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  • 1.
    Arnling Bååth, Jenny
    et al.
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Giummarella, Nicola
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Klaubauf, Sylvia
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Olsson, Lisbeth
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    A glucuronoyl esterase from Acremonium alcalophilum cleaves native lignin-carbohydrate ester bonds2016In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 590, no 16, p. 2611-2618Article in journal (Refereed)
    Abstract [en]

    The Glucuronoyl esterases (GE) have been proposed to target lignin-carbohydrate (LC) ester bonds between lignin moieties and glucuronic acid side groups of xylan, but to date, no direct observations of enzymatic cleavage on native LC ester bonds have been demonstrated. In the present investigation, LCC fractions from spruce and birch were treated with a recombinantly produced GE originating from Acremonium alcalophilum (AaGE1). A combination of size exclusion chromatography and 31P NMR analyses of phosphitylated LCC samples, before and after AaGE1 treatment provided the first evidence for cleavage of the LC ester linkages existing in wood.

  • 2.
    Berglund, Jennie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Angles d’Ortoli, Thibault
    Vilaplana, Francisco
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Widmalm, Göran
    Bergenstråhle-Wohlert, Malin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    A molecular dynamics study of the effect of glycosidiclinkage type in the hemicellulose backbone on the molecularchain flexibility2016In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313XArticle in journal (Refereed)
    Abstract [en]

    The macromolecular conformation of the constituent polysaccharides in lignocellulosic biomass influences their supramolecular interactions, and therefore their function in plants and their performance in technical products. The flexibility of glycosidic linkages from the backbone of hemicelluloses was studied by evaluating the conformational freedom of the φ and ψ dihedral angles using molecular dynamic simulations, additionally selected molecules were correlated with experimental data by nuclear magnetic resonance spectroscopy. Three types of β-(1→4) glycosidic linkages involving the monosaccharides (Glcp, Xylp and Manp) present in the backbone of hemicelluloses were defined. Different di- and tetrasaccharides with combinations of such sugar monomers from hemicelluloses were simulated, and free energy maps of the φ – ψ space and hydrogen-bonding patterns were obtained. The glycosidic linkage between Glc-Glc or Glc-Man (C-type) was the stiffest with mainly one probable conformation; the linkage from Man-Man or Man-Glc (M-type) was similar but with an increased probability for an alternative conformation making it more flexible, and the linkage between two Xyl-units (X-type) was the most flexible with two almost equally populated conformations. Glycosidic linkages of the same type showed essentially the same conformational space in both disaccharides and in the central region of tetrasaccharides. Different probabilities of glycosidic linkage conformations in the backbone of hemicelluloses can be directly estimated from the free energy maps, which to a large degree affect the overall macromolecular conformations of these polymers. The information gained contributes to an increased understanding of the function of hemicelluloses both in the cell wall and in technical products.

  • 3.
    Berglund, Jennie
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Azhar, Shoaib
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Vilaplana, Francisco
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    The structure of galactoglucomannan impactsthe degradation under alkaline conditions2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed)
    Abstract [en]

    Galactoglucomannan (GGM) from sprucewas studied with respect to the degradation behavior inalkaline solution. Three reference systems includinggalactomannan from locust bean gum, glucomannanfrom konjac and the linear water-soluble carboxymethylcellulose were studied with focus onmolecular weight, sugar composition, degradationproducts, as well as formed oligomers, to identifyrelative structural changes in GGM. Initially allmannan polysaccharides showed a fast decrease inthe molecular weight, which became stable in the laterstage. The degradation of the mannan polysaccharidescould be described by a function corresponding to thesum of two first order reactions; one slow that wasascribed to peeling, and one fast that was connectedwith hydrolysis. The galactose side group wasstable under conditions used in this study (150 min,90 C, 0.5 M NaOH). This could suggest that, apartfrom the covalent connection to C6 in mannose, thegalactose substitutions also interact non-covalentlywith the backbone to stabilize the structure againstdegradation. Additionally, the combination of differentbackbone sugars seems to affect the stability of thepolysaccharides. For carboxymethyl cellulose thedegradation was linear over time which furthersuggests that the structure and sugar composition playan important role for the alkaline degradation. Moleculardynamics simulations gave details about theconformational behavior of GGM oligomers in watersolution, as well as interaction between the oligomersand hydroxide ions.

  • 4.
    Bi, Ran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Jennie
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Vilaplana, Francisco
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    McKee, Lauren S.
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    The degree of acetylation affects the microbial degradability of mannans2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 133, p. 36-46Article in journal (Refereed)
    Abstract [en]

    Hemicelluloses as major components of plant cell walls are acetylated to different extents. The biologicalfunctions of acetylation are not completely understood but suggested that one reason is to decrease themicrobial degradability of cell walls. Model seed galactomannan and glucomannan, which are structurallysimilar to an abundant class of wood hemicelluloses, were acetylated to various degrees and usedas sole carbon source on agar plates for microbial growth. When soil samples were inoculated on theplates, significantly fewer strains grew on the agar plates with highly acetylated mannans than withslightly acetylated or non-acetylated mannans. One filamentous fungus isolated and identified as aPenicillium species was shown to grow faster and stronger on non-acetylated than on highly acetylatedmannan. The data therefore support the hypothesis that a high degree of acetylation (DSac) can decreasethe microbial degradability of hemicelluloses. Possible mechanisms and the technological significance ofthis are discussed.

  • 5.
    Bjurhager, Ingela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mechanical behaviour of hardwoods: effects from cellular and cell wall structures2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The aim of this work was to investigate the mechanical properties of different hardwood species and relate the properties to the structure at the cellular and cell wall level. The species examined were European aspen (Populus tremula), hybrid aspen (Populus tremula x Populus tremuloides) and European oak (Quercus robur). The Populus species, including the fast-growing hybrid aspen, are used in a large number of projects using transgene technology, which also has raised the demand for a more extensive determination of mechanical properties of the species. Oak have been a popular construction material for thousands of years, esulting in a vast number of archaeological findings. Preservation of these often includes dimensional stabilization by polyethylene glycol (PEG), an impregnation agent which affects the mechanical properties. To which extent is not properly investigated, however. The study on European and hybrid aspen included development of a method for tensile testing of small, juvenile specimens in the green condition, where strain was measured using the digital speckle photography (DSP) technique. Mechanical performance of the species in terms of longitudinal tensile stiffness and strength were of special interest. Inferior mechanical properties of hybrid aspen corresponded well to mean values of density, which were lower for the hybrid aspen compared to European aspen.

    Oak was examined in the swollen state, where swelling was induced by PEG with molecular weight 600. Longitudinal tensile stiffness and strength as well as radial stiffness and yield strength in compression were compared. Longitudinal and radial strain was measured using video extensiometry and DSP, respectively. Additional characterization of the material included imaging from scanning electron microscopy (SEM), X-ray microtomography and determination of microfibril angle using wide angle X-ray scattering (WAXS). Tensile stiffness and strength in the axial direction were only slightly affected by PEG-impregnation. WAXS measurements showed that microfibril angles were close to zero which implicates that cell wall properties are strongly dependent on the microfibrils, and only marginally influenced by the plasticization effects from PEG on the lignin/hemicellulose matrix. In the radial direction, on the other hand, mechanical performance was strongly decreased by PEG-impregnation. This was believed to originate from softening of rays.

