Electret Polyvinylidene Fluoride Nanofibers/Polytetrafluoroethylene Composite Fibrous Membrane For Air Filtration

Owing to the abominably environmental particular matter pollution and severely global energy crisis,ever-increasing research efforts have been committed to develop filter materials with high filtration efficiency to effectively wipe out particles and ultralow air resistance to attain the anticipated purpose of energy conservation.The conventional fibrous filtration materials such as melt-blown fibers and glass fibers,with tortuous porous structures and comparatively high porosity,have become the most pivotal materials for air filtration.However,conventional fibrous filtration materials based on mechanical filtration manner,are incapable of meeting the requirements of highefficiency and low-resistance due to the compacted stacking structure or large aperture size.Benefiting from the ability of quasi-permanent reserving abundant charges and creating an external macroscopic electric field on the periphery of fibers,electret fibrous membranes have been proven to be a feasible,efficient and promising materials to intensively absorb PM2.5 by long-range electrostatic force.Many electret technologies,such as corona charging have some drawbacks.The defects are relatively slight dipole charges and unsatisfactory charge stability Electrospinning as a burgeoning technology for nanofiber-fabrication,which provides a versatile method for in situ charges injection before the formation of fibers,could effectively address the bottleneck of common electret techniques.Up to now,just a handful of efforts have been committed to investigate the electret performance and air filtration properties of electrospun membranes.Some electrospun filter media,such as polyamide-6/boehmite,polystyrene /polyacrylonitrile,polyetherimide /silica,have been successfully fabricated.However,the resultant fibrous membranes mentioned above are still subjected to several deficiencies,which seriously impeded its practical utilization.Accordingly,fabricating cost-effective electret materials for air filtration with abundant charges and excellent charge stability by simple approach is still a big challenge to be resolved.Herein,we present a facile strategy to fabricate electret fibrous membranes with elevated surface potential and enhanced charge stability via electrospinning.Firstly,polyvinylidene fluoride(PVDF)as matrix polymer and polytetrafluoroethylene nanoparticles(PTFE NPs)as inspiring charge enhancer dissolved in N,N-dimethylfomaimide(DMF)were electrospun by adjusting the processing parameter of different concentrations of PTFE NPs nanofibrous membranes.Thinking about the morphology and the properties of PVDF/PTFE nanofibrous membranes,the best properties could be acquired when the content of PTFE NPs achieved 0.05 wt%.High energy injection strategy which could effectively promote the depth of energy level,was adopted to further increase quantity and reinforce stability of charge under various electrospinning voltages using PVDF/PTFE fibrous membranes.Under the injection energy of 40 k V,the resultant electret PVDF/PTFE fibrous membranes exhibited the high surface potential and excellent charge stability.The fibrous membranes are endowed with elevated surface potential from 0.42 to 3.63 k V and reduced decrement of charges from 75.4 to 17.5%,In addition,the influence of basic weight and air flow on the PVDF/PTFE fibrous membrane filtration performance is studied.The filtration efficiency increase with the increase in basic weight,the filtration efficiency decrease with the increase in air flow.Furthermore,the influence of PM2.5 on the PVDF/PTFE fibrous membrane purification performance is studied.Meanwhile,to compare with other electret fibrous membranes,benefiting from the high mechanical filtration efficiency with extraordinary stability of charge,the novel electret PVDF/PTF fibrous membranes were equipped with both high filtration efficiency of 99.972% and low pressure drop of 57 Pa.We envision that this novel electret materials which have excellent filtration performance and charge stability would open up an opportunity for the development of filters.