Study On Fabrication And Mechanism Of Cylindrical-electrode-assisted Solution Blowing Spinning Nanofibers

Compared with conventional fibers,nanofibers have excellent properties such as ultra-high specific surface area,super-high length-diameter ratio,size effect and surface effect.Therefore,nanofibers have become one of the research hotspots in the global academia.Research on nanofibers has involved many disciplines such as:materials science,polymer science,chemistry,physics,instruments instrumentation,electrochemistry,biochemistry molecular biology,cell biology,energy fuels,pharmacology pharmacy,spectroscopy,crystallography,biophysics,biotechnology applied microbiology,mechanics,environment science ecology,radiology nuclear medical imaging,microscopy,general internal medicine,physiology,optics,agriculture,water resources,etc.At present,the main fabrication methods of nanofibers include electrospinning,solution blowing spinning,centrifugal spinning,phase inversion,template synthesis,etc.Among them,solution blowing spinning is considered to be one of the most probable nanofiber fabrication methods for industrialization.Nanofibers prepared by solution blowing spinning have been used in many fields such as filter materials,biomedical materials,adsorbent materials,and electrode materials.However,the solution blowing spinning nanofibers have many natural defects such as large fiber diameter,uneven diameter,and bead fiber.These defects severely degrade the quality of the nanofibers and also limit the application of nanofibers.Therefore,it is imperative to develop a new method for preparing nanofibers.In order to achieve this goal,this paper introduced a new nanofiber fabrication technology and named it as cylindrical-electrode-assisted solution blowing spinning?CSBS?.In this article,the production equipment,production process and fiber formation mechanism of the technology were introduced in detail.The main research contents of this paper are as follows:?1?A novel nanofiber fabrication technology which named cylindrical-electrode-assisted solution blowing spinning?CSBS?was introduced.A cylindrical electrode was added to the solution blowing spinning device to form the CSBS device.The jet in the CSBS system is subjected to the shearing force of the airflow and the electric field force to form the nanofiber.This article compared the quality of nanofibers prepared by two techniques?CSBS and traditional solution blowing spinning?.The results show that the diameter standard deviation of the CSBS nanofibers is 21%lower than that of the traditional solution blowing spinning nanofibers,and the average diameter of the CSBS nanofibers is 6.17%lower than the average diameter of the traditional solution blowing spinning nanofibers.Therefore,the CSBS is an improvement of the traditional solution blowing spinning.This article also compared the quality of nanofibers prepared by electrospinning and CSBS.The results show that the two techniques can produce nanofibers with similar diameter under the premise of selecting appropriate process parameters.By comparing the CSBS with the electro-blown spinning,it is known that both nanofiber fabrication techniques use electric field force and airflow shear force to stretch the jet.However,there are significant differences between the two technologies in at least the following three areas.First,they have different mechanisms for charging the jet.The CSBS system charges the jet by the electrostatic induction effect,and the electro-blown spinning system directly charges the jet through the circuit connection.Secondly,the equipment components of them are different.The CSBS device has one more cylindrical electrode than the electro-blown spinning device.Finally,the connection relationship between the components in the two devices is different.The power supply of the CSBS device is connected to the cylindrical electrode,and in the electro-blown spinning device,the power source is connected to the blunt needle.Therefore,the CSBS and the electro-blown spinning are two different nanofiber fabrication techniques.?2?The relationship between the process parameters of CSBS and the performance of CSBS nanofibers were systematically studied.The effects of needle to cylinder distance?NCD?,length of cylinder?LC?,diameter of cylinder?DC?,left face of cylinder to collector distance?CCD?and voltage on the diameter of CSBS nanofibers were investigated by single factor experiments.The results show that with the decrease of NCD,the diameter of CSBS nanofibers decreases;the increase of LC will reduce the diameter of nanofibers;the increase of DC will increase the diameter of nanofibers;the effect of CCD on the diameter of CSBS nanofibers is very small;the increase of voltage will cause the diameter of nanofibers to decrease.The effects of seven factors?LC,NCD,DC,CCD,voltage,air pressure,and injection speed?on the diameter of the CSBS nanofibers and the porosity of different layers of nanofiber web were investigated by orthogonal experiment.The results show that the degree of influence of the seven factors on the average diameter of nanofibers is:injection speed>air