| Polytetrafluoroethylene（PTFE）is a polymer material with hydrophobic,chemical stability,thermal stability and other properties,and therefore widely used in aerospace,communications engineering,military industry and other fields.By virtue of the scale effect and the layer upon layer accumulation of micro-nano fibers,the excellent performance of PTFE is further amplified,and the application prospect of PTFE in air filtration,water treatment and other fields is expanded.PTFE micro-nano fibers are prepared by carrier spinning method.This special preparation method makes it difficult to develop micro-structure on the fiber surface to improve the performance.Therefore,how to develop the special structure of PTFE micro-nano fiber is the focus of this paper.Air filtration and oil/water separation are very important applications of PTFE micro/nano fibrous membrane,which requires that the prepared fibrous membrane should have high filtration efficiency and low resistance performance.In this paper,the electrostatic-centrifugal spinning technology was used to prepare PTFE micro-nano fibrous membrane.Combining the advantages of electrospinning and centrifugal spinning,the membrane with high filtration efficiency and low filtration resistance can be obtained,and the yield is relatively high.In Chapter Two,Polyethylene oxide（PEO）and Polyvinyl pyrrolidone（PVP）were mixed with PTFE emulsion to prepare spinning solution.The effects of solute ratio and concentration of spinning solution on the morphology of primary fibers were studied.The similarities and differences between PVP/PTFE and PEO/PTFE spinning solutions in the process of fiber preparation and forming were compared.In the process of spinning,the amount of PEO is less（4%）to produce good fiber morphology,while the amount of PVP is more than 14%to form the fiber.With the decrease of the concentration of spinning solution,the diameter of the prepared primary fiber also becomes smaller.Compared with PEO,the thermal decomposition temperature of PVP is higher（>440°C）,and therefore PVP is more conducive to develop the surface microstructure of PTFE micro-nano fiber.In Chapter Three,the microsphere structure of PTFE micro-nano fibrous membrane was prepared.The influence of the solute ratio on the surface microsphere structure was studied and the influence of the change of microsphere structure on the performance of the fibrous membrane and the application of oil/water separation was discussed.The number and size of microsphere structures can be controlled by changing the solute ratio.The increase of microsphere structures can improve the surface roughness of the fibrous membrane,increase the internal void of the fiber membrane,and then increase the water contact angle（154.6°）and porosity（94.6%）of the fiber membrane,improve the oil-water separation performance of the fibrous membrane.The flux can reach 3650 L m-2h-1,and the separation rate is more than99.1%.The membrane shows good durability,wear resistance and acid/alkali resistance stability.In Chapter Four,the porous PTFE micro-nano fibrous membrane was prepared.The influence of the solute ratio on the porous structure of the fiber surface was studied,and the influence of the change of the porous structure on the mechanical properties and air filtration performance of the fibrous membrane was discussed.The number and size of porous structures can be controlled by changing the solute ratio.With the increase of porous structure,the internal voids of the fiber were increased,and the porosity of the fibrous membrane was further increased（94.1%）,and the permeability of the fiber membrane was improved.The interception rate can reach99.72%,and the air resistance is less than 90 Pa,showing excellent air filtration performance.Moreover,because of the high thermal stability of the fibrous membrane,it has shown great application prospect in the field of high temperature filtration. |
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