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Average Fiber Diameter (average + fiber_diameter)
Selected AbstractsUltrafine Electrospun Polyamide-6 Fibers: Effects of Solvent System and Emitting Electrode Polarity on Morphology and Average Fiber DiameterMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2005Pitt Supaphol Abstract Summary: In the present contribution, polyamide-6 (PA-6) solutions were prepared in various pure and mixed-solvent systems and later electrospun with the polarity of the emitting electrode being either positive or negative. The PA-6 concentration in the as-prepared solutions was fixed at 32% w/v. Some of the solution properties, i.e., shear viscosity, surface tension, and conductivity, were measured. Irrespective of the polarity of the emitting electrode, only the electrospinning of PA-6 solution in formic acid (85 wt.-% aqueous solution) produced uniform electrospun fibers, while solutions of PA-6 in m -cresol or sulfuric acid (either 20 or 40 wt.-% aqueous solution) did not. In the mixed-solvent systems, formic acid (85 wt.-% aqueous solution) was blended with m -cresol, sulfuric acid (either 20 or 40 wt.-% aqueous solution), acetic acid, or ethanol in the compositional range of 10,40 vol.-% (based on the amount of the minor solvent). Generally, the average fiber diameter increased with increasing amount of the minor solvent or liquid. Interestingly, the diameters of the fibers obtained under the negative electrode polarity were larger than those obtained under the positive one. Optical images of electrospun fibers from solutions of polyamide-6 in a mixed solvent of 85 wt.-% formic acid and 20 vol.-% m -cresol under positive (left) and negative (right) electrode polarity. [source] The influence of electrospinning parameters on the structural morphology and diameter of electrospun nanofibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Valencia Jacobs Abstract 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 [source] Processing Conditions and Aging Effect on the Morphology of PZT Electrospun Nanofibers, and Dielectric Properties of the Resulting 3,3 PZT/Polymer CompositeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009Ebru Mensur Alkoy Lead zirconate titanate (PZT) nanofibers are obtained by electrospinning a sol,gel based solution and polyvinyl pyrrolidone (PVP) polymer, and by subsequent sintering of the electrospun precursor fibers. The average diameter of the precursor PZT/PVP green fibers has increased with the aging of the precursor solution along with an increase in the viscosity. Bead-free uniform green PZT/PVP fibers were collected at about an ,230 nm average fiber diameter using a 28 wt% PVP ratio solution with a viscosity of 290 mPa. Shrinkage of 40% was recorded on the fiber diameter after sintering. The X-ray diffraction pattern of the annealed PZT fibers exhibits no preferred orientation and a perovskite phase. Preparation of 3,3 nanocomposites by the infusion of polyvinylester into the nanofiber mat facilitates successful handling of the fragile mats and enables measurements of the dielectric properties. The dielectric constant of the PZT/polyvinylester nanocomposite of about 10% fiber volume fraction was found to be fairly stable and vary from 72 to 62 within the measurement range. The dielectric loss of the composite is below 0.08 at low frequencies and reaches a stable value of 0.04 for most of the measured frequencies. [source] Ultrafine Electrospun Polyamide-6 Fibers: Effects of Solvent System and Emitting Electrode Polarity on Morphology and Average Fiber DiameterMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2005Pitt Supaphol Abstract Summary: In the present contribution, polyamide-6 (PA-6) solutions were prepared in various pure and mixed-solvent systems and later electrospun with the polarity of the emitting electrode being either positive or negative. The PA-6 concentration in the as-prepared solutions was fixed at 32% w/v. Some of the solution properties, i.e., shear viscosity, surface tension, and conductivity, were measured. Irrespective of the polarity of the emitting electrode, only the electrospinning of PA-6 solution in formic acid (85 wt.-% aqueous solution) produced uniform electrospun fibers, while solutions of PA-6 in m -cresol or sulfuric acid (either 20 or 40 wt.-% aqueous solution) did not. In the mixed-solvent systems, formic acid (85 wt.-% aqueous solution) was blended with m -cresol, sulfuric acid (either 20 or 40 wt.-% aqueous solution), acetic acid, or ethanol in the compositional range of 10,40 vol.-% (based on the amount of the minor solvent). Generally, the average fiber diameter increased with increasing amount of the minor solvent or liquid. Interestingly, the diameters of the fibers obtained under the negative electrode polarity were larger than those obtained under the positive one. Optical images of electrospun fibers from solutions of polyamide-6 in a mixed solvent of 85 wt.-% formic acid and 20 vol.-% m -cresol under positive (left) and negative (right) electrode polarity. [source] Co-electrospun composite nanofibers of blends of poly[(amino acid ester)phosphazene] and gelatinPOLYMER INTERNATIONAL, Issue 5 2010Yi-Jun Lin Abstract Electrospinning is known as a simple and effective fabrication method to produce polymeric nanofibers suitable for biomedical applications. Many synthesized and natural polymers have been electrospun and reported in the literature; however, there is little information on the electrospinning of poly[(amino acid ester)phosphazene] and its blends with gelatin. Composite nanofibers were made by co-dissolving poly[(alaninoethyl ester)0.67(glycinoethyl ester)0.33phosphazene] (PAGP) and gelatin in trifluoroethanol and co-electrospinning. The co-electrospun composite nanofibers from different mixing ratios (0, 10, 30, 50, 70 and 90 wt%) of gelatin to PAGP consisted of nanoscale fibers with a mean diameter ranging from approximately 300 nm to 1 µm. An increase in gelatin in the solution resulted in an increase of average fiber diameter. Transmission electron microscopy and energy dispersive X-ray spectrometry measurements showed that gelatin core/PAGP shell nanofibers were formed when the content of gelatin in the hybrid was below 50 wt%, but homogeneous PAGP/gelatin composite nanofibers were obtained as the mixing ratios of gelatin to PAGP were increased up to 70 and 90 wt%. The study suggests that the interaction between gelatin and PAGP could help to stabilize PAGP/gelatin composite fibrous membranes in aqueous medium and improve the hydrophilicity of pure PAGP nanofibers. Copyright © 2009 Society of Chemical Industry [source] Incorporation of fibrin molecules containing fibrinopeptide A alters clot ultrastructure and decreases permeabilityBRITISH JOURNAL OF HAEMATOLOGY, Issue 1 2007Veronica H. Flood Summary Previous studies have shown that a heterozygous mutation in the fibrinogen A, chain gene, which results in an A, R16C substitution, causes fibrinolytic resistance in the fibrin clot. This mutation prevents thrombin cleavage of fibrinopeptide A from mutant A, R16C chains, but not from wild-type A, chains. However, the mechanism underlying the fibrinolytic resistance is unclear. Therefore, this study investigated the biophysical properties of the mutant fibrin that contribute to fibrinolytic resistance. Fibrin clots made from the mutant fibrinogen incorporated molecules containing fibrinopeptide A into the polymerised clot, which resulted in a ,spiky' clot ultrastructure with barbed fibrin strands. The clots were less stiff than normal fibrin and were cross-linked slower by activated FXIII, but had an increased average fiber diameter, were more dense, had smaller pores and were less permeable. Protein sequencing showed that unclottable fibrinogen remaining in the supernatant consisted entirely of homodimeric A, R16C fibrinogen, whereas both cleaved wild-type , chains and uncleaved A, R16C chains were in the fibrin clot. Therefore, fibrinolytic resistance of the mutant clots is probably a result of altered clot ultrastructure caused by the incorporation of fibrin molecules containing fibrinopeptide A, resulting in larger diameter fibers and decreased permeability to fibrinolytic enzymes. [source] | ||||||||||