Preparation And Air Filtration Performance Analysis Of PU/PVB-based Composite Membrane

The rapid development of industry emits large quantities of small diameter pollutant particles（PM）,causing serious air pollution.Inhalation of PM particles can cause human respiratory infections,lung diseases,asthmas and bronchitis,posing a huge threat to human health.Therefore,air pollution management has become a hot issue in international research.At present,commonly used air filtration materials have large pores,uneven fiber thickness and other structural shortcomings which cannot intercept PM particles,while electrospinning fiber membrane has a large specific surface area,small pores,adjusted fiber structure and other advantages which is widely used in the field of air filtration to effectively filter PM particles.In this research,we used polyurethane（PU）and polyvinyl butyral（PVB）as raw materials and introduce polystyrene（PS）micron fibers and barium titanate（BaTiO₃）nanoparticles to prepare high-efficient and low-resistance composite fiber membranes based on the electrospinning process.Firstly,PU/PVB composite nanofiber membranes were prepared by electrospinning.The effects of the mass fraction of PU/PVB solution and the mass ratio of PU to PVB on the morphology of the fibers were investigated.The results showed that changes in mass fraction and mass ratio led to changes in solution viscosity and electrical conductivity,which regulate the diameter and morphological structure of the fibrous material.When the mass fraction of PU/PVB was 14 wt%and the mass ratio of PU to PVB was 8/2,the average diameter of the fibers was 385 nm,which was 51%less than the average diameter of PU;it had excellent mechanical properties,with a fracture stress of 16 MPa,which was 45%higher than the fracture stress of PU nanofiber film,and a fracture strain of148%.It also had a good thermal stability（decomposition onset temperature of 289.37℃）,an average pore size of 1.78μm,a porosity of 77%,a filtration efficiency of 98.851%for PM_0.3,a filtration resistance of 181.7 Pa and a quality factor of 0.0246 Pa^-1.This indicated that PU/PVB nanofiber membranes could effectively intercept microfine particles and thus had a high filtration efficiency.Secondly,in order to further reduce the filtration resistance of the composite nanofiber membrane,this research introduced PS micron fibers.Using two sets of electrospinning machine jet pair spray to prepare PU/PVB-PS multistage composite membranes with fluffy structure.First,investigated the effect of the mass fraction of PS on the fiber diameter and morphological structure,and then analyzed the comprehensive performance of the PU/PVB-PS multistage composite membranes.The results showed that micron-sized PS fibers（1.54 to 3.13μm）could build fluffy fiber support structures for PU/PVB nanofibers,thus regulating the structure of the fibrous membrane.Due to the difference in fiber size by one order of magnitude,the fiber diameters of PU/PVB-PS showed a clear bimodal distribution.In particular,when the mass fraction of PS was 25wt%,the PU/PVB-PS fiber membrane had a fracture stress of 1.53 MPa,a fracture strain of 136%,a good thermal stability of the fiber membrane（decomposition onset temperature of 303.03℃）,an average pore size of 9.38μm,a porosity of 86%,a filtration efficiency of 96.862%for PM_0.3,a filtration resistance of 18.3 Pa,and a quality factor was 0.1892 Pa^-1.This indicated that the construction of the fluffy structure could reduce the filtration resistance of the fiber material and thus improved the quality factor of the fiber material.Finally,in order to further improved the filtration performance of PU/PVB-PS fibrous membranes,ultra-fine nanofibers were prepared by doping BaTiO₃ nanoparticles in PU/PVB to improve the interception capacity of the fibrous membranes for microfine particles.Firstly,the effect of BaTiO₃ mass fraction on the diameter and morphological structure of PU/PVB fibers were investigated,and the results showed that the addition of BaTiO₃ significantly increased the electrical conductivity of the mixed solution and thus reduced the diameter of the composite nanofibers（269-324 nm）.When the mass fraction of BaTiO₃ was 2 wt%,the fracture stress of PU/PVB/BaTiO₃-PS fiber membrane increased to 1.82 MPa,while the addition of BaTiO₃ enhanced the thermal stability of the fiber membrane（the decomposition onset temperature increased to 320.51℃）,an average pore size of 5.99μm,a porosity of 79%,a filtration efficiency of 99.935%for PM_0.3,a filtration resistance of 48.1 Pa,and a quality factor was 0.1524 Pa^-1,indicating that the addition of nanoparticles could further enhance the filtration efficiency of the fibrous material while maintaining the low filtration resistance of the fibrous membrane.The research in this paper provides new ideas for the preparation of high efficiency low resistance composite fiber membranes and their application in the field of air filtration.