Effect of co solvent affinity with water on membrane morphology in immersion precipitation process

In this study Polyvinyl chloride (PVC) membranes were prepared by immersion precipitation method. Dimethylformamide (DMF) and tetrahydrofuran (THF) were used as the solvent and co solvent respectively. Permeation experiments showed that above a certain amount of THF in the initial casting solution, the membranes were impermeable to pure water under the applied pressure, while decreasing the amount of co solvent leads to membranes with a more open structure. This suggests a method to manufacture membranes with different porosities from a single polymer by changing solvent to co solvent ratio. Theoretical kinetic modeling was employed in order to better understanding of the involved processes. Thecalculated precipitation time and observed morphological changes were related to partition coefficient of solvent and co solvent between coagulation bath and solution phases through the model.

Keywords:

Immersion Precipitation , Co Solvent , Kinetic Modeling