NON-IDEALITIES IN THE RHEOLOGICAL BEHAVIOR OF SUSPOEMULSIONS

The viscous flow behaviour of four sets of suspoemulsions (mixtures of suspensions and emulsions) is investigated. Three sets were aqueous systems and one set was a non-aqueous system. In any given set the starting components, i.e. the pure suspension and the pure emulsion, had the same dispersed-phase concentration (volume fraction) and the same continuous-phase, and they were mixed in various proportions to obtain the suspoemulsions. The rheological behaviour of the pure emulsions, in all four sets, was nearly Newtonian. The pure suspensions were Newtonian, yield-pseudoplastic, yield-pseudoplastic, and shear-thickening, respectively. The suspoemulsions are found to exhibit non-ideal behaviour i.e., the viscosity of the suspoemulsions does not vary linearly with the volume percentage of emulsion droplets in the mixed dispersed-phase. Both positive and negative deviations from ideal behaviour are observed. The reasons for the observed non-ideal behaviour are discussed in terms of heteroflocculation (flocculation between emulsion droplets and solid particles), dilution, and screening effects.