| With the development of industrial technology,people have higher and higher requirements for air filtration materials.Traditional air filtration materials are mainly concentrated on nonwovens,which are too large in diameter and large in pore size between internal fibers to achieve efficient and accurate filtration.Electret or composite treatment is required to improve filtration performance.In recent years,nanofibers prepared by simple and easy to operate electrospinning technology have been widely used in air filtration due to their advantages such as fine and controllable fiber diameter,large surface area,small and uniform pore size.However,conventional nanofibers have problems such as poor mechanical properties and dense stacking,making it difficult to balance filtration efficiency and resistance when used as filter materials.Therefore,this article proposes a method of preparing multi-layer structure,high fluffiness polyvinylidene fluoride(PVDF)nanofiber membrane based on electrospinning technology,applying it as an efficient and low resistance air filtration material,and modifying its antibacterial function to apply it to mask protective materials.(1)Firstly,in order to obtain extremely fine nanofibers with a diameter less than 50 nm,this chapter proposes an electrospinning method based on dilute solution,high molecular weight,and high conductivity spinning solution,and studies the effects of molecular weight,spinning concentration,tetrabutylammonium chloride(TBAC)content,voltage,and other factors on the formation of ultra-fine fibers.The results showed that PVDF with a molecular weight of 300000 and a concentration of 20 wt% was the optimal scaffold fiber morphology.With a molecular weight of 600000 and a concentration of 3 wt%,a TBAC content of 5 wt%,and a voltage of 30 k V,the prepared ultra-fine fibers had good morphology and uniform distribution,with an average diameter of about 30 nm.(2)To solve the problems of dense stacking,low porosity,and poor permeability of conventional nanofibers,this chapter constructs a multi-layer and fluffy PVDF fiber membrane based on extremely fine nanofibers.The results showed that when the ratio of scaffold fibers to extremely fine fibers was 2:2,a small and uniformly distributed pore size(0.73)was preparedμ m)and a composite membrane with a high porosity(92.75%),and this is the optimal structure to construct a multi-layer structured nanofiber membrane.The pore structure,wettability,breaking strength and particle trapping performance among single-layer,two-layer and fourlayer nanofiber membranes were compared.It was found that the four-layer nanofiber membrane had small pore size(0.36 μm),high porosity(94.56%),excellent mechanical properties(stress 37.63 MPa,strain 67.03%)and excellent filtration performance(filtration efficiency 99.98%).And it has a certain hydrophobicity(water contact angle is 128.6).Finally,after 10 washing cycles,its filtration efficiency can still be kept above 90%,showing a longterm and stable filtration ability and service life.(3)To broaden the application field of this multi-layer nanofiber membrane,this chapter develops antibacterial modification of multi-layer structured PVDF nanofibers,prepares air filtration materials with antibacterial functions,and applies them to mask protective materials.First,we defluorinate and hydroxylify the nanofiber membrane of PVDF scaffold,then modify it by halamination,and finally give it excellent antibacterial function by chlorination.Also in order to enhance the filtration performance,microfibers are spun on the surface of the PVDF nanofiber membrane of the modified scaffold.After SEM observation,the fibers still maintained their original morphology and structure after antibacterial modification,and the multi-layer fiber membrane had a 99.9% antibacterial effect on E.coli and S.aureus.At an airflow velocity of 32 L/min,the PM0.3 removal efficiency was 99.93 %,and the filtration resistance was 79 Pa,and the antibacterial efficiency remains above 90% after 10 chlorination treatments.To sum up,the developed multi-layer PVDF nanofiber membrane can realize the synergistic effect of high-efficiency filtration and stable and long-lasting antibacterial action,which are of significant significance to the development of air filtration systems and multifunctional protective materials... |
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