| As a special kind of fiber manufacturing technology, electrospinning technology has been widely concerned owing to its simple and effective production of micro/nano fibers. Melt electrospinning technology, one important branch of electrospinning technology, developed rapidly into research focus in the field of mass preparation of micro/nano fiber with great potential owing to its solvent free, non solvent recovery, and high production. However, because of the complicated equipment, high melt viscosity and high technical difficulty, the diameter of the fibers produced using this technology is relatively thick and it is difficult to have the output to reach the level of industrialization. Therefore, fiber refinement and efficiency improvement are of great significance to the development of electrospinning technology and the promotion of industrialization development in our country.In this paper, the analysis of the advantages and disadvantages of existing equipment and technology were given based on the melt differential electrospinning technology developed by our research group in the early. And then some new technologys of melt differential electrospinning were developed, such as electro-blowing spinning,air-suction assistance, multi-cones and so on, based on principles of fiber refinement and efficiency improvement. On the one hand, the explorations and researches has been carried on in principle, device and process separately. On the other hand, the process of the Taylor cone partitioning of the electrospinning was studied based on the self-organization theory.The following aspects are mainly studied in this thesis:1.Melt-blown electrospinning technology was proposed based on the technical characteristics of meltblown and melt differential electrospinning. And the nozzle of meltblown differential electrospinning has been designed. The simulation analysis of the variation of electric field intensity of nozzle tip caused by the change in the form of nozzle was carried out, and the nozzle form was improved according to the simulation results. Using this technology, the melt was divided into stable multiple jet, and stretched into fibers under the effect of air parcel at the same time. It not only ensured the fineness of the fiber, but also maintained the maximum degree of the fiber uniformity. The best parameters such as air velocity and temperature were derived through experiments. It provides a new method and process for the development of high quality fiber membrane products.2.The technology of the air-suction assisted of melt differential electrospinning was proposed. The change of air-suction assisted form,solved the airflow disturbance and fiber accumulation effect on the distribution of the Taylor cone fundamentally, and keep the tensile effect of fiber caused by air. It is can be seen from the experimental results that the mean square error of fiber diameter reduced 84% when the air auxiliary mode was changed from air blowing to air suction. Through the coupling simulation of flow field and electric field, it is concluded that airflow have no obvious effect on electric field intensity induced by spinning nozzle. The electric field and flow field simulation were done,and the influence of air amplifier on electric field intensity and the fiber tensile mechanism of the two air auxiliary forms were studied,respectively. The simulation results provide experience and theoretical guidance for further fiber refinement. The technology has been successfully applied in the industrial production line and provides solutions to improve the quality of fiber products.3.In order to further improve the output efficiency of unit nozzle fiber, a new method of multi cone melt electrospinning was put forward.Through numerical simulation of electric field, the optimum parameters of cone nozzle were found out. The double cone melt differential electrospinning nozzle and the whole device were designed and manufactured, and the relevant experiments and simulations were done.Some conclusions can be drawn: when the distance between the inner cone and the outer cone reached 6 mm, Induction field strength of cone tips inside and outside layer was same, and the consistency of field strength no longer change with the change of the applied voltage; when the diameter of Melt differential electrospinning nozzle increases, the high density distribution of the Taylor cone can be also produced, and the stable jet can be formed; the fiber production of double cone nozzle is three times as much as that of single cone nozzle. At the same time, a new thought for production of multicomponent composite fiber was given.4.The uniform distribution of Taylor cone in the melt differential electrospinning process was explained based on the self-organization. A high-speed camera image acquisition was devoted to explore the self organization process when the melt film was divided into dozens of stable and uniform jet. The influence of electric field intensity on self organization process was analyzed. Following that, the curve of melt drop angle was obtained through analyzing the formation process of a single Taylor cone, which contributed to expand the concept of electrospinning theory research.In summary, a variety of new technology and new equipments were proposed in the aspects of fiber refinement and efficiency enhancement based on the developed melt differential electrospinning technology. And the theoretical and experimental studies are carried out, and the preliminary exploration about self organizing process was conducted. A new research idea for the development of electrospinning technology was provided and lay the foundation for the preparation of ultrafine fibers by electrospinning was laid. |
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