  • 6.
    Bjurhager, Ingela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bardage, Stig
    Sundberg, Björn
    Mechanical characterization of juvenile European aspen (Populus tremula) and hybrid aspen (Populus tremula × Populus tremuloides) using full-field strain measurements2008In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 54, no 5, p. 349-355Article in journal (Refereed)
    Abstract [en]

    Functional analysis of genes and proteins involved in wood formation and fiber properties often involves phenotyping saplings of transgenic trees. The objective of the present study was to develop a tensile test method for small green samples from saplings, and to compare mechanical properties of juvenile European aspen (Populus tremula) and hybrid aspen (Populus tremula × tremuloides). Small microtomed sections were manufactured and successfully tested in tension parallel to fiber orientation. Strain was determined by digital speckle photography. Results showed significantly lower values for juvenile hybrid aspen in both Young's modulus and tensile strength parallel to the grain. Average Young's moduli spanned the ranges of 5.9-6.6 and 4.8-6.0 GPa for European aspen and hybrid aspen, respectively. Tensile strength was in the range of 45-49 MPa for European aspen and 32-45 MPa for hybrid aspen. The average density (oven-dry) was 284 kg/m3 for European aspen and 221 kg/m3 for hybrid aspen. Differences in mechanical properties correlated with differences in density.

  • 7.
    Bjurhager, Ingela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Halonen, Helena
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindfors, E. -L
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Almkvist, G.
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    State of degradation in archeological oak from the 17th century vasa ship: Substantial strength loss correlates with reduction in (holo)cellulose molecular weight2012In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, no 8, p. 2521-2527Article in journal (Refereed)
    Abstract [en]

    In 1628, the Swedish warship Vasa capsized on her maiden voyage and sank in the Stockholm harbor. The ship was recovered in 1961 and, after polyethylene glycol (PEG) impregnation, it was displayed in the Vasa museum. Chemical investigations of the Vasa were undertaken in 2000, and extensive holocellulose degradation was reported at numerous locations in the hull. We have now studied the longitudinal tensile strength of Vasa oak as a function of distance from the surface. The PEG-content, wood density, and cellulose microfibril angle were determined. The molar mass distribution of holocellulose was determined as well as the acid and iron content. A good correlation was found between the tensile strength of the Vasa oak and the average molecular weight of the holocellulose, where the load-bearing cellulose microfibril is the critical constituent. The mean tensile strength is reduced by approximately 40%, and the most affected areas show a reduction of up to 80%. A methodology is developed where variations in density, cellulose microfibril angle, and PEG content are taken into account, so that cell wall effects can be evaluated in wood samples with different rate of impregnation and morphologies.

  • 8.
    Bjurhager, Ingela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ljungdahl, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wallström, Lennart
    Division of Polymer Engineering, Luleå University of Technology (LTU).
    Gamstedt, E. Kristofer
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Effects of polyethylene glycol treatment on the mechanical properties of oakManuscript (Other academic)
  • 9.
    Brodin, Ida
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gellerstedt, Göran L. F.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Sjöholm, E.
    Membrane separated Kraft lignin as feedstock for chemical products2008In: 2008 Nordic Wood Biorefinery Conference, NWBC 2008 - Proceedings, 2008, p. 194-Conference paper (Refereed)
  • 10.
    Dedic, Dina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sandberg, Teresia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Tomas
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Analysis of lignin and extractives in the oak wood of the 17th century warship Vasa2014In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 4, p. 419-425Article in journal (Refereed)
    Abstract [en]

    The wood in the 17th century Swedish warship Vasa is weak. A depolymerization of the wood's cellulose has been linked to the weakening, but the chemical mechanisms are yet unclear. The objective of this study was to analyze the lignin and tannin moieties of the wood to clarify whether the depolymerization of cellulose via ongoing oxidative mechanisms is indeed the main reason for weakening the wood in the Vasa. Lignin was analyzed by solid-state nuclear magnetic resonance [cross-polarization/magic-angle spinning (CP/MAS) C-13 NMR] and by means of wet chemical degradation (thioacidolysis) followed by gas chromatography-mass spectrometry (GC-MS) of the products. No differences could be observed between the Vasa samples and the reference samples that could have been ascribed to extensive lignin degradation. Wood extracts (tannins) were analyzed by matrix- assisted laser desorption ionization (MALDI) combined with time-of-flight (TOF) MS and C-13 NMR spectroscopy. The wood of the Vasa contained no discernible amounts of tannins, whereas still-waterlogged Vasa wood contained ellagic acid and traces of castalagin/vescalagin and grandinin. The results indicate that the condition of lignin in the Vasa wood is similar to fresh oak and that potentially harmful tannins are not present in high amounts. Thus, oxidative degradation mechanisms are not supported as a primary route to cellulose depolymerization.

  • 11.
    Deshpande, Raghu
    et al.
    MoRe Research, SE-89122 Örnsköldsvik, Sweden.
    Giummarella, Nicola
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. Wallenberg Wood Science Center.
    Germgård, Ulf
    Karlstad University, SE-65188 Karlstad, Sweden.
    Sundvall, Lars
    MoRe Research, SE-89122 Örnsköldsvik, Sweden.
    Grundberg, Hans
    Domsjö Fabriker, SE-89186 Örnsköldsvik, Sweden.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The reactivity of lignin carbohydrate complex (LCC) during manufacture of dissolving sulfite pulp from softwood2018In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 115, p. 315-322Article in journal (Refereed)
    Abstract [en]

    The presence of covalent bonds between lignin and polysaccharides was investigated in dissolving pulps made with one-stage and two-stage acidic sulfite pulping for 100% pine heartwood raw material. The covalent bonds between lignin and pulp polysaccharides occurred mainly to xylan and glucomannan and were of the phenyl glycosides and γ–esters types. The α-ethers that are common in wood were missing in the studied pulp samples. Based on these findings and known lignin reactions during sulfite pulping, a mechanism explaining the absence of the α-ethers is discussed. It is suggested that the lignin carbohydrate bonds may play a vital role in lignin recalcitrance.

  • 12.
    Englund, Finn
    et al.
    SP Technical Research Institute of Sweden, Wood Technology.
    Hill, Callum A.S.Militz, HolgerSegerholm, B. KristofferKTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Proceedings of the Fourth European Conference on Wood Modifications2009Conference proceedings (editor) (Refereed)
  • 13. Escalante, Alfredo
    et al.
    Goncalves, Ana
    Bodin, Aase
    Stepan, Agnes
    Sandstrom, Corine
    Toriz, Guillermo
    Gatenholm, Paul
    Wallenberg Wood Sci Ctr, Chalmers, Sweden.
    Flexible oxygen barrier films from spruce xylan2012In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 87, no 4, p. 2381-2387Article in journal (Refereed)
    Abstract [en]

    Arabinoglucuronoxylan was extracted from Norway spruce and films prepared by casting from aqueous solution. The sugar analysis and NMR confirmed that the spruce xylan was composed of arabinose, 4-O-methyl-glucuronic acid and xylose in a ratio of 1:2:11 respectively. Substitutions of 4-O-methyl-alpha-D-GlcpA at O-2 and of alpha-L-Araf at O-3 on the xylose backbone were found by NOE analysis. NOE cross-peaks indicated as well that there is at least one free xylose on the main chain present between two substitutions. Whether the distribution of side chains was random or in blocks was uncertain. The average molecular weight of the sample was determined by size exclusion chromatography to be 12,780 g/mol. Arabinoglucoronoxylan casting yielded transparent flexible films with an average stress at break of 55 MPa, strain at break of 2.7% and a Young's Modulus 2735 MPa. Wide-angle X-ray scattering analysis showed that the arabinoglucuronoxylan films were totally amorphous. Addition of sorbitol as plasticizer resulted in less strong but more flexible films (strain at break of 5%). Peaks of crystallinity could be seen in X-ray which corresponds to sorbitol crystallizing in distinct phases. The dynamic mechanical analysis showed that the arabinoglucuronoxylan film softened at a later relative humidity (80% RH) in comparison with plasticized films (60% RH). The films showed low oxygen permeability and thus have a potential application in food packaging.

