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  • 201. Paakko, Marjo
    et al.
    Vapaavuori, Jaana
    Silvennoinen, Riitta
    Houbenov, Nikolay
    Ras, Robin H. A.
    Ruokolainen, Janne
    Ritala, Mikko
    Lindström, Tom
    Ankerfors, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ikkala, Olli
    Flexible and hierarchically porous nanocellulose aerogels: Templates for functionalities2010Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 239Artikkel i tidsskrift (Annet vitenskapelig)
  • 202. Paakko, Marjo
    et al.
    Vapaavuori, Jaana
    Silvennoinen, Riitta
    Kosonen, Harri
    Ankerfors, Mikael
    Lindström, Tom
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ikkala, Olli
    Long and entangled native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities2008Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently it was shown that enzymatic and mechanical processing of macroscopic cellulose fibers lead to disintegration of long and entangled native cellulose I nanofibers in order to form mechanically strong aqueous gels (Paakko et al., Biomacromolecules, 2007, 8, 1934). Here we demonstrate that ( 1) such aqueous nanofibrillar gels are unexpectedly robust to allow formation of highly porous aerogels by direct water removal by freeze-drying, ( 2) they are flexible, unlike most aerogels that suffer from brittleness, and ( 3) they allow flexible hierarchically porous templates for functionalities, e. g. for electrical conductivity. No crosslinking, solvent exchange nor supercritical drying are required to suppress the collapse during the aerogel preparation, unlike in typical aerogel preparations. The aerogels show a high porosity of similar to 98% and a very low density of ca. 0.02 g cm(-3). The flexibility of the aerogels manifests as a particularly high compressive strain of ca. 70%. In addition, the structure of the aerogels can be tuned from nanofibrillar to sheet-like skeletons with hierarchical micro- and nanoscale morphology and porosity by modifying the freeze-drying conditions. The porous flexible aerogel scaffold opens new possibilities for templating organic and inorganic matter for various functionalities. This is demonstrated here by dipping the aerogels in an electrically conducting polyaniline-surfactant solution which after rinsing off the unbound conducting polymer and drying leads to electrically conducting flexible aerogels with relatively high conductivity of around 1 x 10(-2) S cm(-1). More generally, we foresee a wide variety of functional applications for highly porous flexible biomatter aerogels, such as for selective delivery/separation, tissue-engineering, nanocomposites upon impregnation by polymers, and other medical and pharmaceutical applications.

  • 203.
    Paakko, Marjo
    et al.
    Helsinki Univ Technol, Dept Appl Phys, Espoo 02015, Finland..
    Vapaavuori, Jaana
    Helsinki Univ Technol, Dept Appl Phys, Espoo 02015, Finland..
    Silvennoinen, Riitta
    Helsinki Univ Technol, Dept Appl Phys, Espoo 02015, Finland..
    Kosonen, Harri
    Helsinki Univ Technol, Dept Appl Phys, Espoo 02015, Finland..
    Ras, Robin
    Helsinki Univ Technol, Dept Appl Phys, Espoo 02015, Finland..
    Ankerfors, Mikael
    STFI Packforsk, SE-11486 Stockholm, Sweden..
    Lindstrom, Tom
    STFI Packforsk, SE-11486 Stockholm, Sweden..
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE).
    Ikkala, Olli T.
    Helsinki Univ Technol, Dept Appl Phys, Espoo 02015, Finland..
    Native cellulose I nanofibers allow flexible aerogels and hierarchically porous templates for functionalities2009Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 238Artikkel i tidsskrift (Annet vitenskapelig)
  • 204.
    Pei, Aihua
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Surface-modification of nanocelluloses and their applications in poly(lactic acid)/nanocellulose biocomposites2014Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, s. 163-CELL-Artikkel i tidsskrift (Annet vitenskapelig)
  • 205.
    Pei, Aihua
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Butchosa, Nuria
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Surface quaternized cellulose nanofibrils for high-performance anionic dyes removal in water2012Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikkel i tidsskrift (Annet vitenskapelig)
  • 206.
    Pei, Aihua
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Butchosa, Nuria
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Surface quaternized cellulose nanofibrils with high water absorbency and adsorption capacity for anionic dyes2013Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, nr 6, s. 2047-2055Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface quaternized cellulose nanofibrils were mechanically disintegrated from wood pulp that was pretreated through a reaction with glycidyltrimethylammonium chloride. The resulting quaternized cellulose nanofibrils (Q-NFC) with trimethylammonium chloride contents of 0.59-2.31 mmol g(-1) were characterized by conductometric titration, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). When the trimethylammonium chloride content on cellulose reached approximately 0.79 mmol g(-1) corresponding to a degree of substitution of 0.13 per bulk anhydroglucose unit, highly viscous and transparent aqueous dispersions of cellulose nanofibrils were obtained by mechanical homogenization of the chemically pretreated cellulose/water slurries. AFM observation showed that the dispersions consisted of individualized cellulose I nanofibrils 1.6-2.1 nm in width and 1.3-2.0 mu m in length. Cellulose nanopapers prepared from the Q-NFC aqueous dispersions exhibited high tensile strength (ca. 200 MPa) and Young's modulus (ca. 10 GPa) despite high porosity (37-48%). The nanopapers also demonstrated ultrahigh water absorbency (750 g g(-1)) with high surface cationic charge density. Stable hydrogels were obtained after swelling the nanopaper in water. The Q-NFC nanofibrils also possessed high anionic dye adsorption capability. The adsorption capacity increased with increasing trimethylammonium chloride content on cellulose.

  • 207.
    Pei, Aihua
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Malho, Jani-Markus
    Ruokolainen, Janne
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Strong Nanocomposite Reinforcement Effects in Polyurethane Elastomer with Low Volume Fraction of Cellulose Nanocrystals2011Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 44, nr 11, s. 4422-4427Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyurethane/cellulose nanocrystal nanocomposites with ultrahigh tensile strength and stain-to-failure with strongly improved modulus were prepared by adding cellulose nanocrystals (CNCs) during the preparation of prepolymer. The nanostructure of this polyurethane consisted of individualized nanocellulose crystals covalently bonded and specifically associated with the hard polyurethane (PU) microdomains as characterized by Fourier transform infrared spectroscopy and transmission electron microscopy. The storage modulus and thermal stability of the nanocomposites were significantly improved as measured by dynamic mechanical analysis. This was due to a combination of CNCs reinforcement in the soft matrix and increased effective cross-link density of the elastomer network due to CNC-PU molecular interaction. Tensile test revealed that the nanocomposites have both higher tensile strength and strain-to-failure. In particular, with only 1 wt % of cellulose nanocrystals incorporated, an 8-fold increase in tensile strength and 1.3-fold increase in strain-to-failure were achieved, respectively. Such high strength indicates that CNCs orient strongly at high strains and may also induce synergistic PU orientation effects contributing to the dramatic strength enhancement. The present elastomer nanocomposite outperforms conventional rubbery materials and polyurethane nanocomposites reinforced with microcrystalline cellulose, carbon nanotubes, or nanoclays.

