Preparation of poly(vinylidene fluoride) hollow fiber membranes for microfiltration using modified TIPS process

The porous PVDF hollow fiber membranes with the particulate morphology were successfully prepared through the modified TIPS process and the addition of solvent into non-solvent in the coagulation bath. The structures of formed membranes were investigated using differential scanning calorimetry, X-ray diffraction measurement, and scanning electron microscopy together with the corresponding microfiltration performances such as water flux, rejection rate, and elongational strength. Initially, the asymmetric membranes having spherical particles formed due to crystallization of PVDF transformed to skinless porous structure, leading to the change of crystalline structure from α to β-form crystallines PVDF with increasing solvent into a coagulant bath. Thereby, water flux and mean pore size increased at the expense of reduction of rejection rate and mechanical strength.