Structure and mechanical properties of nanofibrous ZrO2 derived from alternating field electrospun precursors

Nanofibrous zirconia (ZrO₂) meshes were prepared from precursor fibers which were synthesized using the method of free-surface, high-yield alternating field electrospinning (AFES). The weight ratio of zirconyl chloride salt to polyvinylpyrrolidone (PVP) polymer in liquid precursors was investigated for its effect on the spinnability and formation of precursor fibers as well as on the resulting fibrous ZrO₂. The precursor fiber generation measured at a rate up to 5.6 g/h was achieved with a single flat 25-mm diameter alternating current (AC) electrode, which corresponded to production of up to 1.5 g/h of fibrous ZrO₂. The calcination process involved annealing the fibers at temperatures which ranged from 600 °C to 1000 °C and produced 0.1–0.2 mm thick fibrous ZrO₂ meshes. Individual nanofibers were found to have diameters between 50 and 350 nm and either a tetragonal (t-ZrO₂) or monoclinic (t-ZrO₂) structure depending on the calcination temperature. The annealed meshes with total porosity between 98.0 ± 0.2% and 94.6 ± 0.2% showed little deformation or cracking. Tensile strength and modulus of fibrous t-ZrO₂ meshes strongly depended on porosity and varied from 0.07 ± 0.03 MPa to 1.05 ± 0.3 MPa and from 90 ± 40 MPa to 388 ± 20 MPa, respectively. The m-ZrO₂ meshes resulted similar moduli, but much lower strengths due to their brittleness. A power-law relationship between the elastic modulus and porosity of AFES-derived nanofibrous t-ZrO₂ meshes, in comparison with other porous zirconia materials, was also investigated. The results of this study have demonstrated the feasibility of free-surface AFES in sizeable production of zirconia nanofibers and highly porous nanofibrous ceramic structures.     

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     

Polydimethylsiloxane‐modified polyurethane–poly(ɛ‐caprolactone) nanofibrous membranes for waterproof,breathable applications

In this study, we prepared polydimethylsiloxane (PDMS)‐modified polyurethane–poly(?‐caprolactone) nanofibrous membranes with excellent waterproof, breathable performances via an electrospinning technique. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical testing were used to characterize the morphologies and properties of the composite nanofibers. The fiber diameter and porous structure of the membranes were regulated by the adjustment of the temperatures of thermal treatment and the PDMS concentrations. The fibrous membranes obtained at a typical temperature of 70 °C possessed an optimized fibrous structure with a diameter of 514 ± 2 nm, a pore size of 0.55–0.65 µm, and a porosity of 77.7%. The resulting nanofibrous membranes modified with 5 wt % PDMS were endowed with good waterproof properties (water contact angle = 141 ± 1°, hydrostatic pressure = 73.6 kPa) and a high breathability (air permeability rate = 6.57 L m^?2 s^?1, water vapor transmission rate = 9.03 kg m^?2 day^?1). Meanwhile, the membranes exhibited robust mechanical properties with a high strength (breakage stress = 11.7 MPa) and excellent thermal stability. This suggests that they would be promising candidates for waterproof, breathable applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46360.     

The effects of carbonization temperature on the properties and structure of PAN‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate and then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of carbonization temperature of PAN hollow fiber precursor on the microstructure, specific surface, pore‐size distribution, and adsorption properties of PAN‐based carbon hollow fiber (PAN‐CHF) and PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. After the activation process, the surface area of the PAN‐ACHF increased very remarkably, reaching 900 m² g^?1 when carbonization is 1000°C, and the adsorption ratios to creatinine and VB₁₂ of ACHF were much higher than those of CHF, especially to VB₁₂. The different adsorption ratios to two adsorbates including creatinine and VB₁₂ reflect the number of micropores and mesopores in PAN‐ACHF. The dominant pore sizes of mesopores in PAN‐ACHF are from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2155–2160, 2005     