  • 208.
    Pei, Aihua
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Functionalized cellulose nanocrystals as biobased nucleation agents in poly(L-lactide) (PLLA): Crystallization and mechanical property effects2010Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 70, nr 5, s. 815-821Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The important industrial problem of slow crystallization of poly(l-lactide) (PLLA) is addressed by the use of cellulose nanocrystals as biobased nucleation reagents. Cellulose nanocrystals (CNC) were prepared by acid hydrolysis of cotton and additionally functionalized by partial silylation through reactions with n-dodecyldimethylchlorosilane in toluene. Such silylated cellulose nanocrystals (SCNC) were dispersible in tetrahydrofuran and chloroform, and formed stable suspensions. Nanocomposite films of PLLA and CNC or SCNC were prepared by solution casting. The effects of surface silylation of cellulose nanocrystals on morphology, non-isothermal and isothermal crystallization behavior, and mechanical properties of these truly nanostructured composites were investigated. The unmodified CNC formed aggregates in the composites, whereas the SCNC were well-dispersed and individualized in PLLA. As a result, the tensile modulus and tensile strength of the PLLA/SCNC nanocomposite films were more than 20% higher than for pure PLLA with only 1. wt.% SCNC, due to crystallinity effects and fine dispersion.

  • 209. Peltzer, Mercedes
    et al.
    Pei, Aihua
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Jiménez, Alfonso
    Surface modification of cellulose nanocrystals by grafting with poly(lactic acid)2014Inngår i: Polymer international, ISSN 0959-8103, E-ISSN 1097-0126, Vol. 63, nr 6, s. 1056-1062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of biopolymers obtained from renewable resources is currently growing and they have found unique applications as matrices and/or nanofillers in 'green' nanocomposites. Grafting of polymer chains to the surface of cellulose nanofillers was also studied to promote the dispersion of cellulose nanocrystals in hydrophobic polymer matrices. The aim of this study was to modify the surface of cellulose nanocrystals by grafting from L-lactide by ring-opening polymerization in order to improve the compatibility of nanocrystals and hydrophobic polymer matrices. The effectiveness of the grafting was evidenced by the long-term stability of a suspension of poly(lactic acid)-grafted cellulose nanocrystals in chloroform, by the presence of the carbonyl peak in modified samples determined by Fourier transform infrared spectroscopy and by the modification in C1s contributions observed by X-ray photoelectron spectroscopy. No modification in nanocrystal shape was observed in birefringence studies and transmission electron microscopy.

  • 210. Plummer, C. J. G.
    et al.
    Galland, Sylvain
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Ecole Polytech Fed Lausanne, Switzerland.
    Ansari, Farhan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Leterrier, Y.
    Bourban, P. -E
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Manson, J. -AE.
    Influence of processing routes on morphology and low strain stiffness of polymer/nanofibrillated cellulose composites2015Inngår i: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 44, nr 3, s. 81-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The morphology of polymer/nanofibrillated cellulose (NFC) composite sheets produced using different techniques and its influence on low strain stiffness were assessed by optical and transmission electron microscopy. Solvent processing led to relatively homogeneous NFC dispersions and significant reinforcement of the in-plane Young's modulus. The continuous cellular networks obtained by wet comingling of polylactide powder or latex with NFC also provided efficient and essentially scale independent reinforcement, in spite of the extensive agglomeration of the NFC. However, the irreversible nature of these networks is incompatible with low pressure thermoplastic processing routes such as physical foaming, and while they may be broken up by e.g. extrusion, this led to substantial loss in reinforcement, particularly at temperatures above the glass transition temperature of the matrix, consistent with the observation of isolated low aspect ratio NFC aggregates in the extruded specimens.

  • 211. Plummer, C. J. G.
    et al.
    Galland, Sylvain
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland .
    Ansari, Farhan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Leterrier, Y.
    Bourban, P. -E
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Månson, J. -AE.
    Influence of processing routes on the morphology and properties of polymer/nanofibrillated cellulose composites2014Inngår i: 16th European Conference on Composite Materials, ECCM 2014, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The morphology of polymer/nanofibrillated cellulose (NFC) composite sheets produced using different techniques and its influence on low strain stiffness were assessed by optical and transmission electron microscopy. Solvent processing led to relatively homogeneous NFC dispersions and significant reinforcement of the in-plane Young's modulus. The continuous cellular networks obtained by wet-comingling of PLA powder or latex with NFC also provided efficient and essentially scale-independent reinforcement, in spite of the extensive agglomeration of the NFC. However, the irreversible nature of these networks is incompatible with low pressure thermoplastic processing routes such as physical foaming, and while they may be broken up by e.g. extrusion, this led to substantial loss in reinforcement, particularly above Tg, consistent with the observation of isolated low aspect ratio NFC aggregates in the extruded specimens.

  • 212.
    Popov, Sergei
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Marinins, Aleksandrs
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Material- och nanofysik.
    Sychugov, Ilya
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Yan, Max
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Vasileva, Elena
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Li, Yuanyuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Udalcovs, Aleksejs
    RISE Acreo AB, Stockholm, Sweden..
    Ozolins, Oskars
    RISE Acreo AB, Stockholm, Sweden..
    Polymer photonics and nano-materials for optical communication2018Inngår i: 2018 17TH WORKSHOP ON INFORMATION OPTICS (WIO), Institute of Electrical and Electronics Engineers (IEEE), 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Polymer materials offer process compatibility, design flexibility, and low cost technology as a multi-functional platform for optical communication and photonics applications. Design and thermal reflowing technology of low loss polymer waveguides, as well as demonstration of transparent wood laser are presented in this paper.

