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  • 201. Römhild, Stefanie
    et al.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Bergman, G.
    Long-term transport and stability properties of thermoset resins exposed to waterManuskript (Annet vitenskapelig)
  • 202. Römhild, Stefanie
    et al.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Bergman, G.
    The Effect of Water Activity on the Sorption and Diffusion of Water in Thermosets Based on Polyester, Vinyl Ester, and Novolac Resins2012Inngår i: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 52, nr 4, s. 718-724Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 203. Römhild, Stefanie
    et al.
    Yousefi, Habib
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Bergman, G.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Influence of disclination density and crystallinity on the transport properties of a liquid crystalline copolyester2008Inngår i: Journal of macromolecular science. Physics, ISSN 0022-2348, E-ISSN 1525-609X, Vol. 47, nr 2, s. 305-316Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 204.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Bretzler, Victor
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Schmelter, S.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Confined space crystallisation of poly(epsilon-caprolactone) in controlled pore glasses2013Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, nr 8, s. 2073-2081Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 205.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael
    Eriksson, Lars
    Werner, Per-Erik
    Li, Y.
    Hawker, Craig J.
    Gedde, Ulf
    Influence of bulky and hydrogen bonding end groups on molecular packing of monodisperse oligomer Poly-ε-caprolactoneManuskript (preprint) (Annet vitenskapelig)
  • 206.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Eriksson, L.
    Werner, Per Erik
    Yu, L.
    Hawker, C. J.
    Takizawa, T.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Influence of bulky and hydrogen bonding end groups on molecular packing of monodisperse oligomer ε-CaprolactoneManuskript (preprint) (Annet vitenskapelig)
  • 207.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hakala, Risto
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Crystallisation kinetics of a star-shaped poly-ε-caprolactone oligomer confined in controlled pore glassesManuskript (preprint) (Annet vitenskapelig)
  • 208.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Neway, Bereket
    Hedenqvist, Mikael
    Li, Y.
    Hawker, C.J.
    Gedde, Ulf
    Crystallization and melting behaviour of monodisperse oligomer Poly-ε-caprolactoneManuskript (preprint) (Annet vitenskapelig)
  • 209.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Neway, Bereket
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Y.
    Hawker, C. J.
    Takizawa, K.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Crystallization and Melting Behavior of Monodisperse Oligomers of epsilon-Caprolactone2012Inngår i: Journal of macromolecular science. Physics, ISSN 0022-2348, E-ISSN 1525-609X, Vol. 51, nr 10, s. 2075-2092Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Monodisperse epsilon-caprolactone (CL) oligomers with different end groups (t-butyldimethylsilyl, benzyl, hydroxyl, and carboxylic acid) and different numbers of repeating units (4-64) have been studied by differential scanning calorimetry and small-angle X-ray scattering (SAXS) in order to gather information regarding the melting temperature, long period, and melting enthalpy. Oligomers crystallized at their maximum temperatures (different for the different oligomers) to full crystallinity yielded extended-chain crystals for oligomers with 4, 8, and 16 repeating units with the important exception of the oligomers with four and eight repeating units and hydroxyl and benzyl end groups that showed double-layer crystals. Oligomers with 32 and 64 repeating units exhibited remarkably stable once-folded (32-mer) and thrice-folded (64-mer) crystals. Only the oligomer with 16 repeating units showed two crystallization temperature regimes resulting in once-folded crystals (low temperatures) and extended-chain crystals (high temperatures). The end groups had a profound effect on the structures. Hydrogen-bonding groups promoted the formation of crystal bilayers and led to a very high melting enthalpy (150 J g(-1)) exceeding the melting enthalpy of 100% crystalline poly (epsilon-caprolactone). The bulky end groups, in particular t-butyldimethylsilyl, reduced the crystallinity and favored chain tilting and probably preventing the unfolding of crystal stems in the oligomers with 32 and 64 repeating units. Melting temperatures of mature crystals obeyed a linear relationship with inverse CL stem length. The intercept (equilibrium melting temperature) was in the range of 350 to 357 K.

