ζ-Potentials of Synthetic Fibers in Aqueous Solutions of Sodium Alkyl Sulfates and Viscosities of Their Solutions

Abstract

Abstract In order to study the surface-adsorption behavior of anionic surfactants on fibers, the ζ-potentials of some synthetic fibers in aqueous solutions of sodium alkyl sulfates and their mixtures mainly above the critical micelle concentration (CMC), were measured. Further, the viscosities of aqueous solutions of pure surfactants were determined. Consequently, it can be presumed, on the basis of the viscosity data, that the structure of the micelles of these agents varies at the break of the ηspm⁄cm vs. cm curve. The ζ-potentials (negative) of fibers in aqueous solutions of the agents rapidly changed with an increase in the agent concentrations, but it remained nearly constant above the CMC. At much higher concentrations, the ζ values gradually changed; thereafter, passing a break or a minimum, they became approximately constant again. The concentration at the break or the minimum observed nearly corresponded to that at the break of the ηspm⁄cm vs. cm curve. It may, therefore, be suggested that the change in ζ-potentials at high concentrations is connected with that in the structure of the micelles. The ζ-potentials (negative) of fibers in aqueous mixed solutions changed sharply with an increase in the concentration of the mixtures and thereafter, passing a maximum in the vicinity of the CMC, complicatedly changed as the total concentrations and mixing ratios changed.