| Air pollution is a main environmental pollution problem in current.There are many harmful pollutants in the air,especially PM2.5 particles.The aerodynamic diameter of the PM2.5 is less than 2.5μm.It is easy to carry toxic and harmful substances and enter bronchus and lungs with breathing of human,causing cancer,pulmonary fibrosis,and chronic lung diseases.So it’s critical to reduce the PM2.5 exposure level of individuals.At present,the most convenient and effective way to reduce PM2.5 exposure is to wear a mask.Thereby it has spawned a huge market for personal protective equipment.Due to the high demands for protective equipment,there has been much research on high-performance air filtration material,but thermal and wet comfort as an important property of personal protective filter media has been studied too little.In response to the existing problems,this subject developed a high-performance air filtration fiber membrane,which has functions of efficiently separating PM2.5 particles and controlling the one-way transfer of water vapor and quickly removing heat.This media could realize multifunctional synergy of effectively intercepting particles in the air and meanwhile satisfying the heat and humidity comfort of breathing process.Except,this subject also explored the application potential of air filtration media prepared in this study in the field of personal protective equipment.In this study,polyacrylonitrile（PAN）and polyetherimide（PEI）were selected as the solute,and N,N-dimethylformamide（DMF）was used as the solvent.A series of PAN and PEI solutions with a concentration gradient were prepared.During the electrospinning process,the single variable control of the polymer solution concentration,voltage,spinning distance,spinning speed and other parameters,with the SEM morphology observation of PAN and PEI nanofibers,the concentration of the PAN solution was determined to be 10 wt%,12 wt%,14 wt%and 16 wt%,and the concentration of PEI solution was determined to be 10 wt%,the main electrospinning process parameters of both PAN and PEI nanofiber are voltage of 20kV,perfusion speed of 1.5 mL/h,distance of 15 cm.According to known parameters,PAN and PEI fiber membranes（NFMs）and four kinds of PAN/PEI fiber membranes（DNFMs）using different PAN solutions were prepared by electrospinning technology.The structure and properties of each fiber membrane were characterized and tested,it was found that the pore size of NFMs showed a trend of increasing with the increase of fiber diameter,and in the concentration range of 10 wt% to 16 wt%,with the increase of PAN concentration,the performance of DNFMs was effectively improved with the air permeability increasing and respiratory resistance reducing.Then adjusted the weight of DNFMs to explore the effect of weight on its performance.It was found that when the weight of DNFMs was reduced from 7.2 g/m2 to 4 g/m2,the air permeability and pressure drop were also improved.When the basis weight is 7.2g/m2,the membrane with the best comprehensive performance has PAN concentration of 10 wt%,air permeability of 26.62 mm/s,filtration efficiency of 99.88%,pressure drop of 260 Pa,positive moisture permeability（WVTR）of 1.56 kg/（m2*d）andΔWVTR of 0.62 kg/（m2*d）.When the basis weight is 4 g/m2,the membrane with the best comprehensive performance has PAN concentration of 14 wt%,air permeability of 242 mm/s,filtration efficiency of 95.26%,pressure drop of 33 Pa,positive moisture permeability（WVTR）of 1.237 kg/（m2*d）andΔWVTR of 0.458 kg/（m2*d）.Next,using a method of continuous electrospinning and electrospraying,asymmetric superwetting composite nanofiber membranes（SNFM）were prepared.Firstly,prepared a nanofiber membrane of PAN/PEI（10 wt%/10 wt%）via electrospinning,and then assemble the hydrophilic SiO2@PAN microsphere on the surface of the PAN fiber membrane by electrospraying to modify the smooth surface of the PAN membrane and improve the surface hydrophilicity and air filtration performance of the composite membrane,then F-SiO2@PEI microsphere were assembled on the PEI layer by electrospraying to increase the roughness and hydrophobicity of the PEI fiber membrane surface,thus the anisotropic wetting skin layer was integrated with the PAN/PEI fiber membrane,and a multilayer composite nanofiber membrane（SNFM）was obtained with a basis weight of 10.5 g/m2,and three mass ratios of SNFM were prepared to select the best mass ratio of the SNFM.In order to further optimize the performances of asymmetric superwetting PAN/PEI composite nanofiber membranes,strictly controlled the amount of solution in each layer to adjust the basis weight of SNFM,and then obtained SNFMs of multiple groups of various basis weight.After comparative analysis of the SNFMs,it was found that the method of adjusting basis weight to optimize performances of SNFM is directly effective and feasible.The result has shown that reducing the basis weight made the composite fiber membrane be not only lighter in weight,but also maintain high filtration efficiency for PM2.5,and have lower filtration resistance,good breathability and moisture permeability.The final medium SNFM3 has basis weight of 3 g/m2,PM2.5 capture efficiency of 99.3%,filtration resistance of 64 Pa,good air permeability of 278 mm/s,good unidirectional moisture permeability withΔWVTR value of 3.61 kg/（m2*d）,and excellent heat dissipation and cooling performance with infrared transmittance of 99.2%.The results show that reducing the basis weight of fibrous membrane can effectively adjust the wearing comfortability.Finally,SNFM3 was compared with the commercial melt-blown polypropylene（PP）filter material on the market,it’s apparent that the filter media developed in this research would have a broad application in the air filtration field,especially in personal protective equipment for hot and humid environment. |
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