Determination of optimal production parameters for polyacrylonitrile nanofibers

The object of this work is to determine the most suitable values of process and solution parameters for electrospinning of polyacrylonitrile (PAN) nanofibers including solution concentration, applied voltage, and working distance between the needle tip and the collector plate. To investigate the effects of those parameters on the fiber morphology, nanofiber mat samples were produced by changing the value of parameters systematically. The scanning electron microscope images of these samples were analyzed to realize the effects of these parameters on the nanofiber morphology. Our results demonstrate that the diameter of the fibers increases with increasing concentration. However, the diameter reduces as the applied voltage and working distance between needle tip and the collector increase up to a certain value. In addition to this, viscosity and applied voltage have a strong effect on the uniformity and morphology of the nanofibers. Moreover, a relationship between spinning distance, voltage supplied, solution concentration, charge density, bead formation, and the diameter of the electrospun PAN nanofiber were established in the study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal and morphological properties of PVA/4‐vinylbenzene boronic acid hybrid nanofibrous

The aim of this study was to investigate the preparation and characterization of PVA and PVA/4‐VBBA (4‐Vinylbenzene boronic acid) hybrid electrospun nanofiber mat. PVA was mixed with cross‐linkable 4‐Vinylbenzene boronic acid (4‐VBBA), enabling the polymer to cross‐link upon UV irradiation. The photo‐cross‐linking reaction was characterized by a Fourier transform infrared spectroscopy. The structure and morphology of electrospun membranes were investigated by scanning electron microscopy (SEM). SEM images showed that the nanofiber diameter and the nanostructured morphology depended on solution viscosity, applied electric voltage(AV), tip to collector distance (TCD), and the amount of the 4‐VBBA. The thermal properties of PVA and PVA/4‐VBBA hybrid nanofibers were investigated by thermo gravimetric analysis. The photo‐crosslinked nanofibers were insoluble in water. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

静电纺间位芳纶纳米纤维的制备工艺参数

通过静电纺丝方法,将氯化锂/N,N–二甲基乙酰胺(Li Cl/DMAc)溶解间位芳纶(PMIA)制备了PMIA纳米纤维,探索了溶液浓度、接收距离、纺丝电压及接收速度等工艺参数对纤维形貌及其直径分布的影响。通过扫描电子显微镜观察了PMIA纳米纤维形貌及应用Image-J软件测量统计了PMIA纤维直径。结果表明,溶液浓度为8%~10%、纺丝电压为16~18 k V、接收距离为15~20 cm,接收速度60~80 r/min的范围内,间位芳纶纳米纤维成型良好,直径分布范围为100~120 nm;PMIA纳米纤维直径随着溶液浓度的减小、静电电压的增加而减小,随着接收速度的增加纤维取向增加。     

The influence of electrospinning parameters on the structural morphology and diameter of electrospun nanofibers

Electrospinning is a simple method of producing nanofibers by introducing electric field into the polymer solutions. We report an experimental investigation on the influence of processing parameters and solution properties on the structural morphology and average fiber diameter of electrospun poly ethylene oxide (PEO) polymer solution. Experimental trials have been conducted to investigate the effect of solution parameters, such as concentration, molecular weight, addition of polyelectrolyte in PEO solution, solvent effect, as well as governing parameter, such as applied voltage. The concentration of the aqueous PEO solution has shown noteworthy influence on the fiber diameter and structural morphology of electrospun nanofibers. At lower concentrations of PEO polymer solution, the fibers showed irregular morphology with large variations in fiber diameter, whereas at higher concentrations, the nanofibers with regular morphology and on average uniform fiber diameter were obtained. We find that the addition of polyelectrolytes, such as sodium salt of Poly acrylic acid (PAA) and Poly allylamine hydrochloride (PAH), increases the conductivity of PEO solutions and thereby decreases the bead formation in electrospun nanofibers. The increase in applied voltage has been found to affect the structural morphology of nanofiber while the addition of ethanol in PEO solution diminishes the bead defects. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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。     

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     

Alignment and optimization of nylon 6 nanofibers by electrospinning

Nonwoven electrospun nylon 6 nanofibers produced with formic acid under different concentrations have been examined. The effects of the solution properties, electric field, and spinneret‐to‐collection distance on the fiber uniformity, morphology, and average diameter have been established. The optimum polymer solution concentration (20 wt %), applied voltage (15 kV), and spinning distance (8 cm) have been found to make uniform nylon 6 fibers. A simple technique that can produce a bundle of aligned electrospun fibers suspended between two grounded disks is described. Alignment and stretching of the fibers are derived by the electrostatic interactions between the positive electrode on the spinneret and the grounded disks. The gap between the disks and the collection time have been varied to systematically study the degree of alignment and the density of the collected nylon 6 fibers. The number of the distributed fibers in the bundle can be controlled by the alteration of the deposition time, the voltage, and the width of the gap. Scanning electron microscopy images have indicated a greater degree of fiber alignment with increasing disk gaps and collection times. The article also provides a comprehensive review of the design of various mechanisms for nanofiber alignment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

The morphology of electrospun polystyrene fibers

Electrospinning is a process of electrostatic fiber formation which uses electrical forces to produce polymer nanofibers from polymer solution. The electrospinning system consists of a syringe feeder system, a collector system, and a high power supplier. The important parameters in the morphology of electrospun polystyrene fibers are concentration, applied voltage, and solvent properties. Higher concentrations of the polymer solution form thicker fibers and fewer beads. When the concentration is 7 wt%, electrospun fibers have an average diameter of 340 nm, but as the concentration of PS increases to 17 wt%, the fiber diameter gradually thickens to 3,610 nm. The fiber morphology under different solvent mixture ratios and solvent mixtures has also been studied.     

