Preparation And Performance Of Gradient Structured High Efficiency Fluffy Composite Air Filtration Materials

With the rapid economic growth,air pollution has been increasingly important issue,especially for the particle size less than 2.5 micrometer(PM_2.5).Studies on fiber materials acting as basis raw materials for air filtration is the key point in filtration field.High efficiency filtration materials turned to focus on electreted melt-blown polypropylene（PP）nonwoven and nano-scale fibers membrane both in research fields and in industry.However,the decay of surface residual electric charges on electreted filtration material with time or storage and usage conditions is caused attention.Meanwhile,the balance between the filtration efficiency（FE）and the pressure drop（ΔP）of the nanofiber using as filtration materials is an extremely urgent problem.Electrospinning nanofibers have received more and more attention because they have a large specific surface area,high porosity and flexible structural design.In this research,we used poly（lactic acid）（PLA）and polyvinylidene fluoride（PVDF）solution system,respectively,to prepare nano-fiber functional layer via electrispinning,and investigated the influence of curved types of recycled three-dimensional poly（ethylene terephthalate）（R-PET）micro-fibers forming the support layer on filtration performation of material.A simple and novel fluffy composite filtration material composed of micro/nano multi-gradient structure was prepared characterizing by high efficiency and low resistance.The raw material selection,curved structure of R-PET,and composite structure on the air filtration performance were systematically studied.Considering the basis weights of nano-PLA membranes,curved types of R-PET fibers on filtration performance and the dust-holding capacity,we found that R-PET/nano-PLA filtration material with zigzag curved R-PET possesses the best filtration performance with FE of 99.992%,ΔP of 201.11Pa,and a quality factor（QF）of 0.047Pa^-1,while the pressure raising rate is the slowest.R/Z-PET fibers with a fiber curved angle of 90°benefit to the decrease ofΔP at high FE when the location angle of zigzag fiber is 45^o along the airflow direction.Ultrafine ZIF-8/PVDF（UF-ZIF-8/PVDF）composite fiber membranes with nanoscale ZIF-8 particles in/on fibers were firstly prepared by electrospinning on R/Z-PET nonwoven webs（R/Z-PET/UF-ZIF-8/PVDF）.The effect of solution concentration on the morphology of PVDF fibers,surface wettability,structure of UF-ZIF-8/PVDF composite membranes,and the filtration performance of R/Z-PET/UF-ZIF-8/PVDF with different basis weight of UF-ZIF-8/PVDF membranes and number of R/Z-PET/UF-ZIF-8/PVDF layers were systematically studied,respectively.Results show that ZIF-8 nanoparticle can significantly reduce the average diameter of UF-ZIF-8/PVDF composite fibers and the minimum average diameter is 83±11nm.Under optimal spinning conditions,FE andΔP of the fiber mat are improved with increasing the basis weight of the UF-ZIF-8/PVDF membranes or the number of R/Z-PET/UF-ZIF-8/PVDF layers.By the optimal number layers favorite the improvement,when the number of composite layers is two,the optimum filtration performance of composite fiber mat shows FE of 99.510%atΔP of 73.8Pa.A new simple composite filtration mat made of curved micro-PET fiber combining with nano-scale fibers provides an available path to mass production of high efficiency filtration material without electreting process.