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All issues / Volume 7 (2013) / Issue 6 (June)

H-bonding – a chance for novel nano-sized polymers
S. Fakirov
Vol. 7., No.6., Pages 494-494, 2013
DOI: 10.3144/expresspolymlett.2013.45
This is an editorial article. It has no abstract.
Synthesis and characterization of an electrolyte system based on a biodegradable polymer
K. Sownthari, S. A. Suthanthiraraj
Vol. 7., No.6., Pages 495-504, 2013
DOI: 10.3144/expresspolymlett.2013.46
A polymer electrolyte system has been developed using a biodegradable polymer namely poly-ε-caprolactone (PCL) in combination with zinc triflate [Zn(CF3SO3)2] in different weight percentages and characterized during this investigation. Free-standing thin films of varying compositions were prepared by solution casting technique. The successful doping of the polymer has been confirmed by means of Fourier transform infrared spectroscopy (FTIR) by analyzing the carbonyl (C=O) stretching region of the polymer. The maximum ionic conductivity obtained at room temperature (25°C) was found to be 8.8x10–6 S/cm in the case of PCL complexed with 25 wt% Zn(CF3SO3)2 which is five orders of magnitude higher than that of the pure polymer host material. The increase in amorphous phase with an increase in salt concentration of the prepared polymer electrolyte has also been confirmed from the concordant results obtained from X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopic (SEM) analyses. Furthermore, the electrochemical stability window of the prepared polymer electrolyte was found to be 3.7 V. An electrochemical cell has been fabricated based on Zn/MnO2 electrode couple as an application area and its discharge characteristics were evaluated.
A strategy for achieving low percolation and high electrical conductivity in melt-blended polycarbonate (PC)/multiwall carbon nanotube (MWCNT) nanocomposites: Electrical and thermo-mechanical properties
S. Maiti, N. K. Shrivastava, S. Suin, B. B. Khatua
Vol. 7., No.6., Pages 505-518, 2013
DOI: 10.3144/expresspolymlett.2013.47
In this work, polycarbonate (PC)/multiwall carbon nanotube (MWCNT) nanocomposites were prepared by simple melt mixing at a temperature (~350°C) well above the processing temperature of PC, followed by compression molding, that exhibited percolation threshold as low as of 0.11 wt% and high electrical conductivity of 1.38x10–3 S•cm–1 at only 0.5 wt% MWCNT loading. Due to the lower interfacial energy between MWCNT and PC, the carbon nanotubes are excellently dispersed and formed continuous conductive network structure throughout the host polymer. AC electrical conductivity and dielectric permittivity of PC/MWCNT nanocomposites were characterized in a broad frequency range, 101–107 Hz. Low percolation threshold (pc) of 0.11 wt% and the critical exponent (t) of ~3.38 was resulted from scaling law equation. The linear plot of logσDC vs. p–1/3 supported the presence of tunneling conduction among MWCNTs. The thermal property and storage modulus of PC were increased with the incorporation of little amount of MWCNTs. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) confirmed the homogeneous dispersion and distribution of MWCNTs throughout the matrix phase.
Ethylene tetrafluoroethylene nanofibers prepared by CO2 laser supersonic drawing
A. Suzuki, H. Hayashi
Vol. 7., No.6., Pages 519-527, 2013
DOI: 10.3144/expresspolymlett.2013.48
Ethylene tetrafluoroethylene (ETFE) nanofibers were prepared by carbon dioxide (CO2) laser irradiation of asspun ETFE fibers with four different melt flow rates (MFRs) in a supersonic jet that was generated by blowing air into a vacuum chamber through the fiber injection orifice. The drawability and superstructure of fibers produced by CO2 laser supersonic drawing depend on the laser power, the chamber pressure, the fiber injection speed, and the MFR. Nanofibers obtained using a laser power of 20 W, a chamber pressure of 20 kPa, and an MFR of 308 g•10 min–1 had an average diameter of 0.303 µm and a degree of crystallinity of 54%.
