CONCENTRATED EMULSIONS - INVESTIGATION OF POLYDISPERSITY AND DROPLET DISTORTION AND THEIR EFFECT ON VOLUME FRACTION AND INTERFACIAL AREA

Concentrated emulsions with 0.7 < ϕ < 0.9, where ϕ = volume fraction of internal phase, may be produced, in principle, through polydisperse packing of droplets and/or through distortion of the same. By use of an ideal fcc configuration, it is shown that a volume fraction as high as 0.89 may be achieved with spheres of three sizes. Incorporation of a fourth size leads to virtually no further increase in ϕ. Emulsions with higher ϕ (up to 0.98) may also be obtained through progressive distortion of monodisperse droplets. Plots of normalized total interfacial area vs ϕ have been derived for the above cases, keeping the average droplet size constant for the sake of comparison. Experimental studies on emulsion explosive compositions- with paraffin oil as continuous phase, sorbitan monooleate as emulsifier, and aqueous inorganic oxidizer salts as internal phase-indicate that both modes of packing are plausible at ϕ ~ 0.88. Our results suggest that early stages of emulsification favor formation of polydisperse spheres while the droplets exhibit increasing distortion with droplet comminution. The latter effect is best understood in terms of increasing mono-dispersity of droplets upon sustained refinement. © 1990, American Chemical Society. All rights reserved.