Study Of Poly(Phthalazinone Ether Sulfone Ketone)(PPESK) Hollow Fiber Ultrafiltration And Nanofiltration Membranes

Poly(phthalazinone ether sulfone ketone) is a novel membrane material for ultrafiltration and nanofiltration membrane with high glass-transition temperature, good solubility, well membrane-forming ability, good mechanical performance and chemical stability.The phase separation behavior of different nonsolvent additives (NSA: ethanol, glycol, ethylene glycol methyl ether, diethylene glycol, etc.) in PPESK casting solution was studied at different operating temperature according to the linerized cloud point (LCP) correlation. It was found that the phase separation behavior of PPESK casting systems, i.e., PPESK/NMP/H₂O, PPESK/NMP/NSA (ethanol, glycol, ethylene glycol methyl ether, diethylene glycol), all agree with the LCP correlation. The binodal lines of the three systems were calculated according to the LCP correlation. Therefore, the maximum content of NSA in the casting solution can be calculated according to the binodal lines of the system, which is a reliable basis for the establishment for the composition of casting solution and coagulation bath. It can be concluded that NSA has the stronger ability of coagulation, the larger the intercept when the slope of the simulated LCP is the same. In another way, with the increase of NMP content in PPESK/NMP/(H₂O+NMP) system, the absolute value of the intercept and the coagulation ability of the casting solution were decreased, which is beneficial to the delayed phase separation. The coagulation ability of the nonsolvent additives increased as follows: water>glycol>ethanol>acetic acid>diethylene glycol>ethylene glycol methyl ether>methyl ethyl ketone at 20℃ according to the disparity of solubility parameters and ternary phase diagram.Hollow fiber ultrafiltration membranes were prepared successfully from poly(phthalazinone ether sulfone ketone) (PPESK) with a dry/wet phase inversion technique. Organic substances (ethylene glycol methyl ether, diethylene glycol, methyl ethyl ketone and PVP) and LiNO₃ were used as nonsolvent additives, and N-methyl-2-pyrrolidone (NMP) was used as a solvent in membrane preparation. The effects of the facors, such as PPESK concentration, the type of additives, the concentration of NSA and so on, in casting solution on the morphology and performance of hollow fiber ultrafiltration membranes were systematically investigated respectively. A series of PPESK hollow fiber ultrafiltration with different morphology (finger-type or sponge-like) and performance have been successfully prepared. The structures of PPESK hollow fiber membranes including the cross-section, the inner/outer edge (details of the cross-sections at the inner/outer edge of the membrane) and the external surface were characterized by scanning electron microscope (SEM). It was found that the membrane performance is consistent and agrees with membrane morphology. The...