Electrospinning of polyurethane fibers

A segmented polyurethaneurea based on poly(tetramethylene oxide)glycol, a cycloaliphatic diisocyanate and an unsymmetrical diamine were prepared. Urea content of the copolymer was 35 wt%. Electrospinning behavior of this elastomeric polyurethaneurea copolymer in solution was studied. The effects of electrical field, temperature, conductivity and viscosity of the solution on the electrospinning process and morphology and property of the fibers obtained were investigated. Results of observations made by optical microscope, atomic force microscope and scanning electron microscope were interpreted and compared with literature data available on the electrospinning behavior of other polymeric systems.     

Electrospinning and characterization of highly sulfonated polystyrene fibers

Nanofibers of highly sulfonated (IEC ∼4.5 meq/g) polystyrene (SPS) were successfully electrospun. To accomplish this, the process of electrospinning this difficult-to-spin material was studied in detail. Fiber quality was optimized by manipulating the process and solution variables to fabricate continuous bead-free fibers. Bead-free fibers (average diameter 260 nm) were electrospun from 25 wt% SPS (500 kDa) in DMF at an electrode separation of 10 cm, an applied voltage of 16.5 kV and a flow rate of 0.3 mL/h. With increasing solution concentration, and thereby the solution viscosity, the morphology changed from beads to bead-on-string fibers to continuous cylindrical fibers. Beaded fibers and continuous bead-free fibers of SPS (500 kDa) could be spun at ∼2 C_e and 3.5 C_e, respectively, where C_e is the entanglement concentration determined from solution-viscosity measurements. The onset of formation of beaded fibers coincided with a sharp transition in the scaling of the storage modulus-concentration relationship.     

Electrospinning of uniform polystyrene fibers: The effect of solvent conductivity

By means of the electrospinning technique, micron- and nanofibers can be obtained from polymer solutions under a very high electrical field. A special challenge is to produce bead-free uniform fibers since any minor changes in the electrospinning parameters such as slight variations in the polymer solutions and/or electrospinning experimental parameters may result in significant variations in the final nanofiber morphology. Furthermore, it is often not trivial at all to obtain reproducible uniform electrospun nanofibers for the optimized electrospinning conditions. Here we report that the conductivity of the solvent is the key factor for the reproducible electrospinning of uniform polystyrene (PS) fibers from dimethylformamide (DMF) solutions. It is shown that even slight changes in the conductivity of the DMF solutions can greatly affect the morphology of the resulting electrospun PS fibers. Here, we have carried out a thorough and systematic study on the effect of solution conductivity on the electrospinning of bead-free polystyrene (PS) fibers when dimethylformamide (DMF) was used as the solvent. Interestingly, we found out that different grades of solvent as-received (DMF) from various suppliers have slightly different solution conductivities. Consequently, the polymer solutions prepared with the same PS concentration have different conductivities, which are shown to have significant changes on the morphology of the PS fibers resulting in beaded or bead-free uniform fibers when electrospun under the identical electrospinning conditions. Such as, bead-free PS fibers were obtained from PS solutions in the range of 20% (w/v) through 30% (w/v) depending on the DMF grade used. In brief, it was observed that solutions with a higher conductivity yielded bead-free fibers from lower polymer concentrations, which confirms that the solution conductivity plays a very significant role in producing bead-free uniform PS fibers.     

Electrospinning of hydroxypropyl cellulose fibers and their application in synthesis of nano and submicron tin oxide fibers

Synthesis of hydroxypropyl cellulose (HPC) fibers via electrospinning has been demonstrated, for the first time, in this investigation. The HPC solution in two different solvents, anhydrous ethanol and 2-propanol, has been utilized with two different tip-to-collector distance (10 and 15 cm) for synthesizing HPC fibers by varying applied voltage within the range of 10–30 kV. It has been shown that, nano (<100 nm) and submicron (>100 nm) HPC fibers can be obtained under the described electrospinning conditions. Average HPC fiber diameter and its bead formation tendency appear to be a function of nature of the solvent and the applied voltage. Characteristic features of electrospinning of HPC fibers appear to be in consonance with the established mechanism of polymer fiber formation via electrospinning. Use of electrospun HPC fibers in synthesizing and depositing highly porous network of nano and submicron tin oxide (SnO₂) fibers on microelectromechanical systems (MEMS) device has been demonstrated.     

