Emulsions examined with interfacial studies

Foams and Emulsions Examined with Interfacial Studies. 222... 

FOAMS AND EMULSIONS EXAMINED WITH INTERFACIAL STUDIES... 

In a separate experimental study, Aronson and Petko [90] also observed an increase in yield value with increasing salt concentration, for w/o HIPEs. However, the interfacial tension of the emulsions was seen to decrease with addition of a number of electrolytes to the aqueous phase, in contrast to observations made by Pons et al. The reason for this discrepancy is not clear, but may be due to different interactions between the different surfactants and salts used by each group. It is hinted that the increase in yield value on addition of salt, as observed by Aronson et al., is due to a decrease in average droplet size however, this was not examined extensively, and determination of droplet diameters was by optical microscopy only. 

The non-aqueous HIPEs showed similar properties to their water-containing counterparts. Examination by optical microscopy revealed a polyhedral, poly-disperse microstructure. Rheological experiments indicated typical shear rate vs. shear stress behaviour for a pseudo-plastic material, with a yield stress in evidence. The yield value was seen to increase sharply with increasing dispersed phase volume fraction, above about 96%. Finally, addition of water to the continuous phase was studied. This caused a decrease in the rate of decay of the emulsion yield stress over a period of time, and an increase in stability. The added water increased the strength of the interfacial film, providing a more efficient barrier to coalescence. 

---