  • 213.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Innventia, Sweden.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mechanical performance and architecture of biocomposite honeycombs and foams from core-shell holocellulose nanofibersManuskript (preprint) (Annet vitenskapelig)
  • 214.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Architecture of ultra-high porous honeycombs prepared from core-shell nanocellulose: Structure and mechanical performance2014Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, s. 160-CELL-Artikkel i tidsskrift (Annet vitenskapelig)
  • 215.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Medina, Lilian
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mechanical performance and architecture of biocomposite honeycombs and foams from core–shell holocellulose nanofibers2016Inngår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 88, s. 116-122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CNFs (cellulose nanofibers) based on holocellulose have a pure cellulose fibril core, with a hemicellulose coating. The diameter is only around 6–8 nm and the hemicellulose surface coating has anionic charge. These CNFs are used to prepare honeycomb and foam structures by freeze-drying from dilute hydrocolloidal suspensions. The materials are compared with materials based on “conventional” cellulose CNFs from sulfite pulp with respect to mechanical properties in compression. Characterization methods include FE-SEM of cellular structure, and the analysis includes comparisons with similar materials from other types of CNFs and data in the literature. The honeycomb structures show superior out-of-plane properties compared with the more isotropic foam structures, as expected. Honeycombs based on holocellulose CNFs showed better properties than sulfite pulp CNF honeycombs, since the cellular structure contained less defects. This is related to better stability of holocellulose CNFs in colloidal suspension.

  • 216.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Galland, Sylvain
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    High-Performance and Moisture-Stable Cellulose-Starch Nanocomposites Based on Bioinspired Core-Shell Nanofibers2015Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, nr 3, s. 904-912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Moisture stability and brittleness are challenges for plant fiber biocomposites intended for load-bearing applications, for instance those based on an amylopectin-rich (AP) starch matrix. Core-shell amylopectin-coated cellulose nanofibers and nanocomposites are prepared to investigate effects from the distribution of AP matrix. The core-shell nanocomposites are compared with nanocomposites with more irregular amylopectin (AP) distribution. Colloidal properties (DLS), AP adsorption, nanofiber dimensions (atomic force microscopy), and nanocomposite structure (transmission electron microscopy) are analyzed. Tensile tests are performed at different moisture contents. The core-shell nanofibers result in exceptionally moisture stable, ductile, and strong nanocomposites, much superior to reference CNF/AP nanocomposites with more irregular AP distribution. The reduction in AP properties is less pronounced as the AP forms a favorable interphase around individual CNF nanofibers.

  • 217.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Kisonen, Victor
    Xu, Chunlin
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Strong effects from galactoglucomannan hemicellulose on mechanical behavior of wet cellulose nanofiber gelsManuskript (preprint) (Annet vitenskapelig)
  • 218.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Kisonen, Victor
    Abo Akad Univ, Lab Wood & Paper Chem, Johan Gadolin Proc Chem Ctr, SF-20500 Turku, Finland..
    Xu, Chunlin
    Abo Akad Univ, Lab Wood & Paper Chem, Johan Gadolin Proc Chem Ctr, SF-20500 Turku, Finland..
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Strong reinforcing effects from galactoglucomannan hemicellulose on mechanical behavior of wet cellulose nanofiber gels2015Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, nr 22, s. 7413-7423Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Softwood hemicelluloses could potentially be combined with cellulose and used in packaging materials. In the present study, galactoglucomannan (GGM) is adsorbed to wood cellulose nanofibers (CNF) and filtered and dried or hot-pressed to form nanocomposite films. The CNF/GGM fibril diameters are characterized by AFM, and the colloidal behavior by dynamic light scattering. Mechanical properties are measured in uniaxial tension for wet gels, dried films, and hot-pressed films. The role of GGM is particularly important for the wet gels. The wet gels of CNF/GGM exhibit remarkable improvement in mechanical properties. FE-SEM fractography and moisture sorption studies are carried out to interpret the results for hygromechanical properties. The present study shows that GGM may find use as a molecular scale cellulose binding agent, causing little sacrifice in mechanical properties and improving wet strength.

  • 219.
    Prakobna, Kasinee
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Terenzi, Camilla
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Centra, Centrum för Industriell NMR-teknik.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Core-shell cellulose nanofibers for biocomposites: Nanostructural effects in hydrated state2015Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 125, s. 92-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Core-shell wood cellulose nanofibers (CNF) coated by an XG hemicellulose polymer are prepared and used to make biocomposites. CNF/XG biocomposites have interest as packaging materials and as hydrated CNF/XG plant cell wall analogues. Structure and properties are compared between Core-shell CNF/XG and more inhomogeneous CNF/XG. Experiments include XG sorption, dynamic light scattering of CNF nanoparticle suspensions, FE-SEM of nanostructure, moisture sorption, tensile testing in moist conditions and dynamic mechanical analysis. (2)H NMR relaxometry is performed on materials containing sorbed (2)H2O2 in order to assess water molecular dynamics in different materials. The results clarify the roles of CNF, XG and the CNF/XG interface in the biocomposites, both in terms of moisture sorption mechanisms and mechanical properties in moist state. The concept of core-shell nanofiber network biocomposites, prepared by filtering of colloids, provides improved control of polymer matrix distribution and interface structure. Also, present mechanical properties are much superior to comparable plant fiber biocomposites.

  • 220. Rueda, L.
    et al.
    Fernandez d'Arlas, B.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Corcuera, M. A.
    Mondragon, I.
    Eceiza, A.
    Isocyanate-rich cellulose nanocrystals and their selective insertion in elastomeric polyurethane2011Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 71, nr 16, s. 1953-1960Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanocrystals (CNC) were successfully obtained and modified with 1,6-hexamethylene diisocyanate (HE)!) by means of in situ polymerization varying the CNC/HDI molar ratio to evaluate the number of anchored chains to the CNC. The modification was examined by elemental analysis, nuclear magnetic resonance ((13)C NMR) and attenuated total reflection Fourier transform infrared spectroscopy (IR-ATR). Nanocomposites containing 1.5 wt% CNC, modified and unmodified, were prepared by solvent casting. Thermal and mechanical properties of the resulting films were evaluated from the viewpoint of polyurethane microphase separated structure, soft and hard domains. CNC were effectively dispersed in the polyurethane matrix and depending on surface chemistry, the nanoreinforcement interacts selectively with matrix nanodomains. This interpretation is supported by differences in thermal and mechanical properties of the nanocomposites and also confirmed by AFM images. Isocyanate rich cellulose nanocrystals interacted with matrix hard phase, promoting physical association with hard segments, enhancing stiffness and dimensional stability versus temperature of the nanocomposite.

