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.     

The effects of processing parameters on the morphology of PLA/PEG melt electrospun fibers

Electrospinning of a polymer melt is an ideal technique to produce highly porous nanofibrous or microfibrous scaffolds appropriate for biomedical applications. In recent decades, melt electrospinning has been known as an eco‐friendly procedure as it eliminates the cytotoxic effects of the solvents used in solution electrospinning. In this work, the effects of spinning conditions such as temperature, applied voltage, nozzle to collector distance and collector type as well as polyethylene glycol (PEG) concentration on the diameter of melt electrospun polylactic acid (PLA)/PEG fibers were studied. The thermal stability of PLA/PEG blends was monitored through TGA and rheometry. Morphological investigations were carried out via optical and scanning electron microscopy. Based on the results, blends were almost stable over the temperature range of melt electrospinning (170 ? 230 °C) and a short spinning time of 5 min. To obtain non‐woven meshes with uniform fiber morphologies, experimental parameters were optimized using ANOVA. While increasing the temperature, applied voltage and PEG content resulted in thinner fibers, PEG concentration was the most influential factor on the fiber diameter. In addition, a nozzle to collector distance of 10 cm was found to be the most suitable for preparing uniform non‐woven PLA/PEG meshes. At higher PEG concentrations, alterations in the collector distance did not affect the uniformity of fibers, although at lower distances vigorous bending instabilities due to polarity augmentation and viscosity reduction resulted in curly fibrous meshes. Finally, the finest and submicron scale fibers were obtained through melt electrospinning of PLA/PEG (70/30) blend collected on a metallic frame. © 2017 Society of Chemical Industry     

Electrospinning of poly(hydroxybutyrate‐co‐hydroxyvalerate) fibrous tissue engineering scaffolds in two different electric fields

Poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) was electrospun into ultrafine fibrous nonwoven mats. Different from the conventional electrospinning process, which involves a positively charged conductive needle and a grounded fiber collector (i.e., positive voltage (PV) electrospinning), pseudo‐negative voltage (NV) electrospinning, which adopted a setup such that the needle was grounded and the fiber collector was positively charged, was investigated for making ultrafine PHBV fibers. For pseudo‐NV electrospinning, the effects of various electrospinning parameters on fiber morphology and diameter were assessed systematically. The average diameters of PHBV fibers electrospun via pseudo‐NVs were compared with those of PHBV fibers electrospun via PVs. With either PV electrospinning or pseudo‐NV electrospinning, the average diameters of electrospun fibers ranged between 500 nm and 4 μm, and they could be controlled by varying the electrospinning parameters. The scientific significance and technological implication of fiber formation by PV electrospinning and pseudo‐NV electrospinning in the field of tissue engineering were discussed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Studies on the electrospun submicron fibers of SIS and its mechanical properties

The submicron fibers were prepared via electrospinning the styrene–isoprene–styrene (SIS) triblock copolymer from a pure solvent of tetrahydrofuran (THF) and a mixed solvent of THF and N, N‐dimethylformamide (DMF). The addition of DMF to THF resulted in a beneficial effect on the fiber formation and the electrospinnability. The obtained results revealed that the fibers were only formed in a narrow solution concentration range of 8–15 wt %; the morphology, diameter, structure, and mechanical performance of as‐spun fibers from PS and SIS solutions were affected by the composition weight ratio and the solution properties; and those from the solution at the intermediate concentration of 10 wt % exhibited a maximum tensile strength and strain at break. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of applied voltage on diameter and morphology of ultrafine fibers in bubble electrospinning

A novel electrospinning process, bubble electrospinning, was used to produce porous nonwoven fibrous mats, of which the fiber diameter can range from nano‐ to microscales. The deformation of a charged bubble, from which multiple jets were ejected, was observed using a high‐speed motion camera. The effects of different applied voltages on diameter, morphology, and structure of bubble‐electrospun ultrafine fibers were theoretically analyzed and then experimentally validated by scanning electron microscopy and atomic force microscopy. The results showed that the average diameter of fibers increased with the increase of the applied voltage in bubble electrospinning, which is quite different from that in traditional electrospinning process under the similar conditions. The number of beaded fibers decreased with increasing applied voltage. Additionally, the crystallinities of polyvinylpyrrolidone ultrafine fibers obtained in this process were higher than that of polyvinylpyrrolidone powders. The production rate of bubble electrospinning was higher than that of the traditional electrospinning. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Magnetic electrospun fluorescent polyvinylpyrrolidone nanocomposite fibers