Electrospinning functional nanoscale fibers: a perspective for the future

Over the past decade, electrospinning has grown from a small niche process to a widely used fiber formation technique. Applying a strong electric potential on a polymer solution or melt produces nanoscale fibers. These nanofibers form non‐woven textile mats, oriented fibrous bundles and even three‐dimensional structured scaffolds, all with large surface areas and high porosity. Major applications of electrospun membranes include tissue engineering, controlled drug delivery, sensing, separations, filtration, catalysis and nanowires. This perspective article highlights many recent advances in electrospun fibers for functional applications, with an emphasis on the advantages and proposed technologies for these non‐woven fibrous scaffolds. Copyright © 2007 Society of Chemical Industry     

Electrospinning and structural characterization of ultrafine poly(butylene succinate) fibers

Biodegradable ultrafine poly(butylene succinate) (PBS) fibers were continuously electrospun for the first time from PBS solutions in chloroform (CF)/2-chloroethanol (CE) (7/3, w/w), CF/CE (6/4, w/w), dichloromethane (DM)/CE (7/3, w/w), DM/CE (6/4, w/w), and CF/3-chloro-1-propanol (9/1, w/w). These mixed solvents had an appropriate evaporation rate for the continuous electrospinning of PBS. The ultrafine PBS fibers had very high crystallinity and their average diameters were in the range of 125-315 nm. The annealed ultrafine PBS fibers exhibited a lamellar stack morphology containing crystalline and amorphous layers.     

Electrospinning of thermo-regulating ultrafine fibers based on polyethylene glycol/cellulose acetate composite

Ultrafine fibers of polyethylene glycol/cellulose acetate (PEG/CA) composite in which PEG acts as a model phase change material (PCM) and CA acts as a matrix, were successfully prepared as thermo-regulating fibers via electrospinning. The morphology observation from the electrospun PEG/CA composite fibers revealed that the fibers were cylindrical and had a smooth external surface. PEG was found to be both distributed on the surface and within the core of the fibers. Differential scanning calorimeter (DSC) was used to characterize the thermal properties of the composite fibers. The results indicated that the fibers imparted balanced thermal storage and release properties for their thermo-regulating function and the thermal properties were reproducible after 100 heating-cooling cycles.     

Ultra-fine polyelectrolyte fibers from electrospinning of poly(acrylic acid)

Ultra-fine polyelectrolyte fibers have been generated from electrospinning of poly(acrylic acid) in aqueous and DMF solutions. The fiber diameters ranged from 80 to 500 nm and increased with increasing solution concentrations and electrospinning voltages. The fibers generated from the aqueous solutions were more homogeneous in sizes, especially when NaCl or NaOH was added. Higher voltages in electrospinning of the aqueous solutions also resulted in fibers with larger heat capacity in the glass transition region, and higher dehydration temperatures. These polyelectrolyte fibers could be rendered water-insoluble by incorporating β-cyclodextrin (at 20 wt% of PAA) in the aqueous solution, then heat-induced crosslinking was performed at 140 °C for 20 min. The resulting hydrogel fibers showed strongly pH-responsive swelling behaviors.     

Electrospinning of Polymers,Their Modeling and Applications

Although there are several methods for obtaining sub-micro or nanofibers, electrospinning is perhaps the most versatile process. Nanotechnology has been widely accepted as dealing with the science and technology where at least one dimension is of roughly 1 to 100 nm. Electrospinning has been recognized as a feasible technique for the fabrication of polymeric nanofiber yarns. Various materials including polymers, composites, ceramics and metals have been electrospun into nanofibers. The nanofibers thus produced exhibit novel and significantly improved physical, chemical and biological properties due to their nanolevel size. In this article, the electrospinning process, along with its modeling equations and applications have been discussed. Some typical case studies regarding electrospinning under various categories have also been discussed.     

电子纺丝及其制备的纳米纤维的应用

简述了电子纺丝的基本原理及电子纺丝制备纳米纤维的研究进程,对其作为功能性材料在高技术领域的应用进行了重点介绍。     

Electrospinning and mechanical characterization of gelatin nanofibers

This paper investigates electrospinning of a natural biopolymer, gelatin, and the mass concentration-mechanical property relationship of the resulting nanofiber membranes. It has been recognized that although gelatin can be easily dissolved in water the gelatin/water solution was unable to electrospin into ultra fine fibers. A different organic solvent, 2,2,2-trifluoroethanol, is proven suitable for gelatin, and the resulting solution with a mass concentration in between 5 and 12.5% can be successfully electrospun into nanofibers of a diameter in a range from 100 to 340 nm. Further lower or higher mass concentration was inapplicable in electrospinning at ambient conditions. We have found in this study that the highest mechanical behavior did not occur to the nanofibrous membrane electrospun from the lowest or the highest mass concentration solution. Instead, the nanofiber mat that had the finest fiber structure and no beads on surface obtained from the 7.5% mass concentration exhibited the largest tensile modulus and ultimate tensile strength, which are respectively 40 and 60% greater than those produced from the remaining mass concentration, i.e. 5, 10, and 12.5%, solutions.     

