FLOW BEHAVIOR OF SUCROSE STEARATE WATER-SYSTEMS

The aim of this work was to carry out a rheological study of aqueous systems containing a nonionic surfactant derived from sugar. The compositions studied ranged from the micellar region up to the occurrence of fully developed liquid crystals. This study was carried out at 50-degrees-C. Systems up to 2% (wt) sucrose stearate exhibited a power-law decrease in the steady-state apparent viscosity with shear rate. At higher sucrose stearate concentrations, the flow curves exhibited two well-defined regions depending on shear rate, so that the apparent viscosities fitted the Carreau model A [Carreau, P.J., D. De Kee and M. Daroux, Can. J. Chem Eng. 57:135 (1979)]. The existence of three composition ranges is proposed. An increasingly stronger micellar structure, as surfactant concentration rises, extends up to 10% (wt) sucrose stearate. Between 15% and 35% (wt) sucrose stearate, the results obtained are consistent with the occurrence of a lamellar liquid-crystal dispersion in an isotropic micellar solution. The liquid crystalline content in the dispersion steadily increases with surfactant concentration up to reaching a fully developed lamellar liquid crystal at 40% (wt) sucrose stearate.