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  • 151. Römhild, Stefanie
    et al.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Bergman, G.
    The Effect of Water Activity on the Sorption and Diffusion of Water in Thermosets Based on Polyester, Vinyl Ester, and Novolac Resins2012In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 52, no 4, p. 718-724Article in journal (Refereed)
    Abstract [en]

    In this work, the transport properties of water in various thermoset resins typically used for fiber-reinforced plastic process equipment (vinyl ester, novolac, bisphenol-A-epoxy-based polyester, and urethane-modified vinyl ester) were systematically studied with a focus on the effects of water activity. Sorption and desorption studies were carried out in aqueous solutions (water activity = 0.78–1) with different salts (NaCl, MgCl2, Na2SO4, and KCl) and one nonionic substance (sucrose) within the temperature interval 65–95°C. It was found that the water concentration in thermoset resins with different chemical structures could be predicted from the water activity, regardless of the actual solute (salt or sucrose) in the aqueous solution. The water quasi-equilibrium concentration decreased with decreasing water activity, whereas the average diffusion coefficient was considered to be independent of water activity in the studied water activity range. A relationship, based on a power law fit, was established describing the water concentration as a function of the water activity and the concentration of pure water. The relationship was independent of resin chemistry and temperature.

  • 152. Römhild, Stefanie
    et al.
    Yousefi, Habib
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bergman, G.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Influence of disclination density and crystallinity on the transport properties of a liquid crystalline copolyester2008In: Journal of macromolecular science. Physics, ISSN 0022-2348, E-ISSN 1525-609X, Vol. 47, no 2, p. 305-316Article in journal (Refereed)
    Abstract [en]

    The effect of annealing on the structure and transport properties of a compression-molded liquid crystalline co-polyester (Vectra(R) A950) consisting of 73mol% poly(hydroxybenzoic acid) and 27mol% poly(hydroxy-naphthoic acid) was studied. Films were annealed above (310 degrees C) or below (260 degrees C) the melting point. The structure was studied with density measurements, optical microscopy, differential scanning calorimetry and wide-angle X-ray diffraction. It was observed that the density increased as a linear function of the logarithm of annealing time and that the crystallinity increased only on annealing below the crystal melting point. The increase in density above the melting point, and also to a large extent below the melting point, must have occurred through improved molecular packing but without any reduction in disclination density, as revealed by optical microscopy. The methanol diffusivity, obtained from desorption data, showed a moderate decrease with increasing density; the trend was only significant within a 60% confidence limit.

  • 153. Sacui, Iulia A.
    et al.
    Nieuwendaal, Ryan C.
    Burnett, Daniel J.
    Stranick, Stephan J.
    Jorfi, Mehdi
    Weder, Christoph
    Foster, E. Johan
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Gilman, Jeffery W.
    Comparison of the Properties of Cellulose Nanocrystals and Cellulose Nanofibrils Isolated from Bacteria, Tunicate, and Wood Processed Using Acid, Enzymatic, Mechanical, and Oxidative Methods2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 9, p. 6127-6138Article in journal (Refereed)
    Abstract [en]

    This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphology, aspect ratio, and surface chemistry. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymatic, mechanical, and 2,2,6,6-tetramethylpiperidiny1-1-oxyl (TEMPO)-mediated oxidation), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and C-13 cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148 +/- 147 for tunicate-CNCs to 23 +/- 12 for wood-CNCs. Hydrophobic interactions, measured using inverse gas chromatography (IGC), were found to be an important contribution to the total surface energy of both types of cellulose. In all cases, a trace amount of naturally occurring fluorescent compounds was observed after hydrolysis. Confocal and Raman microscopy were used to confirm that the fluorescent species were unique for each cellulose source, and demonstrated that such methods can be useful for monitoring purity during CNC/CNF processing. This study reveals the broad, tunable, multidimensional material space in which CNCs and CNFs exist.

  • 154.
    Sanandaji, Nima
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Different paths to explore confined crystallisation of PCL2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this work, different paths to confined crystallisation of poly(ε-caprolactone) (PCL) havebeen explored. Innate confinement effects due to the presence of bulky end groups wereshown to affect crystalline characteristics for strictly monodisperse ε-caprolactone oligomers. The interaction between end groups and end groups, as well as that between end groups andε-caprolactone repeating units, created an obstacle for unfolding the crystal structures that hadinitially formed even at the high-temperature limit of crystallisation where crystallisationoccurred over hundreds of hours. Very rapid X-ray imaging of the in situ crystallisationprocess showed that rapid shifts in the unit cell occurred during the first minute ofcrystallisation due to the difficulty of fitting the bulky end groups in a stable unit cell.Confinement effects also arose when polymer chains were crystallised in systems with smallpore sizes. For linear poly-ε-caprolactone, chains confinement depended mainly on thedimensionalities of the pores. Linear polymers with Mn = 10 000 and 42 500 were stronglyinhibited from forming crystal structures in 10 nm pore systems, but not hindered in 23 nmpore systems. Linear polymers with Mn = 80 000 also experienced limited confinement in the23 nm pores. A star-shaped oligomer with four arms of approximately Mn = 1 000 each evenexperienced confinement in 290 nm pores, although having smaller molecular size and radiusof gyration compared to the linear chains. The innate confinement created by the challenge ofpacking four arms amplified the effect of physical confinement. Another limitation wascreated on the crystallisation process by solving PCL in supercritical CO2 and depositingduring extremely fast phase transfer to gas-like state. The formed structures were limited bythe very low temperature that resulted from the phase change and by the rapid evaporation ofthe solvent. These limitations resulted in entrapment of crystal structures in metastablephases. As a consequence, crystals of hitherto unreported rectangular form were observed aswell as the common six-sided form. The former crystals had considerably lower melting pointcompared to the latter. X-ray analysis showed that two sets of lattice constants existed,supporting the notion of entrapment in metastable phases. Another way of achievingconfinement was precise deposition of droplets in the pikolitre volume range of highly dilutesolutions. The microcrystals which formed were confined by both the low polymer content ineach droplet and by the time constraint on crystal formation that arose by the rapidevaporation of the small droplets. Confinement led to entrapment into metastable phases,evident by the presence of unusual eight-sided and rectangular crystals.

  • 155.
    Sanandaji, Nima
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Bretzler, Victor
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Schmelter, S.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Confined space crystallisation of poly(epsilon-caprolactone) in controlled pore glasses2013In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, no 8, p. 2073-2081Article in journal (Refereed)
    Abstract [en]

    A series of controlled pore glasses (CPGs) with pore diameters ranging from 10 nm to 293 nm were impregnated with three poly(epsilon-caprolactone)s (PCL) differing in number average molar mass (10-80 kDa), and their crystallisation kinetics were studied with differential scanning calorimetry. Scanning electron microscopy and thermogravimetry confirmed that the polymers were mainly housed within the pore channels. The PCLs housed in the CPG with the finest pores (10 nm) showed a markedly different crystallisation behaviour from that of the corresponding bulk pristine polymers: a significantly slower crystallisation, a low Avrami exponent (<1), a higher product of the surface free energies of the fold and lateral surfaces of the formed PCL crystals and a lower initial melting peak temperature. This behaviour of confinement was similar for the three PCLs studied. In the CPGs with wider pore channels (23-293 nm), the PLCs showed essentially the same crystallisation kinetics as the pristine polymers. These differences in the crystallisation kinetics were attributed to the confinement, i.e. to the small available volume with respect to crystal size and to interactions with the pore walls. The results obtained suggest that the initial stages of crystallisation, presumably including other crystal phases or mesophases, occurred according to different paths for bulk PCL and for PCL housed in narrow nanopores.

