Shear and normal stresses in flow of highly concentrated emulsions

Several peculiarities of rheological behavior were found in a study of flow of highly concentrated (weight concentration of disperse phase up to 94%) emulsions. It concerns the absence of a wall slip, the shape of a flow curve, and unusually high normal stresses in the low shear rate domain. The study was conducted by using emulsions with different concentrations. A plateau in the shear rate dependence of normal stresses in the domain of low shear rates was found. Normal stresses at this plateau exceed shear stresses by several decimal orders. Then normal stresses sharply fall down and this moment correlates with an inflection in a flow curve. In aging of emulsions, normal stresses increase due to slow crystallization of super-cooled solution in a disperse phase.