New continuous process developed for synthesizing sponge-type polyimide membrane and its pore size control method via non-solvent induced phase separation (NIPS)

In this study, the improvement of synthesizing method of sponge-type polyimide (PI) membrane and its newly developed pore size control techniques are mainly described. The sponge-type polyimide membrane with large pore size (0.1–10 µm) and high permeability was successfully synthesized by using non-solvent phase separation method (NIPS) in continuous process and its full polyimidization is confirmed via Fourier-transform infrared technique. The theoretical approach in this research induced by Jurin's law which describes the height of a liquid within a thin capillary tube. In this theory, the pore size of membrane is highly influenced by the interactive tension between the polymer and solvents during synthesizing process of polymer membrane. There are two ways of controlling pore size established from Jurin's law. The validity of the application of Jurin's law was proven via comparison with theoretical and experimental data. Its inner structure of membrane and pore size are identified by field emission-scanning electron microscopy.