The Dyes are classified based on the fibres to which they can be applied and the chemical nature of each dye. Dyes are complex unsaturated aromatic compounds fulfilling characteristics like intense colour, soluability, Substansiveness and fastness. Dyes can be defined as the different type of colouring particles which differ in each type from the other in chemical composition and are used for colouring fabrics in different colours and shades which are completely soluble in liquid media.

In this page

  1. Type of Printing Dyes
  2. Characteristics of Textile Dyes

Type of Printing Dyes

Dyes may be classified in several ways (e.g., according to chemical constitution, application class, end-use). The primary classification of dyes is based on the fibers to which they can be applied and the chemical nature of each dye. Table 6 lists the major dye classes, fixation rates, and the types of fibers for which they have an affinity. Factors that companies consider when selecting a dye include the type of fibers being dyed, desired shade, dyeing uniformity, and fastness (desired stability or resistance of stock or colorants to influences such as light, alkali, etc) (FFTA, 1991).

Most commonly in use today are the reactive and direct types for cotton dyeing, and disperse types for polyester dyeing. Reactive dyes react with fiber molecules to form chemical bonds. Direct dyes can color fabric directly with one operation and without the aid of an affixing agent. Direct dyes are the simplest dyes to apply and the cheapest in their initial and application costs although there are tradeoffs in the dyes’ shade range and wetfastness (Corbman, 1975). Direct and reactive dyes have a fixation rate of 90 to 95 percent and 60 to 90 percent, respectively. A variety of auxiliary chemicals may be used during dyeing to assist in dye absorption and fixation into the fibers. Disperse dyes, with fixation rates of 80 to 90 percent, require additional factors, such as dye carriers, pressure, and heat, to penetrate synthetic fibers (Snowden-Swan, 1995; ATMI, 1997). Disperse dyes are dispersed in water where the dyes are dissolved into fibers. Vat dyes, such as indigo, are also commonly used for cotton and other cellulosic fibers.



Characteristics of Textile Dyes

Dye Class Description Method Fibers Typically Applied to Typical Fixation (%) Typical Pollutants Associated with Various Dyes
Acid water-soluble anionic compounds Exhaust/ Beck/ Continuous (carpet) wool, nylon 80-93 color; organic acids; unfixed dyes
Basic water-soluble, applied in weakly acidic dyebaths; very bright dyes Exhaust/ Beck acrylic, some polyesters 97-98 N/A
Direct water-soluble, anionic compounds;can be applied directly to cellulosics without mordants (or metals like chromium and copper) Exhaust/ Beck/Continuous cotton, rayon, other cellulosics 70-95 color; salt; unfixed dye; cationic fixing agents; surfactant; defoamer; leveling and retarding agents; finish; diluents
Disperse not water-soluble High temperature exhaust Continuous polyester, acetate, other synthetics 80-92 color; organic acids; carriers; leveling agents; phosphates; defoamers; lubricants; dispersants; delustrants; diluents
Reactive water-soluble, anionic compounds; largest dye class Exhaust/ Beck Cold pad batch/ Continuous cotton, other cellulosics, wool 60-90 color; salt; alkali; unfixed dye; surfactants; defoamer; diluents; finish
Sulfur organic compounds containing sulfur or sodium sulfide Continuous cotton, other cellulosics 60-70 color; alkali; oxidizing agent; reducing agent; unfixed dye
Vat oldest dyes; more chemically complex; water-insoluble Exhaust/Package/ Continous cotton, other cellulosics 80-95 color; alkali; oxidizing agents; reducing agents