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Subject: search.filters.subject.Ultrafine fibers

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    Electrospun cellulose acetate fibers: Effect of solvent system on morphology and fiber diameter
    (2007-12-01)
    Tungprapa, Santi
    ;
    Puangparn, Tanarinthorn
    ;
    Weerasombut, Monchawan
    ;
    Jangchud, Ittipol
    ;
    Fakum, Porntiva
    This paper reports an investigation of the effects of solvent system, solution concentration, and applied electrostatic field strength (EFS) on the morphological appearance and/or size of as-spun cellulose acetate (CA) products. The single-solvent systems were acetone, chloroform, N, N-dimethylformamide (DMF), dichloromethane (DCM), methanol (MeOH), formic acid, and pyridine. The mixed-solvent systems were acetone-DMAc, chloroform-MeOH, and DCM-MeOH. Chloroform, DMF, DCM, MeOH, formic acid, and pyridine were able to dissolve CA, forming clear solutions (at 5% w/v), but electrospinning of these solutions produced mainly discrete beads. In contrast, electrospinning of the solution of CA in acetone produced short and beaded fibers. At the same solution concentration of 5% (w/v) electrospinning of the CA solutions was improved by addition of MeOH to either chloroform or DCM. For all the solvent systems investigated smooth fibers were obtained from 16% (w/v) CA solutions in 1:1, 2:1, and 3:1 (v/v) acetone-DMAc, 14-20% (w/v) CA solutions in 2:1 (v/v) acetone-DMAc, and 8-12% (w/v) CA solutions in 4:1 (v/v) DCM-MeOH. For the as-spun fibers from CA solutions in acetone-DMAc the average diameter ranged between 0.14 and 0.37 μm whereas for the fibers from solutions in DCM-MeOH it ranged between 0.48 and 1.58 μm. After submersion in distilled water for 24 h the as-spun CA fibers swelled appreciably (i.e. from 620 to 1110%) but the physical integrity of the fibrous structure remained intact. © Springer Science+Business Media, Inc. 2007.
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    Ultrafine electrospun poly(ethylene glycol)-polydimethylsiloxane-poly(ethylene glycol) triblock copolymer/poly(ethylene oxide) blend fibers
    (2006-10-01)
    Tungprapa, Santi
    ;
    Jangchud, Ittipol
    ;
    Ngamdee, Paradorn
    ;
    Rutnakornpituk, Metha
    ;
    Supaphol, Pitt
    In the present contribution, successful preparation of ultrafine fibers of poly(ethylene glycol)-polydimethylsiloxane-poly(ethylene glycol) (PEG-PDMS-PEG) triblock copolymer in its blends with poly(ethylene oxide) (PEO) via electrospinning process was reported for the first time. Chloroform was used as the solvent, the compositional weight ratios between the copolymer and PEO were 80/20, 70/30, and 60/40 and the total concentration of the solutions was either 4 or 6% w/v. While pure PEG-PDMS-PEG solutions in chloroform were not electrospinnable into fibers, the solutions that contained PEO were. The improvement in the electrospinnability of the PEG-PDMS-PEG solutions in the presence of PEO was thought to be due to the increase in the viscosity of the resulting solutions. The average diameter of the fibers obtained ranged between 2.3 and 2.8 μm. Fourier-transformed infrared spectroscopy measurements confirmed the existence of the copolymer within the as-spun blend fibers. © 2006 Elsevier B.V. All rights reserved.