MASTER BEHAVIOR FOR GELATION IN A SOL-GEL PROCESS UNDER DIFFERENT TEMPERATURE AND PH CONDITIONS

A master behavior for gelation in a sol-gel process as function of temperature and pH is reported in this paper. The sol-gel system was kept at reflux temperature until it reached steady state; then it was cooled to room temperature and the pH was adjusted to some value with in a specific range. Once the pH was adjusted, the temperature of the reaction was set to some value, and the system carried to gelation. The particle size profile of sols was obtained as a function of the reaction time using dynamic light scattering. It was from these gelation profiles obtained under different temperature conditions that a master behavior was obtained. With these master curves, it was possible to build a super-master curve which allows prediction of gelation profiles for systems where both the temperature and pH have been specified. Two predictions for systems with different values of temperature and pH led to excellent agreement between experimental and predicted behavior.