Magnetic nanoparticles (MNPs) were synthesized from facile thermodecomposition of iron pentacarbonyl and the subsequent silica coating on the MNP surface was achieved via a modified Stöber process to obtain the core–shell composite structured particles (MNPs-SiO₂). MNPs-SiO₂ were then incorporated into polyvinylpyrrolidone (PVP) to form nanocomposite fibers via an electrospinning process with optimized operational parameters such as polymer concentration, applied electrical voltage, feed rate and tip-to-collector distance. All these parameters show an unusual effect on the produced fiber diameter. Contrary to the conventional observation, i.e., increasing the applied voltage and feed rate or decreasing the distance could increase the fiber diameter; a reduced average fiber diameter was observed in this study and could be explained from the stretching and contraction force balance within the fiber during electrospinning. The size of the resulting PVP fibers is correlated to the corresponding rheological behaviors of the PVP solutions with different concentrations. The MNPs-SiO₂/PVP nanocomposite fibers exhibit a similar thermal decomposition temperature (386.3 °C) as that (387.8 °C) of pure PVP. Meanwhile, unique fluorescent and magnetic properties have been incorporated simultaneously in the nanocomposite fibers with the addition of small amount of MNPs-SiO₂ nanoparticles.     

熔体直写电纺聚己内酯纤维有序沉积工艺

目前聚合物熔体电纺技术制备的纤维大多以杂乱无序的无纺布形式存在,限制了电纺技术在组织工程支架以及机器人等需要有序结构领域的应用。本文将熔体电纺技术与三维运动平台相结合,采用自主设计的熔体电纺可控成型实验装置,对聚己内酯（PCL）进行熔体直写静电纺丝,获得了有序纤维。研究了喷头移动速度、接收距离和纺丝电压对熔体直写电纺纤维沉积形貌的影响。结果表明,纤维直径随着喷头移速、接收距离和纺丝电压的增大而减小,其中接收距离的改变对直径的影响最为显著;接收距离的增大虽然有利于纤维的细化,但是距离过大会使纤维沉积的有序性变差;当射流下落速度与喷头移动速度相匹配时,射流才能实现有序沉积;增大接收距离和纺丝电压会引起射流鞭动,需要相应地增大喷头移动速度才能实现有序沉积。     

The effect of solvent dielectric properties on the collection of oriented electrospun fibers

A simple approach to electrospinning has been developed that enables the collection of polymer, ceramic, and multiphase composite fibers, in quantity, with a high degree of spatial orientation. It has been demonstrated that a careful choice of solvent effectively eliminates the onset of the characteristic “bending” instability that is commonly associated with the electrospinning process. This allows collection of spatially oriented submicron electrospun fibers on a rotating drum without the need for elaborate mechanical or electrostatic manipulation of the electrospinning jet and/or collection target (Deitzel, J. M.; Kleinmeyer, J. D. et al. Polymer 2001, 42, 8163, Zussman, E.; Theron, A.; et al. Appl Phys Lett 2003, 82, 973, and Li, D. Wang, Y. L.; et al. Nano Lett 2003, 3, 1167). Fibers have been electrospun from a series of model polyethylene oxide/CHCl₃ solutions with a range of conductivities. The experimental data confirms theoretical predictions that the onset of the bending instability is a function of the available “free” charge in the solution, which in turn is strongly influenced by the dielectric constant of the solvent. The results show that fiber orientation becomes random as the conductivity increases, indicating the need for the surface charge density to exceed a critical threshold in order for the bending instability to initiate. This method has been experimentally demonstrated with other low-dielectric constant solvents and other common polymer, ceramic, and composite materials. Furthermore, it has been demonstrated that fibers electrospun from these solutions can be mechanically drawn to submicron dimensions (∼ 200–500 nm) by controlling drum speed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of spinning temperature and blend ratios on electrospun chitosan/poly(acrylamide) blends fibers

We report the formation of non-woven fibers without bead defects by electrospinning blend solutions of chitosan and polyacrylamide (PAAm) with blend ratios varying from 75 wt% to 90 wt% chitosan using a modified electrospinning unit wherein polymer solutions can be spun at temperatures greater than ambient up to 100 °C. Electrospinning at elevated temperature leads to further expansion of the processing window, by producing fibers with fewer defects at higher chitosan weight percentage in the blends. Effects of varying blend ratios, spinning temperatures, and molecular weights on fiber formation were studied and optimum conditions for formation of uniform non-woven fiber mats with potential applications for air and water filtration were obtained. Uniform bead-less fiber mats with fiber diameter as low as 307 ± 67 nm were formed by spinning 90% chitosan in blend solutions at 70 °C.     

