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  • 1.
    Barreto, Carlos
    et al.
    University of Oslo, Norway; Norner AS, Norway.
    Altskär, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Fredriksen, Siw Bodil
    Norner AS, Norway.
    Hansen, Eddy Walther
    University of Oslo, Norway.
    Rychwalski, Rodney W.
    Chalmers University of Technology, Sweden.
    Multiwall carbon nanotube/PPC composites: Preparation, structural analysis and thermal stability2013In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, no 8, p. 2149-2161Article in journal (Refereed)
    Abstract [en]

    The focus of this report concerns the preparation nanocomposites from poly(propylene carbonate) (PPC) and multiwall carbon nanotubes (MWNTs). A solvent route using tetrahydrofuran, ethoxylated non- ionic surfactants combined with sonication was found to be successful in deagglomerating and dispersing the nanotubes. Transmission electron microscopy revealed highly disentangled and dispersed nanotubes and was supported by the qualitative stability evaluations. The morphology and molecular mobility of the prepared nanocomposites (0.5, 3.0 and 5.0 wt% of nanotubes) were characterized by rheology, microscopy, low-field solid-state nuclear magnetic resonance, and electrical conductivity. The networking of nanotubes was highest with a stearyl alcohol ethoxylate surfactant, and was found to improve with the sonication time. Nanotube percolation was established, both rheologically and electrically, from a filler content of approximately 0.5 wt%. A higher tendency toward particle agglomeration was observed at higher MWNT loadings. Only minor changes in the glass transition temperature were measured presumably due to the presence of solvent and surfactant residues. The thermal stability was marginally improved by increasing the loading and dispersion of the nanotubes, and appeared to be modified by solvent and surfactant residues.

  • 2.
    Chen, Fei
    et al.
    KTH Royal Institute of Technology, Sweden.
    Monnier, Xavier
    KTH Royal Institute of Technology, Sweden.
    Gällstedt, Mikael
    RISE, Innventia.
    Gedde, Ulf Wiel
    KTH Royal Institute of Technology, Sweden.
    Hedenqvist, Mikael Stefan
    KTH Royal Institute of Technology, Sweden.
    Wheat gluten/chitosan blends: A new biobased material2014In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 60, p. 186-197Article in journal (Refereed)
    Abstract [en]

    Wheat gluten and chitosan are renewable materials that suffer from some poor properties that limit their use as a potential replacement of petroleum-based polymers. However, polymer blends based on wheat gluten and chitosan surprisingly reduced these shortcomings. Films were cast from acidic aqueous or water/ethanol solutions of wheat gluten and chitosan. Wheat gluten was the discontinuous phase in the 30-70 wt.% wheat gluten interval investigated. The most homogeneous films were obtained when reducing agents were used (alone or together with urea or glycerol). They consisted mainly of 1-2 μm wheat gluten particles uniformly distributed in the continuous chitosan phase. Slightly smaller particles were also observed in the water/ethanol solvent system, but together with significantly larger particles (as large as 200 μm). Both small and large particles were observed, albeit in different sizes and contents, when surfactants (both with and without a reducing agent) or urea (without a reducing agent) were used. The particles were often elongated, and preferably along the film, the most extreme case being observed when the glyoxal crosslinker was used together with sodium sulfite (reducing agent), showing particles with an average thickness of 0.6 μm and an aspect ratio of 4.2. This film showed the highest transparency of all the blend films studied. For one of the most promising systems (with sodium sulfite), having good film homogeneity and small particles, the mechanical and moisture solubility/diffusivity properties were studied as a function of chitosan content. The extensibility, toughness and moisture solubility increased with increasing chitosan content, and the moisture diffusivity was highest for the pristine chitosan material. It is noteworthy that the addition of 30 wt.% wheat gluten to chitosan reduced the moisture uptake, while the extensibility/toughness remained unchanged.