  • 14.
    Geng, Xiumei
    et al.
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Zhang, Yelong
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Jiao, Li
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Yang, Lei
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Hamel, Jonathan
    Department of Mechanical and Industrial Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115, United States .
    Giummarella, Nicola
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhu, Hongli
    Bioinspired Ultrastable Lignin Cathode via Graphene Reconfiguration for Energy Storage2017In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 5, no 4, p. 3553-3561Article in journal (Refereed)
    Abstract [en]

    Lignin extracted from trees is one of the most abundant biopolymers on Earth. Quinone, a sub-structure in lignin, can be used for energy storage via reversible redox reactions through absorbing and releasing electrons and protons. However, these efforts have encountered hindrances, such as short life cycle, low cycling efficiency, and a high self-discharge rate. All of these issues are related to electrode dissolution by electrolyte solvents and the insulating nature of lignin. Addressing these critical challenges, for the first time we use a reconfigurable and hierarchical graphene cage to capture the lignin by mimicking the prey-trapping of venus flytraps. The reconfigurable graphene confines the lignin within the electrode to prevent its dissolution, while acting as a three-dimensional current collector to provide efficient electron transport pathways during the electrochemical reactions. This bioinspired design enables the best cycling performance of lignin reported so far at 88% capacitance retention for 15000 cycles and 211 F g-1 capacitance at a current density of 1.0 A g-1. This study demonstrates a feasible and effective strategy for solving the long-term cycling difficulties of lignin-based electrochemically active species, and makes it possible to utilize lignin as an efficient, cheap, and renewable energy storage material.

  • 15.
    Giummarella, Nicola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Fundamental Aspects of Lignin Carbohydrate Complexes (LCC): Mechanisms, Recalcitrance and Material concepts2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Covalent bonds between lignin and carbohydrates, forming a matrix referred to as lignin carbohydrate complexes (LCC), remain one of the most controversial topics in wood chemistry. A key issue is whether they are formed during chemical and mechanical pretreatments of the compact wood structure or actually present in wood prior to isolation. A fundamental understanding of their origin and reactivity is vital to unravel their role in wood formation and recalcitrance. Recalcitrance, specifically, has affected the successful development of effective and clean fractionation of wood polymers.

    To address the above-mentioned concerns, we have developed a novel mild universal and quantitative fractionation protocol of LCC that, when combined with robust spectroscopic analytical tools, including a variety of NMR techniques, GC MS and SEC, reveals deeper insights into the molecular structure of LCC.

    This method was applied to both hardwood and softwood LCCs and revealed interesting findings on molecular-level regulatory mechanism for lignin carbohydrate (LC) bond formation such as the role of acetylation in hemicelluloses. Moreover, the role of LC bonds on recalcitrance during subcritical water extraction was unveiled.

    Bio-mimicking in vitro lignin polymerization was adopted to investigate whether LC bonds are native or formed during isolation from wood. For the first time, direct evidence lending support that they are formed in wood cells was demonstrated, thus corroborating the mechanisms suggested in the literature.  

    Furthermore, based on the overall LCC study, we suggest a sequence for how LC bonds may form in vitro.

    Finally, of special interest to material science, the unveiled LC bond formation mechanism inspired a green, biomimetic, one-pot synthesis of functionalized lignin starting from monomeric components. Excellent selectivity of functionalization is reported and production of lignin-based recyclable materials, based on the premise of this functionalization philosophy, is discussed.

    The full text will be freely available from 2019-05-15 11:59
  • 16.
    Giummarella, Nicola
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Gioia, Claudio
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Civil, Chemical, Environmental and Materials Engineering. Universita´ di Bologna.
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    A One-Pot Biomimetic Synthesis of Selectively Functionalized Lignins from Monomers: A Green Functionalization Platform2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Article in journal (Refereed)
    Abstract [en]

    Lignin is the most abundant renewable source of phenolic compound with great application potential in renewable materials, biofuels and platform chemicals. Current technology for producing cellulose-rich fibers co-produces heterogeneous lignin, which includes an untapped source of monomeric phenolics. One such monomer also happen to be the main monomer in soft wood lignin biosynthesis, namely coniferyl alcohol. Herein, we investigate the potential of coniferyl alcohol as a platform monomer for the biomimetic production of tailored functionalized oligolignols with desirable properties for material synthesis. Accordingly, a bifunctional molecule with at least one carboxyl-ended functionality is included with coniferyl alcohol in biomimetic lignin synthesis to, in one-pot, produce a functionalized lignin. The functionalization mechanism is a nucleophilic addition reaction to quinone methide intermediate of lignin polymerization. The solvent systems applied were pure water or 50% aqueous acetone. Several bi-functional molecules differing in the second functionality were successfully inserted in the lignin demonstrating the platform component of this work. Detailed characterizations were performed by a combination of NMR techniques which include 1H NMR, COSY-90, 31P NMR, 13C NMR, 13C APT, HSQC, HMBC and HSQC TOCSY. Excellent selectivity towards benzylic carbon and high functionalization degree were noted. The structure of lignin was tailored through solvent system choice, with the 50% aqeuous acetone producing a skeletal structure favorable for high functionalization degrees. Finally, material concepts are demonstrated using classical Thiol-ene- and Diels Alder- chemistries to show potential for thermoset- and thermoplastic- concepts, respectively. The functionalization concept presents unprecedentent opportunities for green production of lignin-based recyclable biomaterials.

  • 17.
    Giummarella, Nicola
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Structural Basis for the Formation and Regulation of Lignin–Xylan Bonds in Birch2016In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 4, no 10, p. 5319-5326Article in journal (Refereed)
    Abstract [en]

    The covalent connectivity between lignin and polysaccharides forming the so-called lignin–carbohydrate complexes (LCCs) is important to obtain fundamental knowledge on wood formation and may shed light on molecular aspects of wood processing. Although widely studied, unequivocal proofs of their existence in native-state biomass are still lacking, mainly because of harsh preanalytical fractionation conditions that could cause artifacts. In the present study, we applied a mild protocol for quantitative fractionation of LCCs and performed detailed structural studies using 2D HSQC NMR spectroscopy, 31P NMR spectroscopy, and thioacidolysis in combination with GC–MS and GC with flame ionization detection. The detailed structural analysis of LCCs, including both lignin and the carbohydrate skeleton, unveiled insights into the role of molecular structure of xylan on the type of lignin–carbohydrate (LC) bonds formed. More specifically, it is shown that xylan LCCs differ in the degree of substitution of hydroxyl functionality on the xylan skeleton by the presence of acetyl- or 4-O-methylglucuronic acid. The highly substituted xylan had a lower prevalence of phenyl glycosidic and benzyl ether LC bond types than the lowly substituted xylan. In addition, structural differences in the lignin part of the LCCs were observed. On the basis of the results, it is suggested that acetylation on xylan regulates the type and frequency of LC bonds.

  • 18.
    Giummarella, Nicola
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Structural Insights on Recalcitrance during Hydrothermal Hemicellulose Extraction from Wood2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, no 6, p. 5156-5165Article in journal (Refereed)
    Abstract [en]

    Hydrothermal extraction of hemicelluloses from lignocellulosic biomass for conversion to renewable materials or fuels has captured attention. The extraction is however partial and some lignin is codissolved. Herein, we investigated the role of molecular structure in the recalcitrance. Wood meal of Spruce and Birch were subjected to pressurized hydrothermal extraction at 160 °C for 2 h, which extracted 68–75% of the hemicelluloses. 2D heteronuclear single quantum coherence (HSQC) NMR, HSQC-TOCSY, and 13C NMR were applied for structural studies of both extracts and residues. Subsequent to the known partial hydrolysis of native carbon-2 and carbon-3 acetates in hemicellulose, some acetylation of primary alcohols on hemicelluloses and lignin was observed. Lignin carbohydrate complexes (LCC) were detected in both the extracts and residues. In Spruce extracts, only the phenyl glycoside-type of LCC was detected. Birch extracts contained both the phenyl glycoside and benzyl ether-types. In the hydrothermal wood residues of both species, benzyl ether- and gamma (γ)-ester-LCC were present. Structural changes in lignin included decrease in aryl ether (βO4) content and increases in resinol- (ββ) and phenyl coumaran (β5) contents. On the basis of the overall analysis, the mechanisms and contribution of molecular structure to recalcitrance is discussed.