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

静电纺丝抗菌聚氨酯纳米纤维的结构与性能

在聚氨酯/四氢呋喃-N,-二甲基甲酰胺(PU/THF-DMF)溶液中分别添加质量分数为5%的TiO_2-Ag,HM-98,三氯均二苯胺(TCC),4-氯-3,5-二甲基苯酚(PCMX),2,4,4'-三氯-2'-羟基二苯酚(DP 300),ε-聚赖氨酸(ε-PLYS)抗菌剂通过静电纺丝技术制备了PU抗菌纳米纤维,并对其性能和结构进行了研究。结果表明:含ε-PLYS,HM-98,TiO_2-Ag,DP300抗菌剂的抗菌PU纳米纤维对金黄色葡萄球菌和大肠杆菌的抗菌效果较为优良,抗菌率均达到了99.9%以上,TCC、PCMX抗菌剂的抗菌效果较差;添加HM-98抗菌剂降低了纺丝溶液的可纺性,但纤维直径有所下降;抗菌剂在PU中的分散性好。     

Study on the preparation of hyperbranched polyethylene fibers and hyperbranched polyethylene composite fibers via electrospinning

This contribution mainly studied the preparation of hyperbranched polyethylene (HBPE) fibers and HBPE/multiwalled carbon nanotube (MWCNT) composite fibers via electrospinning for the first time. Firstly, the effects of solvents, solution concentration, voltage, and rotating speed of collector on the morphology of HBPE fibers were studied. Among the factors, solvent type, concentration, and voltage showed notable influence on the morphology of HBPE fibers. HBPE has an excellent dispersion effect on CNT in organic solvents. Through ultrasonic dispersion, the HBPE solutions with dispersed MWCNT were obtained. Then HBPE/MWCNT composite fibers were obtained with different contents of MWCNT via electrospinning. The effects of voltage and working distance on the morphology of HBPE/MWCNT composite fibers were investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42517.     

Superparamagnetic flexible substrates based on submicron electrospun Estane® fibers containing MnZnFe?Ni nanoparticles

Flexible, elastomeric, and superparamagnetic substrates were prepared by electrospinning a solution of elastomeric polyurethane containing ferrite nanoparticles (～14 nm) of Mn? Zn? Ni. The flexible mats were characterized in terms of fiber morphology and magnetic properties. Field emission scanning electron microscopy (FESEM) indicated that the diameter of these composite fibers was ～300–500 nm. Furthermore, the back‐scattered electron FESEM images indicated agglomeration of the nanoparticles at higher wt % (ca. 17–26 wt %) loading in the electrospun fibers. The induced specific magnetic saturation and the relative permeability were found to increase linearly with increasing wt % loading of the ferrite nanoparticles on the submicron electrospun fibers. A specific magnetic saturation of 1.7–6.3 emu/g at ambient conditions indicated superparamagnetic behavior of these composite electrospun substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4935–4942, 2006     

Synthesis of ultrafine poly(styrene‐maleic anhydride) and polystyrene fibers by electrospinning

Fiber formation from atactic polystyrene (aPS) and alternating poly(styrene‐maleic anhydride) (PSMA) synthesized by free radical polymerization (AIBN, 90°C, 4 h) were investigated by electrospinning from various solutions. aPS was soluble in dimethylformamide (DMF), tetrahydrofuran (THF), toluene, styrene, and benzene, whereas PSMA was soluble in acetone, DMF, THF, dimethylsulfoxide (DMSO), ethyl acetate, and methanol. aPS fibers could be electrospun from 15 to 20% DMF and 20% THF solutions, but not from styrene nor toluene. PSMA, on the other hand, could be efficiently electrospun into fibers from DMF and DMSO at 20 and 25%, respectively. Few PSMA fibers were, however, produced from acetone, THF, or ethyl acetate solutions. Results showed that solvent properties and polymer–solvent miscibility strongly influenced the fiber formation from electrospinning. The addition of solvents, such as THF, generally improved the fiber uniformity and reduced fiber sizes for both polymers. The nonsolvents, however, had opposing effects on the two polymers, i.e., significantly reducing PSMA fiber diameters to 200 to 300 nm, creating larger and irregularly shaped aPS fibers. The ability to incorporate the styrene monomer and divinylbenzene crosslinker in aPS fibers as well as to hydrolyze PSMA fibers with diluted NaOH solutions demonstrated potential for post‐electrospinning reactions and modification of these ultrafine fibers for reactive support materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of ultra-fine α-Al2O3 fibers via electrospinning method