  • 210.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Oko, A.
    YKI, Ytkemiska Institutet AB, Institute for Surface Chemistry, Sweden.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Tholén, E.
    Intermodulation Products AB.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Inkjet printing as a possible route to study confined crystal structures2013Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, nr 1, s. 203-208Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 211.
    Sanandaji, Nima
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ovaskainen, Louise
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Klein Gunnewiek, M.
    Vansco, M. S.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Yu, L.
    Eriksson, L.
    Roth, S. V.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Unusual crystals of poly(epsilon-caprolactone) by unusual crystallisation: The effects of rapid cooling and fast solvent loss on the morphology, crystal structure and melting2013Inngår i: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 54, nr 5, s. 1497-1503Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 212. Sanchez-Garcia, M. D.
    et al.
    Nordqvist, David
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lagaron, J. M.
    Incorporating Amylopectin in Poly(lactic acid) by Melt Blending Using Poly(ethylene-co-vinyl alcohol) as a Thermoplastic Carrier. II. Physical Properties2011Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, nr 6, s. 3708-3716Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study adds to a previous morphological work (paper I) with further characterization of the developed poly(lactic acid) (PLA) blends containing amylopectin, which made use of an ethylene-vinyl alcohol copolymer (EVOH) as a melt-compoundable carrier for the polysaccharide in the biopolyester. The effect of using glycerol as compatibilizer was also characterized. Water and oxygen transport parameters, mechanical properties, and comparative biodegradability tests were evaluated for the blends. From the results, the barrier properties to oxygen were only seen to improve at 0% RH and mostly for the PLA-EVOH blends, which furthermore showed a positive deviation from the rule of mixtures. At high relative humidity, the blends showed somewhat poorer barrier performance due to the comparatively higher improvement in barrier of the neat PLA at 80% RH. Interestingly, room temperature biodegradability testing suggested that low additions of the blending elements seemed to facilitate the biodegradability of the biopolyester. Despite the fact that properties were not so dramatically improved, incorporating renewable resources within PLA seems as a potentially viable route to reduce PLA supply dependency, retain good optical properties and to overcome some drawbacks associated to the use of this biopolyester. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 3708-3716, 2011

  • 213. Santoro, G.
    et al.
    Buffet, A.
    Döhrmann, R.
    Yu, S.
    Körstgens, V.
    Müller-Buschbaum, P.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    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, DESY2014Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, nr 4, s. 043901-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 214. Sarossy, Zsuzsa
    et al.
    Blomfeldt, Thomas O. J.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Koch, Christian Bender
    Ray, Suprakas Sinha
    Plackett, David
    Composite Films of Arabinoxylan and Fibrous Sepiolite: Morphological, Mechanical, and Baffler Properties2012Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, nr 7, s. 3378-3386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hemicelluloses represent a largely unutilized resource for future bioderived films in packaging and other applications. However, improvement of film properties is needed in order to transfer this potential into reality. In this context, sepiolite, a fibrous clay, was investigated as an additive to enhance the properties of rye flour arabinoxylan. Composite films cast from arabinoxylan solutions and sepiolite suspensions in water were transparent or semitransparent at additive loadings in the 2.5-10 wt % range. Scanning electron microscopy showed that the sepiolite was well dispersed in the arabinoxylan films and sepiolite fiber aggregation was not found. FT-IR spectroscopy provided some evidence for hydrogen bonding between sepiolite and arabinoxylan. Consistent with these findings, mechanical testing showed increases in film stiffness and strength with sepiolite addition and the effect of poly(ethylene glycol) methyl ether (mPEG) plasticizer addition. Incorporation of sepiolite did not significantly influence the thermal degradation or the gas barrier properties of arabinoxylan films, which is likely a consequence of sepiolite fiber morphology. In summary, sepiolite was shown to have potential as an additive to obtain stronger hemicellulose films although other approaches, possibly in combination with the use of sepiolite, would be needed if enhanced film barrier properties are required for specific applications.

  • 215. Siró, I.
    et al.
    Plackett, D.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ankerfors, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Lindström, Tom
    Highly Transparent Films from Carboxymethylated Microfibrillated Cellulose: The Effect of Multiple Homogenization Steps on Key Properties2011Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, nr 5, s. 2652-2660Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We produced microfibrillated cellulose by passing carboxymethylated sulfite-softwood-dissolving pulp with a relatively low hemicellulose content (4.5%) through a high-shear homogenizer. The resulting gel was subjected to as many as three additional homogenization steps and then used to prepare solvent-cast films. The optical, mechanical, and oxygen-barrier properties of these films were determined. A reduction in the quantity and appearance of large fiber fragments and fiber aggregates in the films as a function of increasing homogenization was illustrated with optical microscopy, atomic force microscopy, and scanning electron microscopy. Film opacity decreased with increasing homogenization, and the use of three additional homogenization steps after initial gel production resulted in highly transparent films. The oxygen permeability of the films was not significantly influenced by the degree of homogenization, whereas the mean tensile strength, modulus of elasticity, and strain at break were increased by two or three extra homogenization steps.

