Effects Of The Mechanical Model And Process Parameters On Bubble-Electrospinning

Electrospinning has now become one of the most direct and effective methods to producing nanofibers, for their distinctive netted or porous structure, high specific surface area and their excellent application performance. Electrospun nanofibers have been widely applied to clothing industry, environment protecting, bioscience and biotechnology and so on.Chapter1firstly reviews the development course and the present situation of nanofiber, and introduces the properties and application of nanometer materials and the preparation of nanometer fiber technology. Then introduces the theory and development process of traditional electrospinning, and based on this, the traditional electrospinning equipment and craft was introduced At the same time, it points out the bottleneck of traditional electrospinning industrialization which has become the obstacle to further development. In order to overcome the deficiency of the traditional electrospinning, a new kind of electrospinning method-single bubble electrospinning was introduced. Finally this chapter puts forward the content and significance of research.After introducing the bubble electrospinning method and device in detail, Chapter2aims electrically at theoretical study of the single bubble electrospinning. Firstly, the method and whole process of the single bubble electrospinning is described systematically, including formation of the single bubble and the Taylor-like cones, motion of the jets, and solidification and deposit of the nanofibers onto the grounded plane. This kind of the method not only overcomes the multi-bubble instability, but also simplifies electrospinning environments, where a single bubble can produce multiple jets solidified on the collector. This kind of device is very much suitable for both theoretical analysis and experimental verification. Secondly, according to the characteristics of electrostatic charge distributed in the bubble electrospinning system, electric field distribution is evaluated by the electric image method. Solving the governing equations for the electric field distribution reveals that the electric field is extremely non-uniform, that will greatly affect the spinning process. Thirdly, the electric current in each charged jet, consisting of conduction current and displacement current, is studied, which induces a magnetic field in the electrospinning space, and as a result a magnetic force is excited acting on the jets during the electrospinning procedure. A reasonable explanation of the initial instability of the jet motion is discovered through analysis of the magnetic effects. It is argued that the jet instability results in a longer way of each jet to the collector, and it is helpful for complete stretching and solidifying process of the electrospun nanofibers.In retrospect the previous work about the establishment of traditional electrospinning mechanics models, Chapter3introduces the bubble electrospinning constant model, improved SPIVAK-DZENIS model and heat-electricity-fluid dynamic model. Based on this, the one-dimensional model of the coupled multi-field electrospinning is proposed, and the we analyse the mechanical model in the process of the bubble electrospinning. With understanding the bearing model in the process of the bubble electrospinning, the optimization method is put forward for spinning process parameters.Chapter4aims at analyzing the effect of the spinning process parameters on the fiber morphology, including the influence of quality score, plus voltage, receiving distance and temperature and humidity on the fiber structures through the design of spinning experiments. Experiments show that with the increase of polymer solution quality score, the diameter of fiber gradually increases, with the positive relationship; along with the increase of spinning voltage, diameter of fiber also increases, spinning voltage and nano fiber diameter relationship by nonlinear curve fitting can basically conform to, and in the fiber morphology structure, the bubbles electrospinning fiber surface has ’income pits’, and the quantity decreases as voltage increases; the increase of receiving distance makes the diameter of fiber greatly decrease, approximate match; when the distance is greater than12cm, fiber diameter distribution no longer conform to normal distribution; in PVP nanofiber preparation process, normal nanofiber can not got when more than60%RH, in the preparation process of PAN fiber process, when below65%RH, the fiber would immediately dry and form well, while above72%RH, it will overlap new fiber without drying, and the white points increase on the receiving board and affect the fibre felt appearance.Chapter5focuses itself on the effect of solution system to electrospinning nanofiber morphological structure. Begin with an analysis on the relationship between solution surface tension and fiber diameter. The conductivity function in the process of electrospinning and the influence of the conductive particles to the fiber structures are analyzed through an experiment. At last, we designed the experimental to analysis the influence of physical parameters to fiber diameter in the process of spinning bubble electrostatic.