Preparation And Properties Of Porous Polyamide Porous Films

Membrane material is an important part of membrane separation technology. There is an increasing demand that new high performance membrane materials are urgently developed, as waste treatment fields are continually broadened and water pollution are increasingly serious. Poly (p-phenylene terephthamide) (PPTA) is a kind of typical lyotropic liquid crystalline polymer, which has high degree of crystallinity. Because PPTA with high mechanical properties, great thermal resistance and solvent resistance, is an ideal material for producing high performance fiber. However, there are rarely relevant researches in the field of membrane at home and abroad. Therefore, this article focuses importantly on the preparation of PPTA porous membrane process, then their structure and performances are analyzed and discussed.To begin with, PPTA flat membranes were fabricated via solution phase inversion method. PPTA as the membrane material, concentrated sulfuric acid (H2SO4) as the solvent and polyethylene glycol (PEG) as the pore-creating agent were used in this article. The results showed that the PPTA flat membrane was a kind of asymmetrical membrane, which had a dense upper surface. The dissolved pore-creating agents brought about the fibrillar micro-porous structure on the lower surface. The decrease of PPTA concentration, increase of the molecular weight, and the promotion of coagulation bath temperature would bring about an obvious enhancement of the pure water flux and porosity. Besides, the rejection rate of egg albumin reached more than 90%, while the pump oil/water emulsion reached more than 70%.Furthermore, based on the principle of organic/inorganic phase separation, PPTA/SiO2 hybrid porous membranes were fabricated via solution phase inversion method for the first time. The morphologies and pore structure were controlled by the addition of SiO2 content, and explored their effects on the membrane performances. The research on PPTA/SiO2 hybrid porous membranes was shown as follow:The additions of SiO2 particles made the upper surface become rougher, increasing the effective filter area. The SiO2 particles could introduce the interfacial pores, which improved the permeation and mechanical properties. The addition of mixed pore-creating agents, while the separation and mechanical properties were retained, also promoted the pure water flux of PPTA/SiO2 hybrid porous membranes. As for the study on anti-fouling of PPTA/SiO2 hybrid porous membranes, the rejection and backwash of protein solution and pump oil/water emulsion were tested. Therefore, the results showed that both rejection rates could reach beyond 90%, meanwhile, the parameter of FRR could also reach 90%, which exhibited the good anti-fouling performance.Then, PPTA hollow fiber membranes were fabricated by dry-wet spinning method for the first time. The thermal and solvent resistance as well as anti-fouling performances were studied in this article. The properties of thermal stability were characterized by pure water flux, BSA rejection, mechanical strength, FITR and pore size distribution, and the properties of chemical resistance were characterized by organic solvents flux. The results showed that PPTA hollow fiber membrane was a kind of inner and outer dual skin layer structure. The flux could reach 500L/(m2h) in hot water, and the flux was stable in different organic solvents. The pore size distributions were hard to damage during high temperature experiment. Moreover, the properties of anti-fouling were characterized by simulated activated sludge filtration. The fouled PPTA membranes were cleaned by ultrasonic, citric acid and alkali, and the membrane surface was detected by Energy Dispersive X-Ray Spectroscopy (EDX). The results showed the effect of the citric acid was more preferable to the other ways, which indicated inorganic substance was easily adsorbed on the membrane surface compared with organic substance. Meanwhile, the fouling mechanism of PPTA hollow fiber membrane was mainly due to concentration polarization, and the surface adsorption had nearly no influence on PPTA membrane pollution.Finally, based on the principle of the polymer surface and interfacial bonding, hollow tubular braids as the matrix and the PPTA casting solution as the surface separation were in this article. The homogeneous reinforced (homo-reinforced) PPTA hollow fiber membranes were fabricated by concentric circle method. The results showed that, under high PPTA concentration in casting solution, the interfacial bonding between the PPTA hollow tubular braids and the surface separation were still tightness. The pure water flux and mean pore size were not obvious fluctuation, and tensile stress was beyond 600N. Moreover, the produced ultrafiltration water qualities from membrane modules were stable in MBR system.