  • 221. Rueda, L.
    et al.
    Saralegi, A.
    Fernandez-d'Arlas, B.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Alonso-Varona, A.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mondragon, I.
    Corcuera, M. A.
    Eceiza, A.
    In situ polymerization and characterization of elastomeric polyurethane-cellulose nanocrystal nanocomposites. Cell response evaluation2013Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, nr 4, s. 1819-1828Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyurethane/Cellulose nanocrystal (CNC) nanocomposites have been prepared by means of in situ polymerization using CNCs as precursors of polyurethane chains. Thermal, mechanical and morphological characterization has been analyzed to study the effect of CNC on the micro/nanostructure, which consisted of individualized nanocellulose crystallites covalently bonded to hard and soft segments of polyurethane. The incorporation of low CNC content led to a tough material whereas higher amount of CNC provoked an increase in soft and hard segments crystallization phenomenon. Moreover, from the viewpoint of polyurethane and polyurethane nanocomposites applications focused on biomedical devices, biocompatibility studies can be considered necessary to evaluate the influence of CNC on the biological behaviour. SEM micrographs obtained from cells seeded on top of the materials showed that L-929 fibroblasts massively colonized the materials surface giving rise to good substrates for cell adhesion and proliferation and useful as potential materials for biomedical applications.

  • 222. Rueda, L.
    et al.
    Saralegui, A.
    Fernandez d'Arlas, B.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Corcuera, M. A.
    Mondragon, I.
    Eceiza, A.
    Cellulose nanocrystals/polyurethane nanocomposites. Study from the viewpoint of microphase separated structure2013Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 92, nr 1, s. 751-757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanocrystals (CNC) successfully obtained from microcrystalline cellulose (MCC) were dispersed in a thermoplastic polyurethane as matrix. Nanocomposites containing 1.5.5. 10 and 30 wt% CNC were prepared by solvent casting procedure and properties of the resulting films were evaluated from the viewpoint of polyurethane microphase separated structure, soft and hard domains. CNC were effectively dispersed in the segmented thermoplastic elastomeric polyurethane (STPUE) matrix due to the favorable matrix-nanocrystals interactions through hydrogen bonding. Cellulose nanocrystals interacted with both soft and hard segments, enhancing stiffness and stability versus temperature of the nanocomposites. Thermal and mechanical properties of STPUE/CNC nanocomposites have been associated to the generated morphologies investigated by AFM images.

  • 223.
    Saito, Tsuguyuki
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Kuramae, R.
    Wohlert, Jakob
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Isogai, A.
    An ultrastrong nanofibrillar biomaterial: The strength of single cellulose nanofibrils revealed via sonication-induced fragmentation2013Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, nr 1, s. 248-253Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the mechanical strength of native cellulose nanofibrils. Native cellulose nanofibrils, purified from wood and sea tunicate, were fully dispersed in water via a topochemical modification of cellulose nanofibrils using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. The strength of individual nanofibrils was estimated based on a model for the sonication-induced fragmentation of filamentous nanostructures. The resulting strength parameters were then analyzed based on fracture statistics. The mean strength of the wood cellulose nanofibrils ranged from 1.6 to 3 GPa, depending on the method used to measure the nanofibril width. The highly crystalline, thick tunicate cellulose nanofibrils exhibited higher mean strength of 3-6 GPa. The strength values estimated for the cellulose nanofibrils in the present study are comparable with those of commercially available multiwalled carbon nanotubes.

  • 224.
    Saito, Tsuguyuki
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Kuramae, Ryota
    Wohlert, Jakob
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Isogai, Akira
    Mechanical strength of single cellulose nanofibrils estimated from sonication-induced fragmentation2013Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245Artikkel i tidsskrift (Annet vitenskapelig)
  • 225.
    Salajkova, Michaela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cervin, Nicholas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Schülz, Christina
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Stockholm University.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Bergström, Lennart
    Stockholm University.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Salazar Alvarez, German
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Stockholm University.
    Super-slippery omniphobic self-standing films and coatings based on nanocelluloseManuskript (preprint) (Annet vitenskapelig)
  • 226.
    Salajkova, Michaela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. Brno University of Technology, Czech Republic .
    Sehaqui, Houssine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nanostructured composite materials from microfibrillated cellulose and carbon nanotubes2009Inngår i: ICCM-17 17th International Conference on Composite Materials, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Thin composite films were prepared from the mixture of the aqueous suspension of microfibrillated cellulose (MFC) and multi-walled carbon nanotubes (MWCNTs). The morphology, electrical conductivity, and mechanical properties of the composites were characterized. Good electrical properties were obtained when the MWCNTs content was higher than 2 wt%.

  • 227.
    Salajkova, Michaela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Valentini, Luca
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Tough nanopaper structures based on cellulose nanofibers and carbon nanotubes2013Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 87, s. 103-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon nanotube (CNT) nanocomposites based on CNT in a polymer matrix typically have low strain to failure in tensile loading. Furthermore, mixing of more than a few percent of CNT with either molten thermoplastics or monomers in bulk often results in agglomeration of CNT. Here, multiwalled CNT (MWCNT) are mixed with nanofibrillated cellulose (NFC) in aqueous suspension and filtered into tough nanopaper structures with up to 17 wt% of MWCNT commingled with NFC nanofibrils. Carbon nanotubes were surface treated with a surfactant, and homogenous suspensions of carbon nanotubes in water miscible with the NFC suspension was obtained. NFC/CNT nanopaper structures were characterized for porosity using mercury displacement, and studied by FE-SEM and AFM. Mechanical properties were tested in uniaxial tension and electrical conductivity was measured. The processing route is environmentally friendly and leads to well-mixed structures. Thin coatings as well as thicker films can be prepared, which show a combination of high electrical conductivity, flexibility in bending and high tensile strength.