Electrospinning preparation and characterization of cadmium oxide nanofibers

Using a facile synthesis route, cadmium oxide (CdO) nanofibers in the diameter range of 50–60 nm have been prepared employing the electrospinning technique followed by a single-step calcination from the aqueous solution of polyvinyl alcohol (PVA) and cadmium acetate dihydrate. Electron microscopy (EM) and the Brunauer–Emmett–Teller (BET) technique were employed to characterize the as-spun nanofibers as well as the calcined product. The specific surface area of the product was calculated to be 42.6711 m² g⁻¹. Infrared (IR) absorbance spectroscopy and X-ray powder diffractometery were conducted on the samples to study their chemical composition as well as their crystallographic structure. The study on the optical properties based on the photoluminescence (PL) spectrum demonstrated that the emission peaks of CdO nanofibers are centered at 493 and 528 nm. The direct bandgap of the CdO nanofibers was determined to be 2.51 eV.     

Electrospinning of native cellulose from nonvolatile solvent system

Improving and understanding the electrospinnability of native cellulose in room temperature ionic liquids (RTIL) have been a hot issue in recent years. In this study, the electrospinning of cellulose in a highly efficient RTIL of 1-allyl-3-methylimidazolium chloride (AMIMCl) was investigated. The introduction of co-solvent dimethyl sulfoxide (DMSO), which significantly decreased the surface tension, viscosity and entanglement density of the network and increased the conductivity of the spinning dope, contributed to a continuous jet. The problems lying in nonvolatility and the high ionic strength of the RTIL, which unavoidably led to the standing up vertically, adhesion and contractions of the wet fibers during the electrospinning process, were successfully resolved using a rotating copper-wire drum as a collector and solidifying the jet under high relative humidity. The water vapor played an important role in leading to “skin formation” which helped to stabilize the fibrous morphology, and finally smooth ultra-thin regenerated cellulose fibers were obtained. The combination of solvent system and collecting apparatus and conditions provided not only an effective method of producing ultra-thin native cellulose fibers on a large scale, but also a fundamental solution to other electrospinning systems with high ionic strength and nonvolatility. Measurements on WAXD and FT-Raman indicated that the electrospun cellulose fibers were almost amorphous with a little crystallization presented the polymorph of Type-II, which was totally different from the native cellulose with the dominated polymorph of Type-I.     

Electrospinning of polymer nanofibers with specific surface chemistry

Electrospinning is a process by which sub-micron polymer fibers can be produced using an electrostatically driven jet of polymer solution (or polymer melt). Electrospun textiles are of interest in a wide variety of applications including semi-permeable membranes, filters, composite applications, and as scaffolding for tissue engineering. The goal of the research presented here is to demonstrate that it is possible to produce sub-micron fibers with a specific surface chemistry through electrospinning. This has been accomplished by electrospinning a series of random copolymers of PMMA-r-TAN from a mixed solvent of toluene and dimethyl formamide. X-ray Photoelectron Spectroscopy (XPS) analysis shows that the atomic percentage of fluorine in the near surface region of the electrospun fibers is about double the atomic percentage of fluorine found in a bulk sample of the random copolymer, as determined by elemental analysis. These results are in good agreement with XPS and water contact angle results obtained from thin films of the same copolymer materials.     

Electrospinning and thermal treatment of yttria doped zirconia fibres

As compared to a bulk material, the fibres exhibit novel physical and chemical properties arising from their unique geometric features such as high surface area, surface to volume ratio and small fibre diameter. This paper is focused on the fabrication of nanosized 8 mol% yttria doped zirconia fibres by electrospinning from propoxide/polyvinylpyrrolidonebased precursors and physical-chemical characterization of the ceramic fibres with an energy application potential. Fully crystalline composition of cubic zirconia was detected after fibre heat treatment at 700 °C. The fibre morphology was changed with increasing temperature from flexible nonsintered nanoparticle system at 700 °C through porous nanograin structure at 900 °C and nonporous structure with coarser nanograins at 1100 °C to fragile chain-like fibre structure formed of elongated submicrometer grains at 1300–1450 °C. The densification and grain growth kinetics were described in two stages in the temperature range from 700 °C up to 1450 °C.     