  • 19.
    Giummarella, Nicola
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. CleanFlow Black AB, Sweden.
    Lindgren, Christofer
    CleanFlow Black AB, Sweden.
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. CleanFlow Black AB, Sweden.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lignin Prepared by Ultrafiltration of Black Liquor: Investigation of Solubility, Viscosity, and Ash Content2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 2, p. 3494-3510Article in journal (Refereed)
    Abstract [en]

    Technical lignin, which can be potentially obtained in large amounts as a by-product from kraft pulping, represents a potential resource for manufacturing fuels and chemicals. Upgrading of lignin, by lowering its molecular weight, is a valuable alternative to precipitation from black liquor, which occurs in the Lignoboost process. The solubility properties of Lignoboost lignin and filtered lignin in a number of technically feasible solvents were compared, and it was found that both lignins were dissolved in similar solvents. With the exception of furfural, the best lignin solvents generally were organic solvents miscible with water, such as methanol. It was possible to dissolve more filtered lignin in higher concentrations than Lignoboost lignin; additionally, the viscosities of the filtered lignin solutions were also considerably lower than those of Lignoboost lignin, especially at higher concentrations. Methods for non-organic component removal from filtrated lignin were tested, and it was concluded that several cold acidic treatments after dewatering can lower the ash content to values below 0.5% by weight.

  • 20.
    Giummarella, Nicola
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Wallenberg Wood Science Center.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Wallenberg Wood Science Center.
    Structural features of mildly fractionated lignin carbohydrate complexes (LCC) from spruce2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 48, p. 42120-42131Article in journal (Refereed)
    Abstract [en]

    A protocol for the quantitative fractionation of lignin carbohydrate complexes (LCC) from wood under mild conditions has been developed. All operations occur at near-neutral pH conditions and low temperatures, in order to preserve the native structure. The protocol also achieved the fractionation of hemicelluloses of relatively high purity enabling for the first time estimates of hemicelluloses fractions not chemically bound to lignin in wood. 2D HSQC NMR was applied to decipher the structure of LCCs and was complemented by thioacidolysis-GC MS techniques. The carbohydrates linked to lignin in LCC are hemicelluloses, mainly arabinoglucuronoxylan (AGX) and galactoglucomannan (GGM). Benzylether (BE) and phenyl glycosidic (PG) linkages were detected. Significant structural differences in the lignin part of LCCs are also reported. The novelty of this work is that we report the first quantitative pH neutral protocol for LCC fractionation and detailed chemical analyses unveil important structural differences of relevance to fundamental knowledge in lignin polymerization and wood-based biorefineries.

  • 21. Gordobil, O.
    et al.
    Moriana, Rosana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhang, Liming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Labidi, J.
    Sevastyanova, Olena
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Assesment of technical lignins for uses in biofuels and biomaterials: Structure-related properties, proximate analysis and chemical modification2016In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 83, p. 155-165Article in journal (Refereed)
    Abstract [en]

    The potential of organosolv and kraft eucalyptus and spruce lignin as feedstock for polymeric materials and biofuel applications was assessed. Proximate analysis was used to predict the heating values and char formation. Chemical modification, based on the esterification reaction with methacryloyl chloride, was applied to introduce vinyl groups into the lignin macromolecules for enhanced reactivity. Kraft eucalyptus and spruce lignins had a more condensed structure than organosolv lignins, which resulted in greater thermal stability for these lignins. For different species within the same process, the thermal parameters showed a correlation with certain structural and compositional parameters (ash and sugars content, molecular weight and degree of condensation). Organosolv spruce lignin produced the highest heating value of 24. MJ/Kg, which is suitable for biofuel applications. The content of phenolic OH groups was higher for kraft lignins and especially higher for softwood lignins, both organosolv and kraft. The degree of methacrylation, estimated from the content of vinyl groups per C9 lignin unit, was significantly greater for organosolv lignins than for kraft lignins despite the higher OH-groups content in the latter.

  • 22. Gosselink, Richard J. A.
    et al.
    van Dam, Jan E. G.
    de Jong, Ed
    Gellerstedt, Göran
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Scott, Elinor L.
    Sanders, Johan P. M.
    Effect of periodate on lignin for wood adhesive application2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 2, p. 155-162Article in journal (Refereed)
    Abstract [en]

    Development of eco-friendly binders with no harmful emission during its complete life cycle is of high interest for the wood-based industry. In this paper, a fully renewable binder based on activated lignin and poly-furfuryl alcohol and a partly renewable lignin based phenol-formaldehyde (PF) binder were evaluated. Activation of kraft and soda lignins, isolated respectively from softwood and non-woods, by periodate oxidation was performed to improve lignin reactivity and application in wood adhesives. Periodate oxidation of lignin leads to higher lignin acidity, formation of quinonoid groups under more severe conditions, higher molar mass and higher reactivity towards the curing of furfuryl alcohol within a temperature range currently used in industry. Comparison of a 100% furan-based glue with a furan-based glue substituted by 10% lignin yields comparable product properties. However, periodate-activated lignin leads to lower wood failure, which might be caused by incompletely solubilised lignin particles in the acidic formulation disturbing crosslinking of the furan resin. Unmodified softwood kraft lignin performs well in a PF resin formulation at substitution levels up to 30% (w/w). Periodate oxidation of soda lignins enhances the glue performance because higher wood failure is attained. The higher molar mass after periodate treatment could be an important parameter for development of a stronger wood binder.

  • 23.
    Hassel, Ivon
    et al.
    Laboratory of Structural Function, Research Institute for Sustainable Humanosphere, Kyoto University.
    Berard, Pierre
    Laboratory of Sustainable Materials, Research Institute for Sustainable Humanosphere, Kyoto University.
    Modén, Carl S.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    The single cube apparatus for shear testing: Full-field strain data and finite element analysis of wood in transverse shear2009In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 69, no 7-8, p. 877-882Article in journal (Refereed)
    Abstract [en]

    The design and analysis of wood structures require accurate data for shear properties, where transverse shear in particular has been neglected in the past. The single cube apparatus (SCA) was applied to transverse shear of Norway spruce (Picea Abies), due to the importance of this species in wood structures, such as glulam, and also its allegedly low value of GRT . Full-field strain data and FEA were used to analyze the potential of the method. The presence of a large central region of homogeneous and close to pure shear strain was confirmed. The SCA method is therefore a strong candidate for improved shear test procedures in wood and other materials, where porosity (gripping problems), heterogeneity on mm-scale and polar orthotropy (annual ring curvature) may cause particular difficulties. In contrast to many other shear test studies, the accuracy of the present GRT data is supported by documented large and homogeneous specimen stress- and strain-fields in almost pure shear, direct measurements of strain field, and careful stress analysis based on FEA.

  • 24.
    Hassel, Ivon
    et al.
    Laboratory of Structural Function, Research Institute for Sustainable Humanosphere, Kyoto University.
    Modén, Carl S.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Functional gradient effects explain the low transverse shear modulus in spruce: Full-field strain data and a micromechanics model2009In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 69, no 14, p. 2491-2496Article in journal (Refereed)
    Abstract [en]

    An important failure mechanism in glulam beams is cracking caused by out-of-plane transverse loads. It has been demonstrated that the low transverse shear modulus G(RT) in spruce contributes to large transverse strain inhomogeneities due to the annual ring structure in combination with shear coupling effects. In the present study, improved understanding of annual ring effects is achieved by the development of a micromechanical model. It relates the functional density gradient in spruce annual rings to shear modulus GRT. The geometrical basis is a hexagonal cell model, and in shear it is demonstrated to deform primarily by cell wall bending. Full-field strain measurements by digital speckle photography (DSP) show very strong correlation with predicted shear strains at the annual ring scale. Predictions are obtained by implementation of the micromechanics model in a finite element (FE) model developed for the single cube apparatus shear specimen. The low GRT of spruce is due to the strong dependence of GRT on relative density rho/rho(s)(G(RT) proportional to (rho/rho(s))(3)). This is particularly important in spruce. Even though average density is typically quite high, the functional gradient structure includes local densities as low as 200 kg/m(3).