  • 228.
    Salajková, Michaela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Hydrophobic cellulose nanocrystals modified with quaternary ammonium salts2012Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 37, s. 19798-19805Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An environmentally friendly procedure in aqueous solution for the surface modification of cellulose nanocrystals (CNCs) using quaternary ammonium salts via adsorption is developed as inspired by organomodified layered silicates. CNCs with a high carboxylate content of 1.5 mmol g(-1) were prepared by a new route, direct hydrochloric acid hydrolysis of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose from a softwood pulp, and characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). Four quaternary ammonium cation surfactants bearing long alkyl, phenyl, glycidyl, and diallyl groups were successfully used to modify CNCs carrying carboxylic acid groups as characterized by Fourier transform infrared spectroscopy (FTIR). The modified CNCs can be redispersed and individualized in an organic solvent such as toluene as observed by scanning transmission electron microscopy (STEM). One may envision removing excess surfactant to obtain CNC with a monolayer of surfactant. The toluene suspension of the modified CNCs showed strong birefringence under crossed polars but no further chiral- nematic ordering was observed. The model surface prepared by the CNCs modified with quaternary ammonium salts bearing C18 alkyl chains showed a significant increase in water contact angle (71 degrees) compared to that of unmodified CNCs (12 degrees). This new series of modified CNCs can be dried from solvent and have the potential to form well-dispersed nanocomposites with non-polar polymers.

  • 229.
    Salajková, Michaela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Valentini, Luca
    Zhou, Qi
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Tough and conductive nanopaper structures, based on cellulose nonofibrils an carbon nanotubes, prepared by processing of aqueous suspensionsManuskript (preprint) (Annet vitenskapelig)
  • 230. Schauer, E.
    et al.
    Berglund, Lars A.
    Pena, G.
    Marieta, C.
    Mondragon, I.
    Morphological variations in PMMA-modified epoxy mixtures by PEO addition2002Inngår i: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, nr 4, s. 1241-1248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermoplastic epoxy blends are successfully used commercially. The thermoplastic may serve as a toughening agent although other properties may also be improved. In the present study, microscopy and mechanical testing techniques were used to study morphology and ultimate properties of ternary epoxy/Poly(methyl methacrylate) (PMMA)-Poly(ethylene oxide) (PEO) blends. PEO is functioning like a compatibilizer by which the morphology of the resulting polymer mixture may be changed dramatically by only small amounts of PEO. Whilst stiffness was controled by the corresponding matrix of the ternary mixture, both strength and fracture toughness were a function of the defined morphology. However, the most efficient toughening agent was PMMA, in particular when present as a co-continuous PMMA-rich phase within the epoxy-rich matrix.

  • 231.
    Schütz, Christina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Sort, Jordi
    Bacsik, Zoltan
    Oliynyk, Vitaliy
    Pellicer, Eva
    Fall, Andreas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Bergström, Lennart
    Salazar-Alvarez, German
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Hard and Transparent Films Formed by Nanocellulose-TiO2 Nanoparticle Hybrids2012Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, nr 10, s. e45828-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of hybrids of nanofibrillated cellulose and titania nanoparticles in aqueous media has been studied. Their transparency and mechanical behavior have been assessed by spectrophotometry and nanoindentation. The results show that limiting the titania nanoparticle concentration below 16 vol% yields homogeneous hybrids with a very high Young's modulus and hardness, of up to 44 GPa and 3.4 GPa, respectively, and an optical transmittance above 80%. Electron microscopy shows that higher nanoparticle contents result in agglomeration and an inhomogeneous hybrid nanostructure with a concomitant reduction of hardness and optical transmittance. Infrared spectroscopy suggests that the nanostructure of the hybrids is controlled by electrostatic adsorption of the titania nanoparticles on the negatively charged nanocellulose surfaces.

  • 232.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Allais, Mael
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wood cellulose biocomposites with fibrous structures at micro- and nanoscale2011Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 71, nr 3, s. 382-387Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-strength composites from wood fiber and nanofibrillated cellulose (NFC) were prepared in a semiautomatic sheet former. The composites were characterized by tensile tests, dynamic mechanical thermal analysis, field-emission scanning electron microscopy, and porosity measurements. The tensile strength increased from 98 MPa to 160 MPa and the work to fracture was more than doubled with the addition of 10% NFC to wood fibers. A hierarchical structure was obtained in the composites in the form of a micro-scale wood fiber network and an additional NFC nanofiber network linking wood fibers and also occupying some of the micro-scale porosity. Deformation mechanisms are discussed as well as possible applications of this biocomposites concept. (C) 2010 Published by Elsevier Ltd.

  • 233.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Kochumalayil, Joby
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Liu, Andong
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Zimmermann, Tanja
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Multifunctional Nanoclay Hybrids of High Toughness, Thermal, and Barrier Performances2013Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 15, s. 7613-7620Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To address brittleness of nanoclay hybrids of high inorganic content, ductile polymers (polyethylene oxide and hydroxyethyl cellulose) and montmorillonite (MTM) have been assembled into hybrid films using a water-based filtration process. Nacre-mimetic layered films resulted and were characterized by FE-SEM and XRD. Mechanical properties at ambient condition were studied by tensile test, while performance at elevated temperature and moisture conditions were evaluated by TGA, dynamic vapor sorption, and dynamic thermomechanical and hygromechanical analyses. Antiflammability and barrier properties against oxygen and water vapor were also investigated. Despite their high MTM content in the 60-85 wt % range, the hybrids exhibit remarkable ductility and a storage modulus above 2 GPa even in severe conditions (300 degrees C or 94% RH). Moreover, they present fire-shielding property and are amongst the best oxygen and water vapor barrier hybrids reported in the literature. This study thus demonstrates nanostructure property advantages for synergistic effects in hybrids combining inexpensive, available, and environmentally benign constituents.

  • 234.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Liu, Andong
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Fast Preparation Procedure for Large, Flat Cellulose and Cellulose/Inorganic Nanopaper Structures2010Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, nr 9, s. 2195-2198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanostructured materials are difficult to prepare rapidly and as large structures. The present study is thus significant because a rapid preparation procedure for large, flat, smooth, and optically transparent cellulose nanopaper structures is developed using a semiautomatic sheet former. Cellulose/inorganic hybrid nanopaper is also produced. The preparation procedure is compared with other approaches, and the nanopaper structures are tested in uniaxial tensile tests. Optical transparency and high tensile strength are demonstrated in 200 mm diameter nanopaper sheets, indicating well-dispersed nanofibrils. The preparation time is 1 h for a typical nanopaper thickness of 60 pm. In addition, the application of the nanopaper-making strategy to cellulose/inorganic hybrids demonstrates the potential for "green" processing of new types of nanostructured functional materials.

