Design And Research On A New Spinneret Based On Simulation Of Electric Field In Electrospinning

Eletrospinning is a straightforward and cost effective method for fabricating submicron fibers. The electric force used as drawing force is one of the most remarkable differences between electrospinning and traditional dry/wet spinning. The electric-field distribution of spinneret has very important influence on the formation and trajectory of jets. Therefore it is very necessary to research the electric field in electrospinning. The computational software Ansoft Maxwell12was adopted to simulate the electric field of spinneret, which could show the electric-field distribution simply and intuitively. By this way, the effect of electric intensity on formation of fibers is analyzed in depth, to provide the reference for industrial production of electrospinning nanofibers.At first, the electric field of traditional single needle electrospinning was simulated, by figuring out the critical shape of droplet at the apex of syringe needle at any given potential, establishing the geometric model, setting the material attributes of model, adding excitations. Consequently, the electric-field distribution was shown. By analyzing the equipotential lines and vector diagrams of electric intensity and image of electric intensity cloud, combined the electrohydrodynamics, it was conclusion that the electric intensity was maximum at the tip of droplet with the maximum surface charge density, where electric force would overcome surface tension more easily, to extracted a jet.The major technical barrier for manufacturing electrospun fabrics for applications, however, is the low production rate. Based on the simulation of electric field in traditional single needle electrospinning, the principle of multiple jets from single spinneret was proposed, that is to say, the free surface of spinning solution dripped on the surface of conductor was formed a cambered surface, not a plane. When applied a high voltage, the surface charges would gather on the cambered surface with the maximum curvature, resulting in spiking to form multiple Taylor cones and eject multiple jets.According to the shape of free surface of10%PVA aqueous solution dripped on the copper plate, the geometric model was established. After calculation and simulation of electric field, the conclusion was drawn that the whole round cambered surface at the edge of free surface with the maximum curvature had the highest electric intensity, which proved the principle of multiple jets from single spinneret was available.To make the spinning solution form more ideal cambered surfaces in a smaller space, umbrella spinneret was designed. According to the critical shape of spinning solution on each layer of copper planes in experiment, using the software Ansoft Maxwell12, the geometric model of umbrella spinneret electrospinning was established. After simulation and analysis of electric field, it concluded that cambered surfaces at the edge of spinning solution on each layer of copper planes had the highest electric intensity, which provided a theoretical condition for erupting of multiple jets.Using umbrella spinneret electrospinning machine self-designed,10%PVA aqueous solution was electrospun. In the experiment, obvious multiple jets erupting from the cambered surfaces at the edge of spinning solution on each layer of copper planes could be observed, which approximately corresponded with simulation of electric-field distribution and prediction of trajectory. Electrospun naofibers diameters almost distributed among200～300nm, with small discreteness, and the nanofibers throughput was more than180g/h, which demonstrated that it is available for umbrella spinneret to produce nanofibers and improve output of electrospinning.On the ground of simulation of traditional single needle electrospinning, the optimum technological condition combination of electrospinning cellulose acetate nanofibers was determined, and then the nanofibers membrane was electrospun. By tested, its specific surface area was7.87m2/g, which showed large surface energy. There were two methods to prepare samples:one was that the nanofibers membrane was built in cigarette filter, and the other was that cellulose acetate nanofibers were directly electrospun on cigarette paper of filter tip. Some testes of two samples were done, including draw resistance, filter efficiency, filtration and adsorption on pernicious gases. It concluded that the electrospinning cellulose acetate nanofibers membrane possessed excellent filtration and adsorption performance, which broadened the application area of acetate fibers.