Study on fabrication of a porous thin-film composite membrane composed of polyurea network

Abstract

Porous thin-film composite (TFC) membranes composed of polyurea network (UN) were fabricated by using thermal rearrangement and concentration polarization induced gelation of UN nanogel/polymer mixed sol. A colloidal dispersion of UN nanoparticles was synthesized via crosslink-polymerization of tetrakis(4-aminophenyl)methane (TAPM) and 1,6-hexamethylene diisocyanate (HDI). A thin UN selective layer was obtained as the diluted UN nanogel was passed through a porous substrate by concentration polarization induced gelation. The UN TFC membrane was heated above 250℃ for increasing micropores by rearranging the urea bond to more stable chemical structures. The chemical analysis was performed by IR and the morphology of UN and rearranged UN (RUN) was characterized by SEM. The coating thickness control was studied. The pore generations were confirmed by single gases permeation test and mixed gas separation test. Through the free RUN porosity data, the microporosity of UN and RUN TFC membrane was estimated. The other thin coating using UN nanogel/polystyrene (PS) mixed sol was similarly obtained by passing through a porous substrate. The resulted membranes were characterized by SEM. The morphologies could be controlled by the polymerization time of UN and the amount of PS.