MICRORHEOLOGY OF LOW-CONCENTRATION COLLOIDAL GELS - MECHANISMS OF THRESHOLD EFFECTS

The effect of irreversible compression of low-concentration colloidal gels (LCG) with threshold compressive stresses and the effect of a rev ersible jump in the viscosity of these gels with threshold shear stres ses were analyzed. Three possible mechanisms were examined based on co ncepts concerning the fractal structure of LCG. The effect with compre ssion was interpreted as adhesion of structural elements of the gel in one case and as rupture of overstressed structural elements in the ot her case. The effect in shear is like a percolation transition in a ne twork of broken and restored bonds.