Fabrication and characterization of hollow nanofibrous PA6 yarn reinforced with CNTs

Core-sheath nanofibrous yarns were obtained through electrospinning of polyamide 6 (PA6) solution containing different concentrations of multi-wall carbon nanotubes (MWNTs) as sheath and PVA multifilament as the yarn core. By dissolving PVA, for obtaining conductive hollow nanofibrous PA6/MWNTs yarn, two types of porosity could be obtained including hollow central tube due to the structure of hollow yarn and nano-porous areas embedded in electrospun nanofibers. SEM results showed that the diameters of nanofibers were varying in the range of 103–145 nm obeying MWNTs concentrations and TEM results revealed that the MWNTs were embedded in nanofiber matrix as straight and aligned form. DSC analysis showed that electrospinning process caused the formation of less-ordered γ phase in nanofibers. The electrical conductivity of yarns increased from 10^?13 S m^?1 to 2.4?×?10^?6 S m^?1 with increasing the concentration of nanotubes from 0 wt.% to 7 wt.%.     

Effects of activation temperature on the properties and structure of PAN‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation temperature of a precursor fiber on the microstructure, specific surface, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. After the activation process, the BET surface area of the PAN‐ACHF and surface area of mesopores in the PAN‐ACHF increased very remarkably and reached 1422 m² g^?1 and 1234 m² g^?1, respectively, when activation temperature is 1000°C. The adsorptions to creatinine and VB₁₂ of PAN‐ACHF were much high and reached 99 and 84% respectively. In PAN‐ACHF which went through the activation at 700°C and 800°C, the micropore filling mainly occurred at low relative pressures, multimolecular layer adsorption occurred with the increasing of relative pressure, and the filling and emptying of the mesopores by capillary condensation occurred at high relative pressures. But in PAN‐ACHF which went through the activation at 900°C, a mass of mesopores resulted in the large pore filling by capillary condensation. The dominant pore sizes of mesopores in PAN‐ACHF are from 2 nm to 5 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3778–3783, 2006     

Effects of ammonium dibasic phosphate pretreatment time on the structure and properties of PAN‐based activated carbon hollow fibers

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate aqueous solution, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of pretreatment time of PAN hollow fibers in ammonium dibasic phosphate aqueous solution on the microstructure, specific surface, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. After the activation process, the Brunaner–Emmett–Teller (BET) surface area of the PAN‐ACHF and surface area of mesopores in the PAN‐ACHF increases and reaches 513 m² g^?1 and 66 m² g^?1 respectively, when the dipping time of PAN hollow fibers in ammonium dibasic phosphate aqueous solution is 30 min. The adsorptions to creatinine and VB₁₂ of PAN‐ACHF are much high, reach 95% and 86% respectively, when dipping time is 30 min. The dominant pore sizes of mesopores in PAN‐ACHF range from 2 nm to 5 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2448–2453, 2006     

Adsorption capability of heavy metals by chitosan/poly(ethylene oxide)/activated carbon electrospun nanofibrous membrane

In this study, activated carbon (AC) was synthesized by chemical activation process from rice husk, with the BET surface area of 2180 m²/g. Chitosan/poly(ethylene oxide) (PEO)/AC nanofibrous membrane (CPANM) was synthesized by electrospinning process. The average fiber diameter was found to be 83 ± 12.5 nm. Incorporation of AC lead to increase in the surface area of CPANM than chitosan/PEO fiber (CPF) by 371 m²/g. X‐ray photoelectron spectroscopy survey and narrow scan analysis further proved the presence of AC in the membrane. CPANM showed higher adsorption capability than CPF. Analysis of the mechanism of heavy metals adsorption by CPANM and CPF hypothesized that, (? NH2) is the only active group in CPF, whereas both (? NH2) and (? COOH) contributed in adsorption for CPANM. Maximum adsorption capacity of CPANM for Cr(VI), Fe(III), Cu(II), Zn(II), and Pb(II) ion was found to be 261.1, 217.4, 195.3, 186.2, and 176.9 mg g^?1 respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45851.     