  • 235.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Morimune, Seira
    Nishino, Takashi
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Stretchable and Strong Cellulose Nanopaper Structures Based on Polymer-Coated Nanofiber Networks: An Alternative to Nonwoven Porous Membranes from Electrospinning2012Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, nr 11, s. 3661-3667Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nonwoven membranes based on electrospun, fibers are of great interest in applications such as biomedical, filtering, and protective clothing.. The poor, mechanical performance is a limitation, as is some of the electrospinning Solvents. To address these problems, porous nonwoven membranes based on nanofibrillated cellulose (NFC) modified by a hydroxyethyl cellulose (HEC) polymer coating. are prepared. NFC/HEC aqueous suspensions are subjected to simple vacuum filtration: in a Paper-making fashion,, followed by supercritical CO2. drying., These nonwoven nanocomposite membranes are truly nanostructured and exhibit a nanoporous, network structure with high specific surface area, as analyzed by nitrogen adsorption and FE-SEM. Mechanical properties by tensile tests show high strength combined with remarkable high strain to failure up to 55%. XRD analysis revealed significant fibril realignment during tensile stretching. After postdrawing of the random mats, the modulus and strength are strongly increased. The present preparation route uses components from renewable resources, is environmentally friendly, and results in permeable membranes of exceptional imechanical performance.

  • 236.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Mushi, Ngesa Ezekiel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Morimune, Seira
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Nishino, Takashi
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cellulose Nanofiber Orientation in Nanopaper and Nanocomposites by Cold Drawing2012Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, nr 2, s. 1043-1049Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To exploit the mechanical potential of native cellulose fibrils, we report on the preparation of nanopaper with preferred orientation of nanofibrillated cellulose (TEMPO-NFC) by cold drawing. The preparation route is papermaking-like and includes vacuum filtering of a TEMPO-oxidated NFC water dispersion, drawing in wet state and drying. The orientation of the fibrils in the nanopaper was assessed by AFM and wide-angle Xray diffraction analysis, and the effect on mechanical properties of the resulting nanopaper structure was investigated by tensile tests. At high. draw ratio, the degree of orientation is as high as 82 and 89% in and cross-sectional planes of the nanopaper, respectively, and the Young's modulus is 33 GPa. This is much higher than mechanical properties of isotropic nanopaper. The cold drawing method can be also applied to NFC nanocomposites as demonstrated, by preparation of TEMPO-NFC/hydroxyethyl cellulose (HEC) nanocomposites. The introduction of the soft HEC matrix allows further tailoring of the mechanical properties.

  • 237.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. Brno University of Technology, Czech Republic .
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Biomimetic aerogels from microfibrillated cellulose and xyloglucan2009Inngår i: ICCM-17 17th International Conference on Composite Materials, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cellulose aerogels with density of 7-100 kg/m3 were prepared by freeze drying from microfibrillated cellulose water suspensions, and biomimetic aerogels were prepared with the addition of xyloglucan. Their microstructures and physical properties were characterized by scanning electron microscopy, nitrogen adsorption measurements, and tensile tests.

  • 238.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mechanical performance tailoring of tough ultra-high porosity foams prepared from cellulose I nanofiber suspensions2010Inngår i: Soft Matter, ISSN 1744-683X, Vol. 6, nr 8, s. 1824-1832Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-density structures of mechanical function in plants, arthropods and other organisms, are often based on high- strength cellulose or chitin nanofibers and show an interesting combination of flexibility and toughness. Here, a series of plant-inspired tough and mechanically very robust cellular biopolymer foams with porosities as high as 99.5% (porosity range 93.1-99.5%) were therefore prepared by solvent-free freeze-drying from cellulose I wood nanofiber water suspensions. A wide range of mechanical properties was obtained by controlling density and nanofiber interaction in the foams, and density property relationships were modeled and compared with those for inorganic aerogels. Inspired by cellulose-xyloglucan (XG) interaction in plant cell walls, XG was added during preparation of the toughest foams. For the cellulose-XG nanocomposite foams in particular, the mechanical properties at comparable densities were superior to those reported in the literature for clay aerogel/cellulose whisker nanocomposites, epoxy/clay aerogels, polymer/clay/nanotube aerogels, and polymer/silica aerogels. The foam structure was characterized by high-resolution field-emission scanning electron microscopy and the specific surface area was measured by nitrogen physisorption. Dynamic mechanical thermal analysis and uniaxial compression tests were performed. The foam was thermally stable up to 275 degrees C where cellulose started to degrade.

  • 239.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    High-porosity aerogels of high specific surface area prepared from nanofibrillated cellulose (NFC)2011Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 71, nr 13, s. 1593-1599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-density aerogels based on nanofibrillated cellulose (NFC) from wood pulp were prepared from NFC aqueous dispersions using solvent exchange from water to tert-butanol followed by tert-butanol freeze-drying. In the present study, the dispersion of NFC nanofibers in the hydrocolloid was very well preserved in the aerogels. The "effective" diameter of the NFC nanofibers in the aerogels is around 10-18 nm corresponding to specific surface areas as high as 153-284 m(2) g(-1). Aerogels based on different NFC nanofibers were studied by FE-SEM, BET analysis (nitrogen gas adsorption), and mechanical properties were measured in compression for different densities of aerogels. The properties are compared with polymer foams and inorganic aerogels. Compared with cellular NFC foams, the present nanofibrous aerogels have lower modulus and show lower stress in compression for a given strain. Tert-butanol freeze-drying can therefore be used to create "soft" aerogels.

  • 240.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nanofibrillated cellulose for enhancement of strength in high-density paper structures2013Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, nr 2, s. 182-189Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to enhance dry and wet strength properties of paper, handsheets were made of wood pulp fibers and nanofibrillated cellulose (NFC). 10% NFC was mixed with wood pulp fibers (90%) subjected to different number of beating revolutions. Effects from xyloglucan (XG) hemicellulose addition were also studied. High density paper handsheets from these mixtures were prepared using a laboratory handsheet former. Strength properties were measured and densities of the materials estimated. Scanning electron microscopy was used to observe paper sheet surfaces. NFC significantly enhances strength for the paper handsheets both at 50% relative humidity and in the wet state so that NFC addition may be an alternative to mechanical beating. The main reason for property improvements is increased density of the final material. Tensile energy absorption improved strongly through favorable fiber-fiber interaction. NFC or NFC/XG addition combined with some mechanical beating may decrease energy needs compared with beating only.

