화학공학소재연구정보센터
Industrial & Engineering Chemistry Research, Vol.37, No.5, 2052-2058, 1998
Rheology of liquid membranes
The rheology of a primary water-in-oil (W/O) emulsion and a multiple water-in-oil-in-water (W/O/W) emulsion (liquid membrane) was investigated using a controlled-stress rheometer. The dispersed-phase (water) concentration of the primary W/O emulsion was 68% by volume. The primary W/O emulsion behaves like a highly shear-thinning fluid. Upon aging, there occurs a dramatic decrease in the zero-shear viscosity and storage modulus of the primary W/O emulsion over the first few hours of storage. The multiple W/O/W emulsion was prepared with a primary W/O emulsion concentration of 73 vol %. The fresh multiple W/O/W emulsion behaves like a shear-thinning non-Newtonian fluid. Upon aging, the rheological parameters (viscosity, storage, and loss moduli) of the multiple W/O/W emulsion initially increase with an increase in storage time and then decrease with a further increase in storage time. These observations are explained in terms of droplet size changes that occur during aging. The multiple W/O/W emulsion also exhibits shear-thickening (dilatancy) under certain conditions.