  • 156.
    Sanandaji, Nima
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Eriksson, L.
    Werner, Per Erik
    Yu, L.
    Hawker, C. J.
    Takizawa, T.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Influence of bulky and hydrogen bonding end groups on molecular packing of monodisperse oligomer ε-CaprolactoneManuscript (preprint) (Other academic)
  • 157.
    Sanandaji, Nima
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hakala, Risto
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Crystallisation kinetics of a star-shaped poly-ε-caprolactone oligomer confined in controlled pore glassesManuscript (preprint) (Other academic)
  • 158.
    Sanandaji, Nima
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Oko, A.
    YKI, Ytkemiska Institutet AB, Institute for Surface Chemistry, Sweden.
    Haviland, David B.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tholén, E.
    Intermodulation Products AB.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Inkjet printing as a possible route to study confined crystal structures2013In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, no 1, p. 203-208Article in journal (Refereed)
    Abstract [en]

    Inkjet printing is a technique for the precise deposition of liquid droplets in the pL-volume range in well-defined patterns. Previous studies have shown that inkjet printing is attractive in polymer technology since it permits the controlled deposition of functional polymer surfaces. We suggest that the technique might also be useful for studying crystallization, in particular confined crystallization. Inkjet printing is a non-contact deposition method with minimal risk of contamination, which allows the exact deposition of both polymer solutions and polymer melts. This paper demonstrates the possibility of utilizing the technique to create surfaces where polymer chains form isolated small structures. These structures were confined by both the low polymer content in each droplet and the time constraint on crystal formation that arose as the result of the rapid solvent evaporation from the pL-sized droplets. In theory, inkjet printing enables the exact deposition of systems with as few as a single polymer chain in the average droplet. With appropriate instrumentation, the versatile inkjet technology can be utilized to create whole surfaces covered with polymer structures formed by the crystallization of small, dilute and rapidly evaporating droplets. 110 pL droplets of a 10 -6 g L -1 poly(ε-caprolactone) solution in 1-butanol have been deposited and studied by atomic force microscopy. Small structures of ca. 10 nm thickness and ca. 50 nm diameter also seemed to exhibit crystalline features. Some of the small structures had unusual rectangular forms whilst others were interpreted to be early precursors to six-sided single crystals previously observed for poly(ε-caprolactone). The unusual forms observed may have resulted from the entrapment of crystal structures into metastable phases, due to the limited amount of polymer material present and the rapid evaporation of the droplets.

  • 159.
    Sanandaji, Nima
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ovaskainen, Louise
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Klein Gunnewiek, M.
    Vansco, M. S.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Yu, L.
    Eriksson, L.
    Roth, S. V.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Unusual crystals of poly(epsilon-caprolactone) by unusual crystallisation: The effects of rapid cooling and fast solvent loss on the morphology, crystal structure and melting2013In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 54, no 5, p. 1497-1503Article in journal (Refereed)
    Abstract [en]

    The lateral habit, unit cell structure and melting behaviour of single crystals of poly(epsilon-caprolactone) (PCL) prepared by the rapid expansion of a supercritical solution technique was studied by AFM at ambient and higher temperatures and by grazing-incident X-ray scattering using a synchrotron source. After dissolving PCL in a solution of supercritical CO2 and 0.1 vol.% chloroform, an extremely fast phase transfer from a supercritical to a gas-like state occurred during expansion into atmospheric conditions, leading to a temporary temperature drop to below -;50 degrees C at the silica surface where the crystals were deposited. Single crystals of a hitherto unreported rectangular lateral habit were observed. Six-sided crystals were also observed, but they were fewer than the rectangular crystals and in addition the angles between the lateral faces were different from the theoretical angles between adjacent {110} faces and {110} and {100} faces. X-ray scattering indicated a polymorphic structure also including the orthorhombic (110) and (200) diffraction peaks. Distinct low angle peaks essentially along the c-axis indicated a stacking on a very fine scale (3.7-4.7 nm) within the crystals. The equatorial diffraction peaks indicated a less dense packing of the PCL stems. Rectangular single crystals with a height according to AFM of 11-27 nm melted between 40 and 45 degrees C, which is lower than the melting points (55 degrees C) recorded for the distorted six-sided crystals. The unusual conditions for crystallisation used gave the polymer molecules a severe limitation to rearrange from the initial random coil state. The facetted crystals consisted of a stack of 4 nm thick blocks; these blocks most probably constituted a regular variation in molecular packing, i.e. molecular order. The pronounced changes in the angles between adjacent faces from those observed in mature PCL crystals and the wide-angle X-ray scattering data indicated the presence of conformational disorder in the crystals.

  • 160. Santoro, G.
    et al.
    Buffet, A.
    Döhrmann, R.
    Yu, S.
    Körstgens, V.
    Müller-Buschbaum, P.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Roth, S. V.
    Use of intermediate focus for grazing incidence small and wide angle x-ray scattering experiments at the beamline P03 of PETRA III, DESY2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 4, p. 043901-Article in journal (Refereed)
    Abstract [en]

    We describe the new experimental possibilities of the micro- and nanofocus X-ray scattering beamline P03 of the synchrotron source PETRA III at DESY, Hamburg (Germany), which arise from experiments with smaller beam sizes in the micrometer range. This beamline has been upgraded recently to perform new kinds of experiments. The use of an intermediate focus allows for reducing the beam size of microfocused hard X-rays while preserving a large working distance between the focusing elements and the focus position. For the first time, this well-known methodology has been employed to grazing incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS). As examples, we highlight the applications to in situ studies using microfluidic devices in GISAXS geometry as well as the investigation of the crystallinity of thin films in GIWAXS geometry.

  • 161.
    Schmidt, Torsten
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Zhang, Miao
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Yu, Shun
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Fabrication of ultra-high aspect ratio silicon nanopores by electrochemical etching2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 12, p. 123111-Article in journal (Refereed)
    Abstract [en]

    We report on the formation of ultra-high aspect ratio nanopores in silicon bulk material using photo-assisted electrochemical etching. Here, n-type silicon is used as anode in contact with hydrofluoric acid. Based on the local dissolution of surface atoms in pre-defined etching pits, pore growth and pore diameter are, respectively, driven and controlled by the supply of minority charge carriers generated by backside illumination. Thus, arrays with sub-100 nm wide pores were fabricated. Similar to macropore etching, it was found that the pore diameter is proportional to the etching current, i.e., smaller etching currents result in smaller pore diameters. To find the limits under which nanopores with controllable diameter still can be obtained, etching was performed at very low current densities (several mu A cm(-2)). By local etching, straight nanopores with aspect ratios above 1000 (similar to 19 mu m deep and similar to 15 nm pore tip diameter) were achieved. However, inherent to the formation of such narrow pores is a radius of curvature of a few nanometers at the pore tip, which favors electrical breakdown resulting in rough pore wall morphologies. Lowering the applied bias is adequate to reduce spiking pores but in most cases also causes etch stop. Our findings on bulk silicon provide a realistic chance towards sub-10 nm pore arrays on silicon membranes, which are of great interest for molecular filtering and possibly DNA sequencing.

  • 162. Sobhani, Sarah
    et al.
    Bastani, Saeed
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sari, Morteza Ganjaee
    Ramezanzadeh, Bahram
    Network formation and thermal stability enhancement in evolutionary crosslinked PDMS elastomers with sol-gel-formed silica nanoparticles: Comparativeness between as-received and pre-hydrolyzed TEOS2017In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 113, p. 117-125Article in journal (Refereed)
    Abstract [en]

    Filler formation and crosslinking normally take place in PDMS/TEOS elastomers yielded via sol-gel technique, while a few was reported about the competitiveness between such phenomena. A combined rheological/thermogravimetric analysis was applied in this work varying the curing time (8, 24, 48, 72, and 168 h) to track and compare silica formation as well as three-dimensional elastomer networks in PDMS matrices treated with as received and pre-hydrolyzed TEOS. It was found that use of pre-hydrolyzed TEOS facilitates nanosilica formation leading to in-situ formation of nanocomposites exhibiting higher thermal stability and mechanical properties, as compared with the reference elastomers prepared at stoichiometric ratio. Silica formation was detected by means of TEM. Experimental results showed that during the first 8 h of the reaction between PDMS and as received TEOS a three-dimensional network was formed, while silica precipitation was dominant when PDMS was treated with pre-hydrolyzed TEOS. Tensile measurements reveal that silica precipitation in non-stoichiometric samples enhances tensile strength and elongation at break compared to the samples prepared at stoichiometric ratio, especially for samples cured with pre-hydrolyzed TEOS. Silica domain size was ca. 150 and 200 nm for the networks cured with TEOS and pre-hydrolyzed TEOS, respectively.

