Rheology of oil-in-water emulsions with added solids

Abstract

This paper presents experimental results on the rheology of oil-in-water emulsions with added solids. The oil used was a refined mineral oil (Bayol-35). The oil concentration, solids-free basis, was varied up to 70% by volume. The added solids were irregular shaped silica sand and spherical glass beads. The size of the solids was varied from 9 to 44 μm. The solids volume fraction was varied up to 0.2 of the total mixture. When the oil concentration was 40% or below, the solids-free emulsions behaved as Newtonian fluids; above 40%, these emulsions exhibited shear thinning behaviour. The addition of solids to the emulsions increased their viscosity and enhanced their non-Newtonian behavior. The type of added solids played an important role. Solids of irregular shape (silica sand) gave a much higher viscosity than the spherical solids (glass beads) at the same solids volume fraction. For given oil and solids concentrations, the smaller solids gave a higher viscosity than the larger solids. This effect was observed for both silica sand and glass beads. The data analysis indicated that the studied emulsion can be treated as a continuous phase towards the solids when the ratio of the solid particle size to the oil droplet size is greater than 3.