Breathable properties of m‐Aramid nanofibrous membrane with high thermal resistance

Electrospinning of m‐aramid in dimethyl acetamide/LiCl solution was investigated to develop thermo‐resistant nanofibrous membranes for breathable waterproof materials. The m‐aramid nanofibers were continuously generated and densely mounted to the membrane without the blockage of the spinning tip during electrospinning. In order to obtain the electrospun m‐aramid nanofibers with different fiber diameters, the polymer concentration in the solution and the spinning distance were varied. Electrospun m‐aramid nanofibrous membranes of various fiber diameters and thicknesses were prepared, and then compared with two commercial expanded polytetrafluoroethylene (ePTFE) membranes with respect to water vapor permeability and pore size. The m‐aramid nanofibrous membrane showed a good water vapor permeability that satisfied the criterion of a breathable membrane, higher than those of the ePTFE porous membranes. Therefore, m‐aramid nanofibrous membrane with thermal and mechanical resistance has great potential for breathable waterproof materials and filters. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41515.     

Needleless emulsion electrospinning for scalable fabrication of core–shell nanofibers

This article reports a new needleless emulsion electrospinning method for scale‐up fabrication of ultrathin core–shell polyacrylonitrile (PAN)/isophorone diisocyanate (IPDI) fibers. These core–shell fibers can be incorporated at the interfaces of polymer composites for interfacial toughening and self‐repairing due to polymerization of IPDI triggered by environmental moisture. The electrospinnable PAN/IPDI emulsion was prepared by blending PAN/N,N‐dimethylformamide and IPDI/N,N‐dimethylformamide solutions (with the solute mass fraction of 1 : 1). The electrospinning setup consisted of a pair of aligned metal wires as spinneret (positive electrode) to infuse the PAN/IPDI emulsion and a rotary metal disk as fiber collector (negative electrode). The formed ultrathin core–shell PAN/IPDI fibers were collected with the diameter in the range from 300 nm to 3 μm depending on the solution concentration and process parameters. Optical microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy were used to characterize the core–shell nanostructures. Dependencies of the fiber diameter on the PAN/IPDI concentration, wire spacing, and wire diameter were examined. Results show that needleless emulsion electrospinning provides a feasible low‐cost manufacturing technique for scalable, continuous fabrication of core–shell nanofibers for potential applications in self‐repairing composites, drug delivery, etc. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40896.     

Electrospun waterproof breathable membrane with a high level of aerosol filtration

In this study, several nanofibrous polyurethane (PU) webs were electrospun (ES) by changing different effective parameters (e.g., polymeric concentration, voltage, feed flow, etc.). The physical–chemical properties of the webs (i.e., average fiber diameters, thickness, areal density, porosity, contact angle, waterproofness, air permeability (AP), water vapor transmittance, and aerosol filtration) were studied based on the standard test methods. A commercially available waterproof breathable (WPB) fabric was used as a reference for benchmarking. The beads‐free webs with an average fiber diameter as small as 200 nm were achieved from electrospinning of 10 wt % PU in N,N‐dimethylformamide, at feed rate of 0.5 mL/h, applied voltage of 25 kV, and tip‐to‐collector distance of 15 cm. By optimizing the electrospinning parameters, a web with a high level of waterproofness, high AP, and high water vapor transmission rate (WVTR) was obtained. In addition, the selected ES membrane showed very promising aerosol filtration efficiency with complete removal of particles larger than 0.5 µm, and 94% reduction in the concentration of smaller particles. We found a linear empirical equation for the estimation of AP and WVTR based on the average pore size diameter, the membrane thickness, and the porosity with very high regression coefficients (R² > 0.97). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45660.     