  • 163. Stefelova, Jana
    et al.
    Slovak, Vaclav
    Siqueira, Gilberto
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Tingaut, Philippe
    Zimmermann, Tanja
    Sehaqui, Houssine
    Drying and Pyrolysis of Cellulose Nanofibers from Wood, Bacteria, and Algae for Char Application in Oil Absorption and Dye Adsorption2017In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 5, no 3, p. 2679-2692Article in journal (Refereed)
    Abstract [en]

    Native cellulose nanofibers (CNF) constitute an abundant resource for pyrolysis leading to char materials offering a wide range of properties and application possibilities. With the aim to produce chars having large surface area and pore volume for dyes adsorption and oil absorption, respectively, we herein explore the slow pyrolysis process of cellulose nanofibers from wood, Cladophora algae and bacteria that were subjected to various drying routes. Whereas algae CNF with their large crystallites lead to high surface area (S-BET) substrates using conventional drying from aqueous suspension, CNF from wood having smaller crystallites requires drying from solvents to reach high S-BET substrates, which results in chars with a good adsorption capacity for both anionic and cationic dyes. Moreover, the porosity of the CNF substrate can be tuned via an ice-templating freeze-drying procedure reaching values as high as 99.7% and corresponding chars capable of absorbing 64-120 g g(-1) of various oils and organic solvents. Besides the absorption/adsorption properties of the chars, we report effects of CNF source and structure on the thermal properties assessed by thermogravimetric and thermomechanical analyses, differential scanning calorimetry, and mass spectrometry, and we identified over 20 decomposition products and 3 expansion events occurring during CNF pyrolysis.

  • 164. Strain, I. N.
    et al.
    Wu, Qiong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Electrospinning of recycled PET to generate strong mesomorphic fibre membranes for smoke filtrationManuscript (preprint) (Other academic)
  • 165. Strain, I. N.
    et al.
    Wu, Qiong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Electrospinning of recycled PET to generate tough mesomorphic fibre membranes for smoke filtration2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 4, p. 1632-1640Article in journal (Refereed)
    Abstract [en]

    Tough fibrous membranes for smoke filtration have been developed from recycled polyethylene terephthalate (PET) bottles by solution electrospinning. The fibre thicknesses were controlled from 0.4 to 4.3 mu m by adjustment of the spinning conditions. The highest fibre strength and toughness were obtained for fibres with an average diameter of 1.0 mu m, 62.5 MPa and 65.8 MJ m(-3), respectively. The X-ray diffraction (XRD) patterns of the fibres showed a skewed amorphous halo, whereas the differential scanning calorimetry (DSC) results revealed an apparent crystallinity of 6-8% for the 0.4 and 1 mu m fibres and 0.2% crystallinity for the 4.3 mu m fibres. Heat shrinkage experiments were conducted by exposing the fibres to a temperature above their glass transition temperature (T-g). The test revealed a remarkable capability of the thinnest fibres to shrink by 50%, which was in contrast to the 4.3 mu m fibres, which displayed only 4% shrinkage. These thinner fibres aka showed a significantly higher glass transition temperature (+15 degrees C) than that of the 4.3 mu m fibres. The results suggested an internal morphology with a high degree of molecular orientation in the amorphous segments along the thinner fibres, consistent with a constrained mesomorphic phase formed during their rapid solidification in the electric field. Air filtration was demonstrated with cigarette smoke as a model substance passed through the fibre mats. The 0.4 mu m fibres showed the most effective smoke filtration and a capacity to absorb 43x its own weight in smoke residuals. whereas the 1 mu m fibres showed the best combination of filtration capacity (32x) and mechanical robustness. The use of recycled PET in the form of nanofibres is a novel way of turning waste into higher-value products.

  • 166.
    Strömberg, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Environmental degradation of bio- and nanocomposites2008Conference paper (Refereed)
    Abstract [en]

    Environmental degradation is a summary of all those degradation factors that can decrease the life-time of polymeric materials outdoors. Chemical, physical, mechanical and biological factors have an impact on the materials and the degradation may occur quickly or at a rather slow pace.

     

    In many cases the degradation factors are effective synergistically or even consecutive. Usually chemical, physical and mechanical factors enable a later biodegradation where biofilms are particular notorious to appear on nearly every surface. Biofilm forms when bacteria adhere to surfaces in aqueous environment and begin to excrete a slimy, glue-like substance that can anchor them to all kinds of material – such as metals, plastics, soil particles, medical implant materials, and tissue. Composites, consisting of synthetic or biodegradable polymeric matrix and natural fibres as reinforcement have been successfully applied in various applications: automotive, packaging, construction, etc. Natural fibres present a series of advantages such as low density, high specific strength and modulus, renewable and biodegradable characteristics, and reasonable processibility at low cost.

     

    The presentation will address results from ongoing studies conducted in order to compare how both bio- and nancomposite materials are affected by the environment. The materials were subjected to photo-oxidation, hydrolysis, thermal oxidation and a microorganism environment in order to simulate the environments that the products might be exposed to. The focus of these studies was to investigate chemical-, physical- and mechanical property changes as well as emissions of particles, applying various analytical techniques.

  • 167.
    Strömberg, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Modelling degradation of polymers, biobased composites and nanocomposites2007Conference paper (Refereed)
  • 168.
    Strömberg, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Photo- and thermo-oxidation of polypropylene, recycled polypropylene and polylactide biocomposites in a microenvironment chamber2010In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 1, no 1, p. 1-15Article in journal (Refereed)
    Abstract [en]

    This work presents and discusses the photo- and thermo-oxidation of some sustainable biocomposites based on biodegradable materials from renewable resources and virgin and recycled petroleum-based polymeric materials as matrix and reinforced with natural fibres. PP/wood fl our, recycled PP/cellulose and PLA/wood fl our composites were degraded by photo-oxidation in a microenvironment chamber, in parallel thermo-oxidation was performed in a forced-ventilation oven. Physical and chemical property changes were monitored by tensile testing, DSC, FTIR and SEM.

    Both PPW and recPPcell composites showed deterioration of the mechanical properties after 15 days of thermo-oxidation, indicating that the incorporated natural fi bres infl uenced the thermal stability of the whole composite. PLAW showed a smaller increase in crystallinity (13%) and a decrease in melt temperature than the corresponding neat PLA. The advantages of reinforcement of PLA by natural fi bres are shown by the dramatically improved thermal properties of PLAW compared to the neat polymer.

  • 169.
    Strömberg, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Vilaplana, Francisco
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Characterisation techniques for quality assessment of recycled plastics2005Conference paper (Other academic)
    Abstract [en]

    Polymers suffer physical and chemical changes and they interact with impurities during their processing and service life. Quality assessment is very important to guarantee a suitable use of recycled plastics in further applications. Reprocessing and accelerated ageing of PP, HDPE and HIPS were performed and the materials were analysed by spectroscopic techniques, thermal analysis and tensile tests to study the effects of the recycling processes and to assess the quality properties of recyclates.

  • 170.
    Strömberg, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Vilaplana, Francisco
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ågren, Staffan
    Ribes-Greus, Amparo
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Quality assessment of recycled plastics2005Conference paper (Refereed)
    Abstract [en]

    Polymers are subjected to physical and chemical changes during their processing and service life, and they may also interact with impurities that can alter their composition. These changes substantially modify the stabilization mechanisms and the mechanical properties of recycled polymers. Consequently, quality assessment is a matter of significant importance in order to guarantee a suitable employment of recycled plastic materials in further applications. Latest research has focused on the employment of new and reliable techniques for the characterization of recycled polyolefins and the determination of low molecular weight compounds contained in recycled materials.

     

    Simulated recycling of polypropylene (PP), high density polyethylene (HDPE) and high-impact polystyrene (HIPS) was carried out in order to assess the changes occurring in the materials during repeated processing. The materials were also subjected to accelerated ageing so as to simulate their performance during service life. The samples were analysed with spectroscopic techniques, DSC (Differential Scanning Calorimetry) and tensile testing. Alterations in melt index were also investigated. Low-molecular weight compounds were extracted from the recycled plastics and analyzed by chromatographic techniques coupled with mass spectrometry. The results of the analyses were compared with corresponding data from recycled materials collected at industrial recycling centres so as to reach a deeper knowledge about the complex chemical composition and to assess the quality properties of recyclates.

