Optimization of the electrospinning conditions for preparation of nanofibers from polyvinylacetate (PVAc) in ethanol solvent

In order to fabricate polyvinylacetate (PVAc) fiber by electrospinning, we have been examined electrospun polyvinylacetate (PVAc) under various conditions after dissolving it in ethanol solution. As the concentration of spinning solution increased, the diameter of the electrospun PVAc fiber increased. At the concentration lower than 10 wt.%, beads were formed while over the 25 wt.%, distinct fiber was not observed. At the tip-collector distance (TCD) of 7.5 cm or less, the jet of spinning solution was unstable and the fiber diameter decreased. On the other hand, at the TCD of 10 cm or more, the strength of electric field became too weak and the fiber diameter increased. As the flow rate of spinning solution increased, the fiber diameter increased and at the flow rate of 300 μl/min or more, it increased sharply. For 15 wt.% PVAc, the fiber diameter decreased as the applied voltage increased. At a high-applied voltage, however, charge acceleration caused the spinning solution not to be separated and thus the fiber diameter increased. As a result of dissolving PVAc in ethanol and electrospinning it in the following conditions, a fiber with the diameter of about 700 nm was spun: the concentration of 15 wt.%, the TCD of 10 cm, the spinning solution flow rate of 100 μl/min, and the applied voltage of 15 kV.     

Process Optimization and Empirical Modeling for Electrospun Poly(D,L‐lactide) Fibers using Response Surface Methodology

Summary: Ultrafine fibers were spun from poly(D ,L ‐lactide) (PDLA) solution using a homemade electrospinning set‐up. Fibers with diameter ranging from 350 to 1 900 nm were obtained. Morphologies of fibers and distribution of fiber diameters were investigated varying concentration and applied voltage by scanning electron microscopy (SEM). Average fiber diameter and distribution were determined from about 100 measurements of the random fibers with an image analyzer (SemAfore 5.0, JEOL). A more systematic understanding of process parameters of the electrospinning was obtained and a quantitative relationship between electrospinning parameters and average fiber diameter was established by response surface methodology (RSM). It was concluded that the concentration of polymer solution played an important role in the diameter of fibers and standard deviation of fiber diameter. Lower concentration tended to facilitate the formation of bead‐on‐string structures. Fiber diameter tended to increase with polymer concentration and decrease with applied voltage. Fibers with lower variation in diameter can be obtained at lower concentration regardless of applied voltage. Fibers with uniform diameter and lower variation in diameter can be obtained at higher concentration and higher applied voltage. Process conditions for electrospinning of PDLA could be chosen according to the model in this study.

Contour plots of average fiber diameter as a function of concentration and applied voltage.     

静电纺丝制备聚醚酮酮超细纤维

用溶液静电纺丝方法制备了聚醚酮酮超细纤维,用扫描电子显微镜研究了实验过程中纺丝电压、纺丝距离、流量、纺丝液浓度对于聚醚酮酮纤维直径和形貌的影响,并对多个纺丝参数的影响规律进行了分析。实验结果表明,在一定条件下纺丝电压和纺丝距离对纤维直径影响较小,而流量和纺丝液浓度能显著影响纤维直径,在小流量、低浓度容易得到较细的纤维,并且纤维直径分布集中。     

