Dependence of creaming and rheology of monodisperse oil-in-water emulsions on 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-hexadecane oil-in-water emulsions stabilized by sodium dodeycl sulfate (SDS) was studied. Creaming was monitored by measuring the back-scattered light from an emulsion as a function of its height. Apparent viscosity and shear modulus were measured using a dynamic shear rheometer. The creaming velocity of the 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 elastic characteristics and did not exhibit creaming when the droplet concentration exceeded about 40% because of close packing of the droplets. The viscosity and creaming behavior of monodisperse emulsions could be described using the same equations as for monodisperse suspensions. (C) 2000 Elsevier Science B.V. All rights reserved.