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  • 1.
    Backman, Anna
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Lange, Jakob
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Transport properties of uniaxially oriented aliphatic polyketone2004In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 42, no 6, p. 947-955Article in journal (Refereed)
    Abstract [en]

    The oxygen, carbon dioxide, and water-transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5-10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X-ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress-strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw-induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30-40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen-bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology.

  • 2. Endrődi, Balázs
    et al.
    Samu, Gergely Ferenc
    Fejes, Dora
    Németh, Zoltan
    Horváth, Endre
    Pisoni, Andrea
    Matus, Peter Krisztian
    Hernádi, Klara
    Visy, Csaba
    Forro, Laszlo
    Janáky, Csaba
    Challenges and rewards of the electrosynthesis of macroscopic aligned carbon nanotube array/conducting polymer hybrid assemblies2015In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 53, p. 1507-1518Article in journal (Refereed)
    Abstract [en]

    Hybrid assemblies based on conducting polymers and carbon nanomaterials with organized nanoscale structure are excellent candidates for various application schemes ranging from thermal management to electrochemical energy conversion and storage. In the case of macroscopic samples, however, precise control of the nanoscale structure has remained a major challenge to be solved for the scientific community. In this study we demonstrate possible routes to homogeneously infiltrate poly(3-hexylthiophene), poly(3,4-ethylenedioxythiophene), and polyaniline into macroscopic arrays of vertically aligned multiwalled carbon nanotubes (MWCNTAs). Electron microscopic images and Raman spectroscopic analysis (performed along the longitudinal dimension of the hybrid samples) both confirmed that optimization of the electropolymerization circumstances allowed fine tuning of the hybrid structure towards the targeted application. In this vein, three different application avenues were tested. The remarkable anisotropy in both the electrical and thermal conductivity of the nanocomposites makes them eminently attractive candidates to be deployed in thermal management. Thermoelectric studies, aimed to understand the effect of organized nanoscale morphology on the important parameters (Seebeck coefficient, electrical-, and thermal conductivity) compared to their non-organized hybrid counterparts. Finally, extraordinary high charge storage capacity values were registered for the MWCNTA/PANI hybrids (500 F g−1 and 1–3 F cm−2). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1507–1518

  • 3. Fonseca, R. D.
    et al.
    Correa, D. S.
    Paris, E. C.
    Tribuzi, V.
    Dev, Apurba
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Voss, T.
    Aoki, P. H. B.
    Constantino, C. J. L.
    Mendonca, C. R.
    Fabrication of zinc oxide nanowires/polymer composites by two-photon polymerization2014In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 52, no 4, p. 333-337Article in journal (Refereed)
    Abstract [en]

    We present an approach to fabricate ZnO nanowires/polymer composite into three-dimensional microstructures, based on two-photon polymerization direct laser writing, a fabrication method that allows submicrometric spatial resolution. The structural integrity of the structures was inferred by scanning electron microscopy, while the presence and distribution of ZnO nanowires was investigated by energy dispersive X-ray, Raman spectroscopy, and X-ray diffraction. The optical properties of the produced composite microstructures were verified by imaging the characteristic ZnO emission using a fluorescence microscope. Hence, such approach can be used to develop composite microstructures containing ZnO nanowires aiming at technological applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 333-337 Zinc oxide (ZnO) has proven to be a promising material for optoelectronic devices operating in the blue to near-UV spectral region. While ZnO/polymer composite films have been readily produced via cast and spin coating, these standard approaches do not allow the fabrication of three-dimensional (3D) microstructures due to the lack of spatial resolution. In this work, 3D microstructures of composites made up of acrylic resin and ZnO nanowires are created by using two-photon polymerization.

  • 4. Gallstedt, M.
    et al.
    Tornqvist, J.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Properties of nitrocellulose-coated and polyethylene-laminated chitosan and whey films2001In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 39, no 10, p. 985-992Article in journal (Refereed)
    Abstract [en]

    Chitosan (chitosan acetic acid salt) and whey (65% protein) films were coated with a nitrocellulose lacquer or laminated with polyethylene to enhance their water resistance and gas barrier properties in humid environments. The barrier properties were measured by the Cobb,, test and water-vapor (100% relative humidity) transmission and oxygen (90% relative humidity) permeability tests. Mechanical properties were obtained with tensile tests. Packaging properties were studied with crease and folding tests. The Cobb,, test revealed that the coated films were resistant to liquid water, at least for a short exposure time, if the coating thickness was at least 10-17 mum. Water-vapor transmission rates comparable to those of polyethylene-laminated films were obtained for coated chitosan at a coating thickness of 5-7 mum. The coated films possessed low oxygen permeability despite the high humidity. Coated films dried for 3 weeks showed oxygen permeabilities at 90% relative humidity that were similar to values for dry ethylene-co-vinyl alcohol at 0% relative humidity. The lacquer partly penetrated the whey films, and this led to excellent adhesion but poor lacquer toughness. The lacquer coating on chitosan was tougher, and it was possible to fold these films 90 degrees without the coating fracturing if the coating thickness was small. The coated whey films were readily creasable.