  • 25.
    Hergenröder, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Modén, Carl S.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Method to determine the transverse shear modulus (GRT) of softwoods using full field strain measurements in off-axis compressionIn: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840Article in journal (Other academic)
  • 26.
    Kallas, Åsa
    KTH, School of Biotechnology (BIO), Wood Biotechnology.
    Heterologous expression, characterization and applications of carbohydrate active enzymes and binding modules2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Wood and wood products are of great economical and environmental importance, both in Sweden and globally. Biotechnology can be used both for achieving raw material of improved quality and for industrial processes such as biobleaching. Despite the enormous amount of carbon that is fixed as wood, the knowledge about the enzymes involved in the biosynthesis, re-organization and degradation of plant cell walls is relatively limited. In order to exploit enzymes more efficiently or to develop new biotechnological processes, it is crucial to gain a better understanding of the function and mechanism of the enzymes. This work has aimed to increase the knowledge about some of the enzymes putatively involved in the wood forming processes in Populus. Xyloglucan endotransglycosylases and a putative xylanase represent transglycosylating and hydrolytic enzymes, respectively. Carbohydrate binding modules represent non-catalytic modules, which bind to the substrate.

    Among 24 genes encoding for putative xyloglucan endotransglycosylases or xyloglucan endohydrolases that were identified in the Populus EST database, two were chosen for further studies (PttXTH16-34 and PttXTH16-35). The corresponding proteins, PttXET16-34 and PttXET16-35, were expressed in P. pastoris, purified and biochemically characterized. The importance of the N-glycans was investigated by comparing the recombinant wild-type proteins with their deglycosylated counterparts. In order to obtain the large amounts of PttXET16-34 that were needed for crystallization and development of biotechnological applications, the conditions for the large-scale production of PttXET16-34 in a fermenter were optimized.

    In microorganisms, endo-(1,4)-β-xylanases are important members of the xylan degrading machinery. These enzymes are also present in plants where they might fulfill a similar, but probably more restrictive function. One putative endo-(1,4)-β-xylanase, denoted PttXYN10A, was identified in the hybrid aspen EST library. Sequence analysis shows that this protein contains three putative carbohydrate-binding modules (CBM) from family 22 in addition to the catalytic module from GH10. Heterologous expression and reverse genetics were applied in order to elucidate the function of the catalytic module as well as the binding modules of PttXYN10A.

    Just as in microorganisms, some of the carbohydrate active enzymes from plants have one or more CBM attached to the catalytic module. So far, a very limited number of plant CBMs has been biochemically characterized. A detailed bio-informatic analysis of the CBM family 43 revealed interesting modularity patterns. In addition, one CBM43 (CBM43PttGH17_84) from a putative Populus b-(1,3)-glucanase was expressed in E. coli and shown to bind to laminarin (β-(1,3)-glucan), mixed-linked β-(1,3)(1,4)-glucans and crystalline cellulose. Due to their high specificity for different carbohydrates, CBMs can be used as probes for the analysis of plant materials. Generally, they are more specific than both staining techniques and carbohydrate-binding antibodies. We have used cellulose- and mannan binding modules from microorganisms as tools for the analysis of intact fibers as well as processed pulps.

  • 27.
    Källbom, Susanna
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Johansson, Leena-Sisko
    Aalto University, Finland.
    Campbell, JM
    Department of Forest Products Technology, Aalto University.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden, Sweden.
    Jones, Dennis
    SP Technical Research Institute of Sweden.
    Laine, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Water vapour sorption characteristics and surface chemical composition of thermally modified spruce (Picea abies karst)2016In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 7, no 3, p. 116-123Article in journal (Refereed)
    Abstract [en]

    The objective of this work was to study the hygroscopicity and surface chemical composition of thermally modified (TM) spruce. An effort was also made to study if those features were influenced by a previous exposure to a significant increase in relative humidity (RH). TM and unmodified Norway spruce (Picea abies Karst) samples, both in solid and ground form, were prepared. Water vapour sorption characteristics of the ground samples were obtained by measuring sorption isotherms using a dynamic vapour sorption (DVS). The surface chemical composition of the solid samples, both acetone extracted and non-extracted, were analysed using X-ray photoelectron spectroscopy (XPS). The DVS analysis indicated that the TM wood exposed to the 75% RH revealed a decrease in isotherm hysteresis. The XPS analysis indicated a decrease of acetone extractable or volatile organic components and a relative increase of non-extractable components for the samples exposed to the increased RH condition.

  • 28.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. To obtain products of high quality, these so-called "special" pulps must fulfill certain requirements, such as high cellulose content, low hemicellulose content, a uniform molecular weight distribution and high cellulose reactivity. Most, if not all, of the commercial dissolving pulps accomplish these demands to a certain extent. Nevertheless, achieving high cellulose accessibility as well as solvent and reagent reactivity is not an easy task due to the compact and complex structure presented by the cellulose.

    In the first part of this work, three commercial monocomponent endoglucanases were investigated with the purpose of enhancing the cellulose accessibility and reactivity of a hardwood dissolving pulp. A monocomponent endoglucanase with a cellulose-binding domain (CBD) was shown to significantly improve the cellulose reactivity. The positive effect of this enzyme on dissolving-grade pulps was also observed on paper-grade pulps.

    The main focus of the forest industry is the production of paper-grade pulps. Paper-grade pulps are mostly produced by the kraft process. In contrast, dissolving-grade pulps are produced by the sulfite and prehydrolysis kraft processes due to the high purity required for these pulps. The kraft process is known for being the most efficient process in terms of energy and chemical recovery, which makes the production costs of paper-grade pulps lower than those of sulfite dissolving-grade pulps. Besides, the production of dissolving pulps present, among others, higher capital and chemical costs than paper-grade pulps.

    Therefore, the viability of converting paper-grade pulps into dissolving pulps is brought into a question. However, this task is not simple because paper-grade pulps contain a lower cellulose content and a higher hemicellulose content than dissolving pulps. They also present lower cellulose reactivity and an inhomogeneous molecular weight distribution. As a consequence, the second part of this work focused on the study of the feasibility of converting kraft pulps into dissolving pulps. Several sequences of treatments of hardwoods and non-wood pulps were investigated. The best sequence for each suitable pulp was developed, and the parameters involved were optimized. After several attempts, it was demonstrated that pulps from birch, eucalypt and sisal fulfill the requirements of a commercial dissolving pulp for the viscose process after being subjected to a sequence of treatments that included two commercial enzymes, a xylanase and a monocomponent endoglucanase, and alkali extraction steps.

     

  • 29.
    Köpcke, Viviana
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Improvement on cellulose accessibility and reactivity of different wood pulps2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The accessibility and reactivity of cellulose are key parameters on the manufacturing of cellulose derivatives and regenerated cellulose. It is well known that, due to the crystalline structure of cellulose, the accessibility of solvents and reagents is limited. For instance, an inhomogeneous substitution of the hydroxyl groups of the cellulose chain might lead to the production of derivatives of low quality. As a consequence, part of this work has focused on improving the accessibility and reactivity on cellulose by studying the effect of different monocomponent endoglucanases. It has been demonstrated that the presence of the cellulose-binding domain plays an important role on the enhancement of cellulose reactivity; however, the structure of the catalytic domain has been showed to have the highest influence on this parameter. Furthermore, the influence of mechanical treatment prior to enzymatic treatment has been examined. The combination of pretreatments showed a positive effect enhancing to a larger extent the cellulose reactivity.

