Research On Principle Of DC Electrospinning Based On Forced Reorganization Of Surface Liquid And Characterization On Its Product

The bottleneck problem in the scale and industrialization of electrospinning technology is that it is difficult to find a perfect spinneret,which can quickly,continuously,high-quality,high-yield,and safely prepare nanofiber materials without plugging holes and uncontrollable feeding,edge effect,unstable spinning process,unsafe and other phenomena.In order to obtain a new type of electrospinning spinneret with both needle and needle-free advantages,the following research scheme is adopted in the project:(1)use mechanical drawing software to model the structure of the new type of spinneret;(2)use the step coupling method of flow field and electric field to study electrohydrodynamic characteristics of the spinneret:Firstly,the flow field numerical simulation of the new spinneret based on a 14wt%polyacrylonitrile(PAN)spinning solution was carried out,and the basic structural parameters and spinning droplet spreading shape of the new four-electrode and six-electrode truncated spinnerets were determined,respectively;On this basis,the finite element software is used to simulate the electric field intensity and distribution on the surface of the solid needle electrode and the spinning droplet,optimize the structural parameters of the solid needle electrode,obtain the simulation values of the electric field intensity at different positions on the droplet surface,and calculate the Taylor The critical electric field strength E_c required for cone formation,and compared with the theoretical simulation value,any site with field strength greater than or equal to E_c will form a Taylor cone and emit a spinning jet;(3)Electrospinning experiments demonstrate the theoretical model,and compared with ordinary needle electrospinning,the performance characteristics of the new spinneret are explained.Firstly,the basic size parameters of truncated spinneret are determined through experimental test,theoretical solution and numerical simulation of the flow field.Based on the analysis principle of minimum the pressure drops of expansion flow and theoretical calculation,it is determined that the included angle in the vertical direction between the vertical channel and round platform channel of frustum of a cone spinneret is 30.74°.The ANSYS Fluent numerical simulation software was used to analyze the influence of the inner diameter of the truncated spinneret on the spreading of the spinning fluid.The results show that the inner diameter of the truncated spinneret is preferably 1.5mm when spinning downwards,and the inner diameter of the truncated spinneret is better than 3mm when spinning upwards.Secondly,the structural parameters of the solid needle electrode and the field strength of the spinning liquid surface are determined by electric field simulation and curve fitting optimization.The results show that the smaller the diameter of the electrode,the farther the distance from the center point,and the closer the protruding length is to the spinning end face,the greater the field strength.The field strength is greatest when the shape is a solid tipped needle.when the shape is a solid needle with a tip,the field strength is the largest.The electrode structure parameters of the four-electrode truncated spinneret:the diameter is 0.6 mm,the distance from the center point is 3.5 mm,and the protruding length is flush with the lower end surface of the spinneret.At this time,the average field strength of the spinning end surface at the electrode is 5.07×10~6V/m.The optimal structure parameters of the electrode of the six-electrode truncated spinneret:diameter 0.6mm,distance from the center point 6mm,protruding length 1.9mm,the average field strength of the spinning end face at the electrode is4.07×10~6V/m.Calculated by theoretical formula,the critical field strength is 2.32×10~6V/m,and the minimum jet spacing of four-electrode and six-electrode truncated spinneret is about1.09mm and 2.47mm,respectively,which are smaller than the distance between electrodes.The optimized new spinneret can excite the emission current at the corresponding position.Finally,the experimental demonstration of electrospinning was carried out using the new spinneret.The results show that both four-electrode and six-electrode truncated spinneret can excite multi-jet at their respective positions.The number of jets excited by the four-electrode truncated spinneret is the most when spinning upwards.The average diameter of the prepared PAN nanofibers is 340.9 nm,the CV value is 21.3%,and the output is about 115 times that of the traditional single needle.The prepared PVB nanofibers The average diameter is 707.1nm,the CV value is 27.2%,and the yield is about 82 times that of the traditional single needle,and the average diameter of the prepared PVA nanofibers is 661.3nm,the CV value is 22.8%,and the yield is about 105 times that of the traditional single needle.