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  • 1.
    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.

  • 2.
    Dedic, Dina
    et al.
    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.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Cellulose degradation in the Vasa: The role of acids and rust2013In: Studies in Conservation, ISSN 0039-3630, E-ISSN 2047-0584, Vol. 58, no 4, p. 308-313Article in journal (Refereed)
    Abstract [en]

    The oak timbers of the Swedish warship Vasa are deteriorating. High amounts of oxalic acid have been found along with a low pH and low molecular weight cellulose deep in the wood timbers. The iron-rich surface wood differs from the interior wood in that it displays higher pH and cellulose with higher molecular weight. The objective of this study was to determine why there is a difference in cellulose degradation, pH, and oxalic acid amount between the surface region and the interior of the Vasa timbers. Analysis of cellulose weight average molecular weight by size exclusion chromatography was performed, as well as quantification of oxalic acid and iron by high-performance anion exchange chromatography and atomic emission spectroscopy, respectively. It was found that a decrease in iron content coincides with an increase in oxalic acid concentration and a drop in pH at a certain depth from the wood surface. When iron-rich surface wood samples from the Vasa were mixed with an aqueous solution of oxalic acid, a fast increase of pH over time was observed. Neither interior wood poor in iron nor the fresh oak reference showed the same neutralizing effect during the time of measurement. This indicates that the presence of iron (rust) causes a neutralization of the wood, through the formation of iron(III) oxalato complexes, thus protecting the wood from oxalic acid hydrolysis. This effect was not observed to the same extent for other acids observed in Vasa wood (sulfuric, formic, glycolic, and acetic acids).

  • 3.
    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.

  • 4.
    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.
    Analysisof lignin and extractives in the oak wood of the 17th century warship Vasa2011Manuscript (preprint) (Other (popular science, discussion, etc.))
  • 5.
    Halonen, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    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.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mercerized cellulose biocomposites: A study of influence of mercerization on cellulose supramolecular structure, water retention value and tensile properties2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 1, p. 57-65Article in journal (Refereed)
    Abstract [en]

    In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites.

  • 6.
    Li, Dongfang
    et al.
    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. Innventia AB, Drottning Kristinas väg 61, SE-114 86 Stockholm, Sweden.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Hydrophobic materials based on cotton linter cellulose and an epoxy-activated polyester derived from a suberin monomer2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed)
    Abstract [en]

    Suberin is a natural hydrophobic material that could be used to improve the water repellency of cellulose surfaces. It is also abundant in the outer bark of birch (Betula verrucosa); birch bark is a side-stream product in Scandinavia from the forest industry, which is generally burned for energy production. A suberin monomer, cis-9,10-epoxy-18-hydroxyoctadecanoic acid, was isolated from birch outer bark and polymerized via lipase (immobilized Candida antarctica lipase B). The resulting epoxy-activated polyester was characterized by nuclear magnetic resonance (NMR) imaging, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, and size exclusion chromatography. Then the polyester was cured with tartaric or oxalic acid, and the crosslinked polyesters were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry. Hydrophobic materials were prepared by compression molding of polyester-impregnated cellulose sheets, and the final products were characterized by FTIR, cross-polarization magic angle spinning 13 C NMR, and field-emission scanning electron microscopy. The water contact angle was significantly increased from 0 ° for the original cellulose sheets to over 100 ° for the produced hydrophobic materials.

  • 7. Nilsson, H.
    et al.
    Olsson, Ann
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Areskogh, Dimitri
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Iversen, Tommy
    Lipase Catalyzed Co-polymerization of the Suberin Monomercis-9,10-Epoxy-18-hydroxyoctadecanoic Acid with LactonesManuscript (preprint) (Other academic)
  • 8.
    Nilsson, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Galland, Sylvain
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    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.
    Gamstedt, E. Kristofer
    Uppsala University.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Compression molded wood pulp biocomposites: A study of hemicellulose influence on cellulose supramolecular structure and material properties2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 3, p. 751-760Article in journal (Refereed)
    Abstract [en]

    In this study, the importance of hemicellulose content and structure in chemical pulps on the property relationships in compression molded wood pulp biocomposites is examined. Three different softwood pulps are compared; an acid sulfite dissolving grade pulp with high cellulose purity, an acid sulfite paper grade pulp and a paper grade kraft pulp, the latter two both containing higher amounts of hemicelluloses. Biocomposites based the acid sulfite pulps exhibit twice as high Young's modulus as the composite based on paper grade kraft pulp, 11-12 and 6 GPa, respectively, and the explanation is most likely the difference in beating response of the pulps. Also the water retention value (WRV) is similarly low for the two molded sulfite pulps (0.5 g/g) as compared to the molded kraft pulp (0.9 g/g). The carbohydrate composition is determined by neutral sugar analysis and average molar masses by SEC. The cellulose supramolecular structure (cellulose fibril aggregation) is studied by solid state CP/MAS 13C-NMR and two forms of hemicellulose are assigned. During compression molding, cellulose fibril aggregation occurs to higher extent in the acid sulfite pulps as compared to the kraft pulp. In conclusion, the most important observation from this study is that the difference in hemicellulose content and structure seems to affect the aggregation behaviour and WRV of the investigated biocomposites.

