Influence of polymer structure on thermal stability of composite membranes

Novel thermal stable polymer, poly(phthalazinone ether sulfone ketone)s (PPESK), was used as the support material of the thin film composite (TFC) membranes fabricated via interfacial polymerization. Influence of polymer structure of both the support layer and the active layer on thermal stability of TFC membrane was studied, respectively. With the same fully aromatic polyamide (PA) active layer, thermal stability of PA/PPESK TFC membrane is better than that of PA/PSF. On the other hand, with the same PPESK support layer, thermal stability of TFC membranes with different active layer follows such sequence: fully aromatic > alicyclic aromatic > aliphatic aromatic. At 1.2 MPa pressure, 20 °C, fully aromatic PA/PPESK TFC membrane rejected 2000 ppm NaCl solution by 98% and water flux was 10.1 L/m2 h. When solution temperature rose from 20 °C to 80 °C, water flux increased more than two-fold with stable salt rejection. Its permeation properties were almost unchanged from the original value after being operated at 90 °C for 8 h and then restarted at 20 °C.