Electrospinning of polycarbonate urethane biomaterials

Polycarbonate urethane (PCU) nano-fibers were fabricated via electrospinning using N,N- dimethylformamide (DMF) and tetrahydrofuran (THF) as the mixed solvent. The effect of volume ratios of DMF and THF in the mixed solvent on the fiber structures was investigated. The results show that nano-fibers with a narrow diameter distribution and a few defects were obtained when mixed solvent with the appropriate volume ratio of DMF and THF as 1∶1. When the proportion of DMF was more than 75% in the mixed solvent, it was easy to form many beaded fibers. The applied voltage in the electrospinning process has a significant influence on the morphology of fibers. When the electric voltage was set between 22 and 32 kV, the average diameters of the fibers were found between 420 and 570 nm. Scanning electron microscopy (SEM) images showed that fiber diameter and structural morphology of the electrospun PCU membranes are a function of the polymer solution concentration. When the concentration of PCU solution was 6.0 wt-%, a beaded-fiber microstructure was obtained. With increasing the concentration of PCU solutions above 6.0 wt-%, beaded fiber decreased and finally disappeared. However, when the PCU concentration was over 14.0 wt-%, the average diameter of fibers became large, closed to 2 μm, because of the high solution viscosity. The average diameter of nanofibers increased linearly with increasing the volume flow rate of the PCU solution (10.0 wt-%) when the applied voltage was 24 kV. The results show that the morphology of PCU fibers could be controlled by electrospinning parameters, such as solution concentration, electric voltage and flow rate.     

Rapid fabrication of poly(ε‐caprolactone) nanofibers using needleless alternating current electrospinning

Poly(ε‐caprolactone) ( PCL) biopolymer nanofibers and micro‐fibers have been fabricated for the first time at the rates up to 14.0 g per hour using a needleless and collectorless alternating current electrospinning technique. By combining the ac‐voltage, “green” low toxicity glacial acetic acid (AA) as the solvent and sodium acetate (NaAc) as an additive, beadless PCL fibers with diameters tunable from 150 nm to 2000 nm, varying surface morphology and degree of self‐bundling are obtained. In this new approach, the addition of NaAc plays a crucial role in improving the spinnability of PCL solution and fiber morphology. NaAc reveals the concentration‐dependent effect on charge transfer and rheological properties of the PCL/AA precursor, which results in broader ranges of spinnable PCL concentrations and ac‐voltages suitable for rapid manufacturing of PCL‐based fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43232.     

Effect of air blowing on the morphology and nanofiber properties of blowing‐assisted electrospun polycarbonates

Polycarbonate (PC) nanofibers are prepared using the air blowing‐assisted electrospinning process. The effects of air blowing pressure and PC solution concentration on the physical properties of fibers and the filtration performance of the nanofiber web are investigated. The air blowing‐assisted electrospinning process produces fewer beads and smaller nanofiber diameters compared with those obtained without air blowing. Uniform PC nanofibers with an average fiber diameter of about 0.170 μm are obtained using an applied voltage of 40 kV, an air blowing pressure of 0.3 MPa, a PC solution concentration of 16%, and a tip‐to‐collection‐screen distance (TCD) of 25 cm. The filtration efficiency improvement of the air blowing‐assisted electrospun web can be attributed to the narrow distribution of fiber diameter and small mean flow pore size of the electrospun web. Performance results show that the air blowing‐assisted electrospinning process can be applied to produce PC nanofiber mats with high‐quality filtration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of Electrospinning Parameters on Gelatin/Poly(ϵ‐Caprolactone) Nanofiber Diameter

An electrospinning procedure was carried out to fabricate gelatin/poly(?‐caprolactone) (Gt/PCL) nanofibers. Response surface methodology based on a three‐level, four‐variable Box‐Behnken design technique was used to model the resultant diameter of the as‐spun nanofibers. A second‐order model was obtained to describe the relationship between the fiber diameter and the electrospinning parameters, namely Gt concentration, PCL concentration, content of acetic acid in the overall solvent, and content of Gt solution in the blend solution. The individual and the interactive effects of these parameters on the fiber diameter were determined. Validation experiments verified the accuracy of the model which provided a simple and effective method for fabricating nanofibers with a controllable and predictable fiber diameter.     

Selective Bragg reflection of visible light from coaxial electrospun fiber mats

Electrospinning is a relatively unsophisticated technique for generating continuous fibers whose diameters can approach nanoscale dimensions. In coaxial electrospinning, two different liquids can be spun, one inside the other, to produce a composite fiber with a core-sheath structure. We prepared dual-core fibers consisting of poly vinyl-pyrrolidone sheaths and cores of the short-pitched chiral nematic mixture CB15:E9. The flow rates, polymer concentration, and applied voltage were optimized prior to fiber production. The fibers were deposited as uniform nonwoven mats that displayed selective reflection of visible light from the blue phase of the confined chiral liquid crystal. These reflections are both temperature dependent and reversible and such mats offer potential as flexible sensors.     

