Dependence of creaming and rheology of monodisperse oil-in-water emulsionson droplet size and concentration

The influence of droplet concentration (1-67 vol.%) and size (r = 0.43 and 0.86 mu m) on the creaming stability and rheology of monodisperse n-hexadec ane oil-in-water emulsions stabilized by sodium dodeycl sulfate (SDS) was s tudied. Creaming was monitored by measuring the back-scattered light from a n emulsion as a function of its height. Apparent viscosity and shear modulu s were measured using a dynamic shear rheometer. The creaming velocity of t he emulsions decreased with increasing droplet concentration. The apparent viscosity of the emulsions increased with increasing droplet concentration, decreasing droplet size and decreasing shear stress. Emulsions gained elas tic characteristics and did not exhibit creaming when the droplet concentra tion exceeded about 40% because of close packing of the droplets. The visco sity and creaming behavior of monodisperse emulsions could be described usi ng the same equations as for monodisperse suspensions. (C) 2000 Elsevier Sc ience B.V. All rights reserved.