    Currently, dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. The requirements for these so-called “special pulps” are a high cellulose content and a low hemicelluloses and lignin content. As a result of these specific demands, the production costs of these pulps are higher than those of common kraft pulps. The second part of this work, therefore, has been focused on the study on the viability of converting kraft pulps into dissolving pulps. It has been demonstrated that the combination of enzymatic treatments using a monocomponent endoglucanase and a xylanase together with the addition of an alkaline step could fulfil the requirements of a commercial dissolving pulp in terms of cellulose reactivity and cellulose and hemicellulose content.

  • 30.
    Köpcke, Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ibarra, David
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Increasing accessibility and reactivity of paper grade pulp by enzymatic treatment for use as dissolving pulp2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 4, p. 363-368Article in journal (Refereed)
    Abstract [en]

     In this study, the feasibility of using different kraft pulps as dissolving pulps for the viscose process was investigated. Two different bleached hardwood kraft pulps from eucalypt (Eucalyptus globulus) and birch (Betula pendula) were subjected to several enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of the pulps and to reduce the hemicellulose content. Enzymatic treatments were carried out using a commercial monocomponent endoglucanase and a commercial xylanase. Chemical treatment consisted of an alkali extraction. The effects of these pretreatments on reactivity and viscosity were assayed. In both pulps, the endoglucanase enhanced the cellulose reactivity and reduced the viscosity. The sequential combination of xylanase and endoglucanase enhanced the positive effect of endoglucanase treatment alone for eucalypt but showed no major effect for birch. The addition of an alkali extraction step after the xylanase followed by endoglucanase treatment as a final step significantly reduced the hemicellulose content to 24% while the reactivity reached the value of a commercial dissolving pulp (65-70%). The viscosity, on the other hand, showed a considerably decrease.

  • 31.
    Köpcke, Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Nanko, Hiroki
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The effect of different monocomponent endoglucanases on cellulose accessibility in dissolving pulpsManuscript (Other academic)
  • 32.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Hughes, Mark
    Wood densification and thermal modification: hardness, set-recovery and micromorphology2016In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, no 5, p. 883-894Article in journal (Refereed)
    Abstract [en]

    The density of wood can be increased by compressing the porous structure under suitable moisture and temperature conditions. One aim of such densification is to improve surface hardness, and therefore, densified wood might be particularly suitable for flooring products. After compression, however, the deformed wood material is sensitive to moisture, and in this case, recovered up to 60 % of the deformation in water-soaking. This phenomenon, termed set-recovery, was reduced by thermally modifying the wood after densification. This study presents the influence of compression ratio (CR = 40, 50, 60 %) and thermal modification time (TM = 2, 4, 6 h) on the hardness and set-recovery of densified wood. Previously, set-recovery has mainly been studied separately from other properties of densified wood, while in this work, set-recovery was also studied in relation to hardness. The results show that set-recovery was almost eliminated with TM 6 h in the case of CR 40 and 50 %. Hardness significantly increased due to densification and even doubled compared to non-densified samples with a CR of 50 %. Set-recovery reduced the hardness of densified (non-TM) wood back to the original level. TM maintained the hardness of densified wood at an increased level after set-recovery. However, some reduction in hardness was recorded even if set-recovery was almost eliminated.

  • 33.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Hughes, Mark
    Department of Forest Products Technology, Aalto University.
    Källbom, Susanna
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jones, Dennis
    SP Tech Res Inst Sweden.
    Hardness, set-recovery and micromorphology studies of densified and thermally modified wood2015Conference paper (Other academic)
    Abstract [en]

    The purpose of the work reported in this paper was to increase the density of Scots pine wood in order to improve its hardness. Density was increased by compressing the porous structure of wood between heated metal plates in the radial direction by 40, 50 or 60% of the thickness. The compressed state was stabilised by thermally modifying (TM) the samples at 200 °C under steam conditions for 2, 4 or 6h. Set-recovery was almost eliminated (<1%) with TM of 6h for samples compressed 40 and 50%. It was discovered that hardness of densified wood was in some cases even three times higher compared to untreated wood. However, the hardness of the densified, non-TM wood was reduced after soaking and drying back to the original untreated level, while TM of 4 and 6h maintained an increased level of hardness.

  • 34.
    Laine, Kristiina
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Hughes, Mark
    Department of Forest Products Technology, Aalto University.
    Rowell, Roger
    Department of Biological Systems Engineering, University of Wisconsin, Madison, WI USA.
    Acetylation and densification of wood2015Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to explore the possibility to surface densify acetylated solid wood. The aim of surface densification is to improve mechanical properties, such as hardness, at the very surface of wood where the property improvements are mostly needed (e.g. in flooring and decking). However, when subjected to moisture, surface densified wood may swell back almost to the original dimensions. Therefore, acetylated and non-acetylated wood was surface densified in order to investigate whether the dimensional stability of densified wood may be improved by pre-acetylation. Surface densification was performed by compressing the acetylated radiate pine samples between metal plates with only one side heated (150°C) in order to target the deformation to one surface only. The original thickness of the samples was 20 mm and the target thickness 18 mm which was controlled by metal stops. The recovery of the deformation (set-recovery) was measured by soaking the samples in water and measuring the oven-dry thickness before and after soaking in repeated cycles. It was found that acetylated wood may be surface densified and indeed the set-recovery of the pre-acetylated wood was significantly lower (17.4 %) compared to non-acetylated wood (72.8 %). Further studies in adjusting the process parameters might lead to even higher reduction in set-recovery.

  • 35.
    Le Normand, Myriam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Mélida, Hugo
    KTH, School of Biotechnology (BIO), Glycoscience.
    Holmbom, Bjarne
    Åbo Akademi.
    Michaelsen, Terje E.
    Unversity of Oslo.
    Inngjerdingen, Marit
    University of Oslo.
    Bulone, Vincent
    KTH, School of Biotechnology (BIO), Glycoscience.
    Paulsen, B.S.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Hot-water extracts from the inner bark of Norway spruce with immunomodulating activities2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 101, no 1, p. 699-704Article in journal (Refereed)
    Abstract [en]

    The inner bark of Norway spruce (Picea abies) was sequentially extracted with hot water at 100 degrees C, 140 C and 160 degrees C. The hot-water extracts (IB 100 degrees C, IB 140 degrees C and IB 160 degrees C) contained pectic polysaccharides and showed immunostimulating activities. Structural analyses of their carbohydrate content, including glycosidic linkage analyses, revealed the presence of pectins with a large rhamnogalacturonan RG-I domain ramified with highly-branched arabinans. IB 100 degrees C also contained a large amount of terminal glucosyl residues, indicating the presence of highly substituted polymers. IB 160 degrees C was mainly composed of starch. The hot-water extracts were tested for two biological activities, namely complement fixation and macrophage stimulation. IB 100 degrees C exhibited the highest complement fixation activity, with a 1.7-times higher IC(H)50 than the control pectin, while IB 140 degrees C and IB 160 degrees C gave similar IC(H)50 values as the control. Macrophages were stimulated by IB 100 degrees C and IB 140 degrees C in a dose-dependent manner, but not by IB 160 degrees C. IB 100 degrees C presented the highest activity toward macrophages, comparable to the control pectin.

  • 36. Lewis, W. J. T.
    et al.
    Agg, A.
    Clarke, A.
    Mattsson, Tuve
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Chew, Y. M. J.
    Bird, M. R.
    Development of an automated, advanced fluid dynamic gauge for cake fouling studies in cross-flow filtrations2016In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 238, p. 282-296Article in journal (Refereed)
    Abstract [en]

    Fluid dynamic gauging (FDG) has previously been demonstrated as a technique for the estimation of fouling layer thickness during membrane filtration. Subsequently, FDG has been developed to allow faster, more accurate, and automated readings. Previous experimental data has been re-examined and shortcomings of the methodology used are discussed. In this work the operating procedures of FDG were refined and tested with a mixture of sticky, amorphous foulant and monodispersed glass spheres. The results demonstrate how cake growth rates can be confidently estimated in-situ. The technique also provides strong evidence of a difference in cake structure through destructive thickness testing, despite cake thicknesses being almost equivalent.

