Research On Surface Electrostatic Dissipation And Retention Of Electrospun Micro/Nano Fiber Mats

In this work, submicron Polyvinylidene fluoride (PVDF),Polyacrylonitrile (PAN) andPolystyrene(PS) fibers were prepared by electrospinning. Scanning electron microscopywas used to observe the morphology of the electrospun fiber. Surface residual potential in thefiber mats was measured using electrostatic induction method. The influence of solutionconcentrations, applied voltages, voltage polarities, receiver distance, spinning speed, andsubstrutes on fiber morphology, fiber diameter and electrical properties were systematicallystudied. The feasibility of electrospinning to prepare electret was also discussed.Micro/nano-size PVDF, PAN and PS fibers with better morphology can be fabricated byelectrospinning. Solution concentration was the most important factor which affects the fibermorphology and diameter. The average fiber diameter was increased rapidly as theconcentration increases. Applied voltage and receiver distance had few effects on fiberdiameter and morphology. Effect of voltage polarity on electrospinning was not obvious. Incontrast, applied positive voltage on the solution directly is in faver of getting fine anduniform fibers. The fiber diameter is 100nm thicker, and more ununiform when appliedvoltage on the receiver board.The factors such as solution concentration, applied voltage and the distance between thespinning nozzle to the receive have influence on the surface residual potential , but differentsolutions have different amount of influence. In electrospun PVDF, PAN mats, the surfaceresidual potential is proportional to the solution concentration, but in PS fiber mat, there is nonoticeable relationshio between the solution concentration and the surface residual potential.However, the residual potential of all polymers are increased with the increase of appliedvoltage up to 2.2kv. The polarity of residual potential is as same as that of the applied voltage.The residual potential was increased by the increased of the spinning time. However, theresidual potential was induced by the increase of the distance between the spinning nozzle andthe receiver, by increasing the promote speed, and by the increase of the invironmentaltemperature. The addition of salt increased the ionic conductivity. As a result, there was noresidual potential. In addition, substrates with different dielectric constant have an directeffects on the surface residual potential, it was found that among all kinds of substrate non-woven polypropylene had the highest retention potential up to 1.4kv, followed by plasticfilm and tin foil, while paper and metal materials have the least. Orthogonal experimentalresults shows that spinning voltage and solution concentration are the mainly processparameters The receiver distance and promote speed have little influence.The structure and properties of polymer material are the most important factors whichaffect the amount of surface residual potential and its'stability. The order as the decline ofsurface residual potential is: PS> PAN> PVDF> PLA> PCL. PS has the most, nearly 1kv,while the residual potential in the PVDF fiber mats can reach as much as 0.3~0.4kv, togetherwith high strength make it the most suitable candidate material to fabricate electret throughelectrospun. PVDF, PAN, PS fiber mats have the same potential decay laws mats, first decayrapidly, and then slowly till stabilize. The length of retention time is different, PS> PAN>PVDF. Dissipation of residual electric potential and the speed depends on the structure andproperties material, less affected by processing conditions. The residual charge distribution islike a bell-shape curve. the quantity of residual charge has some relationship with thethickness of fiber mat, thicker places has a high value of residual potential.PVDF/PAN, PVDF/PS composite fibers were prepared by electrospinning. ElectrospunPVDF / PAN blend solution is available to form composite fibers with good morphology anduniform diameter distribution, there is no obvious phase separation. The ratio andconcentration of composite solution do not influence stability of electrospinning andmorphology of fibers. Higher voltage and widened receiver distance are of benefit to fabricatefiner fiber. As the increase of total concentration of PVDF / PS blend solution, there was morefine fibers in the electrospun fiber mat, and the degree of fibrillation was more obvious. Atdifferent ratios, with the increase of PVDF amount in the blend solution, it is inclined to getfibers with different thickness, and the proportion of finer fibers increased quickly, more than60%. And increasing electrospinning voltage has the same trend.