| Electrospinning polymer nanofibers have many advantages,such as large aspect ratio and small diameter,showing much potential in applications of energy,personal protection,environmental treatment,sensor technology,et al.Electrospinning technology is an important and effective technology for preparing nanofibers directly,including needle-type capillary electrospinning and needle-less free surface electrospinning technology.Needle-less electrospinning technology is considered to have the most potential for mass production of nanofiber materials in industry.In recent years,it has been developed a variety of needleless electrospinning technology,but there are still some problems,such as operation safety problem caused by high electrospinning voltage,the wide distribution of nanofibers diameter,and low productivity,which reveals the fiber quality and mass production capacity need to be further improved.In this project,a novel technology of polymer string wave differential electrospinning is proposed,which realizes the single wave electrospinning generated by the action of the pluck and the multi-wave electrospinning generated by the end point excitation of the vibrator,namely the single wave and the standing wave electrospinning.The main work of this study is as follows:(1)The overall experimental device of polymer string wave differential electrospinning was designed and built,including the mechanical wave regulation module,the solution storage tank module,the high voltage electrospinning module and the nanofiber deposition receiving module.The mathematical physical model of plucked string was established,and the dynamic analysis of string dipping was carried out.The feasibility of preparing nanofibers by string wave differential electrospinning under low voltage was verified.The verification experiment showed that the spinning threshold voltage was 15 kV,and the nanofibers with diameter of about 100 nm were prepared,with the smallest diameter of 56.2 nm.Secondly,the further research and optimization of the plucked single wave electrospinning process with different parameters were carried out.Combined with motion simulation and finite element electric field simulation,the spinning process and basic principle of the string in the state of plucking motion were revealed.(2)The device of standing multi-wave electrospinning was designed and updated,and the mathematical model of standing wave control was established,and the standing wave motion simulation and finite element electric field simulation of string were carried out.The process parameters including spinning voltage,receiving distance and standing wave number were explored and optimized.Meanwhile,the device parameters including string diameter,string surface morphology and string conductivity were explored.The threshold voltage(18 kV)of standing multi-wave electrospinning is 30%lower than that of most needle free electrospinning technologies.A batch of high-quality nanofiber membranes with diameter of 173±48 nm were prepared by a single string with the spinning voltage of 28 kV,spinning distance of 10 cm and standing wave number of 3,and the productivity was 1.15 g/h.(3)The mechanism of standing wave electrospinning technology was systematically analyzed,including the analysis of standing wave dynamics and jet behavior in spinning process.At the same time,the forming mechanism of fibers with different morphologies obtained by this method under some process conditions was investigated.Combined with experiments and finite element simulation,the feasibility of industrial application of this technology was analyzed objectively.The results show that the modularized expansion can be carried out through the array distribution of strings,and the productivity of nanofibers can be improved.It provides a feasible and effective method to produce the nanofibers.According to the results of electric field simulation and optimization,the output of nanofiber of this device is expected to reach 1.02kg/(day·m2)if the electric field interference rate is controlled within 10%,and the string spacing is set at 40 mm.(4)Based on the technology of standing wave differential electrospinning,multi-stage filtration membrane for air filtration and dye adsorption nanofiber membrane were developed,respectively.The filtration nanofibers by both melt and solution composite electrospinning with electret treatment exhibited great efficiency.The filtration efficiency,resistance and quality factor were turned out to be 98.8%,98.26 Pa and 0.0432 respectively.This can provide a new method for the research and development of green air filtration membrane.In addition,the green PVA/PAA cross-linked nanofiber membrane prepared has obvious adsorption effect on methylene blue,and the removal rate can reach up to 98.43%.In conclusion,based on the polymer string wave differential electrospinning,high-quality nanofibers can be prepared under low applied voltage.The mathematical physical models of string wave were constructed,and the process parameters and device parameters were explored and optimized.The mechanism and industrial feasibility of string wave differential electrospinning are systematically analyzed,which can provide a feasible technical reference for the mass production and application of nanofibers.The multi-stage composite air filtration membrane and dye adsorption nanofiber membrane have been prepared,and remarkable application effects have been achieved.The research provides a new feasible method and device for the development of new electrospinning technology for mass production of high-quality nanofibers,and has a certain reference significance for developing high efficiency and low air resistance of filtration membrane and dye adsorption membrane. |
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