Rheological Monitoring of Gelation Kinetics of Silica Sols

Dynamic oscillatory measurements at low strains are used to monitor the gelation kinetics of particulate aqueous sols composed of alkoxide-derived silica powders. The dynamic storage modulus is sensitive to the sizes of the growing clusters below the gel point. A transition in the modulus is observed and large oscillating normal forces are measured at the gel point. These tests do not disrupt gel structure (in contrast to shear viscosity measurements) and therefore the measurement process does not alter the gelation kinetics.