  • 241.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Nanostructured biocomposites of high toughness-a wood cellulose nanofiber network in ductile hydroxyethylcellulose matrix2011Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 16, s. 7342-7350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanopaper from wood-based nanofibrillated cellulose (NFC) offers vastly improved strength and strain-to-failure compared with plant fiber-based paper and plant fiber biocomposites. In the present study, unique nanostructural toughening effects are reported in cellulose nanofiber/hydroxyethylcellulose (HEC) biocomposites. HEC is an amorphous cellulose derivative of high molar mass and toughness. A previously developed preparation route inspired by paper-making is used. It is "green", scalable, and allows high reinforcement content. In the present concept, nanostructural control of polymer matrix distribution is exercised as the polymer associates with the reinforcement. This results in nanocomposites of a soft HEC matrix surrounding nanofibrillated cellulose forming a laminated structure at the submicron scale, as observed by FE-SEM. We study the effect of NFC volume fraction on tensile properties, thermomechanical stability, creep properties and moisture sorption of the nanocomposites. The results show strong property improvements with NFC content due to the load-carrying ability of the NFC network. At an NFC volume fraction of 45%, the toughness was more than doubled compared with cellulose nanopaper. The present nanocomposite is located in previously unoccupied space in a strength versus strain-to-failure property chart, outside the regions occupied by microscale composites and engineering polymers. The results emphasize the potential for extended composites mechanical property range offered by nanostructured biocomposites based on high volume fraction nanofiber networks.

  • 242.
    Sehaqui, Houssine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för bioteknologi (BIO), Glykovetenskap.
    Ikkala, Olli
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Strong and Tough Cellulose Nanopaper with High Specific Surface Area and Porosity2011Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, nr 10, s. 3638-3644Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to better understand nanostructured fiber networks, effects from high specific surface area of nanofibers are important to explore. For cellulose networks, this has so far only been achieved in nonfibrous regenerated cellulose aerogels. Here, nanofibrillated cellulose (NFC) is used to prepare high surface area nanopaper structures, and the mechanical properties are measured in tensile tests. The water in NFC hydrogels is exchanged to liquid CO(2), supercritical CO(2), and tert-butanol, followed by evaporation, supercritical drying, and sublimation, respectively. The porosity range is 40-86%. The nanofiber network structure in nanopaper is characterized by FE-SEM and nitrogen adsorption, and specific surface area is determined. High-porosity TEMPO-oxidized NFC nanopaper (56% porosity) prepared by critical point drying has a specific surface area as high as 48(2) m(2) g(-1). The mechanical properties of this nanopaper structure are better than for many thermoplastics, but at a significantly lower density of only 640 kg m(-3). The modulus is 1.4 GPa, tensile strength 84 MPa, and strain-to-failure 17%. Compared with water-dried nanopaper, the material is softer with substantially different deformation behavior.

  • 243. Shams, Md Iftekhar
    et al.
    Nogi, Masaya
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Yano, Hiroyuki
    The transparent crab: preparation and nanostructural implications for bioinspired optically transparent nanocomposites2012Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, nr 5, s. 1369-1373Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An optically transparent crab-shell with an intact original shape and substantial morphological detail is presented. Inorganic calcium carbonate particles, proteins, lipids and pigments are removed from a native crab-shell, and the remaining chitin nanofibrous structure is impregnated by a monomer and polymerized. The nanostructural implications for man-made nanocomposites are discussed. An important application of the finding is demonstrated as heterogeneous micro-scale crab shell chitin particles are successfully used to process transparent nanocomposites. The incorporation of nanostructured chitin macro-particles not only retains transparency of the matrix resin but also drastically reduces the coefficient of thermal expansion of the polymer. Moreover, the optical transmittance of the composite is stable over a large range of temperatures despite significant inhomogeneity at the mm scale and the large temperature changes in the refractive index of the resin in its isolated state. This class of materials is an interesting candidate for transparent substrates in next-generation electronic devices such as flexible displays and solar cells.

  • 244. Shipsha, Andrey
    et al.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Shear coupling effects on stress and strain distributions in wood subjected to transverse compression2007Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 67, nr 08-jul, s. 1362-1369Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanical behaviour of a wood board subjected to transverse compression is relevant to the performance of glulam beams and solid wood structures. The wood material can be described as polar orthotropic, due to the annual ring structure and to the differences in moduli in different directions in the radial-tangential plane. Strain measurements are performed on single wood boards using a whole-field digital speckle photography technique. Finite element analysis is performed and compared with experimental data. Good agreement in terms of strain fields and apparent moduli is observed between predictions and data. The experimental data show strong variations in local strain due to the polar orthotropic behaviour of wood in this plane, and the extremely low value for shear modulus G(rt) as compared with the other moduli. This leads to shear coupling effects resulting in large local shear deformation and correspondingly low effective stiffness under transverse global loading.

  • 245. Sjögren, B. A.
    et al.
    Berglund, Lars A.
    The effects of matrix and interface on damage in CRP cross-ply laminates2000Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 60, nr 1, s. 9-21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study has been made of the transverse cracking behavior of a series of cross-ply laminates with different matrices, fiber coatings (sizes) and fiber volume fractions. On the basis of unpublished results, a correlation was assumed between material effects on leakage pressure in pressure vessels of given stacking sequence and transverse cracking behavior in cross-ply laminates. Mechanisms for crack initiation and growth were studied by optical microscopy. The strain ai the onset of transverse cracking, epsilon(TOS), increased and the slope, K. of the curve of crack density as a function of strain decreased as the G(IC) of the matrix increased. Improved fiber/matrix adhesion and lower fiber content had similar effects. The properties of polyester-based composites were usually inferior to those of vinylester composites as a consequence of pre-existing debonds and subcritical cracks resulting from microlevel curing stresses. From observations of failure mechanisms one may infer that proof testing of pipes or pressure vessels will increase the extent of subcritical damage in the material.

