MAP OF GEL TIMES FOR 3 PHASE REGION TETRAETHOXYSILANE, ETHANOL AND WATER

The sol-to-gel transition for different starting compositions of tetraethoxysilane (TEOS), ethanol, and water mixtures under acidic catalyzed conditions are reported. According to the physical appearance of the mixtures after mixing, four different types of behavior can be identified. For these systems, opened to an approximately 70% relative humidity atmosphere, seven regions of the phase diagram have been distinguished according to gelling times. The gelling times are sensitive to the starting composition and have been organized for presentation as functions of the concentration of ethanol [EtOH], the ratio [H2O]/[TEOS], and [TEOS]/[EtOH]. Gelling time increases with increasing [EtOH]. As [H2O]/[TEOS] ratio increases, the gelling time first decreases and increases with a minima at the equilibrium concentration.