Morphology transition in electrospinning polymers by a dual‐capillary system

An experimental investigation of the fiber morphology change of fibers prepared by a dual‐capillary electrospinning system, operated in the cone‐jet mode, was carried out for poly(vinyl acetate) polymers of three molecular weights. The substrate morphology of the electrospun poly(vinyl acetate) could be changed significantly when the polymer's molecular weight, concentration, solvent, and outer liquid flow rate were varied. The onset of bead‐to‐fiber transition was determined by the critical chain overlap concentration. For solutions with a high concentration, the fiber diameter and surface were significantly affected by the physical properties of the solvents. To produce fibers of small diameter, electrospinning with a higher conductivity solution was desirable. On the other hand, a high‐conductivity solution needed to be avoided to keep the fiber uniform in diameter and smooth on the surface. The comparison of electrospun fibers produced by both single‐capillary and dual‐capillary systems was also addressed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of solvent on morphology of electrospinning ethyl cellulose fibers

The influence of the composition of a multicomponent solvent on the surface morphology and diameter distribution of ethyl cellulose fibers produced by electrospinning technology was investigated. The results showed that the average diameter of the fibers using the multicomponent solvent was thinner than when using either of the two components and the diameter distribution of the fibers became narrower. Tiny tubercles formed on the fiber surface, which may improve the specific surface area and broaden the applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1292–1297, 2005     

Orthogonal design preparation of phenolic fiber by melt electrospinning

Through orthogonal experimental methods, the melt electrospinning of pure phenolic fibers has been achieved. The preparation is based on an orthogonal experimental method, which was designed to investigate the optimal conditions for production through integrated effects of spinning temperature, gap between spinneret and collector, as well as applied voltage. We found that optimal spinning conditions at 160°C, a spinneret‐to‐collector gap of 8 cm, and applied voltage at 40 kV produce an average electrospun fiber diameter reaching 4.44 ± 0.76 μm, with narrow variance distribution. The fibers were cured in a solution with 18.5% formaldehyde and 12% hydrochloric acid, heated from room temperature to 80°C and maintained 1h. In this report, the morphology, structural changes, and heat resistance of the fibers are characterized. Obtained results reveal that curing the fiber reduces crystallization and improves heat resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42574.     

Thermochromic core–shell nanofibers fabricated by melt coaxial electrospinning

Microcapsule/nanocapsule and encapsulation techniques have great potential for devices of functional materials. Also, electrospinning has attracted great attention for the fabrication of microstructures and nanostructures. The fluidity after melting limits the application of phase‐transformation thermochromic materials. In this study, with the melt coaxial electrospinning technique, a phase‐transformation thermochromic material was encapsulated in poly(methyl methacrylate) nanofibers. A device of this phase‐transformation thermochromic material was realized. With a poly(methyl methacrylate) shell with good optical transmission and a thermoresponsive core made of crystal violet lactone, bisphenol A, and 1‐tetradecanol core, the fibers had good thermal energy management, fluorescent thermochromism, and reversibility. The fabrication of thermochromic core–shell nanofibers has further potential in the preparation of temperature sensors with good fluorescence signals and body‐temperature calefactive materials with intelligent thermal energy absorption, retention, and release. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Continuous aligned poly(meta‐phenylene isophthalamide) fibers via stable jet electrospinning

Continuous aligned poly(meta‐phenylene isophthalamide) (PMIA) fibers are first fabricated by Stable Jet Electrospinning (SJES) with a collection distance of 15 cm. The unfolded length of every single fiber is calculated to be several hundred to several thousand meters. Morphology analysis by field emission scanning electron microscopy (FE‐SEM) shows that these fibers are well arranged and uniformly distributed and their average fiber diameters decrease gradually with increasing collection speed. The effects of ambient temperature and humidity on the duration of stable jet are also discussed. Moderate temperatures and humidity are preferred for fabricating PMIA fibers with ultra‐long size. Besides, the changes of the thermal and crystalline properties of PMIA fibers are also investigated. The significant decline in crystallinity should be responsible for its decreased thermal property. Further improvements to its thermal and crystalline performance must be given consideration in future applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43690.     

