Studv On The Preparation Of Centrifugal Spinning-Electrostatic Collecting High Efficiency Air Filtration Ultrafine Fiber Membrane

With the rapid development of industry,the problem of air pollution has become increasingly serious.Haze mainly refers to PM2.5 particles that cause serious harm to the human body.Its particle size is less than or equal to 2.5 μm,which is easily inhaled by the human body and has strong adsorption capacity.Studies have shown that long-term exposure to PM2.5 particles can cause diseases such as lung cancer,myocardial infarction,and vascular disease.Aiming at PM2.5 pollution,this thesis aims to study an ultrafine fiber membrane with high efficiency air filtration performance.The fiber membrane exhibits larger fiber specific surface area,higher porosity,and smaller pore size with the smaller fiber diameter.Ultrafine fiber has a wide range of applications in filtration and other fields,because it can absorb dust,particles,liquids with 7 times of its own weight.At present,the spinning technologies for preparing ultrafine fiber membranes mainly include electrostatic,centrifugation,self-assembly and phase separation.Among them,electrostatic spinning and centrifugal spinning are the two most commonly used technologies.Due to the high voltage,the polarity requirements of the solution,and the compacted structure of the prepared fiber membrane during the electrospinning process,the air resistance during filtration is large;the fiber assembly prepared by centrifugal spinning has a fluffy structure,which can reduce the air resistance of the fiber membrane,while centrifugal spinning is difficult to directly form a film due to the spiral trajectory of the fiber.Therefore,how to prepare ultra-fine fiber membrane with high efficiency and low resistance is the research focus of this paper.Centrifugal spinning-electrostatic collection is a new technology which effectively combine the electrostatic spinning and centrifugal spinning to produce ultrafine fibers.This technology not only absorbs the advantages of centrifugal spinning,but also breaks through the limitations of electrostatic spinning.Through centrifugal spinning-electrostatic collection technology,a fluffy fiber membrane with a fiber diameter of less than 1 μm can be directly obtained.Therefore,the centrifugal spinning-electrostatic collection spinning technology has greater advantages in the field of preparing air filtration ultrafine fiber membranes.The second chapter studied the molecular weight of raw material polyacrylonitrile(PAN),the ratio of polyacrylonitrile(PAN)/N,N-dimethylformamide(DMF),the diameter of the needle,and the spinning speed on the spinnability and morphological influence of ultrafine fibers.The results indicated that when the PAN molecular weight,PAN/DMF ratio,needle size,and spinning speed are too large or too small,the fiber membranes appeared fiber bonding,disordered,uneven fiber distribution and a large number of beads.By adjusting parameters to the optimal conditions,the obtained fiber membranes performed a good morphology,a uniform fiber diameter and no beading.Among them,the optimal conditions for each spinning parameter are:PAN molecular weight is 150,000,PAN/DMF mass ratio is 15%/85%,needle size is 27 G,and spinning speed is 2500 rpm.The average fiber diameter is around 700 nm.The third chapter studied the effect of the basis weight of the ultrafine fiber membrane on the filtration efficiency and air resistance of the fiber membrane prepared.The larger basis weight,the filtration efficiency reflected higher filtration efficiency.When the basis weight was 0.3 g/m2,the filtration efficiency of the fiber membrane was 61.22%,and the filtration efficiency was 98.89%with the basis weight was increased to 2.1 g/m2.By testing the performance changes of ultrafine fiber membranes in long-term use,the results demonstrated that with the increase of the use time,the filtration efficiency of ultrafine fiber membranes increase unceasingly,while the air resistance continues to increase.The fourth chapter studied the effects of thermal bonding and adhesive bonding on the filtration performance of fiber membranes.In thermal bonding,the optimal thermal bonding temperature was determined to be 130℃ by observing changes in the surface of the fiber membrane,fiber morphology,and their effects on the filtration efficiency and resistance of the fiber membrane by changing the bonding temperature.In adhesive bonding,the filtration performance of fiber membrane was reduced to 83.66%,and the air resistance was increased to 43 Pa.By comparing the effect of thermal bonding and adhesive bonding on the filtration performance of fiber membranes,the thermal bonding showed better results.