Preparation of poly(ether sulfone) nanofibers by gas‐jet/electrospinning

Poly(ether sulfone) (PES) nanofibers were prepared by the gas‐jet/electrospinning of its solutions in N,N‐dimethylformamide (DMF). The gas used in this gas‐jet/electrospinning process was nitrogen. The morphology of the PES nanofibers was investigated with scanning electron microscopy. The process parameters studied in this work included the concentration of the polymer solution, the applied voltage, the tip–collector distance (TCD), the inner diameter of the needle, and the gas flow rate. It was found from experimental results that the average diameter of the electrospun PES fibers depended strongly on these process parameters. A decrease in the polymer concentration in the spinning solutions resulted in the formation of nanofibers with a smaller diameter. The use of an 18 wt % polymer solution yielded PES nanofibers with an average diameter of about 80 nm. However, a morphology of mixed bead fibers was formed when the concentration of PES in DMF was below 20 wt % during gas‐jet/electrospinning. Uniform PES nanofibers with an average diameter of about 200 nm were prepared by this electrospinning with the following optimal process parameters: the concentration of PES in DMF was 25 wt %, the applied voltage was 28.8 kV, the gas flow was 10.0 L/min, the inner diameter of the needle was 0.24 mm, the TCD was 20 cm, and the flow rate was 6.0 mL/h. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

静电纺丝工艺参数对丝素/壳聚糖纳米纤维的形貌及直径的影响

以98%的甲酸为溶剂,不同质量分数的再生丝素溶液和3.5%的壳聚糖溶液以质量比70:30共混静电纺丝。用扫描电子显微镜(SEM)观察了丝素质量分数、电压和极距(喷丝口到收集装置的距离)对丝素/壳聚糖纳米纤维的形貌及直径的影响。正交试验结果表明:在丝素/壳聚糖溶液静电纺丝的工艺参数中,对纤维平均直径的影响因素由大到小依次为丝素质量分数、电压、极距。单因素试验表明:丝素/壳聚糖纳米纤维的平均直径及其分布范围随丝素质量分数的增加而增大;在15￣30kV范围内纤维的平均直径随电压增大而减小;当极距大于12cm时,对纤维直径影响不大。最佳工艺条件为:丝素质量分数13%,电压30kV,极距为12cm,制得的纳米纤维平均直径104nm。     

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。     

Electrospun nanofibers of block copolymer of trimethylene carbonate and ϵ‐caprolactone

The electrospinning behavior of a block copolymer of trimethylene carbonate (TMC) and ε‐caprolactone dissolved in N,N‐dimethylformamide (DMF) and methylene chloride (MC) was studied. The effects of the blended solvent volume ratio, concentration, voltage, and tip–collector distance (TCD) on the morphology of the electrospun fibers were investigated by scanning electron microscopy. The results indicated that the diameter of the electrospun fibers decreased with a decreasing molar ratio of MC to DMF, but beads formed gradually. With a decreasing concentration of the solution, the fiber diameter decreased; at the same time, beads also appeared and changed from spindlelike to spherical. A higher voltage and larger TCD favored the formation of smaller diameter electrospun fibers. The results of differential scanning calorimetry and X‐ray diffraction showed that the crystallinity and melting point of the electrospun fibers decreased when increasing the TMC content in the copolymer. Compared with the corresponding films, the crystallinity and melting point of the electrospun fibers were obviously increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1462–1470, 2006     

Use of artificial neural networks to determine parameters controlling the nanofibers diameter in electrospinning of nylon‐6,6

This study aimed to find out the primary factors influencing the diameter of electrospun nanofibers of nylon‐6,6 using artificial neural networks (ANNs). Four variables, namely, polymer concentration, working distance, injection rate, and applied voltage were considered as input parameters and the nanofibers diameter measured by scanning electron microscopy was taken as the output. The data were modeled and validated against a set of unseen data. The generated model was used to study the interactions occurring between the input variables and their effect on the diameter. Results show that the injection rate and the polymer concentration are major factors affecting the nanofibers diameter with inverse and direct relations with the diameter, respectively, while the working distance and the applied voltage have direct but minor effects on nanofibers diameter. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124:1589–1597, 2011     