静电纺丝过程中的非稳定性研究

通过静电纺聚丙烯腈纳米纤维,研究了静电纺丝过程中的非稳定性。结果表明:静电纺丝电压和接受距离是影响静电纺丝过程中的非稳定性因素,电压和接受距离增大,纳米纤维摆动加大,电压增加到一定量后,纳米纤维的摆幅在一定范围内,不会无限扩大,趋于一个固定值,接收距离超过一定范围后,纳米纤维出现不规则扰动,出现彼此缠绕。     

In situ synthesis of iron oxide nanoparticles on poly(ethylene oxide) nanofibers through an electrospinning process

Iron oxide nanoparticle coated poly(ethylene oxide) nanofibers as organic–inorganic hybrids with 200–400‐nm diameters were prepared by the in situ synthesis of iron oxide nanoparticles on poly(ethylene oxide) nanofibers through the electrospinning of a poly(ethylene oxide) solution having Fe²⁺ and Fe³⁺ ions in a gaseous ammonia atmosphere. Transmission electron microscopy analysis proved the presence of iron oxide nanoparticles on the polymer nanofibers. The thermal properties of the nanofiber mat were also studied with differential scanning calorimetry and thermogravimetric analysis techniques. X‐ray diffraction showed that the formed iron oxide nanoparticles were maghemite nanoparticles. The results were compared with those of the electrospinning of a poly(ethylene oxide) solution having Fe²⁺ and Fe³⁺ ions and a pure poly(ethylene oxide) solution in an air atmosphere. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Fabrication and properties of elastic fibers from electrospinning natural rubber

Electrospinning natural rubber (NR) to get elastic nano-/microfibers has attracted much attention. Suitable solvent such as tetrahydrofuran (THF) was selected by considering solubility, toxicity, and electrospinning results. Dynamic light scattering testing was used to measure the hydrodynamic diameter (D_h) of the solutions with different solvents and the critical concentrations (C*) of NR/THF solution. For NR solutions with the same concentration from different solvents, the larger D_h the solution, the larger the electrospun fiber diameter. Stable electrospinning concentration window ranging from 25 to 50 g/L, which corresponds to 38 > [ŋ]C > 19, was identified. Mechanical properties of both electrospun NR fiber mats and single fibers were estimated from tensile testing. Fibrous mats with excellent elasticity at about 439 to 505% elongation were demonstrated; however, the elongation rate of single fibers was 44%. Electrospun fiber mats with high elasticity of NR materials can be potentially used in soft tissue engineering and strain sensor areas. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48153.     

Investigation and prevention of clogging during electrospinning of zein solution

Electrospinning is the only known technique for fabrication of long non‐woven ultrafine‐fibers. However, a number of limitations, including low productivity and clogging of a spinneret, substantially paralyses industrial scale up of the process. Clogging is indeed an unavoidable phenomenon during electrospinning of biopolymers and the exact reason for clogging is still unclear. The aim of the present study was thus to investigate the clogging phenomenon via the study of a solution of zein/ethanol, which was used as a model biopolymer system. The gel‐like substance causing clogging at the spinneret was collected and its infrared spectrum and rheological properties were determined via Fourier transform infrared (FTIR) spectrophotometry and rheometry, respectively. The results indicated that clogging was due to solvent evaporation, which led to formation of a highly viscous semi‐solid at the spinneret. Moreover, the results also revealed that the applied voltage and polymer concentration were the key parameters affecting clogging. A means to help avoid clogging and hence an ability to continuously perform electrospinning was also proposed and tested. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Copolymerization of poly(1‐naphthylamine) with aniline and o‐toluidine

The commercial use of polyaniline has been impeded by its intractable nature and insolubility. The use of substituted polyaniline has been attempted mainly to increase the processibility of polyaniline, but this approach usually results in the lowering of the conductivity. This study reports the synthesis of poly(1‐naphthylamine), a fused ring derivative of polyaniline, and its copolymers with aniline and o‐toluidine via a chemical polymerization method. Spectral, thermal, morphological, and conductivity studies were carried out to elucidate the influence of the incorporation of aniline and o‐toluidine units into poly(1‐naphthylamine). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

高黏度聚乳酸(PLA)熔体微分离心静电纺丝

离心纺丝已成为制备超细纤维的有效途径,将离心纺丝和静电纺丝结合起来的离心静电纺丝,纺丝效率高、纤维细度低。但是目前离心静电纺丝相关的研究十分有限,且主要涉及溶液离心静电纺丝。为了解决这一问题,本文设计了一种基于熔体微分的熔体离心静电纺丝装置,选取聚乳酸（PLA）作为研究对象,探究了挤出机转速和流量的关系,得出挤出机转速在20r/min、流量为1.6089g/min时纺丝效果最佳。研究了离心盘转速、纺丝电压等因素对纤维的影响,得出增加离心盘转速可大幅细化纤维直径,离心盘转速提高1倍,纤维直径减小77.26%;纺丝电压的加入不仅可以细化纤维直径,而且可以提高纤维的结晶度。结果表明：熔体微分离心静电纺丝可以高效制备PLA超细纤维,并且通过改变实验参数可以控制纤维特征,为离心静电纺丝产业化提供实验依据。     

Evolution of fiber morphology during electrospinning

In this study, the morphological evolution of poly(acrylonitrile) (PAN) nanofibers during electrospinning was examined via immersion precipitation of newly electrospun filaments in ethanol, and subsequently associating the fiber morphologies with the electrospinning distances (2 to 10 cm). We have observed that an uneven fiber stretching happened throughout the electrospinning process. A massive filament‐thinning took place at the initial stage of whipping instability, and fiber stretching at the later whipping stage was mainly concentrated on the bead sections, leading to improved uniformity of the resultant fibers. This work has provided a new insight into the fiber formation mechanism in the electrospinning process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Optimization of electrospinning an SU‐8 negative photoresist to create patterned carbon nanofibers and nanobeads

The optimization of electrospinning SU‐8 2100 negative photoresist was performed to create carbon micro/nanofibers and beads that can be patterned after electrospinning by using UV radiation. The fiber diameters had a range of 300 nm to 1 μm, based upon the selected electrospinning parameters. Low concentrations of the SU‐8 2100 resulted in beads while specific higher concentrations produced well‐defined fibers. Fibers and beads were converted to carbon through pyrolysis and retained their three dimensional structure. By utilizing the photosensitive properties of the SU‐8 negative photoresist, the electrospun fibers were patterned by UV photolithography. The fibers and beads were characterized by SEM and Raman microscopy, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A study on the effect of the collector properties on the fabrication of magnetic polystyrene nanocomposite fibers using the electrospinning technique

The role of the collector properties in changing the fiber morphology in electrospinning has not been completely understood yet. In this work, we studied the effect of different collectors on the helicity of the magnetic polystyrene nanocomposite fibers containing superparamagnetic magnetite nanoparticles. Aluminum and ice were used as solid collectors. Ethanol, ethanol-deionized (DI) water mixture, sodium dodecyl sulfate, Triton X-100, deionized water, and NaCl baths were used as liquid collectors. Ice, when surrounded by a conductive foil, produced excellent fiber alignment, but increased local humidity, inhibiting the continuous jet formation. The deionized water and NaCl bath exhibited minimum helicity. The surfactant bath produced different structures such as coiled, helical, and zig-zag with varied diameters. Ethanol and DI/Ethanol baths were found to retain the structure of the deformed fiber formed due to jet instability. The helicity of the fibers was observed to increase with decreasing surface tension. Incorporation of the magnetic phase affected the viscosity of the polymer solution and the hydrophobicity of the polystyrene fibers further influencing the obtained morphologies.     

Influence of cooling rate on the thermal behavior and solid‐state morphologies of polyhydroxyalkanoates

The influence of cooling rates on the thermal behavior and solid‐state morphologies of polyhydroxyalkanoates have been investigated. The thermal behavior was studied by differential scanning calorimetry (DSC). The crystal structures (～ Å), lamellar (tens of nanometers), fibrillar (several hundred nanometers), and spherulitic (～ μm) morphologies of poly (3‐hydroxybutyrate) (PHB) and the copolymers of poly (3‐hydroxybutyric acid‐co‐3‐hydroxyvaleric acid) (PHBV) and poly (3‐hydroxybutyric acid‐co‐3‐hydroxyhexanoic acid) (PHBHx) crystallized under different cooling rates were studied using simultaneous small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering, simultaneous ultra small angle X‐ray scattering (USAXS) and SAXS, and polarized optical microscopy, respectively. The experimental results showed that the lamellar and spherulitic morphologies depended strongly on cooling rates. However, there was little influence of cooling rates on the crystal structures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of injection molding process parameters on mechanical and fracture behavior of polycarbonate polymer

