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

The sol-gel transformation of silica in aqueous solution was studied b y viscosity measurements. Both the temperature and the pH value are fo und to have a great influence on the rate of sol formation. A theoreti cal model is suggested for the evaluation of experimentally determined viscosity-time data. The model is shown to correlate with the experim ent in all the cases studied. It allows calculation of the kinetic par ameters of the polymerisation of silica. Estimated values of the energ y of activation of polycondensation, and of the order of reaction with respect to the hydroxyl ion concentration, are of the same order of m agnitude as those reported in the literature. Our results, however, pe rmit the testing of an evaluation method which can determine both quan tities, i.e. the energy of activation and the order of reaction, simul taneously in one procedure.