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Substantive dyes work best on textiles with high contents of cellulose, such as cotton. In contrast to direct dyes, wool and leather goods are dyed by the process of ion exchange, exploiting the cationic nature of proteins near neutral pH. The development of substantive dyes helped make mordant dyes obsolete. [2]
Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dye bath, at or near boiling point, with the addition of either sodium chloride (NaCl) or sodium sulfate (Na 2 SO 4) or sodium carbonate (Na 2 CO 3). Direct dyes are used on cotton, paper, leather, wool, silk and nylon.
The term "direct dye application" stems from some dyestuff having to be either fermented as in the case of some natural dye or chemically reduced as in the case of synthetic vat and sulfur dyes before being applied. This renders the dye soluble so that it can be absorbed by the fiber since the insoluble dye has very little substantivity to the ...
Some dyestuffs, such as indigo and lichens, will give good color when used alone; these dyes are called direct dyes or substantive dyes. The majority of plant dyes, however, also require the use of a mordant, a chemical used to "fix" the color in the textile fibres. These dyes are called adjective dyes or "mordant dyes". By using different ...
direct dye Same as substantive. dye Dyes are color-bearing organic compounds that can be dissolved in water or another liquid so that they will penetrate fibers. [19] dyebath A dyebath is a solution of dye and water or other liquid in which textiles are dyed. [20] dyed in the wool
Cationization of cotton enables salt free dyeing and enhances the dyeability of the substrate with anionic dyes such as reactive dyes and direct dyes. Water and salt consumption are one of the major problems in the dyeing especially cotton which leads to substantial environmental impact with extra time and cost. Secondly washing off the ...
Textile dyeing plants generate wastewater that contains synthetic (e.g., reactive dyes, acid dyes, basic dyes, disperse dyes, vat dyes, sulfur dyes, mordant dyes, direct dyes, ingrain dyes, solvent dyes, pigment dyes) and natural dyestuff, gum thickener (guar) and various wetting agents, pH buffers and dye retardants or accelerators.
Also called direct dyes, substantive dyes are employed for cellulose-based textiles, which includes cotton. The dyes bind to the textile by non-electrostatic forces. In another classification, azo dyes can be classified according to the number of azo groups. Trypan blue is an example of a direct dye, used for cotton.