Sorption-diffusion in heterogeneous systems. Part 4.—Dyeing rates in organic fibres

Abstract

Earlier papers of this series have presented an analysis of sorption behaviour in media where diffusive entry interacts with processes of immobilization. Observed dyeing rates in cellulose as well as synthetic fibres are examined using that analysis. The magnitudes of the observed rates, for many dye species and fibre materials, are consistent with a model whereby dye molecules are mobile in solvent(water) within that volume fraction of the fibre capable of containing it, and are immobilized on or in hydrophobic regions of the polymer. The model consistently yields a diffusion coefficient for the mobile solute equal in magnitude to the classical dye-in-water diffusivities. Occasional reduction below this magnitude appears to occur due to size inhibition, when molecular size approaches the dimensions of solvent-containing channels.