Free surface electrospun fibers: The combined effect of processing parameters

In this study, a free surface electrospinning experimental setup was developed based on rotating spiral copper wire electrode and used as the spinneret. The scheme was investigated by varying processing parameters including polymer solution concentration, distance between the electrode and the collector, applied voltage between the electrode, and the collector and wire electrode diameter. An average of fiber diameter ranged between 202 and 543 nm and a relative standard deviation ranged between 11.0 and 26.9% were obtained. The combined effects of processing parameters on the resulting fiber morphology were investigated. The analysis shows that in a multiple variable process like electrospinning, the interaction between the different processing parameters played an important role, rather than one parameter separately in obtaining desired nanofibers. Knowing the relative combined effects of processing parameters on fiber morphology should be useful for process control and prediction of electrospun fiber quality as it has been demonstrated in this study. POLYM. ENG. SCI., 54:189–197, 2014. © 2013 Society of Plastics Engineers     

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     

Investigation of β phase formation in piezoelectric response of electrospun polyvinylidene fluoride nanofibers: LiCl additive and increasing fibers tension

As a piezoelectric polymer, poly (vinylidene fluoride) (PVDF) is attractive in energy conversion applications between electrical and mechanical forms because of its low cost, high flexibility, and biocompatibility. The piezoelectricity of electrospun PVDF polymer is due to changes in the crystalline structure (e.g., creating the β‐phase) during the electrospinning process. This research focuses on two approaches for investigation of β Phase formation: (1) addition of LiCl in different concentrations (0.001, 0.00133, 0.002, 0.004 wt%) as inorganic salt to the polymer solution, (2) increasing tension along the fiber axis by increasing the collector drum speed during the aligning process. Performances of these structures were evaluated by using X‐ray diffraction (XRD), Fourier Transform Infrared (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). A one‐step nano‐generator and cost‐effective package based on electrospun nanofibers was presented to measure output voltages as a performance factor. Results show that the addition of LiCl leads to β Phase formation in the crystalline structure, decreasing fiber diameter to 65 nm, and increment in the work of rupture and piezoelectric output. Moreover, the results show that increasing collector drum speed causes the alignment of β‐crystallites along the fiber axis and subsequently no considerable effect on the formation of β‐phases and output voltage. POLYM. ENG. SCI., 56:61–70, 2016. © 2015 Society of Plastics Engineers     

Electrospinning silica/polyvinylpyrrolidone composite nanofibers

Small diameter nanofibers of silica and silica/polymer are produced by electrospinning silica/polyvinylpyrrolidone (SiO₂/PVP) mixtures composed of silica nanoparticles dispersed in polyvinylpyrrolidone solutions. By controlling various parameters, 380 ± 100 nm diameter composite nanofibers were obtained with a high silica concentration (57.14%). When the polymer concentration was low, “beads‐on‐a‐string” morphology resulted. Nanofiber morphology was affected by applied voltage and relative humidity. Tip‐to‐collector distance did not affect the nanofiber diameter or morphology, but it did affect the area and thickness of the mat. Heat treatment of the composite nanofibers at 200°C crosslinked the polymer yielding solvent‐resistant composite nanofibers, while heating at 465°C calcined and selectively removed the polymer from the composite. Crosslinking did not change the nanofiber diameter, while calcined nanofibers decreased in diameter (300 ± 90 nm) and increased in surface area to volume ratio. Nanofibers were characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40966.     

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.     

Effects of some electrospinning parameters on morphology of natural silk‐based nanofibers

Natural silk, from Bombyx mori solutions were electrospun into nanofibers, with diameters ranged from 60 to 7000 nm. The effects of electrospinning temperature, solution concentration and electric field on the formation nanofibers were studied. Optical and scanning electron microscope were used to study the morphology and diameter of electrospun nanofibers. It was observed that the nanofibers became flattened with ribbon‐like shape with increasing the electrospinning temperature. The nanofiber diameter increases with the increase in the concentration of silk solution at all electrospinning temperature. With increasing the voltage of electric field at 50°C, morphology of the nanofibers changes from ribbon‐like structure to circular cross section. Referring to the literature the probable mechanism responsible for the change of morphology is pointed out. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Assessment of parameters influencing fiber characteristics of chitosan nanofiber membrane to optimize fiber mat production

Electrospun chitosan nanofiber mats have been obtained using chitosan solutions in a mixture of trifluoroacetic acid and dichloromethane. The relationship between processing parameters (solvent composition, polymer concentration in the solution, feeding rate, applied voltage, traveling distance between the needle, and the collector) and fiber morphology was studied. Taguchi's methodology was followed to determine which parameters have the strongest influence on mean fiber diameter and fiber homogeneity. Chitosan nanofibers obtained with this procedure were water soluble due to the protonation of amine side groups but were successfully neutralized by immersion in calcium carbonate solutions. It was established that fiber diameter is mainly determined by the solution concentration and the distance from the needle to the collector while other parameters have less influence. The set of parameters that produce the thinnest fibers were a concentration of 8 wt%, a TFA/DCM ratio of 80:20 (v/v%), a voltage of 30 kV, a flow rate of 6.0 mL/h, a gap distance of 10 cm, using a needle diameter of 0.5, allowing to produce randomly oriented mats with a mean fiber thickness of 66 nm. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers