Coexistent phases in concentrated polydisperse emulsion flocculated by non-adsorbing polymer

We report a study of the creaming behavior of an alkane-in-water emulsion at varying oil volume fractions in the presence of the nonadsorbing polymer, hydroxyethylcellulose (HEC). Pairwise interaction potentials predict a shallow secondary minimum for this system arising from the attractive potential produced by the so-called depletion effect. Use of an ultrasonic creaming monitor has allowed us to verify the predicted flocculation and quantify the separation of the system into colloidrich and colloid-poor phases. The phase diagram for 20.2% v/v oil and varying polymer concentrations has been determined. At 0.02% w/w HEC we have investigated the effect of oil volume fraction on the phase composition of the system. The observed behavior has been compared with that predicted from the available theoretical treatments for phase separation but with due regard to the possible effects of polydispersity.