THE INFLUENCE OF THE FILM CONTACT ANGLE OF EMULSION DROPLETS ON THE DISPERSIBILITY OF THEIR SEDIMENTS.

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Abstract
In certain W/0 emulsions, the films between the flocculated water droplets and the adjoining menisci show a very large contact angle θ. Because this phenomenon indicates a strong interaction of the droplets, we investigated its influence on the redispersion of sediments formed in such emulsions. Two models describing the yield stress of such sediments were developed using calculations that relate the yield stress of a string of emulsion droplets to the value of θ. The first model estimates the maximum yield stress that can be accounted for by capillary forces. The second model considers the yield stress of sediments consisting of droplet aggregates joined by single chains of droplets. These theories were found to describe satisfactorily cone penetration and redispersion experiments performed on two series of W/O emulsions that exhibited a wide range of values of Θ.