Preparation Of Micro/nano Fibrous Air Filter And Study Of Its Performance In Filtration And Antibacteria

According to the data of World Health Organization(WHO),92%humans live in the heavily polluted areas.About 3 million people died because of exposing in outdoor air pollution every year.In order to deal with this problem and protect people's health,many researches about air filtration products have been studied.In the early stage,the research on air filtration materials mainly focused on the process control and production of nonwovens.However,the traditional nonwoven materials have defects such as large fiber diameter and low filtration efficiency,which usually require electret and compound treatment to achieve high filtration performance.With the development of electrospinning technology,the nanofiber materials with small fiber diameter,high specific surface area and small pore diameter can be directly prepared by electrospinning technology,which has high filtration performance.Nevertheless,the research on high-efficiency and low-resistance filter materials is still a problem at present.To overcome the above problems,this thesis mainly studied the relationship between structural regulation and filtration performance for nanofiber air filtration materials.By change the structure of nanofiber,the diameter and filtration performance can be controlled,which provided a positive research and development of high-efficiency and low-resistance filtration materials.Polyvinylidene fluoride(PVDF)nanofibers were compounded with nonwoven materials,and the structure of nanofibers and microfibers was used to improve the filtration performance of nonwoven materials.The composite of silver nanoparticles and PVDF nanofibers enables the filter material have both high filtration performance and excellent antibacterial function.Specific achievements are as follows:(1)Study the relationship of nanofiber air filter materials between structure and performance of filtration.First,change the diameter of electrospinning nanofibers and get the analysis of fiber formation and influencing factors.It is found that the diameter of electrospinning nanofibers is affected by many factors,and different factors play different roles in different stages of formation.Different prediction formulas were used to predict the fiber diameter,but when the effect of each factor on fiber diameter was analyzed separately,there will be a large deviation between the experimental value and the predicted value,and the prediction accuracy was not high.Therefore,comprehensively analyze the influence of these factors and modify the established fiber diameter prediction formula,the experimental data shows that the modified empirical formula has higher prediction accuracy for fiber diameter;for the reason of the air filter material aiming at between 0.2?0.5?m particles,so the filtration mechanism is mainly determined by interception,brownian diffusion,interception and brownian diffusion.The prediction formula of the filtration efficiency and pressure drop of the filter material was determined by the three filtration mechanisms,single fiber capture efficiency.The experimental data showed that the interception effect is the strongest among the three filtration mechanisms,and the comparison between the predicted value and the experimental value shows that the formula for filling rate was 7%?23%and 90?110 nm in diameter.The filtration efficiency of nanomaterials shown better prediction precision,the pressure drop of deviation of the predicted values and the experimental value was bigger,and the experimental values were larger than the predicted values.The reason is multifaceted,the intercepted filter particles were loaded on the fiber and then form an intercepting effect on the subsequent particles,thereby causing the pore size of the nanofiber membrane to decreased and the filtration resistance to increased,so the effects of particle deposition should also be considered when the theoretical analysis of the pressure drop;(2)By means of electrospinning technology,high-performance PVDF nanofiber was directly compounded with the nonwoven fabric which worked as the receiving material.In this mothed,the process of late thermal bonding can be eliminated,and the composite of the two materials can be intact without destroying the morphology and structure of the fiber,so as to form a composite micro/nano fiber with high efficiency filtration performance.The test data of the pore size and filtration performance has improved after composited,because of chosen two kinds of fiber materials were hydrophobic material,so the composite will not change its original hydrophobic properties.In the future,it also could be select two different properties of composite materials and to get double filter media with different hydrophobic properties.Meanwhile,the application field of composite micro/nano fiber will be further expanded.(3)In order to give nanofiber membrane versatility.The size of about 10 nm silver particles was prepared by liquid phase reduction method.Then,mix up the particles and PVDF solution.Finally,it was obtained a high filtration efficiency and antibacterial function nanofibrous membrane by electrospinning,the SEM(Scanning Electron Microscope)of nanofiber morphology and X ray diffraction diagram was proved that the reduction of precipitation of silver particles load on the surface of fiber,some exist in the fibers;It was found from the test data of water contact angle that the addition of appropriate amount of silver particles would not change the hydrophobic property of the original PVDF nanofibrous membrane.The antibacterial test results show that the fiber material added with silver particles have high efficient and lasting antibacterial properties against staphylococcus aureus(S.aureus)and escherichia coli(E.coli),the bacteriostasis rate of the two strains was still 100%after two weeks when the content of silver was 0.12g.Filter performance testing results indicated that compare with origin PVDF nanofibrous membrane,the nanofibrous membrane with silver particles have a better performance,because the "tree-like"nanofiber after add silver nanoparticles not only reduced the nanofibrous membrane's pore size,also improve the filtration efficiency of the filter,although the pressure drop fluctuates up and down,but the fluctuation amplitude is small,and the quality factor reaches the maximum value of 0.0575 when the silver content is 0.08g.