Preparation and characterization of microfiltration flat polymeric membranes for biomedical applications

Dissertation presented to Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa for obtaining the master degree in Membrane Engineering

The optimal methodology for flat supported hydrophobic microporous poly(vinylidene) fluoride (PVDF) industrial membranes (Fortex 0.1, Fortex 0.2, Fortex 1.2 and Fortex 3.0) production were developed with implementation of wet phase-inversion technique. The effect of different indicators of the production conditions, such as composition of polymer solution, quantity and type of additives, dissolving temperature, composition and temperature of the coagulation bath were studied. All the comparisons were performed in the narrow range of values in order to have better understanding of how slight deviation of each parameter can influence the performance of the industrially manufactured membrane. During the development process it was observed that the increase of dissolving temperature results in formation of membrane with more open structure, justified by higher values of air flow (AF) and lower critical water entry pressure (water break through (WBT)). Moreover, the low molecular weight inorganic lithium salt has stronger effect on membrane performance than organic pore former applied. After the optimization of production parameters for each type of membranes at the laboratory scale, the implementation of these conditions was realized at industrial scale. The good reproducibility of membrane characteristics prepared at laboratory and industrial scale was observed for three membrane types. The industrial trial for Fortex 0.2 membrane was not successful and this result was hypothetically related to the high viscosity of the casting solution. Additionally, it was demonstrated that absorbance of air moisture by polymer solution may significantly influence properties of manufactured membranes. Moreover, the industrially manufactured membranes as well as laboratory samples of Fortex 0.2 were characterized by means of scanning electron microscope, permporometry and Fourier Transform Infrared Spectroscopy. It was shown that usage of different solvent/non-solvent pairs (DMAc/water and DMAc/alcohol) was leading to the different membrane morphologies. Basing on permporometry test results, the largest active pores inside membranes were identified. Finally, it was shown that all the developed membranes possess β and γ crystalline phases and only Fortex 0.1 exhibited presence of α structure.

The EM3E Master is an Education Programme supported by the European Commission, the European Membrane Society (EMS), the European Membrane House (EMH), and a large international network of industrial companies, research centres and universities