  • 37. Li, T.
    et al.
    Cai, J. -B
    Avramidis, S.
    Cheng, D. -L
    Wålinder, Magnus E.P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Zhou, D. -G
    Effect of conditioning history on the characterization of hardness of thermo-mechanical densified and heat treated poplar wood2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 6, p. 515-520Article in journal (Refereed)
    Abstract [en]

    Poplar wood was modified by a combination of thermo-mechanical densification (TMD) and heat treatment (HT) process at five temperatures ranging from 170 to 210°C. A new two-step conditioning method (CM) is suggested, in the course of which the modified wood is submitted to 50°C/99% RH→25°C/65% RH, where RH means relative humidity in the climate chamber. The traditional one-step CM (25°C/65% RH) served as reference. The effects of conditioning history on hardness were observed and analyzed along with the change of dimensional stability. The hardness of the modified wood was lower in the case of the proposed CM due to more set-recovery release, but the extent of that decreased with the HT temperature. For a good hardness, HT200°C should be selected with the proposed CM, which is different from the optimization output of 180°C obtained from the traditional CM. In conclusion, a specific assessment method for the performance characterization of this type of modified wood would be beneficial for the combined TMD and HT processes.

  • 38.
    Linkosalmi, Lauri
    et al.
    Department of Forest Products Technology, Aalto University.
    Laine, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Department of Forest Products Technology, Aalto University.
    Life cycle impacts of modified wood products2015Conference paper (Other academic)
  • 39. Marklund, Erik
    et al.
    Varna, Janis
    Neagu, Cristian R.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Gamstedt, Kristofer E.
    Stiffness of aligned wood fiber composites: Effects of microstructure and phase properties2008In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 42, no 22, p. 2377-2405Article in journal (Refereed)
    Abstract [en]

    The effect of wood fiber anisotropy and their geometrical features on wood fiber composite stiffness is analyzed. An analytical model for an N-phase composite with orthotropic properties of constituents is developed and used. This model is a straightforward generalization of Hashin's concentric cylinder assembly model and Christensen's generalized self-consistent approach. It was found that most macro-properties are governed by only one property of the cell wall which is very important in attempts to back-calculate the fiber properties. The role of lumen (whether it filled by resin or not) has a very large effect on the composite shear properties. It is shown that several of the unknown anisotropic constants characterizing wood fiber are not affecting the stiffness significantly and rough assumptions regarding their value would suffice. The errors introduced by application of the Hashin's model and neglecting the orthotropic nature of the material behavior in cylindrical axes are evaluated. The effect of geometrical deviations from circular cross-section, representing, for example, collapsed fibers, is analyzed using the finite element method (FEM) and the observed trends are discussed.

  • 40.
    Martinez-Abad, Antonio
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. AlbaNova University Centre.
    Giummarella, Nicola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Vilaplana, Francisco
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Differences in extractability under subcritical water reveal interconnected hemicellulose and lignin recalcitrance in birch hardwoods2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Article in journal (Refereed)
    Abstract [en]

    Hardwoods constitute an essential renewable resource for the production of platform chemicals and bio-based materials. A method for the sequential extraction of hemicelluloses and lignin from hardwoods is proposed using subcritical water in buffered conditions without prior delignification. This allows the cascade isolation of mannan, xylan and lignin-carbohydrate complexes based on their extractability and recalcitrance in birch lignocellulose. The time evolution of the extraction was monitored in terms of composition, oligomeric mass profiling and sequencing of the hemicelluloses, and molecular structure of the lignin and lignin-carbohydrate complexes (LCCs) by heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR). The minor mannan and pectin populations are easily extractable at short times (<5 min), whereas the major glucuronoxylan (GX) becomes enriched at moderate extraction times. Longer extraction times results in major hydrolysis exhibiting GX fractions with tighter glucuronation spacing and lignin enrichment. The pattern of acetylation and glucuronation in GX is correlated with extractability and with connectivity with lignin through LCCs. This interconnected molecular heterogeneity of hemicelluloses and lignin has important implications for their supramolecular assembly and therefore determines the recalcitrance of hardwood lignocellulosic biomass.

  • 41.
    Modén, Carl S.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Micromechanics of softwoods in the transverse plane: effects on cell and annual ring scales2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Transverse mechanical properties of wood are important in many practial applications and an interesting scientific subject. A very low transverse shear modulus has been identified in spruce, which causes large strain concentrations in wood structures. In this thesis, experimental characterization of local density variations as well as local strain fields are carried out using the SilviScan apparatus and digital speckle photography, respectively. This is combined with micromechanical modeling based on hexagonal wood cells in combination with finite element analysis. Problems addressed include the moduli in the transverse plane, including variations at the scale of individual annual rings. The relative importance of cell wall bending and stretching deformation mechanisms is analysed as a function of wood cell geometry, relative density and direction of loading (radial, tangential and shear). Transverse anisotropy is also analyzed, including its dependency of earlywood and latewood characteristics. The wood cell shape angle variation and density effects are sufficient to explain transverse anisotropy in softwoods (no ray effects), and the influence of earlywood/latewood ratio is explained. As a practical test method for shear modulus measurements, an off-axis compression test with full-field strain determination is proposed. The advantage is a simple fixture and large region of representative strain required for a heterogeneous material such as wood. As an alternative, the single cube apparatus (SCA) for shear tests is evaluated. The SCA is used to determine the shear strain distribution within the annual rings. Based on the density distribution of the shear test specimen and a micromechanics model, a finite element model is developed, and predictions are compared with the measured shear strains. The agreement between predicted and measured shear strains at the annual ring scale are remarkably good. It shows that the low GRT of spruce is due to the low earlywood density and the large cell wall bending deformation resulting from shear loading. Furthermore, it illustrates the need for improved understanding of annual ring scale effects. For example, fairly low transverse global loads will lead to lage local shear strains.

  • 42.
    Modén, Carl S.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    A two-phase annual ring model of transverse anisotropy in softwoods2008In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 68, no 14, p. 3020-3028Article in journal (Refereed)
    Abstract [en]

    Transverse anisotropy in softwoods is an important phenomenon of both scientific and industrial interest. Simple one-phase hexagonal honeycomb cell models for transverse moduli of softwoods are based on cell wall bending as the only deformation mechanism. In the present study, a two-phase annual ring model is developed and includes both cell wall bending and stretching as deformation mechanisms. The proportion of cell wall bending and stretching for different cases is analysed and the importance of stretching is confirmed. A two-phase annual ring model is presented based on fixed densities for earlywood and latewood. Such a model is motivated by the large difference in density between earlywood and latewood layers. Two-phase model predictions show much better agreement with experimental data than predictions from a one-phase model. Radial modulus is dominated by bending at low density and by stretching at high density. For tangential modulus, bending is more important at all densities.

  • 43.
    Modén, Carl S.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Elastic deformation mechanisms of softwoods in radial tension: Cell wall bending or stretching?2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 5, p. 562-568Article in journal (Refereed)
    Abstract [en]

    Radial softwood modulus ER is typically twice as high as the tangential modulus ET. The reason for this is unclear, although cell geometry is likely to contribute. The established hexagonal honeycomb model for prediction of ER is based on a cell wall bending mechanism only. If cell wall stretching also takes place, the dependence of ER on relative density will be different. If experimental data for ER as a function of relative density show deviations from cell wall bending predictions, this may indicate the presence of cell wall stretching. A SilviScan apparatus is used to measure density distribution. A procedure by means of digital speckle photography is then developed for measurements of local ER within the annual rings of spruce. Comparison is made between experimental data and the two expected density dependencies from cell wall bending and from stretching. The hypothesis of cell wall stretching as a contributing mechanism is supported based on the observed linear dependence of ER over a wide density range.

