Comparison of the membrane morphology based on the phase diagram using PVP as an organic additive and TiO2 as an inorganic additive

- Determination of binodal line experimentally by titration of PVDF/DMAc/TiO2/Water by a new method.
- Calculation of kinetic and thermodynamic parameters to predict membrane morphology.
- Different tests such as permeability, porosity and FESEM images were done to determine membranes characterization.

The morphology of symmetric and asymmetric membranes obtained by precipitation can be rationalized by thermodynamic and kinetic parameters. Such parameters which the former relates to thermodynamic effect and the latter controls the time of separation of the cast solution film immersing in the non-solvent bath from the glass plate were calculated as dimensionless parameters for further analysis. Phase diagram was used to consider the role of thermodynamic. The kinetic properties of the membranes could be investigated by the rate of mass transfer between solvent and non-solvent. By adding additives to the polymer solution the desire for becoming two phase and also viscosity of the solution increase and mass transfer rate between solvent and non-solvent decreases. In this study, TiO2 as an inorganic additive and PVP as an organic additive were used in PVDF/DMAc solution and two main parameters including demixing process and precipitation rate which affect the morphology of the membranes were determined for PVDF/TiO2/DMAc/Water and PVDF/PVP/DMAc/Water systems and the morphology of the membranes were predicted by comparing these two parameters. Quadratic phase diagram for PVDF/TiO2/DMAc/Water system was drawn experimentally with a new method. The prepared membranes were characterized by measuring permeability, porosity and contactangle. The results showed that by increasing additive concentration, until thermodynamic parameter was greater than relative kinetic parameter, permeability and porosity increased. When PVP was used up to 5% the structure was finger like. Sponge like structure was obtained for concentrations of TiO2 greater than 0.5%.

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