Polyacrylonitrile microscaffolds assembled from mesh structures of aligned electrospun nanofibers as high-efficiency particulate air filters

Electrospun polyacrylonitrile (PAN) fibers of very small diameters have potential for integration into filters capable of increasing the particle filtration efficiency. To fulfill the requirements for high-efficiency particulate air (HEPA) filters with a reasonable pressure drop, we generated aligned electrospun PAN fibers through pre-alignment at various rotation rates and subsequent solvent vapor annealing (SVA) under a loading. We evaluated the properties of microscaffold filters assembled from aligned electrospun PAN fibers in the form of linear, square, and triangular multiple meshes. The microscaffolds featuring multiple square meshes exhibited dramatically increased filtration efficiency without a significant pressure drop. A nine-layer cross-ply structure provided a filtration efficiency of 99.98% for 0.25-μm particles at a face velocity of 10 cm s^?1; its filtration quality factor was the highest among all of the tested microscaffolds. Thus, HEPA filters featuring a low packing density can be achieved using PAN fibers.

© 2016 American Association for Aerosol Research     

Preparation of ultrafine polyurethane fiber web by laser‐electrospinning combined with air blowing

Thermoplastic polyurethane fiber webs were prepared using a laser‐heated electrospinning process combined with air blowing. The effect of spinning conditions such as air flow rate and air temperature on fiber diameter and molecular weight was investigated. Although the average fiber diameter decreased with increased air flow rate at each air temperature, the diameter increased when the air flow rate was >15 NL min^?1. In addition, the fiber was comparatively thicker with an increase in the air temperature. The variation in the fiber diameter tends to increase with the air flow rate, and a reduction in the molecular weight of the fiber by thermal degradation was suppressed. The thinnest and most uniform fiber with a diameter of 0.9 µm and a diameter coefficient variation of 15% was obtained at an air temperature of 25°C under an air flow rate of 15 NL min^?1. This fiber also had a minimum of decreased molecular weight. POLYM. ENG. SCI., 54:2605–2609, 2014. © 2013 Society of Plastics Engineers     

Fabrication of PLA/PEG/MWCNT electrospun nanofibrous scaffolds for anticancer drug delivery

In the present study, polylactic acid (PLA)/polyethylene glycol (PEG)/multiwalled carbon nanotube (MWCNT) electrospun nanofibrous scaffolds were prepared via electrospinning process and their applications for the anticancer drug delivery system were investigated. A response surface methodology based on Box–Behnken design (BBD) was used to evaluate the effect of key parameters of electrospinning process including solution concentration, feeding rate, tip–collector distance (TCD) and applied voltage on the morphology of PLA/PEG/MWCNT nanofibrous scaffolds. In optimum conditions (concentration of 8.15%, feeding rate of 0.2 mL/h, voltage of 18.50 kV and TCD of 13.0 cm), the minimum experimental fiber diameter was found to be 225 nm which was in good agreement with the predicted value by the BBD analysis (228 nm). In vitro drug release study of doxorubicin (DOX)‐loaded nanofibrous scaffolds, higher drug content induced an extended release of drug. Also, drug release rate was not dependent on drug/polymer ratio in different electrospun nanofibrous formulations. The equation of M_t = c₀ + kt^0.5was used to describe the kinetic data of DOX release from electrospun nanofibers. The cell viability of DOX‐loaded nanofibrous scaffolds was evaluated using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide, a tetrazole assay on lung cancer A549 cell lines. We propose that DOX‐incorporated PLA/PEG/MWCNT nanofibrous scaffold could be used as a superior candidate for antitumor drug delivery. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41286.     