静电纺PCL纤维形态与热性能的研究

利用静电纺丝法制备了超细聚ε-己内酯(PCL)纤维;借助扫描电镜仪和差示扫描量热仪表征了PCL纤维的形态与热性能;研究了电纺过程中溶液浓度、电压、接收距离和纺丝速度对纤维形态的影响。结果表明:当纺丝电压为10 kV,接收距离为15 cm,纺丝速度为2 mL/min时,纺丝液中PCL质量分数为6%~12%能获得连续无串珠的纤维;纺丝电压为8~12 kV,电纺过程稳定;接收距离对纤维的直径和形貌无明显影响;与流延成型的PCL膜相比,电纺PCL纤维具有较低的结晶度。     

Electrospinning and Structure of Bicomponent Polycaprolactone/Gelatin Nanofibers Obtained Using Alternative Solvent System

Bicomponent polycaprolactone/gelatin (PCL/Gt) nanofibers were successfully formed for the first time by electrospinning using a novel polymer–solvent system with solvents being alternative to the commonly used toxic solvents like fluorinated alcohols. The mixture of acetic acid (AA) with formic acid (FA; 90:10) was applied. Stable electrospinning was possible despite the fact the mixture of PCL and gelatin in AA/FA solvent showed emulsive structure. From the practical perspective, there is no doubt that it is possible to obtain PCL/Gt fibers using AA/FA mixture with morphology similar to that for fibers spun from hexafluoroisopropanol (HFIP) solutions.     

不同溶剂对静电纺聚乳酸纳米纤维形态结构的影响

以聚乳酸（PLA）为原料,分别用三种不同的溶剂制得三种纺丝液并采用静电纺丝法,制备了聚乳酸纳米纤维。探讨了溶剂、电压、溶液质量分数对纤维形貌和直径的影响。结果表明,溶剂是决定PLA超细纤维形成的关键因素,三氯甲烷（CHC l3）与二甲基甲酰胺（DMF）混合溶剂（体积比为9∶1）是PLA静电纺丝较为理想的溶剂。在PLA质量分数为6%、极距15 cm、电压25 kV,流量2.5 mL/h的工艺条件下,可制备直径为1 200 nm左右的PLA纤维。     

静电纺工艺参数对聚己内酯纳米纤维直径的影响

用静电纺丝法制备组织工程所需的纳米纤维及材料,在实验中主要研究了基本的工艺参数对所获纤维直径的影响。纤维或非织造膜由两种溶剂系统所制备:氯仿与N,N-二甲基甲酰胺(DMF)的混合剂及含少量(约40μg)嘧啶的乙酸溶液。为了研究聚合物浓度、DMF含量、施加电压、极距、溶剂系统等因素的影响,使用了扫描电子显微镜、溶液黏度仪、溶液电导率测试仪等。结果表明:随着聚合物浓度上升,纤维的直径先增加后减小;随着溶液中DMF含量的增加,纤维直径不断减小;电压对纤维直径无明显的影响;极距需适中,过大过小都会产生珠状纤维;含少量嘧啶(40μg的乙酸溶剂所获得的聚己内酯(PCL)纳米纤维比由氯仿和DMF的混合溶剂所获得的PCL纳米纤维更加细而均匀。     

Molecular orientation and mechanical property size effects in electrospun polyacrylonitrile nanofibers

