RHEOLOGY AND DYNAMICS OF WATER-IN-OIL EMULSIONS UNDER STEADY AND DYNAMIC SHEAR-FLOW

The fundamental aspects governing the rheology of water-in-oil emulsio ns, such as viscosity ratio and morphology were considered. The model developed here is based on the early work of Pal and Rhodes (1989) for viscosity equation, combined with the theory of Lee and Park (1994) f or the morphological contributions. Thus, the proposed conception enab les us to predict not only the degree of flocculation but also viscosi ty ratio and morphological effects. The contribution of secondary morp hology caused by the flocculation of droplets on the viscosity of disp ersed emulsions has been found by using the factor, -alpha'q'(xy)/y ov er dot (where alpha is the interfacial tension, q'(xy) is xy-component of anisotropy tensor, and y over dot is shear rate). However, this ap proach is only useful for system below the maximum random packing conc entration. Experimentally, the bulk rheological properties have been e xamined under steady and dynamic shear flow to investigate the structu re of emulsion. The flocculation-deflocculation transition was observe d during the shear rate sweep, resulting in instant dilatancy of visco sity near the critical shear rate y over dot approximate to 100 s(-1). (C) 1997 Academic Press