Dyeing Mechanism Of Direct Dyes
by : Rahul Sharma
DYEING MECHANISM OF DIRECT DYES:
The dyeing mechanism for the application of direct dyes to cellulose fibre involves the adsorption, diffusion and migration over fibre. Several factors persuade the dyeing mechanism; however, most important is the cellulose fibre structure, morphology and the use of electrolytes. When the cellulosic fibre is immersed into water the amorphous regions of the fibre swell to produce small pores in the order of 20-100A units- the smaller size dye molecules diffuse into the fibre structure through these pores. The addition of electrolytes (e.g. Sodium chloride, sodium sulfate) assists the diffusion and exhaustion of direct dye anionic by neutralizing the negative surface charge of cellulosic fibers. Then the dye anions become affixed to the cellulosic fibre through hydrogen bonding and van der waals forces.