Ultra-fine Al₂O₃ fibers were synthesized via electrospinning technique using PVP/ethanol polymer solution and aluminium acetate sol followed by calcinations at higher temperature. The formation, crystalline phase, surface morphology, fibers diameter and surface area of alumina ultra-fine fibers were characterized using FT-IR, TGA/DTA, XRD, SEM, TEM and BET analytical techniques. The results show that pure and crystalline α-Al₂O₃ ultra-fine fibers were formed with fiber diameter in the range of 100–500 nm and BET surface area of the fibers were found to be 40 m²/g.     

Properties of aligned poly(L‐lactic acid) electrospun fibers

Poly(L‐lactic acid) (PLLA)‐aligned fibers with diameters in the nano‐ to micrometer size scale are successfully prepared using the electrospinning technique from two types of solutions, different material parameters and working conditions. The fiber quality is evaluated using scanning electron microscopy (SEM) to judge fiber diameter, diameter uniformity, orientation, and appearance of defects or beads. The smoothest fibers, most uniform in diameter and defect free, were found to be produced from 10% w/v chloroform/dimethylformamide solution using an accelerating voltage from 10–20 kV. Addition of 1.0% multiwalled carbon nanotubes (MWCNT) into the electrospinning solution decreases fiber diameter, improves diameter uniformity, and slightly increases molecular chain alignment. The fibers were cold crystallized at 120°C and compared with their as‐spun counterparts. The influences of the crystalline phase and/or MWCNT addition were examined using fiber shrinkage, temperature‐modulated calorimetry, X‐ray diffraction, and dynamic mechanical analysis. Crystallization increases the glass transition temperature, T_g, slightly, but decreases the overall fiber alignment through shrinkage‐induced buckling of the fibers when heated above T_g. MWCNT addition has little impact on T_g, but significantly increases the orientation of crystallites. MWCNT addition slightly reduces the dynamic modulus, whereas crystallization increases the modulus in both neat‐ and MWCNT‐containing fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41779.     

Orthogonal design study on factors effecting on fibers diameter of melt electrospinning

Melt electrospinning is a much more simple and safe method to produce ultra fine fibers than solution electrospinning. The diameters of melt electrospinning fibers are thicker. To find the factors that affect the fibers diameter in melt electrospinning, orthogonal design was used to examine melt temperature, spinning voltage, spinning distance, and melt flow rate (MFR) of polymer. Results showed that MFR at present three levels has the most important impact both on the average diameters and standard deviations of fiber diameters. The scanning electron microscopy pictures show that all the fibers have smooth surface, which means the melt electrospinning fibers have good mechanical properties. POLYM. ENG. SCI., 50:2074–2078, 2010. © 2010 Society of Plastics Engineers     

Single polymeric bubble for the preparation of multiple micro/nano fibers

Bubble‐electrospinning is suggested to produce micro/nano fibers. Contrary to classical electrospinning where a high voltage is applied to overcome the surface tension of the Taylor's cone, in bubble‐electrospinning, the voltage is applied to overcome the bubble's surface tension, which mainly depends upon the size of the bubble. Instead of single jet, millions of charged jets are observed simultaneously. In this article, we design a single bubble‐electrospinning to primarily study the effect of concentration on the spinning procedure. Polyvinylpyrrolidone (PVP) is used in the experiment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚醚砜的静电纺丝研究

采用聚醚砜(PES)的良溶剂二甲基甲酰胺(DMF)和非良溶剂丙酮(AC)为共溶剂体系,研究了溶剂组成、纺丝成形条件对静电纺丝PES纤维的形貌及纤维直径的影响。结果表明:DMF/AC的配比对于静电纺丝PES纤维形貌具有直接的调控作用,随着DMF/AC混合溶剂中AC用量的增加,纤维平均直径变大,纤维毡中串珠数目明显减少,纤维均一性变好;随着纺丝液浓度的升高,纺丝电压的增大,纤维的平均直径变大;接收距离的变化对纤维平均直径影响不大;PES最佳纺丝工艺条件为纺丝溶液质量分数13%,纺丝电压15 kV,接收距离10 cm,mDMF/mAC为8.5/1.5,在此条件下,可以获得纤维平均直径为96 nm的PES纤维毡。