dyes, etc. The structural characteristics of these dyes and their typical applications are shown in following table.

Dyes Dyes Dyes
DyesStructural CharacteristicsTypical Applications
Direct DyesDirect dyes are a class of water-soluble anionic dyes. Most of the dye molecules contain sulfonic acid groups, and some have carboxylic groups. The dye molecules and cellulose molecules are bound by van der Waals forces and hydrogen bonds.Direct dyes are mainly used in the dyeing of cellulose fibers, and can also be used in the dyeing of silk, paper and leather.
Acid DyesAcid dyes are a class of water-soluble anionic dyes. Acid groups, such as sulfonic acid group and carboxyl group, usually exist in the form of sodium salt in dye molecules.Acid dyes are applied to fibers such as silk, wool, nylon and modified acrylic fibers using neutral to acid dye baths.
Basic DyesBasic dyes are water-soluble cationic dyes. The early basic dyes have amino and other basic groups, often in the form of acid salts.Basic dyes are mainly applied to acrylic fibers, but find some use for wool and silk. Usually acetic acid is added to the dye bath to help the uptake of the dye onto the fiber. Basic dyes are also used in the coloration of paper.
Reactive DyesThis kind of dye contains active groups in its molecular structure, which can be covalently combined with hydroxyl and amino groups in the fiber molecules and firmly dyed on the fiber.Reactive dyes are mainly used in dyeing and printing of cellulose fibers, and can also be used in dyeing of wool and nylon fibers. They are by far the best choice for dyeing cotton and other cellulose fibers at home or in the art studio.
Disperse DyesDisperse dyes are a kind of non-ionic dyes with simple structure, low water solubility and small particles in the dye bath. The chemical structure of disperse dyes is mainly azo and anthraquinones, and there are also heterocyclic disperse dyes.Disperse dyes are mainly used for dyeing and printing polyester fibers, and can also be used for dyeing acetate fibers and polyamide fibers. When dyeing, the dye must be evenly dispersed in the dye solution with the help of a dispersant, and then dyeing all kinds of synthetic fibers.
Vat DyesVat dyes are mostly polycyclic aromatic compounds, and their molecular structure does not contain sulfonic acid group, carboxylic acid group and other water-soluble groups, which are essentially insoluble in water and incapable of dyeing fibers directly.Vat dyes are mainly used for dyeing cellulose fibers. When dyeing, they are reduced to water-soluble leuchromosomal sodium salt in an alkaline solution containing reducing agents (such as Na2S2O4, sodium disulfite), then dyed the fiber.
Sulfur DyesSulfur dyes are a class of dyes that are insoluble in water and are made by mixing and heating aromatic amines or phenolic compounds with sulfur or sodium polysulfide.Sulfur dyes are inexpensive dyes used to dye cotton with dark colors. Dyeing is achieved by heating the fabric in a solution of organic compounds (usually nitrophenol derivatives, and sulfides or polysulfides.).
Mordant DyesMordant dyes are acid dyes having chelating sites to form stable coordination complex with metal ions from metal salts (mordants).Mordant dyes can be used with wool, wool blends, silk, cotton, and certain modified-cellulose fibers.

Nowadays, the application of dyes is not limited to textile dyeing and printing, it has been widely used in many fields such as paint, plastic, paper, leather, photoelectric communication, food, medical treatment and so on. For examples, acid dyes are used to stain basic tissue proteins during microscopic examinations for diagnosis or research. In contrast, basic dyes are used to stain acidic components of the nucleus and other tissues.

Alfa Chemistry's Dyes Products

Alfa Chemistry's product line of dyes can be divided into two categories: dyes (high purity) and dyes (technical grade). Both of two categories contain a wide range of types of dyes. And these products are our star products, with extremely high quality and product consistency. Dyes (high purity) are usually recommended for research and experimental use or for some other purpose that requires high purity dyes. Dyes (technical grade) are usually recommended for industrial production or other areas. You can browse the product list below to find the dyes you need, or you can quickly find the dyes you need by searching for keywords such as product name and CAS number.

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