Application Of Direct Dyes
by : Rahul Sharma
Application Of Direct Dyes:
Direct dyes are usually applied with the addition of electroylet or near the boil in the machine capable of runing at atmospheric pressure. But in HTPH dyeing machines it is carried out at temperatures above the boil in case of pure as well as blended yarns.
An additoin of alkali, usually sodium carbonate, may be made with acid-sensitive direct dyes and with hard water as well as to enhance the dye solubilisation. When cellulose is immersed in a solution of a direct dye it absorbs dye from the solution until equilibrium is attained, and at this stage most of the dye is taken up by the fiber. The rate of absorption and equilibrium exhaustion vary from dye ti dye. The substantivity of the dye for cellulose is the proportion of the dye absorbed by the fiber compared with that remaining in the dyebath.
