The PPTA/PSF Blend Film Was Prepared By In-situ Blending

Blending modification is a combination of different materials with different properties,so that the polymer has more kinds of properties,in order to achieve the combination of "favorable performance".In-situ blending refers to rigid polymer molecules monomer dissolved in the flexible polymer(or monomer),and then provide the polymerization conditions for in-situ polymerization,rigid polymer molecules uniformly dispersed in the polymer matrix,formed in-situ molecular composite materials.In order to improve the compression resistance of polysulfone-based membrane,in this work we introduced poly(p-phenylene terephthalamide)(PPTA)with high strength and high modulus to polysulfone(PSf)/N-methylpyrrolidone(NMP)system.Because the erystalline polymer PPTA chain is highly erdered and its poof solubility,the Conventional blending method is difficult to achievee the uniform dispersion of PPTAin PSf/NMP system.Therefore,in PSf/NMP system,PPD and TPC were used as reaction monomers to synthesize PPTA by in-situ blending method.The results showed that the PPTA could be successfully synthesized in PSf/NMP system by in-situ blending method,and the PPTA/PSf in-situ blending membrane could be further prepared.Firstly,the effect of PPTA/PSf blending ratio,polymer content,cosolvent concentration and acid absorber concentration on the molecular weight of PPTA was investigated,The results showed that the molecular weight of PPTA could be effectively controlled by changing reaction conditions:the molecular weight of PPTA increased with the increase of cosolvent LiCl concentration and acid absorber Py concentration.While the PPTA/PSf blend ratio and the polymer content had a significant effect on the molecular weight of PPTA,high molecular weight PPTA only could be synthesized at appropriate PPTA/PSf blend ratio(8/92)and polymer content(20%).Secondly,the rheological properties of PPTA/PSf in-situ casting solution was studied.The relationship between viscosity,temperature and shear rate of casting solution was discussed.Finally,the properties of PPTA/PSf in-situ blending membranes were characterized.The results showed that the pure water flux of PPTA/PSf blend membranes were improved greatly,but the retention of PEG-20000 was decreased.It was found that the compression resistance of PPTA/PSf blendmembranes were improved remarkably by the addition of PPTA.