  • 216. Strain, I. N.
    et al.
    Wu, Qiong
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Electrospinning of recycled PET to generate strong mesomorphic fibre membranes for smoke filtrationManuskript (preprint) (Annet vitenskapelig)
  • 217. Strain, I. N.
    et al.
    Wu, Qiong
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Electrospinning of recycled PET to generate tough mesomorphic fibre membranes for smoke filtration2015Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, nr 4, s. 1632-1640Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 218. Svagan, A.J.
    et al.
    Bender Koch, C.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Nilsson, Fritjof
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Glasser, G.
    Baluschev, S.
    Andersen, M.L.
    Liquid-core nanocellulose-shell capsules with tunable oxygen permeability2016Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 136, s. 292-299Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 219.
    Svagan, Anna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Reduced water vapour sorption in cellulose nanocomposites with starch matrix2009Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 69, nr 3-4, s. 500-506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of microfibrillated cellulose nanofibers from wood on the moisture sorption kinetics (30% RH) of glycerol plasticized and pure high-amylopectin starch films were studied. The presence of a nanofiber network (70 wt% cellulose nanofibers) reduced the moisture uptake to half the value of the pure plasticized starch film. The swelling yielded a moisture concentration-dependent diffusivity. Quite surprisingly, the moisture diffusivity decreased rapidly with increasing nanofiber content and the diffusivity of the neat cellulose network was, in relative terms, very low. It was possible to describe the strong decrease in zero-concentration diffusivity with increasing cellulose nanofiber/matrix ratio, simply by assuming only geometrical blocking using the model due to Aris. The adjusted model parameters suggested a "simplified" composite structure with dense nanofiber layers oriented in the plane of the film. Still, also constraining effects on swelling from the high modulus/hydrogen bonding cellulose network and reduced amylopectin molecular mobility due to strong starch-cellulose molecular interactions were suggested to contribute to the reductions in moisture diffusivity.

  • 220. Swart, Morne
    et al.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Mallon, Peter E.
    Organic-Inorganic Hybrid Copolymer Fibers and Their Use in Silicone Laminate Composites2010Inngår i: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 50, nr 11, s. 2143-2152Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nonwoven organic-inorganic fiber mats of poly(methyl methacrylate)-graft-poly(dimethyl siloxane) copolymers with various PDMS contents were produced by the electrospinning process. The average fiber diameter increased from 0.7 to 3 mu m with increasing PDMS content. The fiber mats were used in the preparation of silicone-laminated composite materials by distributing them (single, double and triple layer mats) in a silicone matrix prior to thermal curing. The composites showed a remarkably good fiber distribution in the silicone matrix. In general the stiffness and strength increased in the presence of fiber, and surprisingly, so did the toughness/extensibility. An interesting feature was that the most silicon-rich fibers showed clear signs of yielding after tensile testing and failure. This, together with the greater compatibility of the fibers with the matrix because of the higher PDMS content, most probably favored composite toughness. All composite fracture surfaces were characterized by clear signs of fiber pull-out. Fracture initiation areas were difficult to locate, and this is accredited to an even distribution of the individual fibers in the matrix. POLYM. ENG. SC., 50:2143-2152, 2010.

  • 221.
    Tsai, Wen-Chung
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Laiback, Åsa
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Melin, H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ngo, M.
    Trollsas, M.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Physical changes and sorption/desorption behaviour of amorphous and semi-crystalline PLLA exposed to water, methanol and ethanol2016Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 76, s. 278-293Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 222.
    Ture, Hasan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Blomfeldt, Tomas O. J.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gällstedt, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Farris, Stefano
    University of Milan.
    Nanostructured Silica Wheat Gluten Hybrid Materials Prepared by Catalytic Sol-Gel Chemistry2013Inngår i: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 214, nr 10, s. 1131-1139Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 223.
    Türe, Hasan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Blomfeldt, Thomas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gällstedt, Mikael
    Innventia AB.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Properties of Wheat-Gluten/Montmorillonite Nanocomposite Films Obtained by a Solvent-Free Extrusion Process2012Inngår i: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 20, nr 4, s. 1038-1045Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 224.
    Türe, Hasan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gallstedt, Mikael
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Antimicrobial compression-moulded wheat gluten films containing potassium sorbate2012Inngår i: Food Research International, ISSN 0963-9969, E-ISSN 1873-7145, Vol. 45, nr 1, s. 109-115Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 225.
    Türe, Hasan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gallstedt, Mikael
    Kuktaite, Ramune
    Johansson, Eva
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Protein network structure and properties of wheat gluten extrudates using a novel solvent-free approach with urea as a combined denaturant and plasticiser2011Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 19, s. 9416-9423Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 226.
    Türe, Hasan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Gällstedt, M.
    Johansson, E.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Wheat-gluten/montmorillonite clay multilayer-coated paperboards with high barrier properties2013Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 51, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 227.
    Ullsten, Henrik
    et al.
    STFI-Packforsk.
    Cho, Sung-Woo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Spencer, Gwen
    SLU, Alnarp.
    Gällstedt, Mikael
    STFI-Packforsk.
    Johansson, Eva
    SLU, Alnarp.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Properties of Extruded Vital Wheat Gluten Sheets with Sodium Hydroxide and Salicylic Acid2009Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, nr 3, s. 479-488Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a novel approach to improve the barrier and mechanical properties of extruded glycerol-plasticized vital wheat gluten sheets. The sheets were extruded with a single screw extruder at alkaline conditions using 3-5 wt % NaOH. Salicylic acid (SA), known to improve the extrudability of wheat gluten, was also added alone or in combination with NaOH. Oxygen transmission rate and volatile mass measurements, tensile tests, protein solubility, glycerol migration, infrared spectroscopy, and electrophoresis were used to assess the properties of the extrudate. Electrophoresis showed that the gluten/glycerol sheet and the sheet with 3 wt % NaOH and I wt % SA contained the same building blocks in terms of proteins and protein subunits, although the protein solubility in these samples was different. The oxygen barrier, at dry conditions, was improved significantly with the addition of NaOH, On the other hand, the addition of salicylic acid yielded poorer barrier properties. The extrudate was placed on a blotting paper and its aging properties were investigated during the first 120 days. It was observed that the extrudate with 3 wt % NaOH 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 is probably due to low plasticizer migration and an optimal protein aggregation/polymerization.

