Formation kinetics of polyethersulfone with cardo membrane via phase inversion

Formation kinetics of polyethersulfone with cardo (PES-C) membrane via wet phase-inversion process was studied experimentally and theoretically. The gelation process was observed using an online optical microscope-CCD camera experimental system and the precipitation front move X, was measured. The result was different from a commonly accepted conclusion that a single linear correlation between X² and t existed for the whole gelation process. Formation kinetics of skin layer was also studied, gelation rate constant equations of various cast solution parameters on membrane skin layer formation were obtained. The results showed that gelation rate constant decreased with the increase of PES-C concentration and increased with the increase of oxalic acid (OA) concentration. The trend of the gelation rate was exactly the same as the trend of the flux. The higher the gelation rate, the looser the membrane skin layer. The results present here might provide better understanding of the asymmetric membrane skin layer formation process.