  • 171. Svagan, A.J.
    et al.
    Bender Koch, C.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Glasser, G.
    Baluschev, S.
    Andersen, M.L.
    Liquid-core nanocellulose-shell capsules with tunable oxygen permeability2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 136, p. 292-299Article in journal (Refereed)
    Abstract [en]

    Encapsulation of oxygen sensitive components is important in several areas, including those in the food and pharmaceutical sectors, in order to improve shelf-life (oxidation resistance). Neat nanocellulose films demonstrate outstanding oxygen barrier properties, and thus nanocellulose-based capsules are interesting from the perspective of enhanced protection from oxygen. Herein, two types of nanocellulose-based capsules with liquid hexadecane cores were successfully prepared; a primary nanocellulose polyurea-urethane capsule (diameter: 1.66 μm) and a bigger aggregate capsule (diameter: 8.3 μm) containing several primary capsules in a nanocellulose matrix. To quantify oxygen permeation through the capsule walls, an oxygen-sensitive spin probe was dissolved within the liquid hexadecane core, allowing non-invasive measurements (spin-probe oximetry, electron spin resonance, ESR) of the oxygen concentration within the core. It was observed that the oxygen uptake rate was significantly reduced for both capsule types compared to a neat hexadecane solution containing the spin-probe, i.e. the slope of the non-steady state part of the ESR-curve was approximately one-third and one-ninth for the primary nanocellulose capsule and aggregated capsule, respectively, compared to that for the hexadecane sample. The transport of oxygen was modeled mathematically and by fitting to the experimental data, the oxygen diffusion coefficients of the capsule wall was determined. These values were, however, lower than expected and one plausible reason for this was that the ESR-technique underestimate the true oxygen uptake rate in the present systems at non-steady conditions, when the overall diffusion of oxygen was very slow.

  • 172. Tahir, M. Nazir
    et al.
    Bork, Christian
    Risberg, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Horst, Jennifer C.
    Komoss, Christina
    Vollmer, Antje
    Mischnick, Petra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Alkynyl Ethers of Glucans: Substituent Distribution in Propargyl-, Pentynyl- and Hexynyldextrans and -amyloses and Support for Silver Nanoparticle Formation2010In: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 211, no 15, p. 1648-1662Article in journal (Refereed)
    Abstract [en]

    Alkynyldextrans with a DS in the range 0.1-1.67 have been prepared as reactive intermediates for further polymer-analogous functionalisation.. DS and substituent distribution were determined by GLC and GLCMS after hydrolysis and acetylation, or methanolysis and trimethylsilylation. Reactivity was in the order O-2 > O-4 >= O-3 with pronounced differences in the distinct patterns for propargyl ethers and its higher homologous. A large deviation from a random substituent distribution was observed. Propargyldextrans were not stable during long-time storage in the solid state, while terminal pentynyl and hexynyl ethers are. Pentynyldextrans showed structure formation of various geometries. They bound silver efficiently, yielding silver nanoparticles by reduction.

  • 173. Tahir, M. Nazir
    et al.
    Lämmerhardt, Nico
    Mischnick, Petra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Introduction of various functionalities into polysaccharides using alkynyl ethers as precursors: Pentynyl dextrans2012In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 88, no 1, p. 154-164Article in journal (Refereed)
    Abstract [en]

    Following the concept of using O-alkynyl glycans as key precursors of functional polysaccharides. dextran derivatives with nearly the same distritbution pattern, but various functional groups - for common (bio)conjugation reactions, molecular recognition, and antioxidant activity - have been prepared. Pentynyl dextran well characterized with respect to the degree of substitution (DS 0.43) and the distribution of alkynyl groups to the various OH of the glucosyl unit, was further modified by 1,3-dipolar cycloaddition of various functionalized azides, thus introducing amino, hydroxy, thiol, and carboxyl groups with good to quantitative yield. Besides these functional groups, biotin and tocopherol were introduced with about 60% conversion of alkyne groups. Biotinylated dextran was demonstrated to bind specifically to fluorophor-labeled streptavidin, while glucose linked tocopherol did not show loss of antioxidant activity. Formation of triazole derivatives was proved by ATR-IR and NMR spectroscopy, and after methanolysis of the dextran, by ESI mass spectrometry. Degree of conversion was estimated from H-1 NMR spectra, decrease of pentynyl groups in the product mixture analyzed by GLC, and elemental analysis.

  • 174.
    Tsai, Wen-Chung
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Laiback, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Melin, H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ngo, M.
    Trollsas, M.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Physical changes and sorption/desorption behaviour of amorphous and semi-crystalline PLLA exposed to water, methanol and ethanol2016In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 76, p. 278-293Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to study the effects of water, methanol and ethanol on the structure of fully amorphous and semi-crystalline poly(L-lactic acid) (PLLA), which is important for applications in which the material is in contact with body fluids (water), and also in order to tailor properties by adjusting the crystallinity and glass transition temperature using penetrants. Amorphous and semi-crystalline PLLA tubes were exposed to the afore-mentioned liquids at 37 degrees C and the mass crystallinity, fictive temperature and the rigid amorphous fraction were assessed by DSC and WAXS. The diffusivity and solubility of the penetrant were assessed by gravimetric sorption and desorption experiments. Water has a plasticizing effect on the glassy structure, which enhances the equilibration of the glass as revealed by a lowering of the fictive temperature of the subsequently dried samples, but the plasticization was not sufficient to induce cold-crystallisation. The moderate effect of water at 37 degrees C was further demonstrated by the almost constant water diffusivity. Both methanol and ethanol induced cold-crystallisation at 37 degrees C, primarily forming crystals of the alpha'-form, which in the case of methanol led to a marked increase in the fictive temperature and the formation of a rigid amorphous fraction in the subsequent dried samples. The crystal growth was restricted according to an Avrami analysis of the crystallisation kinetics data. The complexity of the sorption and desorption kinetics of methanol and ethanol was caused by the progressing cold-crystallisation on sorption, which resulted in several phenomena. Very notable was the extremely high concentration-dependence of the penetrant diffusivity as revealed on, desorption, which could not be explained by plasticization alone. Instead it is believed that the formed crystals caged a significant fraction of the penetrant molecules.

  • 175.
    Ture, Hasan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Blomfeldt, Tomas O. J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Farris, Stefano
    University of Milan.
    Nanostructured Silica Wheat Gluten Hybrid Materials Prepared by Catalytic Sol-Gel Chemistry2013In: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 214, no 10, p. 1131-1139Article in journal (Refereed)
    Abstract [en]

    The main physicochemical properties of nanostructured silica/wheat gluten hybrid composites are presented. The extraction experiments suggest that the protein phase is intimately encased within the silica matrix, with silica–protein interactions driven by hydrogen bonding, as indicated by IR spectra. Spectroscopic results also show that silica induces a higher degree of constraint of the wheat gluten matrix, despite less aggregation. Moisture diffusion properties of the hybrid materials are investigated by a combined “desorption/sorption” approach. While the reduction of the moisture diffusivity in the presence of silica can be described by the geometrical impedance of a “sintered” porous solid, a time-dependent relaxation/restructuring of the composite apparently occurs during the sorption-desorption cycle.

  • 176.
    Türe, Hasan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Wheat Gluten -Based Materials and Composites: Extrusion, Casting and Antimicrobial Properties2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of bio-based polymers as packaging materials has gained much attention due to increasing environmental concerns regarding non-biodegradable petroleum-derived plastics. Wheat gluten (WG) is a valuable renewable resource for the production of bio-based materials because of its low price, biodegradability, good film-forming properties and good gas barrier properties under dry conditions. This study presents the processing and development of WG-based materials and composites.

    The first part presents a novel approach to obtain high quality WG films in a solvent-free extrusion process. Extrudability of WG was significantly improved by using urea and the films were flexible with remarkable barrier properties. Results indicated that urea-containing films were aggregated/polymerized and contained a considerable amount of b-sheet structure with a high degree of hydrogen bonding.  Adding urea changed the protein structure, and it was found that urea seemed to work as a plasticiser, as observed by the way in which the barrier and mechanical properties changed with increasing urea concentration (Paper I).