  • 228. Ullsten, Henrik
    et al.
    Gällstedt, Mikael
    Johansson, Eva Lena
    Gräslund, Astrid
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Enlarged processing window of plasticized wheat gluten using salicylic acid2006Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, nr 3, s. 771-776Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The temperature window for the extrusion of glycerol-plasticized wheat gluten was increased by the use of salicylic acid, a known scorch retarder and radical scavenger. It was possible to extrude 30 wt % glycerol-wheat gluten films with a die-head temperature as high as 135 °C, rather than 95 °C, by incorporating only 1 wt % salicylic acid. 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/cross-linking, 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. Tensile tests on extrudates revealed that the materials produced at the substantially higher processing temperature were still ductile. The complex shear modulus increased more slowly with increasing salicylic acid content above 110-120 °C, indicating that the aggregation/cross-linking rate was slower with salicylic acid, th t is, that it did have a scorch-retarding effect, besides yielding a lower final degree/complexity of aggregation.

  • 229. Ullsten, Henrik
    et al.
    Gällstedt, Mikael
    Spencer, G. M.
    Johansson, E.
    Marttila, S.
    Ignell, R.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Extrusion of wheat gluten with ammonium hydroxideManuskript (Annet vitenskapelig)
  • 230. Ullsten, Henrik
    et al.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gällstedt, Mikael
    Plasticizers for thermoformed wheat gluten filmsManuskript (Annet vitenskapelig)
  • 231. Ullsten, N. H.
    et al.
    Hedenqvist, Mikael S.
    KTH, Tidigare Institutioner                               , Polymerteknologi.
    A new test method based on head space analysis to determine permeability to oxygen and carbon dioxide of flexible packaging2003Inngår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 22, nr 3, s. 291-295Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new technique for determining oxygen and carbon dioxide permeabilities of flexible packaging was developed and tested on very-low density, low density and high density polyethylene pouches. The pouch head-space and pouch volume of carbon dioxide filled pouches were measured as a function of time until an equilibrium pouch gas composition was established. Permeabilities were obtained from the rates of carbon dioxide loss and oxygen uptake. HSP-method permeability values were in good agreement with those obtained from traditional flat-film permeability techniques. The HSP-method was found to be a valuable tool for determining and quantifying changes in carbon dioxide and oxygen pouch barrier properties due, for example, to exposure to olive oil or due to the existence of poor welds.

  • 232. Vinnerås, Björn
    et al.
    Hedenkvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nordin, Annika
    Wilhelmson, Anders
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Arkitektur.
    Peepoo bag: self-sanitising single use biodegradable toilet2009Inngår i: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 59, nr 9, s. 1743-1749Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unsafe water, sanitation and hygiene together with deficient nutritional status are major contributors to the global burden of disease. Safe collection, disposal and reuse of human excreta would enable the risk of transmission of diseases to be decreased and household food security to be increased in many regions. However, the majority of the 2.5 billion people lacking improved sanitation comprise poor people in societies with weak infrastructure. This study developed a low cost sanitation option requiring little investment and maintenance-a single use, self-sanitising, biodegradable toilet (Peepoo bag) and tested it for smell, degradability and hygiene aspects. It was found that no smell was detectable from a 25 mu m thick bag filled with faeces during 24 h in a 10m(2) room at 30 degrees C. Bags that had been in contact with urea-treated faeces or urine for 2 months in air, compost or water at 24 or 37 degrees C showed little signs of degradation. Furthermore, pathogen inactivation modelling of the 4 g of urea present in the bag indicated that appropriate sanitation of faecal material collected is achieved in the bag within 2-4 weeks, after which the bag can be degraded and reused as fertiliser.

