Fabrication Of PVP Aligned Fibers By Magenetic-filed-assisted Electrospinning Method

The fabrication of polymer nanofibers by electrospinning has received much attention inrecent years. However, electrospinning nanofibers are often collected as a randomly orientedmess due to the bending instability of the highly charged electrospinning jets. The disorderedstructures of these nanofibers limit the application of them. In recent years, well-alignednanofibers can be produced using many novel methods by refitting collectors. Unfortunately,these methods have many certain defects. In this paper, well-aligned PVP nanofibers werefabricated using Magnetic-Field-Assisted electrospinning (MFAES) equipment consisting oftraditional electrospinning equipment and two parallel placed permanent magnets.In this article, firstly the equipment of MFAES has been introduced. And then themoving behavior of the jets during the MFAES process was analyzed. The result indicates thatthe magnetic field creates a radial Lorenz force on the jet, which makes the fibers aligned. Jetmovement process was researched by high-speed camera.Secondly, the influence of solution properties on the fiber morphology and alignmentwere studied. As the result, with the increase of concentration, the fibers get thicker, the fiberdistribution gets wider, the fiber alignment get higher. The best concentration of PVP/Ethanolsolution was12wt.%. Moreover, an excess of LiCl content has bad infect on the fibermorphology and alignment. The best concentration LiCl was0.4wt.%. The influence of ninekinds of solvent systems were studied in this thesis, and in consequence Ethanol,Ethanol/N,N-dime-thylformamide(DMF) and DMF/Acetone were the excellent solventamong them.Lastly, six parameters have been researched, such as Magnetic field intensity, Magnet spacing, Voltage, Distance, Flow rate and Receivers.(1) As the result shown, with theincrease of Magnetic field intensity, the fibers get thicker, the fiber distribution get wider, thefiber alignment fristly get higher and then remain the same. The best Magnetic field intensitywas0.3T.(2) As a result, with the increase of Magnet spacing the fiber diameter increased,the fiber distribution and alignment fristly increased and then decreased. The best level was2.5cm.(3) In consequence, with the increase of voltage the fiber diameter decreased, the fiberdistribution and alignment fristly increased and then decreased. When the voltage was at15kV, uniformly and aligned fibers was obtained.(4) An increase of distance can result indecreasing of fiber diameters and alignment firstly and then increased, broadening of thediameter distribution. And the best distance was15cm.(5) When the solution flow rateremain at lower level, the fiber morphology and aglinment are better. The best level is1.0mL/h.(6) In this thesis, the aluminum foil plate is divided into two pieces and put on thesurface of two magnets. As the result, the fibers become more aligned. Moreover, with theincreasing of the width of aluminum foil plate the fibers become more unifromly and aligned.And the best level was8cm.