  • 9.
    Nilsson, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Galland, Sylvain
    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.
    Larsson, Per Tomas
    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.
    Gamstedt, E. Kristofer
    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.
    Nishino, Takashi
    Dept. of Chem. Sci. and Engng., Kobe Univ. Rokko, Nada, Kobe, Japan.
    Berglund, Lars A.
    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.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    A non-solvent approach for high-stiffness all-cellulose biocomposites based on pure wood cellulose2010In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 70, no 12, p. 1704-1712Article in journal (Refereed)
    Abstract [en]

    All-cellulose composites are commonly prepared using cellulose solvents. In this study, moldable all-cellulose I wood fiber materials of high cellulose purity (97%) were successfully compression molded. Water is the only processing aid. The material is interesting as a "green" biocomposite for industrial applications. Dissolving wood fiber pulps (Eucalyptus hardwood and conifer softwood) are used and the influence of pulp origin, beating and pressing temperature (20-180 degrees C) on supramolecular cellulose nanostructure is studied by solid state CP/MAS C-13 NMR. Average molar mass is determined by SEC to assess process degradation effects. Mechanical properties are determined in tensile tests. High-density composites were obtained with a Young's modulus of up to 13 GPa. In addition, nanoscale cellulose fibril aggregation was confirmed due to processing, and resulted in a less moisture sensitive material.

  • 10. Nilsson, Helena
    et al.
    Olsson, Ann
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindström, Mikael
    Iversen, Tommy
    Bark Suberin as a Renewable Source of Long-Chain omega-Hydroxyalkanoic Acids2008In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 272, no 1, p. 104-106Article in journal (Refereed)
    Abstract [en]

    Polycondensations of cis-9,10-epoxy-18-hydroxyoctadecanoic acid, isolated from birch outer bark, were performed at 75 degrees C in toluene as solvent and at 85 degrees C in bulk using immobilized Candida antarctica lipase B as catalyst. The polycondensation performed in toluene in presence of molecular sieves gave a polyester with DP 50 after 24 h. The same DP was obtained at much shorter reaction time (3 h) by bulk polymerization in an open vial without any drying agent present.

  • 11. Nocanda, Xolani
    et al.
    Larsson, Per Tomas
    Spark, Andrew
    Lush, Tamara
    Olsson, Ann
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Madikane, Mzekelo
    Bissessur, Ajay
    Iversen, Tommy
    Cross polarisation/magic angle spinning C-13-NMR spectroscopic studies of cellulose structural changes in hardwood dissolving pulp process2007In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 61, no 6, p. 675-679Article in journal (Refereed)
    Abstract [en]

    Cross polarisation/magic angle spinning C-13 NMR spectroscopy has been used to study structural changes in cellulose induced by the dissolving pulp process. The cellulose structure in several dissolving pulps was investigated for commercial and laboratory cooked Eucalyptus 92 alpha and 96 alpha. The average lateral dimension, or average thickness, of the cellulose fibril aggregates is related to the amount of surface area exposed and could be one controlling factor for the chemical reactivity of commercial dissolving pulps during modification reactions. The thickness of the cellulose fibril aggregates governs the amount of surface area present in the fibre wall, and cellulose surface material constitutes the part of the cellulose that is directly accessible to reagents. In all sample series investigated, the raw pulp was found to be less aggregated than the corresponding bleached final pulp. Furthermore, an irreversible increase in fibril aggregate width was observed on free drying for both laboratory cooked and commercial pulps. Upon rewetting with water, the freely dried 96 alpha pulp was found to be more aggregated than the freely dried 92 alpha pulp, although sugar analysis showed very similar carbohydrate compositions. As indicated by the molecular mass distribution, the commercial 92 alpha pulp contained larger amounts of degraded cellulose; this may be a plausible explanation for the different behaviour of the 92 alpha and 96 alpha pulps during free drying.

  • 12.
    Olsson, Ann
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindström, Mikael
    Iversen, Tommy
    Lipase-catalyzed synthesis of an epoxy-functionalized polyester from the suberin monomer cis-9,10-epoxy-18-hydroxyoctadecanoic acid2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 2, p. 757-760Article in journal (Refereed)
1 - 12 of 12
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