  • 233.
    Wei, Xinfeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Akhlaghi, Shahin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Kallio, K. J.
    Bruder, S.
    Bellander, M.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Long-term performance of polyamide-based multilayer (bio)diesel fuel lines aged under “in-vehicle” conditions2017Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 144, s. 100-109Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 234.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    De Vico, Loris
    Larroche, Pierre
    Kallio, Kai
    Bruder, Stefan
    Bellander, Martin
    Gedde, Ulf W
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Ageing properties and polymer/fuel interactions of polyamide 12 exposed to (bio) diesel at high temperature2019Inngår i: npj Materials Degradation, ISSN 2397-2106Artikkel i tidsskrift (Fagfellevurdert)
  • 235.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hedenqvist, Mikael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Degradation of polyamide 12 exposed to petroleum diesel, biodiesel and their mixture2018Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Artikkel i tidsskrift (Annet vitenskapelig)
  • 236.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Kallio, K. J.
    Bruder, S.
    Bellander, M.
    Gedde, Ulf W
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Long-term performance of a polyamide-12-based fuel line with a thin poly(ethylene-co-tetrafluoroethylene) (ETFE) inner layer exposed to bio- and petroleum diesel2018Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 156, s. 170-179Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The long-term performance of a polyamide-12 (PA12)-based (bio)diesel fuel line/pipe with a thin poly(ethylene-co-tetrafluoroethylene) (ETFE) inner layer was investigated in “close to real” and high-temperature isothermal conditions with fuel on the inside and air on the outside of the pipe. The inner carbon-black-containing ETFE layer resisted fuel attack, as revealed by the small fuel uptake, the very low degree of oxidation, and the unchanged electrical conductivity, glass transition and melting behaviour. The properties of the ETFE layer remained the same after exposure to all the fuel types tested (petroleum diesel, biodiesel and a blend of 80% diesel with 20% biodiesel). Because of the presence of the ETFE layer on the inside, the fuel pipe experienced noticeable changes only in the outer PA12 pipe layer through migration of plasticizer, annealing and slight oxidation. The evaporation of plasticizer was found to be diffusion-controlled and it led to an increase in the glass transition temperature of PA12 by 20 °C. This, together with a small annealing-induced increase in crystallinity, resulted in a stiffer and stronger pipe with an increase in the flexural/tensile modulus and strength. The oxidation of PA12 remained at a low level and did not lead to an embrittled pipe during the simulated lifetime of the vehicle. This study reveals that fluoropolymers have a great potential for use as fuel-contacting materials in “demanding” motor vehicle fuel line systems. 

  • 237.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Kallio, Kai
    Bruder, Stefan
    Bellander, Martin
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Plasticizer loss in a complex system (polyamide 12): Kinetics, prediction and its effects on mechanical properties2019Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Artikkel i tidsskrift (Fagfellevurdert)
  • 238.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Kallio, Kai
    Bruder, Stefan
    Bellander, Martin
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    High-performance glass-fibre reinforced biobased aromatic polyamide in automotive biofuel supply systemsManuskript (preprint) (Annet vitenskapelig)
  • 239.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Kallio, Kai J.
    Volvo Car Corp, Polymer Ctr, SE-40531 Gothenburg, Sweden..
    Bruder, Stefan
    Scania CV AB, Mat Technol, SE-15187 Sodertalje, Sweden..
    Bellander, Martin
    Scania CV AB, Mat Technol, SE-15187 Sodertalje, Sweden..
    Kausch, Hans-Henning
    Swiss Fed Inst Technol Lausanne EPFL, CH-1015 Lausanne, Switzerland..
    Gedde, Ulf W
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Diffusion-limited oxidation of polyamide: Three stages of fracture behavior2018Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 154, s. 73-83Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyamides (PAs) frequently experience diffusion-limited oxidation (DLO) under elevated temperatures due to their combination of relatively high oxygen barrier properties and high susceptibility to, and rate of, oxidation; under DLO conditions, oxidation is uneven and limited to a thin surface layer. In this study, the reduced extensibility/embrittlement of unstabilized PA6 under DLO conditions was understood by revealing DLO-induced fracture behavior. The DLO was induced by thermally ageing PA6 samples at 180 degrees C; the built-up of the thin oxidized layer by ageing was revealed by infrared microscopy. Notably, the formation of the thin oxidized layer significantly reduced the strain-at-break. Depending on whether the oxidized layer was brittle, two types of surface behavior (voiding and cracking) occurred during the tensile tests, which in turn lead to three types (stages) of tensile fracture behavior. In particular, in the early stage (Stage I) of ageing, the fracture was caused by a long crack formed by the coalescence of adjacent surface voids, leading to a decrease in the strain-at-break from 300% to 30%. In Stage II, multiple surface cracks, which initiated in the oxidized layer, was arrested by the interface between the oxidized and unoxidized material, leading to an almost constant strain-at-break (at or close to the necking strain). Maximum brittleness occurred in Stage III, where a more extensive oxidation of the oxidized layer initiated cracks with high propagation rate, causing the interface to be unable to arrest the cracks. 

