| Popis: |
Interfacial properties of polyoxyethylene(2) oleyl ether and drop size distributions of emulsions prepared with this surfactant are investigated experimentally in this work; 80, 88 and 94% (v) internal phase ratio W/O type emulsions were prepared, where the aqueous phase was 1% sorbitol solution and the oil phase, a 1:1 v/v mixture of surfactant and paraffin oil. Experimental evidence indicated an interaction between the hydrocarbon chains of surfactant molecules and the solvent paraffin oil through van der Waals forces and between the ethoxylate groups and sorbitol, a polyalcohol, in the aqueous phase through hydrogen bonds, notably below the transition temperature. Continuous phase liquid present in the plateau borders was found to act as a reservoir of surface active agents, minimizing the effect of stretching of the film under shear. In cases where the amount of liquid hold up in plateau borders is negligible, the drop size distributions were found to be very sensitive to shearing rate. Interplay between the interfacial shear viscosity and the interfacial tension was found to control the rate of coalescence of drops less than 0.48 μm only in the case of 94% emulsions, corresponding to maximum stretching of interfacial area. In other cases, interfacial film stability seems to control the rate of coalescence. |
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