Study On Synthesis And Property Of Polysulfone Antifouling Membranes By Amphiphilic Polyurea

Polysulfone(PSf)is a remarkable starting material for the preparation of ultrafiltration membrane due to its high chemical and thermal stability,adequate mechanical strength and excellent filmforming ability.However,the hydrophobic nature of membranes made from PSf exacerbates their susceptibility to fouling due to the strong hydrophobic interactions between foulants and the membrane surface.The membrane is easy to be polluted and not easy to be cleaned,which reduces the flux and service life even limits its range of use.Therefore,membrane fouling has been a major problem in membrane filtration and great efforts have been made to overcome the fouling issues.This study introduces the structure composition and preparation method of a amphiphilic polyurea additive with both ends hydrophilic and middle hydrophobic which was blended with polysulfone to prepare ultrafiltration membrane,and explores the relationship between different chain segments,the same chain segment and different addition on the antifouling performance and separation performance of polysulfone blend membrane.The reaction of amidogen in aromatic and initiator with isocyanates at room temperature to generate long polyurea chain.Initiatorwas was actived by high temperature then long polyurea chain segment to break into short chain segment.Through free radical attack on vinylpyrrolidone at both ends to generate free radical of polysurea,forming hydrophilic chain segment.Through adjusting the feeding ratio,three amphiphilic polyurea additives with different molecular weights were synthesized.The polyurea hydrophobic structure in the middle of the additive improves its compatibility and stability in the polysulfone membrane.The hydrophilic chain segments at both ends modify the surface of the polysulfone film,so as to achieve the effect of hydrophilic antifouling and prolong the service life of the film.Three amphiphilic polyurea additives with different molecular weights were doped to prepare the polysulfone antifouling membrane that would have high water flux and high surface energy.On this study the water flux of modified polysulfone can reach up to 417.8 L/(m2 h)under the test pressure of 0.2 MPa.The addition of additives increased the hydrophilicity of the membrane and reduced the water contact angle to61.1°.The hydrophilic property of polysulfon emembrane is effectively antifouling,and its mechanical properties are also enhanced effectively.In the process of membrane immersion precipitation phase transformation,the hydrophilic chain segment migrated to the membrane surface with water,and the hydrophobic chain segment polyure-urea was stably embedded in the membrane matrix to ensure that the hydrophilic group exposed on the membrane surface would not be eluted during the use.For efficient of polysulfone flat membrane,this study applied it to the hollow fiber membrane of polysulfone.The preparation of hollow fiber film was created on the basis of study of platmembrane.By testing,Water flux is highest can reach 228.5L/(m2h),in a note to the pore better thanpolyethylene glycol(PEG).Amphiphilic polyurea is non-toxic,so it can replace PEG to make in the hollow fiber membrane pore and improve hydrophilic.Amphiphilic polyurea make the water contact angle introduced to 67.5°and the molecular weight of 6.8 KDa bovine serum albumin filtrate rate as high as 98% so it can effectively prevent protein adhesion and enhance the mechanical properties at the same time.So amphiphilic polyurea can also be used to modify hollow fiber membrane effectively.