  • 240.
    Wei, Xin-Feng
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Linde, Erik
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Plasticiser loss from plastic or rubber products through diffusion and evaporation2019Inngår i: npj Materials DegradationArtikkel i tidsskrift (Fagfellevurdert)
  • 241.
    Wretfors, Christer
    et al.
    SLU, Alnarp.
    Cho, Sung-Woo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Marttila, S
    SLU, Alnarp.
    Nimmermark, S
    SLU, Alnarp.
    Johansson, Eva
    SLU, Alnarp.
    Use of Industrial Hemp Fibers to Reinforce Wheat Gluten Plastics2009Inngår i: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 17, nr 4, s. 259-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The next generation of manufactured products must be sustainable and industrially eco-efficient, making materials derived from plants an alternative of particular interest. Wheat gluten (WG) is an interesting plant material to be used for production of plastic similar materials due to its film-forming properties. For usage of plastics in a wider range of applications, composite materials with improved mechanical properties are demanded. The present study investigates the possibilities of reinforcing WG plastics with hemp fibers. Samples were manufactured using compression molding (130 A degrees C, 1600 bar, 5 min). Variation in fiber length, content (5, 10, 15 and 20 wt%) and quality (poor, standard, good) were evaluated. Mechanical properties and structure of materials were examined using tensile testing, light and scanning electron microscopy. Hemp fiber reinforcement of gluten plastics significantly influenced the mechanical properties of the material. Short hemp fibers processed in a high speed grinder were more homogenously spread in the material than long unprocessed fibers. Fiber content in the material showed a significant positive correlation with tensile strength and Young's modulus, and a negative correlation with fracture strain and strain at maximum stress. Quality of the hemp fibers did not play any significant role for tensile strength and strain, but the Young's modulus was significantly and positively correlated with hemp fiber quality. Despite the use of short hemp fibers, the reinforced gluten material still showed uneven mechanical properties within the material, a result from clustering of the fibers and too poor bonding between fibers and gluten material. Both these problems have to be resolved before reinforcement of gluten plastics by industrial hemp fibers is applicable on an industrial scale.

  • 242.
    Wretfors, Christer
    et al.
    SLU, Alnarp.
    Cho, Sung-Woo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Kuktaite, R.
    SLU, Alnarp.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Marttila, S
    SLU, Alnarp.
    Nimmermark, S
    SLU, Alnarp.
    Johansson, Eva
    SLU, Alnarp.
    Effects of fiber blending and diamines on wheat gluten materials reinforced with hemp fiber2010Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 45, nr 15, s. 4196-4205Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheat gluten (WG) is a promising base material for production of "green" plastics, although reinforcement is needed in more demanding applications. Hemp fiber is a promising reinforcement source but difficulties exist in obtaining desired properties with a WG-based matrix. This study aimed at improving fiber dispersion and fiber-matrix interactions using a high speed blender and a diamine as a cross-linker. Samples were manufactured using compression molding, two types of blenders and addition of diamine. Mechanical properties were assessed with tensile testing. Tensile-fractured surfaces were examined with scanning electron microscopy (SEM). Protein polymerization and fiber-protein matrix interactions were examined using high performance liquid chromatography (HPLC) and confocal laser scanning microscopy (CLSM). The results showed that a higher-speed grinding yielded a more even distribution of fibers and a more polymerized protein structure compared to a lower-speed grinding. However, these improvements did not result in increased strength, stiffness, and extensibility for the higher-speed grinding. The strength was increased when the grinding was combined with addition of a diamine (Jeffamine(R) EDR-176). HPLC, SEM, and CLSM, indicated that diamine added samples showed a more "plastic" appearance together with a stiffer and stronger structure with less cracking compared to samples without diamine. The use of the diamine also led to an increased polymerization of the proteins, although no effect on the fiber-protein matrix interactions was observed using microscopical techniques. Thus, for future successful use of hemp fibers to reinforce gluten materials, an appropriate method to increase the fiber-protein matrix interaction is needed.

