Anionic Surfactant-Water-Sodium Chloride Systems: Specific Refraction, Specific Volume and Viscosity

Specific refraction, specific volume and viscosity of the anionic surfactant-water-sodium chloride systems were studied, the surfactants in question being sodium alkylether-sulfate, sodium dodecylsulfate and sodium dodecylbenzenesulfonate, in a temperature range from 278 to 313 K.

Surfactant and sodium chloride concentrations up to 20% and 3% (W/W), respectively, were studied.

Rheological behaviour of the systems varies from Newtonian, in the systems with lower surfactant and sodium chloride concentrations, to pseudoplastic (Ostwald-type) and even viscoelastic when those concentrations are high.

It has been found an abnoimal behaviour in the systems containing sodium alkylether-sulfate, where the viscosity shows a maximum at 283 K. It is explained in terms of dehydration of the ethoxy groups as temperature increases.

The addition of sodium chloride increases the dynamic viscosity of the systems, except in AES/water systems at low sodium chloride concentration. This fact is explained considering the changes in micellar structure caused by the electrolyte.