pressure>NCD>DC>LC>voltage>CCD;the degree of influence of the seven process parameters on the standard deviation of fiber diameter is:NCD>DC>voltage>CCD>LC>air pressure>injection speed;the degree of influence of seven factors on the P1 value of nanofiber web is:DC>voltage>air pressure>CCD>injection speed>NCD>LC;the degree of influence of seven factors on the P2 value of nanofiber web is:voltage>DC>injection speed>air pressure>NCD>LC>CCD;the degree of influence of seven factors on the P3 value of nanofiber web is:voltage>NCD>injection speed>air pressure>DC>LC>CCD.For the mean diameter and diameter standard deviation of CSBS nanofibers,the optimal experimental scheme?minimum mean diameter and diameter standard deviation?is:A₂B₂C₂D₁E₂F₂G₁.For P1,P2 and P3 of CSBS nanofiber nonwovens,the optimal?lowest porosity?experimental schemes are A₂B₂C₁D₂E₁F₁G₁,A₂B₂C₁D₂E₁F₂G₁,and A₂B₂C₂D₁E₁F₂G₁.For P1,P2 and P3 of CSBS nanofiber nonwovens,the optimal?maximum porosity?experimental schemes are A₁B₁C₂D₁E₂F₂G₂,A₁B₁C₂D₁E₂F₁G₂,and A₁B₁C₁D₂E₂F₁G₂.The comprehensive analysis of the data of the orthogonal experiment leads to the following conclusion:the adjustment of the voltage can effectively change the porosity of different layers of nanofiber web without causing significant changes in the diameter of nanofiber.?3?Theoretical research on CSBS system was carried out.It was clarified that the charging mode of the jet in the CSBS system is inductive charging.In a CSBS system,if a positive high-voltage power source is used to connect to the electrode,the jet is negatively charged by electrostatic induction.Conversely,if a negative high voltage power supply is used to connect to the electrode,the jet will be positively charged due to electrostatic induction.The charging effect is beneficial to the rupture of the jet,the reason why the diameter of the CSBS nanofiber is smaller than that of the solution blowing spinning nanofiber was theoretically clarified.Combined with the principle of electrostatic induction and the actual situation of CSBS equipment,the physical model?coaxial cylindrical capacitor model?of the electric field between the jet and the cylindrical electrode in the CSBS system was established by using the relevant electrical knowledge.This model was solved by electrical and mathematical knowledge,and several theoretical formulas were obtained.These theoretical formulas can describe the relationship between the electric field indexes?such as electric field strength,charge density,etc.?of the CSBS system and the CSBS process parameters?such as voltage,cylindrical electrode diameter,etc.?.It can be known from these theoretical formulas that the electric field strength at any point between the electrode and the jet is inversely proportional to the natural logarithm of the electrode radius,proportional to the voltage,and inversely proportional to the distance from the point to the jet;The surface charge density of the jet is proportional to the voltage,and inversely proportional to the natural logarithm of the radius of the electrode;the electric field strength of the jet surface is inversely proportional to the natural logarithm of the electrode radius and proportional to the voltage.The conclusion that increasing the voltage or decreasing the diameter of the cylindrical electrode can make the nanofibers thinner can be deduced theoretically by using these formulas and the mechanism of CSBS.?4?The finite element numerical simulation of the CSBS electric field was carried out to explore the spinning mechanism of the CSBS system.The electric field finite element software Ansoft Maxwell was used to establish a three-dimensional physical model of the electric field between the cylindrical electrode and the jet in the CSBS system.Combined with the actual production process of CSBS and the related theory of Ansoft Maxwell software,the finite element simulation of the electric field between the cylindrical electrode and the jet in the CSBS system was carried out.The simulated electric field potential distribution shows that the potential from the electrode to the spinning jet exhibits a decreasing distribution in the case where the positive high voltage power source is connected to the electrode.The field intensity distribution cloud diagram of the simulated electric field shows that the electric field strength at any point between the jet and the electrode decreases with the increase of the diameter of the cylindrical electrode?DC?,the electric field intensity decreases with the decrease of the voltage,and the electric field intensity decreases with the increase of the distance from the jet.The simulation results show that the electric field intensity of the jet surface tends to decrease with the increase of the diameter of the cylindrical electrode or the decrease of the voltage.In this paper,a novel nanofiber fabrication technology?CSBS?is proposed,and the process and mechanism of the technology are studied.This study provides a theoretical basis for the optimal fabrication of CSBS nanofibers,and has practical significance for the design and development of domestic nanofiber production equipment.