  • 3.
    Flodberg, Göran
    et al.
    RISE, Innventia.
    Helland, Irene
    Norner Innovation AS, Norway.
    Thomson, Lars
    RISE, Innventia.
    Bodil Fredriksen, Siw
    Norner Innovation AS, Norway.
    Barrier properties of polypropylene carbonate and poly(lactic acid) cast films2015In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 63, p. 217-226Article in journal (Refereed)
    Abstract [en]

    A comparative study of the barrier properties of cast film of polypropylene carbonate (PPC) and cast film of poly(lactic acid) (PLA) has been made in this paper. Dynamic transmission measurements were conducted to obtain the barrier properties for oxygen transmission and for water vapour transmission. A special algorithm fminsearch in Matlab was used to adapt an exponential expression to the measured values. In this way the time needed to reach a 95% level of steady state was made possible to identify. The oxygen permeability was lower for PPC compared to PLA and this could be explained by a much higher positive enthalpy of solution for oxygen in PPC. The enthalpy of diffusion was close to similar for both PPC and PLA and was higher than for enthalpy of solution. The enthalpy of water vapour permeability was higher for PPC compared to PLA and this resulted in substantially higher water vapour permeability for PLA. The uptake of water vapour was also higher for PLA compared to PPC as shown by dynamic vapour sorption measurements. Differential scanning calorimetry confirmed that PPC is an amorphous polymer and that the PLA used in this study had a minimum of crystallinity which made it comparable to PPC.

  • 4. Gorochovceva, N
    et al.
    Naderi, A
    Dedinaite, A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Makuska, R
    Chitosan–N-poly(ethylene glycol) brush copolymers: Synthesis and adsorption on silica surface2005In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 41, p. 2653-2662Article in journal (Refereed)
    Abstract [en]

    Chitosan–N-poly(ethylene glycol) brush copolymers with different degree of substitution (DS) were synthesized via reductive amination of chitosan by methoxy poly(ethylene glycol) (MPEG) aldehyde. Chitosan–N-MPEG copolymers were high-molecular-weight products with desirable DS; solubility and solution viscosity of those copolymers depended on the method of the synthesis of MPEG aldehyde and on DS. Synthesis of MPEG aldehyde by the use of TEMPO radical/BAIB was not suitable because of partial oxidation of methoxy groups of MPEG resulting in bifunctional PEG derivatives leading to cross-linking. Adsorption studies of chitosanÅ|N-MPEG graft copolymers on silica surface show that these polymers adsorb in highly hydrated layers

  • 5. Krivorotova, T
    et al.
    Makuska, R
    Naderi, A
    Claesson, PM
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Dédinaité, A
    Synthesis and interfacial properties of novel cationic polyelectrolytes with brush-on-brush structure of poly(ethylene oxide) side chains2010In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 46, no 2, p. 171-180Article in journal (Refereed)
    Abstract [en]

    Novel cationic polyelectrolytes with a brush-on-brush structure of poly(ethylene oxide) (PEO) side chains and a charge-containing polyacrylate backbone were synthesized. The PEO side chains were not directly attached to the backbone but via polymethacrylate spacers, thus locating the PEO chains a distance away from the charged units of the backbone. The cationic brush-on-brush polyelectrolytes with high density of PEO chains showed a strong affinity to silica surfaces, provided the backbone charge density was high enough. The adsorption of these polymers was studied by QCM-D giving very high sensed mass, 20 mg/m(2). It was shown by direct force measurements that protective surface layers were formed by the novel polyelectrolytes, generating strongly repulsive steric forces, which provided an effective barrier against flocculation. The adsorbed layer was sufficiently robust to withstand sliding experiments under a pressure of up to 35 MPa. The friction force in water was very low. and the lubrication was characterized by a friction coefficient in the range of 0.02-0.06.

