Abstract
Rheopexy of disperse systems consisting of silica gel particles in a silicone oil was examined in relation with the state of dispersion of the particles. The suspensions were subjected to a double-step shearing test. Particularly, we investigated the effects of particle concentration and of shear rate on rheopectic processes, and obtained following results: (1) The suspensions with high particle concentration exhibit a unique stress overshoot phenomenon in the rheopectic processes.(2) The initial process of aggregate formation obeys a second-order kinetics.(3) The rate of aggregate formation strongly depends on the surface condition of flocs especially on their surface potential.
An equation for aggregate formation and rupture is proposed. The critical condition for aggregate rupture may be expressed as a function of the shear stress and the average degree of aggregation. The condition is independent of particle concentration.