Magnetic‐field‐assisted electrospinning highly aligned composite nanofibers containing well‐aligned multiwalled carbon nanotubes

Composite nanofiber meshes of well‐aligned polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) nanofibers containing multiwalled carbon nanotubes (MWCNTs) were successfully fabricated by a magnetic‐field‐assisted electrospinning (MFAES) technology, which was confirmed to be a favorable method for preparation of aligned composite nanofibers in this article. The MFAES experiments showed that the diameters of composite nanofibers decreased first and then increased with the increase of voltage and MWCNTs content. With the increase of voltage, the degree of alignment of the composite nanofibers decreased, whereas it increased with increasing MWCNTs concentration. Transmission electron microscopy observation showed that MWCNTs were parallel and oriented along the axes of the nanofibers under the low concentration. A maximum enhancement of 178% in tensile strength was manifested by adding 2 wt % MWCNTs in well‐aligned composite nanofibers. In addition, the storage modulus of PAN/PVP/MWCNTs composite nanofibers was significantly higher than that of the PAN/PVP nanofibers. Besides, due to the highly ordered alignment structure, the composite nanofiber meshes showed large anisotropic surface resistance, that is, the surface resistance of the composite nanofiber films along the fiber axis was about 10 times smaller than that perpendicular to the axis direction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41995.     

Preparation and characterization of polyhydroxybutyrate‐co‐hydroxyvalerate/silk fibroin nanofibrous scaffolds for skin tissue engineering

Nanofibrous scaffolds were obtained by co‐electrospinning poly (3‐hydroxybuty‐rate‐co‐3‐hydroxyvalerate) (PHBV) and fibroin regenerated from silk in different proportions using 1,1,1,3,3,3‐hexafluoro‐2‐isopropanol (HFIP) as solvent. Field emission scanning electron microscope (FESEM) investigation showed that the fiber diameters of the nanofibrous scaffolds ranged from 190 to 460 nm. X‐ray diffraction (XRD) and Fourier transform infrared spectroscopy analysis (FT‐IR) showed that the main structure of silk fibroin (SF) in the nanofibrous scaffold was β‐sheet. Compared to the PHBV nanofibrous scaffold, the surface hydrophilicity and water‐uptake capability of the PHBV/SF nanofibrous scaffold with 50/50 were improved. The results of cell adhesion experiment showed that the fibroblasts adhered more to the PHBV/SF nanofibrous scaffold with 50/50 than the pure PHBV nanofibrous scaffold. The proliferation of fibroblast on the PHBV/SF nanofibrous scaffold with 50/50 was higher than that on the pure PHBV nanofibrous scaffold. Our results indicated that the PHBV/SF nanofibrous scaffold with 50/50 may be a better candidate for biomedical applications such as skin tissue engineering and wound dressing. POLYM. ENG. SCI., 55:907–916, 2015. © 2014 Society of Plastics Engineers     

Fabrication of continuous nanofiber yarn using novel multi‐nozzle bubble electrospinning

A novel multi‐nozzle bubble electrospinning apparatus, including spinning unit, metering pump, constant flow pump, metal funnel and yarn winder, was designed for the preparation of continuous twisted polyacrylonitrile nanofiber yarns, and the principle of nanofiber yarn spinning was studied. An innovative spinning unit consisting of nozzle and air chamber was used to improve the production of nanofibers. Double conjugate electrospinning was developed using two pairs of oppositely charged spinning units to neutralize the charges. The effects of applied voltage, air flow rate, overall solution flow rate and funnel rotary speed on the fiber diameter, production rate and mechanical properties of the nanofiber yarns were analyzed. Nanofibers could be aggregated stably and bundled continuously, then twisted into nanofiber yarns uniformly at an applied voltage of 34 kV, air flow rate of 1200 mL min^?1 and overall solution flow rate of 32 mL h^?1. With an increase in the funnel rotary speed, the twist angle of the nanofiber yarns gradually increased when the take‐up speed was constant. The yarn tensile strength and elongation at break showed an increasing trend with increasing twist angle. Nanofiber yarns obtained using this novel method could be produced at a rate from 2.189 to 3.227 g h^?1 with yarn diameters ranging from 200 to 386 µm. Nanofiber yarns with a twist angle of 49.7° showed a tensile strength of 0.592 cN dtex^?1 and an elongation at break of 65.7%. © 2013 Society of Chemical Industry     