Electrospinning of polymeric solutions entails high jet velocities which could orient the polymer molecules along the jet direction. Polarized Fourier Transform IR spectroscopy (FTIR), Wide angle X-ray diffraction (WAXD) and Microelectromechanical System (MEMS)-based single nanofiber mechanical property experiments were employed to investigate the molecular orientation and crystallinity in electrospun polyacrylonitrile (PAN) nanofibers produced under different electrospinning conditions with diameters mainly varying between 100 and 300 nm. FTIR measurements with nanofibers fabricated at three different electrospinning distances, but under the same electric field intensity, revealed an enhanced molecular orientation only for the longest electrospinning distance. At long electrospinning distances the fiber solvent content is substantially reduced resulting in high viscosity, and, therefore, sustained shear stresses, which, in turn, allows for permanent molecular orientation. The orientation factors from polarized FTIR were in good agreement with the mechanical property trends obtained from individual nanofibers, where high elastic moduli and yield strengths were recorded from nanofibers with diameters smaller than 300 nm, which were fabricated at the longest electrospinning distance. WAXD studies on bundles of aligned PAN nanofibers showed small crystallinity which did not follow the trends in the mechanical properties and varied rather non-monotonically from 7%, for fibers spun at the shortest distance, to 17% for fibers spun at the longest distance used in this study.     

气流-静电纺丝法制备聚对苯二甲酸乙二酯纳米纤维

采用50%苯酚和50%1,1,2,2-四氯乙烷的混合溶液为溶剂,通过气流-静电纺丝法制备了聚对苯二甲酸乙二酯(PET)纳米纤维。利用扫描电镜(SEM),研究了聚合物分子质量、溶液浓度、电压、接收距离(喷丝孔到接收板的距离)对电纺纤维形态结构的影响。结果表明:随着聚合物分子质量和溶液浓度增加,纤维平均直径也随之增加;纤维平均直径随电压的增加而减小;随接收距离的增加,纤维平均直径先减小后增加。最佳工艺条件为:聚合物特性黏度为0.818 dL/g,溶液质量分数为15%,电压为32 kV,接收距离为23 cm,所得PET电纺纳米纤维平均直径为85 nm。     

Materials selection and residual solvent retention in biodegradable electrospun fibers

Electrospun tissue engineering scaffolds provide mechanical support to seeded cells that populate the structure while depositing specific extracellular matrix components. The potent sterilizing agent 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) is often used in electrospinning investigations involving biologically‐derived polymers. Surprisingly, there has been no study of solvent retention versus composition even though materials selection should influence organic solvent content. We developed a method quantifying HFIP retention following electrospinning of gelatin, polycaprolactone (PCL), and PCL‐gelatin blends using electro‐spray mass spectroscopy. The acetone content of acetone‐spun PCL was also established. Pure gelatin fiber contained as much as 1600 ppm of HFIP. In contrast, little acetone or HFIP was detected in 100% PCL. Gelatin clearly has a greater affinity for HFIP than PCL and materials selection has a strong influence on the amount of retained solvent. Vacuum + heat treatment at 37 and 45ºC reduced [HFIP] to 10 and 5.6 ppm, respectively, levels having no demonstrated effects on mammalian cell viability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚ε-己内酯/聚乙二醇共混纳米纤维的静电纺丝研究

采用四氢呋喃和无水乙醇为溶剂,利用静电纺丝法制备了聚己内酯(PCL)/聚乙二醇(PEG)共混纳米纤维。研究了共混配比、溶液浓度、无水乙醇的加入以及电纺电压、接收距离等工艺参数对纤维形态和性能的影响。测试结果表明:聚乙二醇和聚己内酯以一定比例共混后改善了聚己内酯纤维毡的亲水性和细胞相容性;随着纺丝原液浓度增加,电纺产品由高分子微/纳米液滴结构渐变为珠状结构较少的平滑纤维,平均纤维直径逐渐增大;一定范围内,纤维平均直径随电压的上升而增大,但与接收距离关系不大;此外,加入无水乙醇后,共混溶液电导率增加,有利于喷射流的劈裂,减少了珠状结构的数量。     

The morphology,mechanical properties,and flammability of aligned electrospun polycarbonate (PC) nanofibers

