The Effect Of Surface Energy Of Nanofibrous Membranes On The Air Filtration Performance In The Dynamic Filtration Process

With the development of society,people pay more and more attention to health and the air environment in where they live.There are also different types of particles in specific environments,and they can generally be classified into two categories: salty aerosol particles and oily aerosol particles.Oily particles are mainly the atomization and condensation of liquids,sub-micron-level droplets generated in industrial processes,and acid mist,alkali mist,and oil mist formed by chemical reactions.It seriously endangers people's health,machine operation,and destroys material materials.However,the most effective way to deal with air particles pollution is to use air filter to isolate the particles.Electrospun nanofibrous nonwovens membranes have advantages such as small fiber diameter,large specific surface area,and high porosity,which make them important in the field of air filtration.Because the oily particles are liquid and have fluidity,they will be greatly affected by the inherent properties of the material when they are in contact with the material.Therefore,this project focuses on the study of the change in the filtration performance of oily particles by air filter materials with different surface energies.By changing the surface roughness and chemical composition of the materials,nanofibrous membranes with different surface energies were prepared,and their mechanical properties and filtration properties were analyzed.Polymer: PAN was first used for electrospun.As the spinning time increased,the thickness of the electrospun nanofibrous membrane and the square meter's weight increased linearly,and the breaking strength of the nanofibrous membranes also increased linearly.The larger the thickness of the electrospun nanofibrous membranes,the smaller the pore size,the more uniform the pore size distribution,and the greater the initial filtration efficiency.The filtration pressure drop of the electrospun nanofibrous membranes will increase with the increase of the filtration efficiency,and it is basically positively related to the thickness of the membranes.The average diameter of the nanofibrous membranes were adjusted by changing the concentration of the spinning solution to obtain samples with different roughness.The rate of dynamic filtration efficiency of the nanofibrous membranes decreases with a negative correlation with the average diameter,and the rate of increase in filtration pressure drop has a negative correlation with the average pore size.The surface roughness of the nanofibrous membrane is a factor that is also affected by the fiber diameter and its distribution of the nanofibrous membranes.Therefore,it cannot be explained that the surface energy of the fiber membrane has a very direct influence on its dynamic filtration performance.In order to prepare nanofibrous membranes with different chemical compositions,two polymer polymers,CA and PVDF,were selected as raw materials.Nanofibrous membranes were prepared by blending with PAN.Considering its fiber diameter,pore size,mechanical properties,and filtration performance,the optimal blending ratio of PAN and PVDF is 7: 3,and the most suitable spinning solution concentration is 12%.The optimal blending ratio of PAN and CA is 8: 2.The most suitable spinning concentration is 8%.In the same time,these two nanofibrous membranes have the same fiber diameter with the pure PAN nanofibrous membrane.Compared with nanofibrous membranes with the same roughness but different chemical composition,the decrease rate of the dynamic filtration efficiency of PAN/PVDF is the fastest,next are PAN,PAN/CA,and the increase rate of the filtration pressure drop of PAN is slower.The filtration pressure drop of PAN/CA & PAN/PVDF rise faster.For the same liquid,the smaller the surface energy of the materials,the worse the wettability of the liquid on its surface.During the filtration process,the oily droplets are less likely to adhere to the lower energy surface,so they are more likely to be blown out or aggregated into large particles,blocking the pore size,cause the filtration efficiency to decrease faster and the filtration pressure drop to rise faster.Composite nanofibrous membranes were prepared by using the above three types of nanofibrous membranes: PAN,PAN/CA,and PAN/PVDF as drainage layers.Compared with a single-structure nanofibrous membrane prepared by 10% PAN spinning solution,composite nanofibrous membranes have a higher initial filtration performance.When the drainage layer of the composite nanofibrous membranes have a larger surface energy,the wettability of the oily particles on the surface is more likely to infiltrate and penetrate the liquid,which greatly reduces the effective capture area of the particles,so its filtration efficiency decreases faster.It is also due to the large surface energy that the liquid's adhesion is greater.When the liquid plugs the pore diameter,it often brings greater pressure drop changes.