The Role of Surfactant Concentration on the Aqueous Stability of a Mono-Azo Disperse Dye

Abstract

The aqueous stability of a mono-azo disperse dye (Resolin Red BBL) is measured as a function of concentration of sodium dodecylsulfate (NaDDS) at 95°C. The rates of dye solubilization, aggregation, and degradation are measured and related to the concentration of NaDDS and to the critical micelle concentration (CMC). Dye stability decreases sharply for concentrations of NaDDS greater than the CMC passing through a minimum at 0.2% NaDDS (2 X CMC) and increases for concentrations of NaDDS greater than 0.2%. The rate of dye solubilization at low surfactant concentrations (<0.3%) is observed to be very slow, taking 9 days to reach a stable dispersion for 0.2% NaDDS. The rate of dye solubilization is greatly increased by initially dissolving the dye in a volatile solvent, such as acetone, referred to as the solvent dispersion technique.