The electrospinning of the polycarbonate (PC) solutions was performed for the variable electrospinning parameters such as polymer concentration, solvent composition, applied voltage, flow rate, and take‐up velocity in order to evaluate changes of morphology, mechanical properties, and flammability of the aligned PC nanofibers as a function of the electrospinning parameters. It was found that the ratio of THF/DMF solvent in the electrospinning parameters had a major effect on the spinnability and fiber morphology. Furthermore, it was confirmed that the mechanical properties were dependent upon the fiber morphology. The spinnability of the PC solutions with a lower THF ratio in THF/DMF solvent was poor. The aligned electrospun PC fiber with the best morphology was made in the range of polymer concentration of 22%, solvent ratio of 50:50 THF : DMF, applied voltage of 14 kV, flow rate of 0.050 ml/m, and a take‐up velocity of 7.3 m/s. The ultimate strength and initial modulus of the 80% drawn 22% PC fiber were 64 ± 2 MPa (commercial 55–75 MPa) and 1.9 ± 0.1 GPa. The heat release capacity (HRC) of the 22 and 25% PC fiber were 275 ± 27 J/g K and 198 ± 1 J/g K. It was found that the flame resistance of the electrospun PC nanofiber was superior to that of the PC raw material (HRC ～360 J/g K). POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Air permeability of electrospun polyacrylonitrile nanoweb

Ultrafine fibers were spun from polyacrylonitrile (PAN) solution in N,N‐dimethylformamide using a homemade electrospinning setup. Fibers with diameter ranging from 80 to 340 nm were obtained. Fiber size and fiber size distribution were investigated for various concentration, applied voltage, and tip‐to‐collector distance using image analysis. The diameters of the electrospun fibers increase when increasing the solution concentration and decrease slightly when increasing the voltage and needle tip‐to‐collector distance. Porosity and air permeability are vital properties in applications of electrospun nanofibrous structures. In this study, effects of process parameters on the porosity and air permeability of electrospun nanoweb were investigated as well. Results of statistical analysis showed that solution concentration and applied voltage have significant influences on pore diameters. It was concluded that nanofiber diameter played an important role on the diameter of pores formed by the intersections of nanofibers. A more realistic understanding of porosity was obtained and a quantitative relationship between nanoweb parameters and its air permeability was established by regression analysis. Two separate models were constructed for predicting air permeability in relation to process parameters. Optimization of electrospinning process for producing nanoweb with desirable air permeability is well achieved by these models. The models presented in this study are of high importance for their ability to predict the air permeability of PAN nanoweb both by process or structure parameters. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

静电纺丝纳米纤维的制备工艺及其应用

简述了静电纺丝制备纳米纤维的原理;探讨了静电纺丝电压、流速、接收距离、溶剂浓度等工艺条件;介绍了同轴静电纺丝制备皮芯结构的超细纤维及中空纤维技术以及静电纺丝纳米纤维毡在生物医药方面的应用。指出静电纺丝纳米纤维材料在生物医用方面具有广阔的应用前景,进一步实现低压纺丝、开发无毒溶剂,控制同轴静电纺丝纳米纤维的释放性能是今后静电纺丝的研发方向。     

Preparation and experimental parameters analysis of laser melt electrospun poly(L‐lactide) fibers via orthogonal design

Laser melt electrospinning is a novel technology to produce micro/nanofibers. This solvent‐free process is more suitable for biomedical applications. In this work, the electrospun poly(L ‐lactide) (PLLA) fibers with diameters ranging from 2 to 7 μm were prepared by this method, and four influencing factors of melt flow rate (MFR), laser current, collector distance, and applied voltage were investigated on the PLLA fiber diameters and its standard deviation (SD) with an orthogonal design method. The results of range analysis showed the order of significance levels as follows: applied voltage, laser current, collector distance, and MFR for fiber diameter. The SD of fiber diameter can be listed in the following order: applied voltage, MFR, laser current, and collector distance. POLYM. ENG. SCI., 52:1964–1967, 2012. © 2012 Society of Plastics Engineers