  • 5.
    Lindström, Annika
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Miscibility and surface segregation in PVC/polyester blends: the influence of chain architecture and composition2007In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 45, no 13, p. 1552-1563Article in journal (Refereed)
    Abstract [en]

    Four poly(butylene adipate) (PBA) polyesters, the structure ranging from linear to highly branched, were synthesized and solution casted with poly(vinyl chloride) (PVC) in 20 or 40 wt % concentrations to evaluate the influence of polyester chain architecture on miscibility, surface segregation, and mechanical properties. The miscibility of PVC and polyesters is based on specific interactions between the carbonyl group in the polyester and PVC. These interactions cause a shift in the carbonyl absorption band in the FTIR spectra. The shifting of the carbonyl absorption band was more significant for all the 40 wt % blends compared with the blends containing 20 wt % of the same polyester. In the 20 wt % blends surface segregation and enrichment of polyester at the blend surface increased as a function of branching. However, all the films containing 40 wt % of polyester had similar surface composition. This is explained by better miscibility and stronger intermolecular interactions in the 40 wt % blends, which counteract the effect of branching on the surface segregation. High degree of branching resulted in poor miscibility with PVC and poor mechanical properties. A linear or slightly branched polyester structure, however, resulted in good miscibility and desirable blend properties.

  • 6. Ritums, J. E.
    et al.
    Mattozzi, A.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bergman, G.
    Palmlof, M.
    Mechanical properties of high-density polyethylene and crosslinked high-density polyethylene in crude oil and its components2006In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 44, no 4, p. 641-648Article in journal (Refereed)
    Abstract [en]

    The tensile and stress-relaxation properties of an uncrosslinked and a loosely silane-crosslinked high-density polyethylene exposed to organic '' crude-oil '' penetrants were assessed. The measurements were performed on penetrant-saturated samples, surrounded by the organic liquid throughout the experiment. The penetrant solubilities in the two polymers were similar and in accordance with predicted values based on the solubility parameter method. The stiffness and strength of the swollen samples were significantly less than those of the dry samples, indicating a plasticization of the amorphous component. Raman spectroscopy on polyethylene exposed to deuterated n-hexane revealed a penetrant-induced partial melting/dissolution of the crystal surface and an intact crystal core component. The stress-relaxation rates, within the time frame of the experiment (similar to 1 s to 18 h), were approximately the same, independent of silane-crosslinks and the presence of penetrants. This indicated that the mechanical alpha-relaxation, which is the main relaxation process occurring in the measured time interval, was not affected by the penetrants. Consequently, its rate seemed to be independent of the crystal surface dissolution (decrease in the content of crystal-core interface). The shape of the '' log stress-log time '' curves of the swollen samples was, however, different from that of the dry samples. This was most likely attributed to a time-dependent saturation of penetrant to a higher level associated with the stretched state of the polymer sample. The silane crosslinks affected only the elongation at break, which was less than that of the uncrosslinked material.

  • 7. Ritums, J. E.
    et al.
    Neway, B.
    Doghieri, F.
    Bergman, G.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, A. S.
    Assessing the transport properties of organic penetrants in low-density polyethylene using free volume models2007In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 45, no 6, p. 723-734Article in journal (Refereed)
    Abstract [en]

    Three models, two of them relying on free volume-the Cohen-Turnbull-Fujita (CTF) model and the Vrentas-Duda (VD) model, and the third being empirical using an exponential concentration dependence of the diffusivity, were applied to desorption data for a series of alkane penetrants (2,2-dimethylbutane, cyclohexane, n-hexane, n-decane, and n-tetradecane) in low-density polyethylene. The CTF model described the desorption data very well and better than the exponential diffusion law. The VD model with the attractive feature of being based on independently determined parameters was unsuccessful in describing the desorption data. Diffusivity data indicated that the three components outside the crystal core were less accessible to n-tetradecane than to the other penetrants. This indication was further substantiated by solubility data.

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