RHEOLOGICAL BEHAVIOR OF HIGHLY CONCENTRATED OIL-IN-WATER (O W) EMULSIONS/

Oil-in-water (o/w) highly-concentrated emulsions have been studied in ternary water/polyethylene oxide-polypropylene oxide-polyethylene oxid e (ABA block copolymer)/hydrocarbon systems in order to compare their theological behavior with that of water-in-oil (w/o) highly concentrat ed emulsions. Viscoelastic measurements have been performed as a funct ion of dispersed phase volume fraction and temperature. The structural parameters of the system, droplet size, interfacial tension and conti nuous phase viscosity have been determined in order to correlate these parameters with the theological behavior. The shear modulus has been shown to depend on the volume fraction according to Princen's equation . The relaxation times were described using a Maxwell liquid model in which the viscosity is related to a reduced continuous phase viscosity . The effect of temperature on the shear modulus and relaxation time i s significantly different from that observed for w/o highly concentrat ed emulsions. These differences in the rheological behavior of the emu lsions were discussed in terms of the chemical structure of the surfac tants.