In this work, the mechanical and failure behavior of injection molded aviation standard optical grade polycarbonate (PC) was investigated through uniaxial tensile testing. The effect of different injection molding process parameters including injection velocity, packing pressure, cooling time, mold temperature, and melt temperature were determined to observe their effect on yield and postyield behavior of PC. Out of these examined parameters, the mold and melt temperature show significant effect on mechanical behavior of studied polymer. The yield and flow stresses in polymer increase with the increase in mold and melt temperature during injection molding. However, other process parameters i.e., packing pressure, injection velocity, and cooling time showed little effect on mechanical performance of the polymer. The molded specimens were annealed at different temperatures and residence time to evaluate its effect on mechanical behavior and fracture morphology. The yield stress increases gradually with the increase in annealing temperature and time. The annealing treatment also changed the failure mode of PC specimens from ductile to brittle. In addition to process parameters, the effect of increased loading rate was also undertaken which shows substantial effect on mechanical and failure behavior of PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44474.     

The influence of process parameters on the properties of electrospun PLLA yarns studied by the response surface methodology

Poly (l ‐lactide) (PLLA) fibrous yarns were prepared by electrospinning of polymer solutions in 2,2,2‐trifluoroethanol. Applying spinning from two oppositely charged needles the spontaneous formed triangle of fibers at a grounded substrate could be assembled into fibrous yarns using a device consisting of a take‐up roller and twister. The effect of processing parameters on the morphology, diameter and mechanical properties of PLLA yarns was investigated by the response surface methodology (RSM). This method allowed evaluating a quantitative relationship between polymer concentration, voltage, take‐up rate and distance between the needles' center and the take‐up unit on the properties of the electrospun fibers and yarns. It was found that at increasing concentrations up to 9 wt % uniform fibers were obtained with increasing mean diameters. Conversely, the fiber diameter decreased slightly when the applied voltage was increased. The take‐up rate had a significant influence on the yarn diameter, which increased as the take‐up rate decreased. The tensile strength and modulus of the yarns were correlated with these variables and it was found that the polymer concentration had the largest influence on the mechanical properties of the yarns. By applying the RSM, it was possible to obtain a relationship between processing parameters which are important in the fabrication of electrospun yarns. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41388.     

Optimization of preparation conditions of carboxymethyl potato starch through orthogonal experimental design

To optimize the preparation conditions of carboxymethyl potato starch (CMPS), the effects of relevant factors on viscosity (η) of 2% CMPS aqueous solution and degree of substitution (DS) were investigated. These condition parameters included etherification temperature, alkalization and etherification time, water content in the mixed solvent, ratio of liquid volume to starch mass, molar ratio of sodium hydroxide to monochloroacetic acid, and molar ratio of monochloroacetic acid to anhydroglucose unit. After individual parameter influencing η and DS was researched one by one, an orthogonal experiment of L₁₈ (2 × 3⁷) was designed to identify the main factors affecting them. In light of range analysis, the comparative importance of factors impacting η and DS was obtained, separately. Results of variance analysis showed that the most effective factor to control DS was etherification temperature, whereas the influences of all factors on η were not significant. Meanwhile, η and DS of the optimized final product were found to be 12,000 mPa.s and 0.68, respectively. In addition, the structure of CMPS was characterized by Fourier transform infrared (FTIR) spectrophotometer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Optimisation of the spark plasma sintering process for high volume fraction SiCp/Al composites by orthogonal experimental design

Based on orthogonal experimental design (OED), the effects of the sintering pressure, sintering temperature and holding time on the mechanical properties of 50 vol% silicon carbide particle (SiCp)/2024Al composites prepared by spark plasma sintering (SPS) were investigated. The sintering pressure had the greatest effect on the density and bending strength of the material among these three factors, followed by sintering temperature and holding time. The optimised process conditions for producing the 50 vol% SiCp/2024Al were sintering at 550 °C for 5 min under 40 MPa, which resulted in a composite material with a density of 99.7% and good interface bonding with a comparatively high bending strength of 766.65 MPa. This work provides a promising method to produce high volume fraction composites that can meet high strength requirements.     

壳聚糖/聚氧化乙烯静电纺丝工艺研究

采用聚氧化乙烯(PEO)与壳聚糖(CS)混合配制PEO/CS的稀醋酸溶液,进行静电纺丝,制得PEO/CS纳米纤维毡.考察了静电纺丝工艺条件对纤维直径和形貌的影响,并对PEO/CS纳米纤维毡进行了形态、结构、结晶性能、亲水性能等方面的表征.结果表明:PEO/CS纳米纤维毡的静电纺丝的最佳参数值为PEO/CS质量比为70/...