  • 243.
    Wu, Qiong
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Holgate, Tim
    Johansson, Eva
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica2014Inngår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, nr 48, s. 20996-21009Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents a novel type of flame-retardant biohybrid foam with good insulation properties based on wheat gluten and silica, the latter polymerized in situ from hydrolysed tetraethyl orthosilicate (TEOS). This led to the formation of intimately mixed wheat gluten and silica phases, where, according to protein solubility measurements and infrared spectroscopy, the presence of silica had prohibited full aggregation of the proteins. The foams with "built-in" flame-retardant properties had thermal insulation properties similar to those of common petroleum- and mineral-based insulation materials. The foams, with a porosity of 87 to 91%, were obtained by freeze-drying the liquid mixture. Their internal structure consisted of mainly open cells between 2 and 144 mu m in diameter depending on the foam formulation, as revealed by mercury intrusion porosimetry and scanning electron microscopy. The foams prepared with >= 30% TEOS showed excellent fire-retardant properties and fulfilled the criteria of the best class according to UL94 fire testing standard. With increasing silica content, the foams became more brittle, which was prevented by cross-linking the materials (using gluteraldehyde) in combination with a vacuum treatment to remove the largest air bubbles. X-ray photoelectron and infrared spectroscopy showed that silicon was present mainly as SiO2 .

  • 244.
    Wu, Qiong
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lindh, Vilhelm H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Johansson, E.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Freeze-dried wheat gluten biofoams; scaling up with water welding2017Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 97, s. 184-190Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a simple and rapid wet welding technique that enables the scaling up of freeze-dried protein (wheat gluten (WG)) biofoams for e.g. thermal insulation applications. The welding occurred by first wetting faces of foam cubes in water and then pressing them together for a limited time period. The water plasticized thin cell-walls of the two foams formed a dense weld when the plasticized cells collapsed under the drying step. The welds were always stronger and stiffer than the surrounding cellular structure. Based on three-point bending, it was shown that welded specimens (four-cube samples) were 7 times stronger than specimens produced directly as one piece with similar total size. This illustrated the problem of freeze-drying larger products; by instead assembling smaller foams into a large object the overall foam structure became more homogeneous. In addition, the dense welds become “walls” that limit gas convection in the mainly open cell structure, beneficial for thermal insulation. This is the first report on combined freeze-drying and water welding. It shows the sustainable potential of the technique for foam production, since only water is used as a foaming/welding agent.

  • 245.
    Wu, Qiong
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Rabu, Julie
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Goulin, Kevin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Sainlaud, Chloe
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Chen, Fei
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Johansson, E.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Flexible strength-improved and crack-resistant biocomposites based on plasticised wheat gluten reinforced with a flax-fibre-weave2017Inngår i: Composites Part A: Applied Science and Manufacturing, ISSN 1359-835X, Vol. 94, s. 61-69Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents strength-improved and crack-resistant wheat gluten biocomposites, using flax-fibre-weaves as reinforcement. The composites were produced by dip-coating of the weave into a wheat gluten/glycerol (WGG) solution, or by compression moulding. The most extensive coverage and wetting of the flax yarns occurred during the compression moulding, and the adhesion between the fibres and the matrix increased with increasing glycerol content. The compression-moulded sheets were, at a comparable flax content, stiffer than those produced by dipping, whereas their strength was similar and their extensibility slightly lower. Tensile tests on notched samples showed that the flax yarn improved the crack-resistant properties significantly; the maximum stress increased from 2 to 29 MPa using a content of 19 wt.% flax fibres. A clear advantage of this novel mechanically flexible biocomposite is that it can be shaped plastically under ambient conditions, while at the same time providing in-plane stiffness, strength and crack-resistance.

