| Recently, abrupt outbreak of epidemical disease, bio-terroristic affair and biological accident all threaten seriously the national security, social stability and the health of people. So many countries focused on the researches of advanced bioprotective equipment, technology and materials. Electrospinning is a technology of obtaining ultrafine fibers by the method that polymer solution or melt is drew by electrostatic force in high voltage field. The diameter of fibers made by electrospinning are often between several decades nanometers and several microns. So the electrospun fiber materials have the properties of large specific surface area and small pores between fibers, which result in that they can be applied in bioprotective field, especially in application of protection against microbe aerosol. PU has an excellent chemical and physical properties, can be produced by industrialized technology, fibers especially elastical fibers can be made easily from PU. So it is very suitable for making functional nanofibers or microfibers by electrospinning. At present, there are few reported researches on microbe protection by PU electrospun fiber materials. In this paper, PU ,which was dissolved in mixed solvent made of tetrahydrofuran(THF) and N,N-dimethyl formamide (DMF), nanofibers were prepared by electrospinning, and antibacterial modification of PU fiber materials was done ,then the capability of protection of the fiber materials against microbe was studied. t is hope to lay a foundation for preparing an advanced bioprotective material.PU as a raw material, which was dissolved in THF/DMF was utilized to prepare the electrospun fibers. The effects of mass ratio of THF to DMF, mass concentration of solution, voltage and distance between the needled tip and the collector on the property of electrospun fibers were studied. The morphology of the PU electrospun fibers were observed by scanning electron microscope(SEM),and the average diameter was calculated by analyzing SEM photos.The results showed the uniformity became worse with increasing quantity of THF. The change of solvent resulted in the variety of viscosity, conductivity and volatility of the solution which all effected on the diameter of the fibers, so the change of the average diameter was complicated. Meanwhile the morphology and diameter of the fibers were nice when THF/DMF was 5/5.The fibers become thicker nonuniform with densifying the solution, which was consistent with other polymers. In this system, morphology and diameter of PU electrospun fibers were nice when the concentration of the solution was 10%.The jet can be formed and PU electrospun fibers can be obtained as the voltage between 20kV and 40kV,jet became unstable with increasing voltage which was disadvantaged to collect fibers, and the stability of jet was also effected by temperature and humidity at the same voltage. But voltage did not have a clear law of effect on the average diameter and uniformity of PU electrospun fibers. The average diameter of PU electrospun fibers achieved the maximum at the distance between the needled tip of 28cm and the minimum at distance of 24cm, but distance also did not have a clear law of effect on the average diameter and uniformity of PU electrospun fibers. To consider the average diameter, morphology of PU electrospun fibers and jet stability when the temperature was between 18℃and 20℃,humidity was between 10% and 15%,the better preparation parameters as follows: THF/DMF was 5/5(mass proportion),the solution concentration was 10%,spinning voltage was 32.5kV,distance was 25cm,spinning flow was 12ml/h. In such conditions, PU electrospun fibers with average diameter of 230nm and good morphology were prepared. The PU electrospun fiber materials prepared respectively 3h and 6h had a better performance of water vapor transmission and mechanical properties, and the water vapor transmission was 8800 g/(m2·d), fracture stress was respectively 10.1MPa and 8.2MPa.PU was dissolved in a mixed solvent of THF/DMF(mass proportion,5/5) and the concentration was 10%.Then the solution was added different kinds of antibacterials, including Ag-loaded titanium dioxide, TCS ,TCC, PCMX,HM-98 andε-PLYS,and the weight of antibacterials in PU electrospun fiber materials was all 5%. In the appropriate condition, PU electrospun fiber mateials which contained different antibacterials were prepared. PU eletrospun fiber materials contained 5% Ag-loaded titanium dioxide, TCS, HM-98 andε-PLYS respectively showed high antibacterial activities against Staphylococcus aureus and Escherichia coli, and the both antibacterial efficiency were more than 99.8%,but the addition of TCC,PCMX did not help the fiber materials show high antibacterial activities. The test of IR spectroscopy and SEM indicated that the antibacterial agents and PU electrospun fibers were mixed evenly and the addition of antibacterial agents did not effect the morphology of fibers much, furthermore, the addition of HM—98 was advantaged to decrease the diameter of the fibers, but which reduced the capability of spinning of the PU solution. After washing the samples, the samples contained Ag-loaded titanium dioxide, TCS retained high antibacterial activity. In this system, it was better to choose Ag-loaded titanium dioxide by considering all the factors.In this study, PU electrospun fibers which contained different amounts Ag-loaded titanium dioxide were prepared in the appropriate condition. The average diameter of the PU electrospun fibers containing 1.0,1.5,2.0,2.5 and 3.0% of Ag-loaded titanium dioxide was 1085,937,827,806 and 664nm respectively. The addition of Ag-loaded titanium dioxide increased the charge density in the jets and resulted in the diameter of the PU electrospun fibers became smaller. The PU electrospun fibers materials contianed more than 1.5% of Ag-loaded titanium dioxide had a high antibacterial efficiency against Escherichia coli and Staphylococcus aureus, and the antibacterial efficiency was more than 99.99% .The mixed mode of PU electrospun fiber and Ag-loaded titanium dioxide nanoparticles was a physical form. The addition of Ag-loaded titanium dioxide did not effect the mechanical property of the fibers much. The method of DOP was utilized to test the filtration efficiency of the PU electrospun fiber materials which contained 1.5% Ag-loaded titanium dioxide and the average weight per square meter was 104.3g/m2 to physical particles aerosol with different diameter by TSI 3160 fractional filtration efficiency tester, and the test flow was 32L/min.The result indicated that the curve of the filtration efficiency was parabola with the increase of aerosol particles diameter, when the diameter was between 0.11μm and 0.13μm,the filtration efficiency was the lowest which was consistent with filter theory. The filtration efficiency to both Escherichia coli and Staphylococcus aureus aerosol of the fiber materials were also tested by microbe aerosol efficiency filtration tester, and the test flow was 28.3L/min.The results showed that the filtration efficiency to Staphylococcus aureus aerosol and Escherichia coli aerosol was 99.97% and 99.99% respectively.The study shows the PU electrospun fiber materials prepared have excellent capability of protection against microbe as well as good physical and mechanical capability, the study will lay a foundation for developing a kind of novel bioprotection material.
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