  • 6.
    Lundahl, Meri
    et al.
    Aalto University, Finland.
    Berta, Marco
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Ago, Mariko
    Aalto University, Finland.
    Stading, Mats
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Rojas, Orlando
    Aalto University, Finland.
    Shear and extensional rheology of aqueous suspensions of cellulose nanofibrils for biopolymer-assisted filament spinning2018In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 109, p. 367-378Article in journal (Refereed)
    Abstract [en]

    The shear and extensional rheology of aqueous suspensions of cellulose nanofibrils (CNF) were investigated under dynamic and steady flow fields. The results were compared to those for two biopolymer solutions, cellulose acetate, CA, and guar gum, GG. Wet-spinning experiments were conducted for each system and the outcome related to the respective rheological profile. The spinnability of the system correlated with strong Newtonian and viscous responses under shear as well as long breakup time in capillary breakup experiments. CA solution was the most spinnable, also displaying the strongest Newtonian liquid behavior and the longest capillary breakup time. In contrast, the most shear-thinning and elastic CNF suspension showed instant capillary breakup and was considerably less spinnable. This is due to the limited entanglement between the rigid cellulose fibrils. In order to enable continuous wet-spinning of CNF without filament breakup, GG and CA were used as carrier components in coaxial spinning. The shear and extensional rheology of the system is discussed considering both as supporting polymers.

  • 7.
    Sanandaji, N.
    et al.
    KTH Royal Institute of Technology, Sweden.
    Oko, Asaf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Haviland, David B.
    KTH Royal Institute of Technology, Sweden.
    Tholén, Erik A.
    Intermodulation Products AB, Sweden.
    Hedenqvist, Mikael Stefan
    KTH Royal Institute of Technology, Sweden.
    Gedde, Ulf Wiel
    KTH Royal Institute of Technology, Sweden.
    Inkjet printing as a possible route to study confined crystal structures2012In: 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.

  • 8.
    Soroudi, Azadeh
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Jakubowicz, Ignacy
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Polymer och fiber.
    Recycling of bioplastics, their blends and biocomposites: A review2013In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, no 10, p. 2839-2858Article in journal (Refereed)
    Abstract [en]

    This review presents scientific findings concerning the recycling of bioplastics, their blends and thermoplastic biocomposites, with special focus on mechanical recycling of bio-based materials. The paper does not include bio-based commodity plastics such as bio-derived polyolefins that are identical to their petroleum-based counterparts and that can be recycled in the same way. During the past few years, recycling of biopolymers and their blends has been studied using both mechanical and chemical methods, whereas in biocomposites, the focus has been on mechanical recycling. This review goes through the findings on the recyclability of various materials, the strengths and weaknesses of applied methods, as well as the potential strategies and opportunities for future improvements. There are still many blends that have not been investigated for their recyclability. Information about commercially available blends containing bioplastics is summarised in the Appendix because of the importance of their possible effects on the conventional plastic recycling streams.

  • 9.
    Sterky, Karin
    et al.
    Chalmers University of Technology, sweden.
    Jacobsen, Harald
    INEOS ChlorVinyls AS, Norway.
    Jakubowicz, Ignacy
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Yarahmadi, Nazdaneh
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Hjertberg, Thomas
    Borealis AB, Sweden.
    Influence of processing technique on morphology and mechanical properties of PVC nanocomposites2010In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 46, no 6, p. 1203-1209Article in journal (Refereed)
    Abstract [en]

    This study aims to compare the influence of processing techniques and procedures on the morphology and mechanical properties of polyvinyl chloride (PVC) nanocomposites. PVC nanocomposites with 5 phr montmorillonite (MMT) clay were prepared on a two-roll mill or in a microcompounder, both were either processed once or via a masterbatch containing 20 phr MMT. The MMT was treated with non-ionic surfactants and analysed by thermo gravimetric analysis and X-ray diffraction prior to being added. The final composites were analysed and tested using X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), tensile test, and Charpy impact test. The dispersion was found to be best in the roll milled samples prepared via the masterbatch and the elongation at break and impact strength was also better for the roll milled samples. E-modulus and tensile strength, on the other hand, were significantly better for the microcompounded samples despite the larger particle size. This can be explained by a higher degree of orientation in these samples. Finally, it must be stated that the change in properties are not satisfactory. Although we see an increase in E-modulus, the decreased impact properties are not acceptable. The main reason for this is the lack of compatibility between the clay particles as observed by high resolution SEM.

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