| The electrospun nanofiber membrane has got a lot of attention from many areas becauseof the characteristics of light weight, good permeability, larger specific surface area, high porerate and good internal pore connectivity, which is especially suitable for used for filteringmaterials. But the nanofiber felt can’t be used alone because of low strong. In allusion to thisfault, this paper chose the biodegradable PLA material to prepare PLA electrospun fibers onthe PLA nonwoven fabrics to prepare compound filter materials. With this method, on the onehand, the nonwoven fabrics can improve the power of the nanofiber membrane. On the otherhand, the nanofiber membrane can improve the filter performance of the filter material. Thispaper aims at solving the existing "indoor air pollution" through adding silver to theelectrospun fibers to prepare air filter with good antibacterial and filter properties. The mainresearch contents have the following several parts:(1) Determine the parameters of electrospinning PLA fibers. Through experiments toanalysis the influence on the electrospun PLA fibers’ morphology and the diameters from theproportion of the spinning solution solvent, the quality score of PLA, the electrospinningvoltage and C-SD in the electrospinning process. The results showed that: the proportion ofCHCl3and DMF in the electrospinning solution has obvious effect on the electrospun PLAfibers. And the best ratio for the solvent CHCl3and DMF is8:2(w/w). Through calculatingand comparing the average diameter, standard deviation and CV value of the electrospunfibers, we determined the parameters: the quality score of PLA is10%, the electrospinningvoltage is17kV, and the C-SD is20cm.(2) Prepare the PLA/Ag composite nanofibers. With different quality of AgNO3in theelectrospinning solutions were used to electrospinning. The PLA fibers containing Ag weremade by the ultraviolet light to reduce the AgNO3to Ag. Through the scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM) to observe and analysis thedistribution of the Ag in PLA fibers and the fluence on the fibers’ morphology. The resultsshow that: with the increase of the content of silver, the fibers’ diameters become thinner. Butwhen silver content reached to3%, the fibers become thick with small influence from theconductivity of the electrospinning solution. The silver can distribute evenly on the fibers.And with the content of silver increased, the distribution of silver on the fiber surface is alsoincreased, the particle of the silver also become larger.(3) Preparation of the composite filter material. Magnetron sputtering and lowtemperature plasma were used to treat the surface of the nonwoven fabrics. FTIR and appliedelectric field are used to analysis the surface of the treated nonwovens, which showed that alarge number of polar groups-COOH on the surface of the sample after plasma’s treatment.The polar groups can improve the capacity of the nonwovens’ fugitive charge. The experimentof the treatment nonwovens composited with the electrospun fibers confirmed that thesurface’s treatment of the non-woven fabric can improve the distributive uniformity of theelectrospun on the nonwovens. And the pore diameters of the composite filter membranebecome smaller, the pore size distribution becomes more even.(4) Influence of the electrospinning time on the parameters and performance of the filters. The composite filtering materials with different thickness of the electrospun nanofiber layerswere made through controlling different electrospinning time. The porosity, pore diameter,pore size distribution, filtration efficiency and pressure drop of the composite materials weretested. The result showed that: the porosity and pore diameter of the composite were reducedwith the increase in electrospinning time. And the pore size distribution was more centralized.When the spinning time increased to2hours, the filtration efficiency of more than0.3μm ofparticle is more than99%, and filtration resistance is low.(5) Different silver content affects the antibacterial properties of the compositemembrane filters. The composite filtering membrane contenting unequal quantities of silverwere used to test the antibacterial performance for Escherichia coli. The result showed that:the antibacterial property of the composite membranes is enhanced with the increasing of thesilver content. But when the silver content reached to a certain value, the silver particles havea high particle agglomeration level, which affects the silver antibacterial performance of thecomposite membranes. When the content of silver reaches to2%, the membrane got the bestantibacterial property. The antibacterial ratio can reach to more than99%.This paper carried out a systematic study and analysis from the process of PLAelectrospinning to the preparation the composite filtering membrane and the filterperformance and antibacterial performance, which provides a theoretical foundation and basisfor the filter material to create a clean space. |
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