  • 246. Soeta, Hiroto
    et al.
    Fujisawa, Shuji
    Saito, Tsuguyuki
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer.
    Isogai, Akira
    Low-Birefringent and Highly Tough Nanocellulose-Reinforced Cellulose Triacetate2015Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, nr 20, s. 11041-11046Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Improvement of the mechanical and thermal properties of cellulose triacetate (CTA) films is required without sacrificing their optical properties. Here, poly(ethylene glycol) (PEG)-grafted cellulose nanofibril/CTA nanocomposite films were fabricated by casting and drying methods. The cellulose nanofibrils were prepared by 2,2,6,6-tetramethylpiperidine-l-oxyl,(TEMPO)-mediated oxidation, and amine-terminated PEG chains were grafted onto the surfaces of the TEMPO-oxidized cellulose nanofibrils (TOCNs) by ionic bonds. Because of the nanosize effect of TOCNs with a uniform width of similar to 3 nm, the PEG-TOCN/CTA nanocomposite films had high transparency and low bitefringence. The grafted PEG chains enhanced the filler-matrix interactions and crystallization of matrix CTA molecules, resulting in the Young's modulus and toughness of CTA film being significantly improved by PEG-grafted TOCN addition. The coefficient of thermal expansion of the original CTA film was mostly preserved even with the addition of PEG-grafted TOCNs. These results suggest that PEG-TOCNs are applicable to the reinforcement for transparent optical films.

  • 247.
    Soeta, Hiroto
    et al.
    Univ Tokyo, Dept Biomat Sci, Grad Sch Agr & Life Sci, Tokyo 1138657, Japan..
    Lo Re, Giada
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Masuda, Akihiro
    Toray Res Ctr Ltd, Morphol Res Labs, Morphol Res Lab 3, Otsu, Shiga 5208567, Japan..
    Fujisawa, Shuji
    Univ Tokyo, Dept Biomat Sci, Grad Sch Agr & Life Sci, Tokyo 1138657, Japan..
    Saito, Tsuguyuki
    Univ Tokyo, Dept Biomat Sci, Grad Sch Agr & Life Sci, Tokyo 1138657, Japan..
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Isogai, Akira
    Univ Tokyo, Dept Biomat Sci, Grad Sch Agr & Life Sci, Tokyo 1138657, Japan..
    Tailoring Nanocellulose-Cellulose Triacetate Interfaces by Varying the Surface Grafting Density of Poly(ethylene glycol)2018Inngår i: ACS OMEGA, ISSN 2470-1343, Vol. 3, nr 9, s. 11883-11889Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Careful design of the structures of interfaces between nanofillers and polymer matrices can significantly improve the mechanical and'thermal' properties of the overall nanocomposites. Here, we investigate]how the grafting density on the surface of nanocelluloses influences the properties of nanocellulose/cellulose triacetate (CTA) composites. 2,2,6,6 The surface of nanocellulose, which was preparedby tetramethylpiperidine-l-oxyl oxidation, was modified with long poly(ethylene glycol) (PEG) chains at different grafting_ densities. The PEG -grafted nanocelluloses were h omogene ously embedded in CTA matrices. The mechanical and thermal properties of the nanocomposites were characterized. Increasing the grafting density caused the soft PEG chains to form denser and thicker layers around the rigid nanocelluloses. The PEG layers were not completely miscible with the CTA matrix. This structure consfderably enhanced the energy dissipation by allowing sliding at the interface, which increased the toughness of the nanocomposites. The thermal and mechanical properties of the composites could be tailored by controlling the grafting density. These findings provide a deeper understanding about interfacial design for nanocellulose-based composite materials.

  • 248.
    Soeta, Hiroto
    et al.
    Univ Tokyo, Tokyo, Japan..
    Saito, Tsuguyuki
    Univ Tokyo, Dept Biomat Sci, Tokyo, Japan..
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Isogati, Akira
    Univ Tokyo, Tokyo, Japan..
    Grafting density design of surface-modified nanocellulose for polymer composites2018Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Artikkel i tidsskrift (Annet vitenskapelig)
  • 249. Stepan, Agnes M.
    et al.
    Ansari, Farhan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Gatenholm, Paul
    Nanofibrillated cellulose reinforced acetylated arabinoxylan films2014Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 98, s. 72-78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, acetylated rye arabinoxylan (AcAX) films were reinforced with nanofibrillated cellulose from spruce (NFC) ranging from I to 10 wt% of the total composition. Free-standing composite films were casted without the use of any plasticizers. The homogeneous dispersion of NFC in the films was confirmed with scanning electron microscopy. The ultimate strength and the Young's modulus determined by tensile tests increased from 65 MPa and 2190 MPa for neat AcAX films to 93 MPa and 3360 MPa for the 10% composite films, respectively. The elongation to break of the 10% NFC composite film was a remarkable 10.5%. The moisture absorbed was still less than 8 wt% for the films with 10% NFC content at 97% relative humidity at room temperature, which is low for hemicellulose-based films. The addition of NFC decreased the water permeability of the films at low NFC contents, which was studied in diffusion cells using radioactive labeled water. Thus NFC can be used in an unmodified form as reinforcement in AcAX films to prepare films or coatings that are more water and humidity resistant than neat hemicellulose-based films.

  • 250.
    Stevanic, Jasna S.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Bergström, Elina Mabasa
    Gatenholm, Paul
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Salmén, Lennart
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Arabinoxylan/nanofibrillated cellulose composite films2012Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, nr 18, s. 6724-6732Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is an increasing interest in substituting petroleum based polymer films, for food packaging applications, with films based on renewable resources. In many of these applications, low oxygen permeability and low moisture uptake of films are required, as well as high enough strength and flexibility. For this purpose, rye arabinoxylan films reinforced with nanofibrillated cellulose was prepared and evaluated. A thorough mixing of the components resulted in uniform films. Mechanical, thermal, structural, moisture sorption and oxygen barrier characteristics of such films are reported here. Reinforcement of arabinoxylan with nanofibrillated cellulose affected the properties of the films positively. A decrease in moisture sorption of the films, as well as an increase in stiffness, strength and flexibility of the films were shown. From these results and dynamic FTIR spectra, a strong coupling between reinforcing cellulose and arabinoxylan matrix was concluded. Oxygen barrier properties were equal or better as compared to the neat rye arabinoxylan film. In general, the high nanofibrillated cellulose containing composite film, i.e. 75 % NFC, showed the best properties.

23456 201 - 250 of 294
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