静电纺丝制备纳米纤维的研究进展

纳米纤维具有直径小、比表面积大和易于实现表面功能化等优点,受到了广泛的关注,而静电纺丝技术被认为是制备聚合物纳米纤维最简单有效的方法,因此国内外学者对静电纺丝技术进行了详细的研究。简单介绍了静电纺丝技术的工作原理,详细阐述了影响静电纺丝的主要工艺参数,包括溶剂、溶液的浓度及黏度、电导率、工作电压、纺丝速度和接收距离等,并叙述了静电纺丝纳米纤维在过滤材料、传感器和生物医学等方面的应用,也指出了该技术存在的一些问题及其应对措施。     

Ethylene/(meth)acrylic acid ionomers plasticized and reinforced by metal soaps

Metal soaps, also known as fatty acid salts, resemble oligomers of ethylene/methacrylic or ethylene/acrylic acid (E/(M)AA) ionomers, in that they contain carboxylic salt headgroups and long methylene sequences in their hydrocarbon tails. Such soaps might thus be expected to form miscible blends with E/(M)AA ionomers under suitable conditions, providing a separate route to increasing an ionomer's ion content and modifying its physical properties. We show here that the structure and property modifications induced by blending metal soaps into E/(M)AA ionomers are complex, and depend on both the neutralizing cation and on whether the hydrocarbon tails are crystallizable. In the melt at sufficiently high temperatures, all blends show a coassembled structure, where the salt groups of the soap coaggregate with the salt groups on the ionomer; despite the high ion content of these blends, they retain the melt processability characteristic of neat E/(M)AA ionomers of much lower ion content. Non-crystallizable magnesium oleate and magnesium erucate act as permanent plasticizers, lowering the matrix glass transition temperature. Magnesium stearate, whose alkyl tails easily form a rotator phase, can slowly ‘cocrystallize’ with ethylene sequences in the ionomers, leading to high moduli; however, primary crystallization is suppressed in these blends. Finally, while sodium stearate is miscible with the ionomers at elevated temperatures, it phase-separates on cooling, prior to crystallization of the ionomer; such blends are essentially composites of pure stearate and ionomer phases, with their associated individual properties, rather than possessing new structures or properties resulting from coassembly.     

静电纺丝法制备PHBV有序纤维

利用静电纺丝转轴法制备羟基丁酸-羟基戊酸共聚酯(PHBV)有序纤维,研究了转轴表面线速度对PHBV纤维结构与性能的影响.结果表明:随着转轴表面线速度的提高,PHBV纤维的排列有序度、晶区取向度及分子链取向度、结晶度以及力学性能提高,10.5m/s时均达到最大值,其后又有所降低;转轴的卷绕对纤维具有拉伸作用,随着转轴表面...     

Template-assisted assembly of electrospun fibers

Ordinarily, the electrospinning process generates one-dimensional fibers which assemble into non-woven membrane structures due to instabilities in the fluid jet. In this paper, an electrospinning procedure is developed that utilizes patterned collectors to produce aligned membranes with designed topological structures. The template-assisted electrospinning approach is demonstrated using polycaprolactone (PCL) fibers to produce patterns including alphanumeric characters and a printed electronic circuit chip, with feature sizes on the order of several hundred microns. The process has a significant impact on micro-manufacturing, and provides the capability for incorporation of oriented fiber materials in patterned micro-composites and electronic components.     

High Precision Deposition Electrospinning of nanofibers and nanofiber nonwovens

Electrospinning is known to produce nanofiber nonwovens with lateral dimensions in 10 cm up to the meter range meeting thus requirements characteristic of filter, textile or even tissue engineering applications. For particular applications other types of deposition pattern are of benefit (i) in which the deposition area is strongly limited in the lateral dimension, (ii) in which a linear deposition path is oriented along a specified direction or (iii) in which the nonwovens are deposited following a predesigned pattern. This paper reports experimental results for the High Precision Deposition Electrospinning (HPDE) approach introduced by us earlier. It is based on a syringe type die-counter electrode set-up used for conventional continuous electrospinning, the key feature being a reduction of the distance between the spinning die and the substrate from the conventional value of 10-50 cm down to the millimeter and below mm range in order to suppress the onset of bending instabilities and the corresponding spread of the deposition area. The architecture of the nonwovens is controlled in this case by buckling processes and deflections of the jet by transiently charged nanofibers on the substrate. A second important feature of the set-up is a counter electrode/substrate which can be subjected to precise motions in the deposition plane. Based on a careful optimization of the spinning parameters and a tight online control of the spinning process a deposition of individual nanofibers or nonwovens is achieved which meets all deposition requirements specified above. This opens the route towards novel applications among others in areas relying on specific surface architectures such as sensorics, microfluidics and possibly also surfaces of implants.