Poly(vinylidene fluoride) membranes by an ultrasound assisted phase inversion method

Poly(vinylidene fluoride) (PVDF) membranes were prepared by an ultrasound assisted phase inversion process. The effect of ultrasonic intensity on the evolution of membrane morphology with and without the addition of pore former LiCl during precipitation process was comprehensively investigated. Besides the inter-diffusion between the solvent and nonsolvent, the ultrasonic cavitation was thought to have significant influences on phase inversion and the resultant membrane morphology. The mutual diffusion between water and solvent during the ultrasound assisted phase inversion process was measured. The crystalline structure was detected by wide angle X-ray diffractometer (WAXD). The thermal behavior was studied by differential scanning calorimeter (DSC). The mechanical strength, forward and reverse water flux, rejection to bovine serum albumin (BSA) and pepsin were also investigated. By the ultrasound assisted phase inversion method, ultra-filtration membrane was successfully prepared, which exhibited more preferable morphology, better mechanical property and more favorable permeability without sacrificing the rejection and thermal stability.