Flow-induced phase behaviour and structure development in aqueous emulsion of associative biopolymers

Abstract

A rheo-optical methodology, based on small angle light scattering and transmitted light intensity measurements, has been used to perform an in-situ and time-resolved investigation on the effect of simple shear flow on associative phase separation, morphology development, and the interfacial tension, using a water–acid gelatin–gum arabic system as a model. It is shown that above a critical shear rate, shear-induced mixing occurs at 45 °C at the length scales probed by the laser light. Shift of the phase diagram at a fixed shear rate (100 s −1) was determined. When flow is stopped after homogenization, phase separation occurs almost instantaneously. When subsequently applying a low shear rate, the structure coarsens due to coalescence of the dispersed droplets. Shear-induced mixing does not occur at 35 °C probably due to the sharp increase of the interfacial tension from 5.5·10 −5 N/m to 9.0·10 −5 N/m.