Creaming stability of flocculated monodisperse oil-in-water emulsions

The influence of droplet flocculation on the creaming stability of monodisp erse n-hexadecane oil-in-water emulsions was studied. The creaming velocity of emulsions with different droplet radii (0.43 and 0.86 mu m), droplet co ncentrations (1-67 vol%), and sodium dodecyl sulfate (SDS) concentrations ( 7-80 mM) were measured. Depletion flocculation was observed in the emulsion s when the aqueous phase SDS concentration exceeded a particular level (sim ilar to 40 mM for 0.43-mu m droplets and similar to 15 mM for 0.86-mu m dro plets). Creaming was monitored by measuring the back-scattered light from a n emulsion as a function of its height. The creaming velocity increased wit h increasing flocculation and decreased with increasing droplet concentrati on. These results have important implications for the formulation of emulsi on-based materials. (C) 2000 Academic Press.