a. Vat Dyes: Vat dyes are insoluble organic compounds and do not have any substantivity to cellulose. These dyes are widely used for cellulose fibers and can also be used for protein and nylon fibers. They produce good color range but limited selection of orange, blue. Bright green are more popular in this class. Large amount of dyes are required to attain deeper shade.
b. Disperse Dyes: These dyes are largely used for dyeing of polyester material. Disperse dyes are Nonionic aromatic compounds with relatively low molecular weight and have an extremely low solubility in water. These dyes are available in the form of powders, granules, liquid or paste form. These dyes can be sublimize at higher temperature and this sublimation property of Disperse dyes at high temperature is used in the transfer printing and rapid dyeing process. Dyeing of polyester is generally carried out at high temperature and high pressure. These dyes are also used for heat transfer printing. Disperse dyes produces very good range of shades except dark blue and black. These dyes are having good -excellent fastness to perspiration, crocking and dry cleaning and Fair-Good fastness to light and washing. When these dyes are used on acetate, it exhibits poor fastness to light and subject to gas fading.
c. Sulfur Dyes: Sulfur dyes are widely used for cellulosic fibers for darker shades. Sulfur dyes are relatively easy to dye cellulosic fiber with good-to-excellent washes and lights fastness at a low cost. It produces a complete range of colors in “dull shade” and gives poor light fastness in pastel shades. These dyes are mainly used for dyeing black, brown, navy blue or olive, in medium to dark shades. Some yellows and blues shades are also available but there is only one red and a green dye. These dyes are also used for improving the wash fastness of the Direct dyed fabric called topping. Sulfur dyes are having good fastness to light, washing, dry cleaning and perspiration. These dyes have poor fastness to chlorine bleach. Sulfur dyed materials cannot be stored for longer periods.
