Flow behavior of sucrose stearate/water systems

Abstract

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°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.