The dyeing of hydrophobic fabric
with disperse dyes may be considered as a process of dye transfer from a
liquire solvent ( water ) to a solid organic solvent(fibre).
Disperse dyes are added to water
with a surface active agent to form an aqueous dispersion. The insolubility of
disperse dyes enablethem to leave the dye liquor as they are more substantive
to the application of that to the dye liquor increases the energy of dye molecules
and accelerates the dyeing of textile fibres.
Heating the dye liquor swell the
fibre to some extent and assists the dye to penetrate the fibre polymer system.
Thus the dye nolecule takes its place in the amorphous regions of the
fibre.withine the fibre polymer system, the dye molecules are held by hydrogen
bonds and van der waals force.
The dyeing is considered to take
place in the following simultaneous steps :-
1)
Diffusion of dye in solid phase, into water by
breaking up into individual molecules. This diffusion depends on dispersibility
and solubility of dyestuff and is aided by the presence of dispersing agent and
increasing temperature.
2)
Adsorption of the dissolved dye from the
solution onto the fibre surface. This dyestuff adsoeption by in the dye bath
and that in the fibre.
3)
Diffusion of the adsorbed dye from the fibre
surface into the interior of the fibre substance towards the centre. In normal
condition, the adsorption rate is always higher than the diffusion rate. Abd this
is the governing step of dyeing.