Antibacterial Hyperbranched Polyamide-Amine Modified PVDF Membrane And Its Properties

PVDF is widely used in membrane technology due to its good chemical stability,high mechanical strength and thermal stability.However,like other membranes,PVDF membranes are also susceptible to membrane fouling and result in reduced membrane flux and reduced service life.Once membrane fouling is formed,membrane fouling will be difficult to remove and will cause irreparable damage to the membrane.Therefore,it is important to prepare a composite membrane having excellent antibacterial and antifouling properties.In the past few decades,researchers have tried many different modification methods to prepare different antibacterial films,such as blending,chemical grafting,coating and interfacial polymerization.At the same time,there are many choices of bacteriostatic agents,which are mainly divided into organic bacteriostatic agents and inorganic bacteriostatic agents.However,inorganic bacteriostatic agents cannot be widely used in the field of membrane modification because of their shortcomings.Therefore,some researchers Started to shift the focus to organic bacteriostatic agents.The hyperbranched polyamide-amine(HPAMAM)used herein has a special hyperbranched structure and a large number of terminal amine groups,and they have similar properties compared to dendrimers with a highly symmetrical structure,but HPAMAM The preparation method is simpler and more convenient,and the production cost is lower.Therefore,it has a good prospect in the field of membrane modification.In this paper,the hyperpolymerized polyamide-amine(HPAMAM)was selected as the aqueous phase and the organic phase benzenetricarboxylic acid chloride(TMC)was reacted on the surface of the membrane to prepare a bacteriostatic PVDF composite membrane,in order to prepare the newly prepared PVDF composite.A large amount of excess amine groups on the surface of the membrane can effectively improve the antibacterial properties of the membrane.At the same time,the carboxyl group produced by TMC can form a mixed potential film surface with the amine group,which effectively improves the membrane anti-pollution ability.Firstly,in this study,HPAMAM was characterized by infrared characterization and nuclear magnetic characterization to determine its chemical structure,and its bacteriostatic test was also carried out by the minimum inhibitory concentration experiment.Furthermore,PVDF composite membranes were prepared by interfacial polymerization.In order to determine the performance of the prepared composite membranes,the rejection and water flux tests were carried out and found to be optimal when the organic phase TMC concentration was 0.2 wt%.Then,the selected T2 composite membrane was subjected to further chemical structure and characterization of antifouling and antibacterial properties.In this paper,the chemical composition,hydrophilicity,membrane mechanical strength and zeta potential of the membrane surface before and after membrane modification were determined by infrared(ATR-FTIR),water contact angle(CA),membrane mechanical strength and membrane surface zeta potential.The chemical composition of the membrane surface changed and the hydrophilicity of the membrane surface of all the modified membranes was significantly improved,and the isoelectric point of the membrane surface increased.The microstructure changes of the membrane surface and pore size before and after membrane modification were observed by scanning electron microscopy(SEM)and atomic force microscopy(AFM).The modified PVDF composite membrane has a reduced pore size and a reduced surface roughness,and both decrease with increasing aqueous phase concentration.Finally,it was found through the inhibition zone experiment and protein contamination experiment that the modified PVDF composite membrane has excellent anti-fouling and antibacterial properties.