    In the second part, wheat gluten/montmorillonite (WG/MMT) nanocomposite films were prepared in a solvent-free extrusion process with urea. The oxygen permeability (OP) and water vapor transmission rate (WVTR) of the films were lowered by the use of montmorillonite clay. At the same time, the stiffness of the films increased without any critical loss of extensibility and the thermal stability of the extrudates was improved by the addition of the clay. Results indicated that the clay particles were layered mainly in the plane of the extruded films and the clay existed as individual platelets, intercalated tactoids and agglomerates (Paper II).

    The third part describes the development of WG/silica hybrid materials obtained by the sol-gel process. The presence of silica constrained the WG component to such an extent that moisture-induced aggregation/denaturation was small. Results suggested that the constraint came from interactions between the silica and wheat gluten phases, mainly due to hydrogen bond interactions. A substantial improvement in the thermal properties was observed as the silica content increased. It was found that reduction of the moisture diffusivity in the presence of silica can be explained by the geometrical impedance imposed by the interpenetrating silica phase (Paper III).

    The fourth part focuses on thermoplastically produced antimicrobial wheat gluten materials. Antimicrobial WG films containing potassium sorbate (PS) were successfully produced by compression moulding. Films containing more than 10 wt.% PS showed antimicrobial activity against Aspergillus niger while films containing 2.5 wt.% or more PS showed antimicrobial activity against Fusarium incarnatum. It was observed that when no seeding with spores was adopted, the PS films, in contrast to the PS-free films, resisted antimicrobial growth for at least one week. It was also found that PS was dissolved in WG films and that when the films were exposed to an agar solution most of the PS was released. In addition to the antimicrobial properties, results also indicated that PS acted as a plasticiser in the WG films (Paper IV).

  • 177.
    Türe, Hasan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    Innventia AB.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Properties of Wheat-Gluten/Montmorillonite Nanocomposite Films Obtained by a Solvent-Free Extrusion Process2012In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 20, no 4, p. 1038-1045Article in journal (Refereed)
    Abstract [en]

    This is, to our knowledge, the first study of wheat-gluten-based nanocomposite films prepared by a solvent-free extrusion process. Wheat gluten/montmorillonite nanocomposite films were obtained in a single screw-extruder using urea as a combined denaturant and plasticizer. The oxygen permeability and water vapor transmission rate of the films decreased by respectively factors of 1. 9 and 1. 3 when 5 wt.% clay was added. At the same time, the stiffness increased by a factor of 1. 5, without any critical loss of extensibility. Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray analysis indicated that the clay particles were layered mainly in the plane of the extruded film. It was possible to identify individual platelets/tactoids with FE-SEM and, together with findings from transmission electron microscopy, atomic force microscopy and X-ray diffraction, it was concluded that the clay existed as individual clay platelets, intercalated tactoids and agglomerates. Thermogravimetric analysis showed that the thermal stability of the extrudates was improved by the addition of clay.

  • 178.
    Türe, Hasan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gallstedt, Mikael
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antimicrobial compression-moulded wheat gluten films containing potassium sorbate2012In: Food Research International, ISSN 0963-9969, E-ISSN 1873-7145, Vol. 45, no 1, p. 109-115Article in journal (Refereed)
    Abstract [en]

    Antimicrobial glycerol-plasticized wheat gluten (WG) films containing potassium sorbate (PS) were successfully produced by compression moulding; a thermoplastic process involving high temperature and high pressure. Antifungal properties of the films were tested against Aspergillus niger and Fusarium incarnatum by the agar diffusion assay. The results indicated that films containing more than 10 wt.% PS showed antimicrobial activity against A. niger while films containing 2.5 wt.% or more of PS showed antimicrobial activity against F. incarnatum. It was also found that when the film was exposed to an absorbing medium (the agar solution), most of the PS was released, an interesting feature for edible active packaging. Despite the loss, a very promising result was that, without seeding of spores, the films resisted microbial growth for at least one week when the films were left in the agar solution. X-ray diffraction and field emission scanning electron microscopy revealed that the PS crystals were dissolved in the wheat gluten material. In addition to the antimicrobial properties, dynamic mechanical, tensile, PS loss, water vapour transmission rate and oxygen permeability data also indicated that PS acted as a plasticiser in the wheat gluten film.

  • 179.
    Türe, Hasan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gallstedt, Mikael
    Kuktaite, Ramune
    Johansson, Eva
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Protein network structure and properties of wheat gluten extrudates using a novel solvent-free approach with urea as a combined denaturant and plasticiser2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 19, p. 9416-9423Article in journal (Refereed)
    Abstract [en]

    This is, to our knowledge, the first success on solvent-free extrusion of wheat gluten (WG) into high quality films without using NaOH/salicylic acid. It was possible by using urea (concentrations: 10, 15 and 20 wt%) in the single screw-extruder process. Tensile testing, oxygen permeability, water vapor transmission rate, infrared spectroscopy (IR), confocal laser scanning microscopy (CLSM) and protein solubility were used to assess the properties of the extrudates. As the urea concentration increased, the strength and stiffness decreased while the extensibility increased. The oxygen permeability was low and increased, as did the water vapor transmission rate, with increasing urea concentration. The protein solubility of urea-containing films was found to be significantly lower than that of the native gluten and glycerol-plasticized WG extrudate. CLSM, together with the protein solubility, indicated that the urea films were aggregated/polymerized and IR spectroscopy revealed that these films contained a sizeable amount of beta-sheets with a high degree of hydrogen bonds associated with protein aggregation. The aggregation did not change with increasing urea concentration, which suggests that the changes in the mechanical and permeability properties were due to urea-induced plasticisation.

  • 180.
    Türe, Hasan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, M.
    Johansson, E.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Wheat-gluten/montmorillonite clay multilayer-coated paperboards with high barrier properties2013In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 51, p. 1-6Article in journal (Refereed)
    Abstract [en]

    This study presents the oxygen-barrier properties of paperboards with a wheat gluten (WG)/montmorillonite clay (MMT) multilayer coating, in which MMT was sandwiched between two layers of WG. Urea was added to the WG to facilitate the coating procedure and the clay was applied as an aqueous dispersion. With a coating thickness of ~20μm, oxygen transmission rates were 8-10cm3/(m2dayatm) at 50% RH, which meant that the oxygen barrier was ca. 25 times better than that given by a single-layer WG-coated paperboard (uncoated paperboard showed infinite values). The water vapor transmission rate (WVTR) was 28-39g/(m2day) using a 50-0% RH gradient, which was 6- to 8-fold lower than the value for uncoated paperboard. Tensile tests revealed small, if any, mechanical effects when the paperboard was coated. A protein solubility analysis indicated that urea-containing WG films were slightly more intermolecularly cross-linked than urea-free WG films. X-ray diffraction revealed that the MMT layer consisted of unswollen tactoids similar to those observed in the MMT powder. The Cobb60 data showed that both WG and clay increased the water absorbency.

  • 181.
    Ullsten, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Processing and Development of Wheat Gluten Plastics2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

