ON THE DETERMINATION OF KINETIC-PARAMETERS OF SOL FORMATION BY RHEOLOGICAL MEASUREMENTS

The sol-gel transformation of silica in aqueous solution was studied by viscosity measurements. Both the temperature and the pH value are found to have a great influence on the rate of sol formation. A theoretical model is suggested for the evaluation of experimentally determined viscosity-time data. The model is shown to correlate with the experiment in all the cases studied. It allows calculation of the kinetic parameters of the polymerisation of silica. Estimated values of the energy of activation of polycondensation, and of the order of reaction with respect to the hydroxyl ion concentration, are of the same order of magnitude as those reported in the literature. Our results, however, permit the testing of an evaluation method which can determine both quantities, i.e. the energy of activation and the order of reaction, simultaneously in one procedure.