Effect of polymer dissolution temperature and conditioning time on the morphological and physicochemical characteristics of poly(Vinylidene fluoride) membranes prepared by non-solvent induced phase separation

This work reports on the production of poly(vinylidene fluoride) (PVDF) membranes by non-solvent induced phase separation (NIPS) using N,N-dimethylformamide (DMF) as solvent and water as non-solvent. The influence of the processing conditions in the morphology, surface characteristics, structure, thermal and mechanical properties were evaluated for polymer dissolution temperatures between 25 and 150 °C and conditioning time between 0 and 10 min. Finger-like pore morphology was obtained for all membranes and increasing the polymer dissolution temperature led to an increase in the average pore size (≈0.9 and 2.1 µm), porosity (≈50 to 90%) and water contact angle (up to 80°), in turn decreasing the β PVDF content (≈67 to 20%) with the degree of crystallinity remaining approximately constant (≈56%). The conditioning time did not significantly affect the polymer properties studied. Thus, the control of NIPS parameters proved to be suitable for tailoring PVDF membrane properties Fundação para a Ciência e a Tecnoloiga (FCT), the Fundo Social Europeu (FSE) and the Programa Operacional Regional Centro 2020 and Norte 2020 for the strategic funding UID/EMS/00151/2020, UID/FIS/04650/2020 and UIDB/04436/2020, projects PTDC/BTM-MAT/28237/2017, PTDC/EMD-EMD/28159/2017, PTDC/FIS-MAC/28157/2017 and the grants SFRH/BD/141642/2018 (J.T.), 2020.02304.CEECIND (V.F.C) and SFRH/BPD/117838/2016 (J.N.P.). Financial support from the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RBC43/AEI/10.13039/501100011033 and from the Basque Government Industry and Education Departments under the ELKARTEK and PIBA (PIBA-2018-06) programs, respectively, are also acknowledged