Preparation Of Polytetrafluoroethylene Nanofiber Membrane And Its Application In Membrane Emulsification

ME is a technology to preparation emulsion that by using the membrane as the contact interface,the dispersed phase enters the continuous phase through the membrane pores to form an emulsion.This process has the advantages of low energy consumption,high efficiency,and narrow emulsion particle size distribution,making it one of the promising emulsion preparation technologies.As the key to the membrane emulsification process,the membrane material should have the advantages of narrow pore size distribution,low flow resistance,excellent chemical durability,high heat resistance,sterilization and low price.Although researchers have done a lot of research on ME and membrane materials,there are very few developments of porous membranes specifically for ME,especially polymer porous membranes.At present,in addition to porous glass(SPG)membranes,membrane emulsification mainly uses microfiltration membrane materials.Due to the wide pore size distribution of most microfiltration membranes,unsatisfactory membrane pore morphology,and solvent resistance,they are not suitable for membrane emulsification,which limits the application of membrane emulsification.In this paper,poly tetra fluoroethylene(PTFE)with high thermal stability and high chemical stability was used as the membrane material,and the PTFE nanofiber membrane was prepared by electrostatic spinning technology.On this basis,through the electrostatic spray technology,the meltable Fluorinated ethylene propylene(FEP)resin was loaded on the surface of the PTFE nanofibers to prepare a porous PTFE nanofiber membrane with a circular pore structure.Then used it for the process of preparing water-in-oil(W/O)emulsion and polymer microspheres by membrane emulsification.The specific research content is as follows:First of all,the PTFE was chosen as membrane materals,and PVA was used as the spinning carrier.Electrospinning was used to prepare the PTFE nanofiber membrane.During which,the FEP resin particles were introduced into the nanofibers by the electrostatic spraying.After which,the prepared precursor nanofiber membranes were sintered,and PTFE nanofiber membrane changes from a three-dimensional disordered network pore structure to a round pore structure.Effects of FEP contents on PTFE nanofiber membranes' structure and performance were investigated,respectively.After that,considering water as the dispersed phase,kerosene as the continuous phase,and Span 80 as the emulsifier,the obtained PTFE nanofiber porous membrane was used in the membrane emulsification process to prepare W/O emulsion,and compared with the emulsion prepared by mechanical stirring.The results show that when the FEP loading is 1.5wt% and the average pore size was 1.36?m,the prepared emulsion has a narrow particle size distribution,with an average particle size of 257 nm,the entire emulsification process lasts for 12 minutes,and the emulsion has good stability.The emulsion prepared by mechanical stirring has a wide distribution,with an average particle size of 20 ?m,and the emulsification process takes 3 hours.Compared with the film emulsification,it shows higher preparation efficiency and higher emulsion stability.Then,based on the study of ME,sodium alginate microspheres were prepared by the emulsification-crosslinking method.The preparation conditions of sodium alginate microspheres were optimized by studying the stirring method,stirring speed,crosslinking agent concentration and crosslinking curing temperature during the crosslinking and curing process.The results show that alginate microspheres prepared under mechanical stirring speed of 300 r / min,the concentration of the crosslinking agent 8%(w / v),the crosslinking temperature is 60 ? relatively more uniformly dispersed condition,a relatively smoother surface.