Preparation And Properties Of Micro-nanofiber Multi-layer Composite Air Filter Material

The combustion of coal,petroleum and other energy,automobile exhaust,industrial waste gas emissions and land desertification have caused serious environmental deterioration,air pollution and other problems,which seriously affect people’s daily life and physical health.Fiber air filters can remove most of the particles in the air,which is one of the effective ways to solve the air pollution problem.Therefore,the development and application of high efficiency and low resistance fiber air filters is the focus of attention.This project combined electrospinning technology,dry-laid process and hot air bonding process to prepare micro-nano ES/PAN fiber multilayer composite filters.Through the design of electrospinning process,the selected process ensured the nanofiber distribution was relatively uniform,the fiber shape was straight and smooth,and the diameter distribution was concentrated.Then the proper hot air bonding temperature and hot air time were selected to ensure that nanofiber web of composite materials was firmly bonded to the base web,composite materials had certain dimensional stability,integrity and large breaking strength,and the possibility of practical application.Then,single factor experiment and orthogonal experiments were performed on multilayer composite filters.The results show that,at the same total areal density and total electrospinning time,when the number of layers is less than 10,the filtration efficiency and filtration resistance of multilayer composite filters are smaller than that of monolayer composite filter,and quality factor(QF)increases,and when the number of layers is more than 10,the filtration efficiency and QF of multilayer composite filters are larger than that of monolayer composite filter,and the resistance is slightly reduced or only increased by 5 Pa.Therefore,micro-nanofiber multilayer composite method is effective to improve the filtration efficiency of filters,but the more the number of layers,the better the effect.At the same total areal density and the number of layers,the filtration efficiency of multilayer composite filters increases significantly with the increase of electrospinning time,but the filtration resistance also increases sharply,so that the QF increases to the maximum value and then decreases.This indicates that the choice of electrospinning time should be reasonable,and the comprehensive filtration performance of materials can not be neglected just to improve the filtration efficiency.In addition,according to the range analysis of orthogonal experiment,the importance of the three factors on air permeability is: total electrospinning time>total areal density of the microfiber web>the number of layers,the importance of the influence on the filtration efficiency and filtration resistance is:total electrospinning time>the number of layers>total areal density of the microfiber web.Finally,two groups of ES/PAN multilayer gradient composite filters were prepared by using electrospinning time and areal density of the microfiber web as gradient respectively.It is found that air permeability of two groups of materials changes little.As the gradient increment of electrospinning time increases,the filtration efficiency of multilayer gradient composite filters for particle with different size is gradually increased,the filtration resistance is slightly increased,and the QF is increased.As the gradient increment of areal density of the microfiber web increases,multilayer gradient composite filters improve slightly the filtration efficiency for particles with different sizes.The filtration resistance remains unchanged,and the QF is increased.In addition,the filtration performance of multilayer gradient composite filters has the same tendency on the front and the back,but the filtration performance on the back side is slightly worse than the front side.