Preparation And Application Of Ultrafiltration Membrane Base On Modified-PES By ?-Ray Irradiation Grafting In Homogenous Phase

In recent years,the development of polyethersulfone(PES)as a kind of membrane matrix has raised a lot of concern.PES is often used for the synthesis of ultrafiltration membrane owning to its good chemical,thermal and mechanical stability.Despite substantial progress achieved in the research of PES membrane,some issues remain to be resolved.One disadvantage of the PES membrane is its high hydrophobicity,which causes its potential fouling.And hydrophilic modification on this material may represent an effective solution.In fact,the grafted copolymer is usually found immiscible with the solvent after grafting by the pre-irradiation method.In this paper,we adopted a new method named ?-ray irradiation in homogenous phase to synthesize grafted PES copolymers with good solubility even at a high degree of grafting(DG),which is critical to prepare the casting solution for membrane fabrication.By choosing this method,monomer MAA was successfully grafted onto PES molecular chains to synthesize PES-g-PMAA copolymer.DG of this copolymer was measured by elemental analysis and FI-IR,the result showed that DG of this copolymer increased with monomer concentration when it was low than 2%,further increase of this value contrarily depresses the value of DG.Thus,we proposed the competitions between three different reactions including monomer's homopolymerization,grafting reaction;PES and grafting molecular chains' degradation during the homogeneous irradiation grafting process to explain this phenomenon.Then,the ultrafiltration(UF)membranes were made from this copolymer.The contact angle tests showed that the hydrophilicity of the modified PES UF membrane is improved with the increase of the DG.SEM images of the cross-section of membranes clearly showed a transformation from a “finger-like” structure of pristine PES membrane to a “sponge-like” structure of PES-g-PMAA membrane with high grafting degree.The structure and performance of these modified PES membranes showed a significant dependence on the pH value.Their pore size gradually reduces along with the increase of pH value of the water solution.The modified PES membrane also shows a thermal-sensitive property.Their water flux and the value of MWCO at different temperature of this modified PES-g-PMAA membrane were also tested,the result showed that both of them increased with the working temperature.In this paper,we also grafted PVP onto PES by our homogeneous grafting method through ?-ray irradiation,and studied the dynamic factors during the synthesis of PESg-PVP copolymers,the result showed that the DG of these copolymer PES-g-PVP increase with the monomer concentration and irradiation dose when monomer concentration was lower than 12%,and irradiation dose was lower than 35 KGy.The phase diagram of the casting solution of PES-g-PVP copolymers was drew.The result shows that the thermodynamic stability of PES-g-PVP copolymers' casting solution was decreased.Since PVP is a kind of widely chosen pore-forming additives,we tried to directly cast membrane of this homogenous solution after ?-ray irradiation grafting,and studied the effect of different type solvent,monomer concentration and irradiation dose on membrane's performance.Meanwhile,we test the retention rate of BSA solution flux for all membranes.The results showed a better retention rate for these modified PESg-PVP membranes,indicating their better antifouling property.