Effects of activation time on the properties and structure of polyacrylonitrile‐based activated carbon hollow fiber

Polyacrylonitrile (PAN) hollow fibers were pretreated with ammonium dibasic phosphate, then further oxidized in air, carbonized in nitrogen, and activated with carbon dioxide. The effects of activation time of a precursor fiber on the microstructure, specific surface area, pore‐size distribution, and adsorption properties of PAN‐based activated carbon hollow fibers (PAN‐ACHF) were studied in this work. The BET surface area of PAN‐ACHF and surface area of mesopores gradually increase with activation time extending, and reach the maximum values, 780 and 180 m² g^?1, respectively, when fibers are activated at 800°C for 100 min. The adsorption ratio to creatinine changes little with activation time extending and all values over all activation time are above 90%. The adsorption ratio to VB₁₂ gradually increases with activation time extending before 60 min, and then becomes relatively constant from 60 to 100 min. The number of pores on the surface of PAN‐ACHF increases with activation time extending. The amount of mesopores in PAN‐ACHF made of fibers activated for different time increases with activation time extending and the dominant pore sizes of mesopores in PAN‐ACHF range from 2 to 5 nm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2565–2569, 2006     

Preparation and evaluation of polyaniline and polypyrrole modified water‐dispersible conducting nanocomposites of polyacrylonitrile with silica

Water‐dispersible conducting nanocomposites were prepared by precipitating polyaniline (PANI)/polypyrrole (PPY) in an aqueous suspension of polyacrylonitrile–SiO₂ (PAN–SiO₂) via K₂CrO₄–NaAsO₂ redox polymerization. Incorporation of PANI and PPY in the composites was confirmed by the FTIR spectrum. Scanning electron microscopic analyses for the PANI–(PAN–SiO₂) and PPY–(PAN–SiO₂) composites indicated formation of lumpy aggregates with irregular sizes. TEM analyses revealed formation of spherical particles with size ranging between 80 and 150 nm for PANI–(PAN–SiO₂) nanocomposite and 75–150 nm for PPY‐(PAN‐SiO₂) nanocomposites, respectively. Thermal stabilities of the PANI–(PAN–SiO₂) and PPY–(PAN–SiO₂) nanocomposites were higher than those of the individual base polymers. Conductivity values of PANI–(PAN–SiO₂) nanocomposite (10^?3 S cm^?1) and PPY–(PAN–SiO₂) nanocomposite (10^?4 S cm^?1) were remarkably improved relative to that for PAN homopolymer (>10^?11 S cm^?1). Both of these composites produced a permanently stable aqueous suspension when the polymerization was conducted in presence of nanodimensional SiO₂ as a particulate dispersant. Copyright © 2004 Society of Chemical Industry     

Co-axial electrospinning with sodium thiocyanate solution for preparing polyacrylonitrile nanofibers

A modified co-axial electrospinning process including electrolyte solution as sheath fluid for preparing high quality polymer nanofibers is investigated. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing the modified process with sodium thiocyanate solutions in N, N-dimethylacetamide (DMAc) as sheath fluids. Field-emission scanning electron microscopy results demonstrated that the sheath sodium thiocyanate solutions had significant influence on the quality of PAN nanofibers. High quality PAN nanofibers in terms of fiber diameters and their distributions, surface morphology and structure have been successfully produced. The diameters of nanofibers (D, nm) could be manipulated simply by adjusting the concentrations of sodium thiocyanate (C, mg ml^-1) in the sheath fluids with a scaling law of D = 324 C ^-0.1806. The mechanism about the influence of sodium thiocyanate solutions on the formation of PAN fibers is discussed and it is felt that co-axial electrospinning with electrolyte solution is a facile process for achieving high quality polymer nanofibers.