Gelling and phase inversion preparation for Al2O3/PVDF hybrid membrane

The casting solution for forming Al2O3/PVDF hybrid membrane (APHM) was prepared using polyvinylidene fluoride (PVDF) modified by KOH in the solution of methanol as a membrane-forming polymer, using vinyl-trimethoxy-silicane as a coupling agent and using aluminum isopropoxide (AIP) as an inorganic precursor, respectively, and APHM linking with chemical bond was obtained by the phrase inversion method. The effects of AIP on the phase behavior and gelling kinetics of the casting solution were studied so as to explore the mechanism of the influence of AIP on the microstructure of the APHM. Results showed that the change in the phase equilibrium of casting solution was encouraged by an increase in AIP concentration and casting solution became thermodynamic unstable, so that compatibility of the casting solution with non-solvent was decreased and the gelling velocity of casting solution was accelerated. The gelling velocity was the during the initial period of membrane formation, and then slowed down. The gelling velocity varied with different casting solutions. Both the gelling velocity and phase separation rate for the casting solutions were improved by the increases in AIP contents, however, the gelling velocity decreased when AIP concentration reached to 20% by weight.