     Renewable packaging materials are of interest for a more sustainable environment. Wheat gluten is one of the most interesting candidates to replace petroleum-based oxygen-barrier polymers for packaging applications. The high amount of hydrogen bonds makes wheat gluten interesting as oxygen barrier films with sufficient elastomeric mechanical properties. Wheat gluten based materials are homogeneous, mechanically strong and relatively water insoluble compared with other biological materials. Several studies of wheat gluten films have been performed on solution cast films and a few studies have been executed on compression molding. Extrusion, without solvents, is the most common and fastest processing method for the production of packaging films. In order to develop wheat gluten films to commercially competitive material it is crucial to make the material extrudable.The temperature window for extrusion of glycerol-plasticized wheat gluten was increased by the use of salicylic acid, a known scorch retarder and radical scavenger. Small effects of shear-induced heating during extrusion at the higher temperatures suggested that the acid acted as a lubricant and viscosity reducer. The latter was suggested to originate primarily from the salicylic-acid-induced reduction in the degree of protein aggregation/crosslinking, as indicated by size-exclusion high-performance liquid chromatography and chemiluminescence. Electron paramagnetic resonance spectroscopy on extruded films indicated that the beneficial effect of salicylic acid was due to its radical scavenging effect. The complex shear modulus increased more slowly with increasing salicylic acid content above 110-120°C, indicating that the aggregation/crosslinking rate was slower with salicylic acid, i.e. that it did have a scorch-retarding effect, besides yielding a lower final degree/complexity of aggregation.Sodium hydroxide was used as an additive to be able to extrude gluten at alkaline conditions. The oxygen barrier, at dry conditions, was improved significantly with the addition of sodium hydroxide. Oxygen transmission rate measurements, tensile tests, protein solubility, glycerol migration, infrared spectroscopy and electrophoresis were used to assess the properties of the extrudate. It was observed that the extrudate with 3 wt.% sodium hydroxide had the most suitable combination of properties, low oxygen permeability, large strain at break and relatively small aging-induced changes in mechanical properties, the reason probably due to high protein aggregation and low plasticizer migration.As an alternative method to get alkaline conditions ammonium hydroxide was added. It resulted in a three times stronger film compared to the pure gluten glycerol material and had an oxygen barrier that can favorably be compared with these of oriented polyethylene terephtalat or Nylon 66.Several plasticizers were examined in a screening test where the extrusion properties were predicted in a plasticorder. The temperature and melt viscosity were recorded during the kneading. The most promising plasticizers were chosen to further studies with tensile tests. Glycerol was shown to be the most efficient plasticizer for thermoformed gluten films.In order to use wheat gluten as a packaging material, it is important to be able to seal it. Wheat gluten films, molded at 100–130°C, were sealed by impulse sealing at 120– 175°C. The lap-shear and peel strength of the sealed films were evaluated. The lapshear strength was greater than or similar to that of polyethylene film, although the peel strength was poorer.

  • 182. Unterieser, Inga
    et al.
    Cuers, Julia
    Voiges, Kristin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Enebro, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mischnick, Petra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Quantitative aspects in electrospray ionization ion trap and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of malto-oligosaccharides2011In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 25, no 15, p. 2201-2208Article in journal (Refereed)
    Abstract [en]

    Mass spectrometry is widely applied in carbohydrate analysis, but still quantitative evaluation of data is critical due to different ionization efficiencies of the constituents in a mixture. Different size and chemical structure of the analytes cause their uneven distribution in droplets (electrospray ionization, ESI) or matrix spots (matrix-assisted laser desorption/ionization, MALDI). In addition, instrumental parameters affect final ion yields. In order to study and optimize the latter, an equimolar mixture of malto-oligosaccharides (DP1-6) was analyzed using varying target masses for ESI as well as different matrices and laser power for MALDI. The sodium adducts and derivatives for positive ion mode (hydra-zones with Girard's T Reagent, GT) and negative ion mode (reductively aminated with o-aminobenzoic acid, oABA) were studied. Negatively charged oABA-labeled malto-oligosaccharides turned out to be unsuitable for quantification of the malto-oligomeric composition. Best agreement was achieved when applying target masses in the range of the highest homolog in the mixture in electrospray ionization ion trap (ESI-IT) (1-2% deviation with GT label or as Na(+) adducts). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) gave best results when the laser power was adjusted significantly over the desorption/ionization threshold (1% deviation with GT label). Both parameters show significant influence on the determined oligomeric composition. Consequently, estimation and even quantitative determination of amounts of oligosaccharides in a mixture can be achieved when the analytes are labeled and the proper instrumental parameters are used.

  • 183. Unterieser, Inga
    et al.
    Mischnick, Petra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Labeling of oligosaccharides for quantitative mass spectrometry2011In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, no 1, p. 68-75Article in journal (Refereed)
    Abstract [en]

    Quantitative analysis of oligosaccharide mixtures and their derivatives by electrospray ionization mass spectrometry (ESI MS) is challenging, for example, due to different affinities of the analytes to alkali ions. To overcome this source of discrimination and to enhance signal intensity, labeling studies with cellobiose as model compound were performed with the goal to develop a rapid, easy, and robust method. Hydrazone formation with the permanently charged Girard's T reagent as well as reductive amination with five different charge providing amines were studied under various conditions. In both reaction types, the removal of water turned out to be the critical step because only under these conditions are the reactions pushed to completion. By working with only a slight excess of reagents, no purification is necessary to achieve excellent signal/noise ratios, avoiding further sources of discrimination. Comparing various reducing agents with respect to their selectivity and stability in the acidic reaction medium, 2-picoline borane turned out to be superior to the commonly used sodium cyanoborohydride. Thus, by replacement of the toxic NaCNBH3 by the more selective and stable, non-toxic 2-picoline borane, complete reductive amination with low amounts of reagents and without unlabeled alditol formation was achieved with o-aminobenzoic acid, a useful reagent for ESI MS in negative mode. For MS in positive mode Girard's T derivatization was very suitable.

  • 184.
    Valentini, Milena
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Lifetime prediction of an EPDM sealing component between dry and wet well in nuclear power plants2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Polymeric seals are widely installed in nuclear power plants. Since the seals are used to operational safety, it is very important to assess long-term behaviour.

    In this study, the polymeric material used is Ethylene-Propylene-diene rubber (EPDM) because it has outstanding mechanical property and the characteristic of having high resistance to heat. An elevated temperature causes its ageing and therefore its degradation. It is great value that the condition of the seal is determined.  This was achieved by studying samples that underwent accelerated ageing by different analytical methods; such as tensile testing, indenter modulus measurements, thermogravimetric analysis and infrared spectroscopy.

    Two EPDM samples were examined which came from the Swedish nuclear power plant company OKG; one had been exposed for 3 years (EPDM aged) and the other one was unaged (EPDM unaged). The lifetime prediction was evaluated by Young’s modulus (the data increased  with ageing time), strain at break (the values decreased as ageing is accelerated) and indenter modulus (the data followed the trend of Young’s modulus). From mechanical testing, there was not difference between EPDM unaged and aged. Therefore, the most important degradation is happened inside the oven at different temperatures. The mechanical data showed Arrhenius temperature dependence with activation energies at about of 50 kJ/mol for Young’s modulus and strain at break and of 40 kJ/mol for indenter modulus. These activation energies were used to extrapolate the lifetimes to dofferent temperatures (30°C, 40°C and 50°C). The composition of EPDM seal was determined by TGA and IR whereas the growing number of crosslinks was tested by density testing and swelling test.

  • 185.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    Universidad Politecnica de Valencia.
    Karlsson, Sigbnitt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    PMSE 354-Analytical assessment of the quality properties of recycled styrenic polymers using spectroscopy and chromatography2008In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235Article in journal (Other academic)
  • 186.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Environmental and resource aspects of sustainable biocomposites2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 11, p. 2147-2161Article in journal (Refereed)
    Abstract [en]

    This review critically discusses the environmental and resource implications for the design of sustainable biocomposites. Sustainable biocomposites should satisfy several requirements: (i) renewable and/or recycled resources should be utilized for their manufacture; (ii) the synthetic, modification, and processing operations should be benign and energy effective; (iii) no hazardous environmental or toxicological effects should arise during any stage of their life cycle; and (iv) their waste management options should be implemented. The future integration of biorefineries and green chemistry will guarantee the availability of a wide range of raw materials for their preparation. The emission of volatile organic compounds and the release of nanoparticles should be evaluated from a toxicological and environmental point of view. Finally, the susceptibility of sustainable biocomposites towards degradation, including abiotic effects (water absorption, thermo- and photo-oxidation) and biofilm formation and biodegradation, must be considered, to guarantee their structural and functional stability during service life, and to ensure their biodegradability and assimilation during composting.

  • 187.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Quality assessment of recycled plastics2008Conference paper (Other academic)
    Abstract [en]

    The project develops polymer characterization models, which are to be used in determination of polymeric properties ofrecycled plastics. In Europe, new standards are developed within the CEN bodies and a new standard on plastic recycling willbe released. The project develops knowledge about the properties that are important for quality assessments and presentlythree items are under investigation: a) degree of degradation, b) degree of blending and c) presence of low molecular weightcompounds. The analytical methods investigated are DSC, TGA, FTIR and chromatography. In a later step, validation of themethods will be made.

