Novel Bubble Electrospinning And The Fabracation Of Selfcleaning Nanofibers Membrane

Electrospinning is a simple but effective method to produce polymer micro/nanofibers, and electrospun fibers not only have many good properties, such as high surface area, good mechanical stability and fiber continuity, but also shown many enormous potential applications in diverse areas, such as filtration, separation, sound absorbtion, energy storage, tissue scaffolds, drug delivery devices, biomaterials, sensors and protective clothing. With the development of application and market requirement, the industrialized manufacturing technology of nanofibers becomes to one of the most important rearch hotpots.Firstly, the morphology, application and manufacturing technology of nanofibers were introduced in this thesis. All the manufacturing technology of nanofibers can be categorized as multiple needles electrospinning and needless electrospinning, and their productivity and industry parameters were detailed introduced. According to the analysis of the advantages and disadvantages in manufacturing process, needleless electrospinning had greater application potential than multiple needles electrospinning.Based on theoretical analysis of needleless electrospinning and traditional bubble electrospinning, the feasibility of more nanofibers production fabricated by bubble electrospinning was explored and the detailed experimental scheme was proposed. This new method for nanofiber fabrication was called as novel bubble electrospinning. According to the principium of novel bubble electrospinning, a simple experimental equipment was set up; its bubble generator was a rotational spinneret as well.Senondly, for directly demonstrating the potential in industrialized manufacturing of nanofibers and the stable quality of nanofibers, the number of jets, the diameter of nanofibers, the morphology of nanofiber membrane and nanofiber and the production of nanofibers were explored. The results indicated that lots of jets were generated from the edge of bubble generator and the rupturing polymer bubble film. During the spinning process, the solvent was volatilized and all the jets flied to the grounded collector to form a piece of nanofiber membrane. We controlled the rotational frequency of bubble generator to controll the number of jets. What`s more, PVP、PVA、PES nanofibers were fabricated by the novel bubble electrospinning, and the diameter respectively were 432±194nm 、255±54nm and 595±155nm. Besides, the production of 30%PVP、30%PES and10% PAN respectively were 3.05g/hour、3.15 g/hour and 1.2 g/hour, which is more than10 times than the production of single needle electrospinning. This result demonstrate d the obvious production advantages of the novel bubble electrospinning compare with single needle electrospinning.Thirdly, based on the statics and dynamics of polymer bubble, the force situation, the expanding and rupture process of charged polymer bubble were analyzed to explore the generated mechanism of lots of jets in novel bubble electrospinning. The results indicated that the smaller size of polymer bubble, the smaller surface tensile and the much easier bubble rupture. What`s more, according to the vedio recored by High Speed Camera, the jets generated during the expanding and rupture process(even after the rupture process) of charged polymer bubble film. During the expending process, a few jets generated from the smaller bubbles on the unstable spherical polymer bubble film; during the rupture process, lots of jets generated from the ‘daughter bubbles’ and tears formed from the ruptured films; after the rupture process, a few jets generated from the edge of bubble generator. Besides, the governing equations of charged jets were established by combining mass conservation equation, charge conservation equation, momentum conservation equation and N-S equation. The motion of charged jets was analyzed by considering charged jets to be non-Newtonian fluid.Finally, the ZnO nanowires nanofiber membrane was fabricated by electrospinning and hydrothermal systhesis and applicated in selfcleaning nonwo ven. In this part, SEM、TEM、FTIR、XRD were used to characterize the morphology of ZnO nano wires nanofiber, the seeding mechanism of ZnO nanoparticle and the growth mechanism of ZnO nanowires. The results also investigated that the diameter and morphology of ZnO nanowires can be controlled by adjusting the concentration of PVDF solution, additive in growth solution, the mass ratio of Zinc Acetate, the growth time. Morover, inspired by the similar micro/nano scale structure with lotus leaf, ZnO nanowires nanofiber membrane was applicated in selfcleaning nonwo ven. Due to the tubular crystals on lotus leaf contain predominantly high amounts of β-diketones, which include primarily-CH2- and-CH3, the bio-coating materials on ZnO nanowires micro/nanofiber membrane give preference to oleic acid. And after oleic acid coating, ZnO nanowires nanofiber membrane performed excellent water repellency. SEM and FTIR were used to characterize the mechanism of bio-lipid coating; water contact angel, water bouching effect, water rolling motion on inclined surface, dirt removal test and water vapour permeability test indicated the ZnO nanowires nanofiber membrane not only had the selfcleaning property but also water vapour permeability which can be applicated in selfcleaning nonwoven.