Research On The Mechanism Of Electrospinning Under Coupled Multi-Field Force

As a simple, effective and economic method for producing nanomaterials, electrospinning technology has obtained world-wide attention. Especially, more and more paper with regarding to the researches of electrospinning technique and its application have been published in recent a decade. However, there are still some unsolved problems in the process of electropinning. Therefore, necessary theoretical and experimental researches will need to be conducted in future.Firstly, a thermo-electro-hydrodynamic model of the vibration-electrospinning process is established on the base of known mathematical models, considering the influence of electric field, vibration force and air drag on the procedure. At the same time, a one-dimensional thermo-electro-hydrodynamic model is established to be convenient for numerical analysis. Secondly, a complete mathematical model of the charged jet under coupled multi-field has been first established, considering the effect of electric field, magnetic field, vibration force and fluid field. The model is a powerful tool to controlling over physical characters. Many basic properties are tunable by adjusting electrospinning parameters such as voltage, flow rate and others, and it can offer in-depth insight into physical understanding of many complex phenomena which can not be fully explained experimentally. It will help understand the electrospinning technique better.The effect of two key parameters on the diameter of fibers and its morphology is studied in this paper. The experimental results show that the diameter of the electrospun fibers increases with the increase of solution concentration and increasing the voltage applied leads to thinner fibers. In addition, electrospun materials with porous structure are prepared via electropinning PBST/CF dilute solution with the weight ratio of 10%. Three possible reasons are presented about the formation of porous structure in the process of electrospinning. The first reason is that polymer-rich and polymer-poor area will be formed separately due to the rapid volatilization of solvent in the process of electrospinning. Finally, Polymer-rich phase becomes solid to be the frame of the nanomaterials, and polymer-poor phase becomes the porosities. The second one is a high voltage applied leads to an long and narrow cone to overcome the surface tension of solution and when it exceeds the threshold voltage, the polymer jet dilates and porous structure comes out instantaneously. The third possibility is that the electric charges distribute regularly and will be compacted tighter and tighter when the jets accelerate in the electric field. The jet will expand on the collective plane owning to the disappearance of electric field force, and the porosities come out. Electrospun nanoporous nanomaterials, with large special surface area, will be possibly applied more widely, such as sound absorption materials, warm-keeping materials, drug release and tissue engineering, etc.A new electrospinning set-up coupled with magnetic field induced by a U-shape permanent magnet or a U-shape electromagnet is designed to study the influence of magnetic field on the diameter and crystalline of electrospun fibers in the experiment. Results show that the magnetic field can decrease the diameter of fibers and increase the crystalline. Stronger the magnetic field, smaller diameter, higher crystalline. It can be seen magnetic field can control the instability of the jet and lead to the recrystallization of the polymer molecular chains.