  • 188. Voiges, Kristin
    et al.
    Adden, Roland
    Rinken, Marian
    Mischnick, Petra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Critical re-investigation of the alditol acetate method for analysis of substituent distribution in methyl cellulose2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 3, p. 993-1004Article in journal (Refereed)
    Abstract [en]

    The alditol acetate method is a common procedure for sugar analysis, also applied to determine the substituent distribution in monomer units of polysaccharide ethers like methyl cellulose by gas liquid chromatography. Consisting of several preparation and work-up steps this procedure is both time consuming and prone to side reactions that promote discrimination of single constituents, especially when no peralkylation step is performed prior to hydrolysis. As a consequence results scatter in dependence on individual treatment and conditions. In the context of this work these critical points were overcome by strict but simplified work-up procedures and using acid instead of alkaline catalyzed acetylation. Under the acidic conditions the tedious removal of borate is no longer necessary and a reduced time requirement was achieved as well as good reproducibility. Comparison with independent reference methods excluded a systematic error of the method and confirmed the results obtained. Without peralkylation, i.e. in the presence of free hydroxyl groups, another fast modification of the method using DMSO as solvent, no removal of borate, and 1-methylimidazole as catalyst for acetylation was found to produce a systematic error.

  • 189. Vollmer, Antje
    et al.
    Voiges, Kristin
    Bork, Christian
    Fiege, Kathrin
    Cuber, Katja
    Mischnick, Petra
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Comprehensive analysis of the substitution pattern in dextran ethers with respect to the reaction conditions2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 395, no 6, p. 1749-1768Article in journal (Refereed)
    Abstract [en]

    Dextrans from Leuconostoc ssp., alpha-1,6-linked glucans branched at O-3, were O-methylated in DMSO with lithium dimsyl and methyl iodide under various conditions. Methyl substituent distribution was comprehensively studied in the terminal, internal, and branched glucosyl units and along and over the dextran macromolecules. The order of reactivity was O-2>O-4 >= O-3. The methyl pattern in the glucosyl units significantly deviates from a random distribution with enhanced amounts of un- and trisubstituted moieties. This deviation was found to proceed on macromolecular level by means of ESI-MS of perdeuteromethylated and partially depolymerized methyl dextrans. Heterogeneity was much more pronounced than for methyl amylose prepared under comparable conditions. DS gradients in and over the material are discussed with respect to dextran structure and the mechanism of Li dimsyl alkylation. For comparison, cyanoethyl dextrans were prepared by sodium hydroxide catalyzed addition of acrylonitrile. Monomer analysis of cyanoethyl dextrans revealed that this thermodynamically controlled reaction gave a random substitution pattern with 48% of cyanoethyl groups at O-2, 33% at O-4, and 19% at O-3.

  • 190. Wang, Weijia
    et al.
    Proeller, Stephan
    Niedermeier, Martin A.
    Koerstgens, Volker
    Philipp, Martine
    Su, Bo
    Gonzalez, Daniel Mosegui
    Yu, Shun
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Roth, Stephan V.
    Mueller-Buschbaum, Peter
    Development of the Morphology during Functional Stack Build-up of P3HT:PCBM Bulk Heterojunction Solar Cells with Inverted Geometry2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 1, p. 602-610Article in journal (Refereed)
    Abstract [en]

    Highly efficient poly(3-hexylthiophene-2,5-diyl) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction solar cells are achieved by using an inverted geometry. The development of the morphology is investigated as a function of the multilayer stack assembling during the inverted solar cell preparation. Atomic force microscopy is used to reveal the surface morphology of each stack, and the inner structure is probed with grazing incidence small-angle X-ray scattering. It is found that the smallest domain size of P3HT is introduced by replicating the fluorine-doped tin oxide structure underneath. The structure sizes of the P3HT:PCBM active layer are further optimized after thermal annealing. Compared to devices with standard geometry, the P3HT:PCBM layer in the inverted solar cells shows smaller domain sizes, which are much closer to the exciton diffusion length in the polymer. The decrease in domain sizes is identified as the main reason for the improvement of the device performance.

  • 191.
    Wei, Xinfeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Kallio, K. J.
    Bruder, S.
    Bellander, M.
    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.
    Long-term performance of polyamide-based multilayer (bio)diesel fuel lines aged under “in-vehicle” conditions2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 144, p. 100-109Article in journal (Refereed)
    Abstract [en]

    The behaviour of a polyamide (PA)-based multilayer fuel pipe was investigated in “close to real” conditions using specially-designed ageing equipment with a program designed according to known customer driving modes and conditions (a key life test). The pipe was exposed to petroleum diesel and a combination of petroleum diesel and biodiesel. The fuel exposure pattern, as well as the temperature profile, followed a specified scheme in the key life test. It allowed for the investigation and understanding of complex ageing mechanisms, often observed in multi-layer systems with a variation in the running conditions. The mechanisms involved included migration of plasticizer from the innermost PA6 layer of the pipe to the fuel, and from the PA12 outer layer to the ambient air. At the same time, fuel was absorbed in the inner layer of the pipe. The oxidation of the innermost PA6 layer was promoted by the oxidation products of biodiesel. The diffusion-limited oxidation of the PA6 layer led to the formation of a 30 μm highly oxidized zone at the inner surface of the pipe, resulting in discoloration and oxidative crosslinking of the polymer. The toughness and extensibility of the pipe decreased significantly after prolonged ageing, and the extensibility was only 7% of that of the unaged pipe after 2230 h.

  • 192.
    Wu, Qiong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sundborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Peuvot, Kevin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Guex, Leonard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 30, p. 18260-18269Article in journal (Refereed)
    Abstract [en]

    Conductive biofoams made from glycerol-plasticized wheat gluten (WGG) are presented as a potential substitute in electrical applications for conductive polymer foams from crude oil. The soft plasticised foams were prepared by conventional freeze-drying of wheat gluten suspensions with carbon nanotubes (CNTs), carbon black (CB) or reduced graphene oxide (rGO) as the conductive filler phase. The change in conductivity upon compression was documented and the results show not only that the CNT-filled foams show a conductivity two orders of magnitude higher than foams filled with the CB particles, but also that there is a significantly lower percolation threshold with percolation occurring already at 0.18 vol%. The rGO-filled foams gave a conductivity inferior to that obtained with the CNTs or CB particles, which is explained as being related to the sheet-like morphology of the rGO flakes. An increasing amount of conductive filler resulted in smaller pore sizes for both CNTs and CB particles due to their interference with the ice crystal formation before the lyophilization process. The conductive WGG foams with CNTs were fully elastic with up to 10% compressive strain, but with increasing compression up to 50% strain the recovery gradually decreased. The data show that the conductivity strongly depends on the type as well as the concentration of the conductive filler, and the conductivity data with different compressions applied to these biofoams are presented for the first time.

  • 193.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB AB.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Reduced and Surface-Modified Graphene Oxide with Nonlinear Resistivity2017In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927Article in journal (Refereed)
    Abstract [en]

    Field-grading materials (FGMs) are used to reduce the probability for electrical breakdowns in critical regions of electrical components and are therefore of great importance. Usually, FGMs are heavily filled (40 vol.%) with semi-conducting or conducting particles. Here, polymer-grafted reduced graphene oxide (rGO) is used as a filler to accomplish percolated networks at very low filling ratios (<2 vol.%) in a semi-crystalline polymer matrix: poly(ethylene-co-butyl acrylate) (EBA). Various simulation models are used to predict the percolation threshold and the flake-to-flake distances, to complement the experimental results. A substantial increase in thermal stability of rGO is observed after surface modification, either by silanization or subsequent polymerizations. The non-linear DC resistivity of neat and silanized rGO and its trapping of charge-carriers in semi-crystalline EBA are demonstrated for the first time. It is shown that the polymer-grafted rGO improve the dispersibility in the EBA-matrix and that the graft length controls the inter-flake distances (i.e. charge-carrier hopping distances). By the appropriate selection of graft lengths, both highly resistive materials at 10 kV mm-1 and FGMs with a large and distinct drop in resistivity (six decades) are obtained, followed by saturation. The nonlinear drop in resistivity is attributed to narrow inter-flake distance distributions of grafted rGO.