  • 44.
    Neagu, Cristian
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Gamstedt, Kristofer
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Berthold, Fredrik
    Stiffness contribution of various wood fibers to composite materials2006In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Journal of Composites Materials, Vol. 40, no 8, p. 663-699Article in journal (Refereed)
    Abstract [en]

    Wood pulp fibers can serve as useful reinforcement of plastics for increased stiffness. To assess the potential of various wood fibers as reinforcement, a method has been developed to determine the contribution of the fibers to the elastic properties of the composite. A micromechanical composite model and classical laminate mechanics are used to relate the elastic properties of the fibers to the elastic properties of the composite. A large variety of composites made of various wood pulp fibers in an epoxy vinyl ester matrix was manufactured. From the tensile test results of the composites, the contributing Young's moduli of the fibers in the longitudinal direction are back-calculated and summarized. One finding is that there is an optimum in fiber stiffness as a function of lignin content. It is also found that industrially pulped hardwood fibers have higher stiffness than the corresponding softwood fibers. One example is kraft-cooked Norway spruce fiber, for which a Young's modulus of 40 GPa is found. The effects of hornification, prehydrolysis, and sulfite processing are also investigated. The results indicate that mild defibration process should be used, that does not damage the cell wall structure so that the inherent high stiffness of the native fibers can be retained. It can be concluded that the proposed method works well to rank the wood fiber candidates in terms of their contribution to the composite stiffness.

  • 45. Neagu, Cristian R.
    et al.
    Gamstedt, Kristofer E.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Modelling of effects of ultrastructural morphology on the hygroelastic properties of wood fibres2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 24, p. 10254-10274Article in journal (Refereed)
    Abstract [en]

    Wood fibres constitute the structural framework of e.g. wood, paper, board and composites, where stiffness and dimensional stability are of importance. An analytical modelling approach has been used for prediction of hygroelastic response, and assessment of the stresses in thick-walled cylinder models of wood fibres. A wood fibre was idealised as a multilayered hollow cylinder made of orthotropic material with helical orientation. The hygroelastic response of the layered assembly due to axisymmetric loading and moisture content changes was obtained by solving the corresponding boundary value problem of elasticity. A simple solution scheme based on the state space approach and the transfer matrix method was employed. This was combined with an analytical ultrastructural homogenisation method, used to link hygroelastic properties of constituent wood polymers to properties of each layer. Predicted hygroelastic response captured experimentally measured behaviour. Fibres that were constrained not to twist showed a stiffer response than fibres allowed twisting under uniaxial loading. It was also shown that the ultrastructure, i.e. the microfibril angle, will control the hygroexpansion in the same way as it controls the compliance of the cell wall. Qualitative failure trends comparable with experimental observations could be established with stress analysis and a simple plane-stress failure criterion.

  • 46.
    Sedighi Moghaddam, Maziar
    et al.
    SP Tech Res Inst Sweden, S-11486 Stockholm, Sweden.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wålinder, Magnus E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wettability and liquid sorption of wood investigated by Wilhelmy plate method2014In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 48, no 1, p. 161-176Article in journal (Refereed)
    Abstract [en]

    The wettability of Scots pine veneers was investigated with different approaches using the Wilhelmy plate method. The probe liquids were water and octane, which differ; in that, water is able to swell the wood sample, whereas octane does not. Novel approaches based on the Wilhelmy plate method to study wettability, liquid penetration, and swelling behavior of wood veneers are introduced. First, immersion to constant depth was performed, and liquid uptake with time was evaluated. Different kinetic regimes, the fastest one associated with contact angle changes and the slowest regime associated with liquid sorption by capillary and diffusion, were observed. Two other approaches, imbibition at constant depth (with initial deeper immersion) and full immersion, were utilized in order to keep the contact angle constant during measurements. Dynamic wettability studies were done by a multi-cycle (10-20 cycles) Wilhelmy method. Based on this, the time-dependent swelling of wood and changes in sample perimeter could be obtained. Generally, water showed higher absorption than octane. In all wettability studies, and for both probe liquids, the penetration process starts with a fast initial sorption, which is followed by swelling in the case of water.

  • 47.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Heydarihamedani, Golrokh
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tuominen, Mikko
    SP Technical Research Institute of Sweden.
    Fielden, Matthew
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Haapanen, Janne
    TUT Tampere University of Technology, Aerosol Physics Laboratory, Department of Physics.
    Mäkelä, Jyrki M.
    TUT Tampere University of Technology, Aerosol Physics Laboratory, Department of Physics.
    Wålinder, E.P. Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Hydrophobisation of wood surfaces by combining liquid flame spray (LFS)and plasma treatment: dynamic wetting properties2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 6, p. 527-537Article in journal (Refereed)
    Abstract [en]

    The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate method, resulting in advancing and receding contact angles as well as sorption behaviour of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and Xray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behaviour. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

  • 48.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Van den Bulcke, Jan
    Wålinder, E.P. Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Calessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Van Acker, Joris
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Microstructure of chemically modified wood using X-ray computedtomography scanning in relation to wetting propertiesManuscript (preprint) (Other academic)
    Abstract [en]

    X-ray computed tomography was utilized to visualize and quantify the 2D and 3D microstructure of acetylated and furfurylated southern yellow pine (SYP) and maple samples. The total porosity and the porosity of different anatomical components, the cell wall thickness and the maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. Our data show significant changes in the wood structure for furfurylated sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for acetylated samples at the resolution of the measurement (0.8 μm). The images obtained for furfurylated maple samples demonstrated that all ray cells and some vessel elements were filled with furan polymer while the fibres largely remained unchanged. Furfurylation significantly decreased the porosity of the sample, and this was observed in both earlywood and latewood regions in southern yellow pine softwood samples. In contrast, the total porosity of this softwood sample was hardly affected by acetylation. These findings are in line with wetting results demonstrating that furfurylation reduces both swelling and capillary uptake in contrast to acetylation which reduces mostly swelling. Cell wall thickness measurements revealed a significant increase after chemical modification especially at higher levels of furfurylation.

  • 49.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden Chem Mat & Surfaces, Sweden.
    Van den Bulcke, Jan
    Wålinder, Magnus E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Van Acker, Joris
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 2, p. 119-128Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (XCT) was utilized to visualize and quantify the 2D and 3D microstructure of acetylated southern yellow pine (pine) and maple, as well as furfurylated pine samples. The total porosity and the porosity of different cell types, as well as cell wall thickness and maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. The data show significant changes in the wood structure for furfurylated pine sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for the acetylated pine samples at the high resolution of 0.8 mu m. The XCT images obtained for the furfurylated maple samples demonstrated that all ray cells and some vessel elements were filled with furan polymer while the fibers largely remained unchanged. Furfurylation significantly decreased the total porosity of both the maple and pine samples. Furthermore, this was observed in both earlywood (EW) and latewood (LW) regions in the pine samples. In contrast, the total porosity of pine samples was hardly affected by acetylation. These findings are in line with wetting results demonstrating that furfurylation reduces both swelling and capillary uptake in contrast to acetylation which reduces mostly swelling. Furfurylation significantly increased the cell wall thickness of both the maple and pine samples, especially at higher levels of furfurylation.

  • 50.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Wålinder, E.P. Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Calessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Wettability and swelling of acetylated and furfurylated wood analyzed by multicycle Wilhelmy plate method2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 1, p. 69-77Article in journal (Refereed)
    Abstract [en]

    The wetting, dimensional stability and sorption properties of a range of modified wood samples obtained either by acetylation or furfurylation were compared with those of unmodified samples of the same wood species via a multicycle Wilhelmy plate method. Wettability measurements were performed with water and octane as the swelling and non-swelling liquids, respectively. It was found that acetylation reduces water uptake mainly by reducing the swelling. In comparison, furfurylation reduces both swelling and the void volume in the sample. To quantify the effect of the modification process of the wood properties, the parameters “liquid up-take reduction” and the “perimeter change reduction” were introduced, which were determined from multicycle Wilhelmy plate measurements. Compared with the acetylated wood, the furfurylated wood with a higher level of weight percent gain exhibited larger property changes on the surface and in terms of swelling and sorption properties.

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