Browsing by Author "El Salmawy, Ahmed"

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    Electrospinning and Characterization of Aligned Nanofibers from Chitosan/Polyvinyl Alcohol Mixtures: Comparison of Several Target Devices Newly Designed
    (SOC FIBER SCIENCE TECHNOLOGY, 2011) Afifi, Amalina M.; Yamamoto, Masaki; Yamane, Hideki; Kimura, Yoshiharu; El Salmawy, Ahmed; Nakano, Shigeyuki
    Electrospinning of pure chitosan or chitosan/poly(vinyl alcohol) (PVA) (blend) was carried out with an optimization of the electrospinning conditions. The electrospinning of the pure chitosan was only possible at a relatively high electric field of 5 kV/cm into fibers with a diameter as thick as 30 gm, and its reproducibility was very poor. Blending of PVA into chitosan significantly improved the spinnability and the chitosan/PVA blend fiber was electrospun for further characterization. Several target devices were designed and examined to collect aligned nanofibers of chitosan/PVA. The most efficient was a rotating collector having grounded short wire bars arranged on a drum. Over 90 % of electrospun fibers were collected in parallel to the take-up direction with this collector. The fiber alignment was further improved with increasing the collector rotation speed up to a maximum speed of 4.7 m/s. The aligned chitosan/PVA fibers were subjected to drawing to 1.5 times and the crystallization of chitosan fractions was induced without indicating the clear crystal orientation.
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    Fiber making directly from poly(tetrafluoroethylene) emulsion
    (ELSEVIER, 2011) Takagi, Yoshihito; Lee, Jae-Chang; Yagi, Shin-ichi; Yamane, Hideki; Wano, Takashi; Kitagawa, Daisuke; El Salmawy, Ahmed
    Poly(tetrafluoroethylene) (PTFE) fiber with a superior mechanical property was prepared directly from its emulsion by the novel manufacturing process. The PTFE emulsion turned into a paste when a high shear flow was applied and the paste was extruded through a nozzle into a strand consisting of fine PTFE particles. The diameter of the strand was reduced stepwise by applying the die-drawing process through a conical die at a low temperature. The strand was further die-drawn down at elevated temperatures into fine PTFE fibers with a highly oriented crystalline structure. The crystalline orientation factor of the PTFE fiber reached very close to unity. Although the fibers obtained have a very high tensile modulus, the tensile strength was not as high as that expected from the crystalline orientation, suggesting that the presence of some defects in the FIFE fiber formed in the instantaneous deformation. (C) 2011 Elsevier Ltd. All rights reserved.