  • 246.
    Wu, Qiong
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Sundborg, Henrik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Peuvot, Kevin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Guex, Leonard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Nilsson, Fritjof
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide2017Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, nr 30, s. 18260-18269Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 247.
    Wu, Qiong
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Yu, Shun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kollert, Matthias
    Mtimet, Mekki
    Roth, Stephan V.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Johansson, Eva
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids2016Inngår i: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 4, nr 4, s. 2395-2404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the absorption, mechanical, and antimicrobial properties of novel types of biofoams based on wheat-gluten (WG) and its biohybrids with silica. The hybrid WG foams were in situ polymerized with silica using two different silanes. When immersed in water, the 90-95% porous WG and silica-modified hybrid WG foams showed a maximum water uptake between 32 and 11 times the original sample weight. The maximum uptake was only between 4.3 and 6.7 times the initial weight in limonene (a nonpolar liquid) but showed reversible absorption/desorption and that the foams could be dried into their original shape. The different foams had a cell size of 2-400 mu m, a density of 60-163 kg/m(3), and a compression modulus of 1-9 MPa. The integrity of the foams during swelling in water was improved by cross-linking with glutaraldehyde (GA) or by a thermal treatment at 130 degrees C, which polymerized the proteins. In the never-dried state, the foam acted as a sponge, and it was possible to squeeze out water and soak it repeatedly. If the foam was dried to its glassy state, then the cells collapsed and did not open again even if the solid foam was reimmersed in water, saving as a sensor mechanism that can be used to reveal unintended exposure to polar liquids such as water under a product's service life. Small-angle X-ray scattering revealed that the gliadin-correlated structure expanded and then disappeared in the presence of water. The foam was made antimicrobial by impregnation with a Lanasol solution (a bromophenol existing in algae). It was also shown that the foam can act as a transfer/storage medium for liquids such as natural oils (rapeseed oil) and as a slow-release matrix for surfactant chemicals.

  • 248.
    Ye, Xinchen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Langton, Maud
    Lendel, Christofer
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    On the role of peptide hydrolysis for fibrillation kinetics and amyloid fibril morphology2018Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, nr 13, s. 6915-6924Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Self-assembly of proteins into amyloid-like nanofibrils is not only a key event in several diseases, but such fibrils are also associated with intriguing biological function and constitute promising components for new biobased materials. The bovine whey protein beta-lactoglobulin has emerged as an important model protein for the development of such materials. We here report that peptide hydrolysis is the rate-determining step for fibrillation of beta-lactoglobulin in whey protein isolate. We also explore the observation that beta-lactoglobulin nanofibrils of distinct morphologies are obtained by simply changing the initial protein concentration. We find that the morphological switch is related to different nucleation mechanisms and that the two classes of nanofibrils are associated with variations of the peptide building blocks. Based on the results, we propose that the balance between protein concentration and the hydrolysis rate determines the structure of the formed nanofibrils.

  • 249.
    Ye, Xinchen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Junel, Kristina
    RISE Bioecon Innventia AB, Drottning Kristinas Vag 61, SE-11486 Stockholm, Sweden..
    Gallstedt, Mikael
    SIG Combibloc, Vasagatan 7, SE-11120 Stockholm, Sweden..
    Langton, Maud
    SLU Swedish Agr Univ, Dept Mol Sci, Box 7015, S-75007 Uppsala, Sweden..
    Wei, Xin-Feng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Lendel, Christofer
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Protein/Protein Nanocomposite Based on Whey Protein Nanofibrils in a Whey Protein Matrix2018Inngår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 6, nr 4, s. 5462-5469Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article describes nanocomposite films with separately grown protein nanofibrils (PNFs) in a nonfibrillar protein matrix from the same protein starting material (whey). Tensile tests on the glycerol-plasticized films indicate an increased elastic modulus and a decreased extensibility with increasing content of PNFs, although the films are still ductile at the maximum PNF content (15 wt %). Infrared spectroscopy confirms that the strongly hydrogen-bonded beta-sheets in the PNFs are retained in the composites. The films appear with a PNF-induced undulated upper surface. It is shown that micrometer-scale spatial variations in the glycerol distribution are not the cause of these undulations. Instead, the undulations seem to be a feature of the PNF material itself. It was also shown that, apart from plasticizing the protein film, the presence of glycerol seemed to favor to some extent exfoliation of stacked beta-sheets in the proteins, as revealed by X-ray diffraction.

  • 250.
    Ye, Xinchen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Lendel, Christofer
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Langton, Maud
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Protein nanofibrils: Preparation, properties, and possible applications in industrial nanomaterials2019Inngår i: Industrial Applications of Nanomaterials, Elsevier, 2019, s. 29-63Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter deals with protein nanofibrils (PNFs), also referred to as amyloid fibrils. This is an emerging field in nanoscience and engineering. Sources for PNFs, ways of making these, including the mechanisms of the fibrillation process, and factors affecting the production process are presented here. Properties of the PNFs themselves as well as properties and preparation of PNF materials in the form of hydrogels, films, and fibers are also described. In this chapter, PNF-based nanocomposites and templates are also considered. Possible applications of PNFs are discussed and put in the perspective of future uses as, or in, industrial nanomaterials.

23456 201 - 250 of 251
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