Sulphur Dyes – There are two main sorts of colourants: pigments and dyes. Dyes are either soluble within the dyeing medium (e. g. water) or can dissolve into the textile substrate. Pigments are neither soluble within the dyeing medium nor can dissolve into the substrate. Both pigments and dyes are often natural or synthetic. Colourants from natural sources like plants are obtained since pre-historic times.
From the appliance point of view, dyes are classified into different groups, each group being suitable surely sorts of textile substrates. Some commonly used dyes and their suitability for various fibres, for instance, the foremost commonly used sort of dye for cotton, polyester and acrylic are reactive dyes, disperse dyes and basic dyes, respectively.
These are named so due to the presence of sulphur atoms in their molecules. Like direct dyes, dyes also are quite cheap for dyeing cellulosic textiles with limited colour fastness properties. differing types of dyes include:
- Sulphur dyes
- Leuco sulphur dyes
- Solubilized sulphur dyes
- Condensed sulphur dyes
The commonly used sulphur dyes aren’t soluble in water and wish to be converted into a soluble form. By reduction with the assistance of a reducer and an alkali. These are usually easier to scale back and harder to re-oxidized as com-pared to vat dyes. General phases within the dyeing of cellulosic materials with sulphur dyes include:
Reduction: conversion of the water-insoluble dye into a soluble form, within the presence of a reducer and alkali
Application: absorption of solubilized sulphur dye by the textile substrate
Rinsing: removal of any loose colour from the substrate before oxidation
Oxidation: conversion of the dye absorbed by the textile substrate back to the insoluble form
Soaping: for increased colour brightness and fastness of the ultimate shade.
Fair Degree Of Sunshine Fastness
It has a fair degree of sunshine fastness thanks to poor stability of the dye molecule to ultraviolet radiations present in sunlight which degrade the dye chromophore. Washing fastness of the dye is poor due to the inherent limitations of the sulphur dye chromophores.
With suitable after-treatment of the dyed textile materials. Unlike direct dyes, the colour range of dyes is sort of limited to black, brown, olive and blue shades. Moreover, dyes aren’t available in as bright colours as are available in other class of dyes. However, dyes are quite cheap and should be economical in dyeing as well as the deep black and navy shades.