Fluid density dependency of the partition coefficient of disperse dyes between synthetic fiber and supercritical CO2 in supercritical dyeing

The poly (ethylene telephthalate) (PET) and polypropylene (PP) fibers were dyed with two different disperse dyes in supercritical carbon (scCO(2)) flu id. The partition coefficients (K) of dyes between polymer phase and scCO(2 ) phase were calculated from the equiliburium dye uptake and the solubiliti es of dyes in scCO(2). A linear relation was found in the plots of the logK vs. log rho (F) (scCO(2) density). The slope roughly depended on solvation number of dye in scCO(2) for all polymer-dye systems. These thermodynamic analysis for the equilibrium dyeing offer some important information for th e dye selection, the design of the dyeing equipment, and the optimization o f dyeing process for the supercritical fluid dyeing. Furthermore, these res ults are applicable for impregnation processes of polymers using supercriti cal CO2.