Shape memory performance of asymmetrically reinforced epoxy/carbon fibre fabric composites in flexure
M. Fejos, J. Karger-Kocsis
Vol. 7., No.6., Pages 528-534, 2013
DOI: 10.3144/expresspolymlett.2013.49
In this study asymmetrically reinforced epoxy (EP)/carbon fibre (CF) fabric composites were prepared and their shape memory properties were quantified in both unconstrained and fully constrained flexural tests performed in a dynamic mechanical analyser (DMA). Asymmetric layering was achieved by incorporating two and four CF fabric layers whereby setting a resin- and reinforcement-rich layer ratio of 1/4 and 1/2, respectively. The recovery stress was markedly increased with increasing CF content. The related stress was always higher when the CF-rich layer experienced tension load locally. Specimens with CF-rich layers on the tension side yielded better shape fixity ratio, than those with reinforcement layering on the compression side. Cyclic unconstrained shape memory tests were also run up to five cycles on specimens having the CF-rich layer under local tension. This resulted in marginal changes in the shape fixity and recovery ratios.
Surface characterization of plasma treated polymers for applications as biocompatible carriers
P. Slepicka, N. Slepickova Kasalkova, E. Stranska, L. Bacakova, V. Svorcik
Vol. 7., No.6., Pages 535-545, 2013
DOI: 10.3144/expresspolymlett.2013.50
The objective of this work was to determine surface properties of polymer surfaces after plasma treatment with the aim of further cytocompatibility tests. Examined polymers were poly(ethyleneterephthalate) (PET), high-density polyethylene (HDPE), poly(tetrafluoro-ethylene) (PTFE) and poly(L-lactic acid) (PLLA). Goniometry has shown that the plasma treatment was immediately followed by a sharp decrease of contact angle of the surface. In the course of ageing the contact angle increased due to the reorientation of polar groups into the surface layer of polymer. Ablation of polymer surfaces was observed during the degradation. Decrease of weight of polymer samples was measured by gravimetry. Surface morphology and roughness was studied by atomic force microscopy (AFM). The PLLA samples exhibited saturation of wettability (aged surface) after approximately 100 hours, while the PET and PTFE achieved constant values of contact angle after 336 hours. Irradiation by plasma leads to polymer ablation, the highest mass loss being observed for PLLA. The changes in the surface roughness and morphology were observed, a lamellar structure being induced on PTFE. Selected polymer samples were seeded with VSMC (vascular smooth muscle cells) and the adhesion and proliferation of cells was studied. It was proved that certain combination of input treatment parameters led to improvement of polymer cytocompatibility. The plasma exposure was confirmed to significantly improve the PTFE biocompatibility.
Mechanical properties of silicone composites reinforced with micron- and nano-sized magnetic particles
P. Song, Z-J. Peng, Y-L. Yue, H. Zhang, Z. Zhang, Y-C. Fan
Vol. 7., No.6., Pages 546-553, 2013
DOI: 10.3144/expresspolymlett.2013.51
Silicone composites filled with different-sized nickel particles were prepared. By applying a permanent magnet, both the micron- and nano-sized particles were found to distribute along the magnetic field direction, resulting in chain-like microstructures, which improved the key mechanical properties of the resultant samples effectively, compared to the samples with randomly-distributed particles. The composites were also tested under various magnetic field strengths. The samples with aligned particles showed larger improvements in shear storage modulus than those with random particles.
Structural and mechanical properties of cellulose acetate/graphene hybrid nanofibers: Spectroscopic investigations
M. Gopiraman, K. Fujimori, K. Zeeshan, B. S. Kim, I. S. Kim
Vol. 7., No.6., Pages 554-563, 2013
DOI: 10.3144/expresspolymlett.2013.52
Cellulose acetate/graphene (CA/graphene) and cellulose acetate/graphene-COOH (CA/graphene-COOH) hybrid nanofibers were fabricated via electrospinning technique, and their morphologies, crystallinity and mechanical properties were investigated. The added amounts of graphene and graphene-COOH were varied from 0.5 to 5.0 wt%. The crystal structures and morphologies of the resultant hybrid nanofibers were investigated by wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Graphene-COOH incorporated CA nanofiber mats showed higher Young’s modulus of about 910 MPa among than those of CA/graphene nanofibers, which is due to molecular interactions between –COOH groups in acid-treated graphene and C=O groups in CA via hydrogen bonding. This specific interaction was demonstrated by spectroscopic studies (Raman and Fourier transform infrared (FT-IR) spectroscopies).
Published by:

Budapest University of Technology and Economics,
Faculty of Mechanical Engineering, Department of Polymer Engineering