  • 194.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Cobo Sanchez, Carmen
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB AB.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Tailoring Dielectric Properties using Designed Polymer-Grafted ZnO Nanoparticles in Silicone Rubber2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, p. 14241-14258, article id C6TA11237DArticle in journal (Refereed)
    Abstract [en]

    Polymer grafts were used to tailor the interphases between ZnO nanoparticles (NPs) and silicone matrices. The final electrical properties of the nanocomposites were tuned by the grafted interphases, by controlling the inter-particle distance and the NP-morphology. The nanocomposites can be used in electrical applications where control of the resistivity is desired. Hansen's solubility parameters were used to select a semi-compatible polymer for grafting to obtain anisotropic NP morphologies in silicone, and the grafted NPs self-assembled into various morphologies inside the silicone matrices. The morphologies in the semi-compatible nanocomposites could be tuned by steering the graft length of poly(n-butyl methacrylate) via entropic matrix-graft wetting using surface-initiated atom-transfer radical polymerization. Image analysis models were developed to calculate the radius of primary NPs, the fraction of aggregates, the dispersion, and the face-to-face distance of NPs. The dielectric properties of the nanocomposites were related to the morphology and the face-to-face distance of the NPs. The dielectric losses, above 100 Hz, for nanocomposites with grafted NPs were approximately one decade lower than those of pristine NPs. The isotropic nanocomposites increased the resistivity up to 100 times compared to that of neat silicone rubber, due to the trapping of charge carriers by the interphase of dispersed NPs and nanoclusters. On the other hand, the resistivity of anisotropic nanocomposites decreased 10–100 times when the inter-particle distance in continuous agglomerates was close to the hopping distance of charge carriers. The electrical breakdown strength increased for compatible isotropic nanocomposites, and the temperature dependence of the resistivity and the activation energy were ∼50% lower in the nanocomposites with grafted NPs. These flexible dielectric nanocomposites are promising candidates for low-loss high-voltage transmission cable accessories, mobile electronic devices, wearables and sensors.

  • 195.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Edmondson, Steve
    School of Materials, University of Manchester.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Correction: Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, p. 13522-13522Article in journal (Refereed)
    Abstract [en]

    Correction in Figure 8 for ‘Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states’ by Martin Wåhlander, et al., Nanoscale, 2016, DOI: 10.1039/c6nr01502f

  • 196.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Edmondson, Steve
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, p. 14730-14745Article in journal (Refereed)
    Abstract [en]

    We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been immobilised on anionic GO and subsequently grafted with hydrophobic polymer grafts. Dense grafts of PBA, PBMA and PMMA with a wide range of average graft lengths (MW: 1–440 kDa) were polymerised by surface-initiated controlled radical precipitation polymerisation from the statistical MI. The surface modification is designed similarly to bimodal graft systems, where the cationic MI generates nanoparticle repulsion, similar to dense short grafts, while the long grafts offer miscibility in non-polar environments and cohesion. The state-of-the-art dispersions of grafted GO were in the isotropic state. Transparent and translucent matrix-free GO-composites could be melt-processed directly using only grafted GO. After processing, birefringence due to nematic alignment of grafted GO was observed as a single giant Maltese cross, 3.4 cm across. Permeability models for composites containing aligned 2D-fillers were developed, which were compared with the experimental oxygen permeability data and found to be consistent with isotropic or nematic states. The storage modulus of the matrix-free GO-composites increased with GO content (50% increase at 0.67 wt%), while the significant increases in the thermal stability (up to 130 °C) and the glass transition temperature (up to 17 °C) were dependent on graft length. The tuneable matrix-free GO-composites with rapid thermo-responsive shape-memory effects are promising candidates for a vast range of applications, especially selective membranes and sensors.

  • 197.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Larsson, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Tsai, Wen-Chung
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Polymer-grafted Al2O3-nanoparticles for controlled dispersion in poly(ethylene-co-butyl acrylate) nanocomposites2014In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 55, no 9, p. 2125-2138Article in journal (Refereed)
    Abstract [en]

    We report a model system to control the dispersion and inter-particle distance of polymer-grafted Al2O3-nanoparticles in high molecular weight poly(ethylene-co-butyl acrylate). The proposed methods make it possible to extend the use of surface initiated atom transfer radical polymerization (SI-ATRP) in combination with more commercial grades of silanes and particles, showing the versatility of this polymerization process. The nanoparticles were surface-modified by an amine-terminated silane, forming multilayered silane coatings to which moieties capable of initiating ATRP were attached. Subsequently, "short" (DP: 117) and "long" (DP: 265) chains of poly(n-butyl acrylate) were grafted from the particles via SI-ATRP. The graft density was found to be in accordance with the density of the accessible amine groups and could therefore be assessed directly after the initial silanization step using UV-Vis spectrometry. From AFM micrographs, the grafted nanoparticles were found to be well-dispersed in the matrix. This observation was corroborated by a novel simulation method capable of transforming the inter-particle distances from 2D to 3D, for the closest and more distant neighbors. Further, we calculated the deviation ratios and concluded that the dispersions were homogeneous and that the inter-particle distances were related to the graft length. The homogeneous dispersions were explained by dominating enthalpic contributions of the polymer grafts to the nanocomposites in combination with shielding of the nanoparticle core-core attraction by the silane multilayer (similar to bimodal systems).

  • 198.
    Yu, Shun
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Deutsches Elektronen-Synchrotron (DESY), Germany.
    Santoro, Gonzalo
    Yao, Yuan
    Babonneau, David
    Schwartzkopf, Matthias
    Zhang, Peng
    Vayalil, Sarathlal Koyiloth
    Wessels, Philipp
    Doehrmann, Ralph
    Drescher, Markus
    Mueller-Buschbaum, Peter
    Roth, Stephan V.
    Following the Island Growth in Real Time: Ag Nanocluster Layer on A1q3 Thin Film2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 8, p. 4406-4413Article in journal (Refereed)
    Abstract [en]

    The progress of organic electronics demands an increased participation of nanotechnology, and it has already been shown that the presence of metallic nanoparticles and/or nanostructured thin films can enhance the device performance. Nevertheless, to gain control over the device final performance, it is crucial to achieve a profound understanding of the nanostructure development and assembly. We investigate the growth kinetics of silver (Ag) on a tris(8-hydroxyquinolinato)aluminum (Alq3) thin film via sputter deposition. The increase of the average electron density of the Ag nanostructured film is observed to follow a sigmoidal shape development as a function of the deposited Ag thickness, as a consequence of dominant island-mediated growth. The nanoclustered film is percolated at around a thickness of 5.0 +/- 0.1 nm. At this film thickness the effective film density is about 50%. Moreover, our simulation results indicate that the shape of the nanoclusters changes from truncated spheres to cylinders upon surpassing the percolation threshold.

  • 199.
    Yu, Wenbin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Deterioration of Polyethylene Exposed to Chlorinated Species in Aqueous Phases: Test Methods, Antioxidants Consumption and Polymer Degradation2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a study of antioxidant depletion in water containing chlorinated species (water containing 10 ppm either Cl2 or ClO2, buffered to pH = 6.8), the degradation products in the aqueous phase, and polyethylene pipe degradation scenarios. A low molecular weight hydrocarbon analogue (squalane) was used instead of solid polyethylene as the host material for the antioxidants, and the depletion of antioxidants has been studied. The phenolic antioxidant Irganox 1010 was consumed ca. 4 times faster in water containing 10 ppm ClO2 than in water containing 10 ppm Cl2. The different degradation products in extracts from the aqueous phase identified by infrared, liquid chromatography and mass spectrometry revealed the different degradation mechanisms between ClO2 (" cleavage) and Cl2 (hydrogen substitution). The squalane test shows no energy barrier between 30 and 70 °C, and the activation energy of the antioxidant in solid PE was found to be ca. 21 kJ mol-1. A linear relationship has been established between the time to reach antioxidant depletion in the polyethylene tape samples and the time to reach depletion in samples based on squalane containing the same antioxidants. The surface oxidation and surface embrittlement of PE tape on long time exposure have been studied by IR and SEM. Pressure testing on medium density PE pipes with a controlled pH aqueous media (6.8 ± 0.2) containing 4 ppm either ClO2 or at 90 °C showed that the stabilizers were rapidly consumed towards the inner pipe wall and the rate of consumption in ClO2 was 4 times greater than in Cl2 solution. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that, in the surface layer which came into contact with the oxidizing medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains.

  • 200.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hjertberg, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Deterioration of polyethylene exposed to water containing chlorine dioxide: Testing methods, antioxidant consumption, and polymer degradation2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal (Other academic)
12345 151 - 200 of 202
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