The Effects of Hydrolysis and Condensation Reactions of Mixed Si(OC2H5) 4 and Zr(O-nC3H7) 4 Solutions on the Rheological Behaviors and the Structure of Polymers in the Silica-Zirconia Sol-Gel Process

Abstract

The hydrolysis and condensation reactions of mixed alkoxide solutions in the Si(OC2H5)4·Zr(O-nC3H7)4-H2O-C2H5OH-HCl system with H2O/total alkoxide molar ratios (r) from 1.0 to 8.0 were investigated by gas chromatography, the number average molecular weight ( ) and the intrinsic viscosity [η] of the benzene solutions of the TMS polymers were measured. It is found that the amounts of evolved ethanol in the partial hydrolysis of Si(OC2H5)4 reaches an equivalent values within 20 minutes, and do not depend on the temperature. In the mixed alkoxide solutions containing a large content of H2O, the hydrolysis is fully completed, whereas the hydrolysis of solutions containing small contents of H2O are not fully completed. Investigations on the relationship between (ηsp/C) and C or the relationship between [η] and ( ) have made it clear that spinnable solutions have polymers with a linear structure and the non-spinnable solutions contain polymers with a 3-dimensional structure. It has been established that the spinnable solutions exhibit a Newtonian flow behavior up to high viscosities, where fibers can be drawn, while the non-spinnable solutions exhibit a structural viscosity.