Preparation And Properties Of Polyethersulfone Modified And Microporous Membranes

Polyethersulfone(PES)has been used as a membrane substrate in many fields due to itsexcellent properties.The structure and properties of PES microporous membranes are easily affected by the composition of membrane and the conditions of film formation,and PES is easy to be modified.Therefore,it is meaningful to explore the factors affecting the structure and properties of PES microporous membranes before and after modification,so that PES membranes can be applied to different objects and requirements.In this paper,PES microporous membranes were prepared by phase inversion method,using polyethersulfone(PES)as the main material and N-methyl pyrrolidone(NMP)as solvent,by changing the content of polyethylene glycol(PEG)and PES and wet film residence time under constant temperature and humidity.By testing the viscosity of the film forming solution,it is found that the viscosity of the film forming solution is too large or too small,which will affect the film forming process.And by testing the microstructure,pore size,porosity,moisture content,air permeability and mechanical properties of the membrane,it was found that when the PEG content in the casting solution was 60%,the PES content was 12%and the evaporation time of the film was2 minutes,it was more suitable to prepare the membrane.The chloromethylated PES(CMPES)was synthesized by 1,4-dichloromethoxybutane(BCMB)as chloromethylation reagent and Catalyst zinc chloride under certain reaction conditions.The chloromethylation degree of PES was 72%by FTIR and ~1H-NMR analysis.Then,the quaternized PES was prepared with N-methylimidazole as the quaternization reagent under the conditions of reaction time of 4 h and reaction temperature of 80 degrees,and the degree of quaternization of CMPES was 55.4%by infrared spectroscopy and nuclear magnetic resonance spectroscopy.Quaternized PES microporous membranes were prepared by changing the content of N-methylimidazole in the quaternized PES formulation.Based on a series of test results,it wasfound that the increase of N-methylimidazole content could not improve the degree of quaternization.When the ratio of CMPES to N-methylimidazole was 1:5,the performance and structure of quaternized PES microporous membranes were better.The commercial E and Q membranes of PES were tested and analyzed.It was found thattheir quaternization degree was not high.E membrane and Q membrane were subjected to endotoxin filtration test,and it was found that E membrane had endotoxin filtration effect,and Q membrane had no endotoxin filtration effect.It is presumed that E membrane has the function of charge adsorption and pore size interception,and thus has the function of endotoxin removal.