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  • 1.
    Dedic, Dina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The warship Vasa: A Study of Lignin, Extractives and Acids in the oak wood2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The oak wood timbers of the 17th century Swedish warship Vasa are weak. The weakening has been attributed to cellulose degradation, which is more extensive in the interior of the timbers compared to the surface regions. Further, the mechanism of cellulose degradation was attributed to oxidative reactions involving iron as a catalyst. In this work, the non-cellulosic wood components (lignin and extractives) in the wood of the Vasa have been studied in order to assess the level of degradation possibly caused by oxidative reactions. Because the interior of the wood timbers is more acidic and its cellulose more depolymerized than at the near surface regions, a general study of organic acidand iron concentrations with respect to different depths from the surface was also performed.

    Characterization of lignin in the wood of the Vasa was done by means of wet chemical degradation (thioacidolysis) and subsequent GC-MS analysis of the degradation products, as well as CP/MAS 13C NMR spectroscopy of the wood. Dry acetone- and water extracts of the wood were analyzed by 13C NMR spectroscopy and MALDI-TOF mass spectroscopy in order to study the presence of gallo- and ellagitannins. No severe lignin degradation and no discernible amounts of hydrolysable tannins in the oak wood of the Vasa were detected, indicating that oxidative reactions are not the primary route to cellulose depolymerization.

    High amounts of oxalic acid (analyzed by HPIEC) and a low pH have been found in the interior of the wood timbers, supporting acid hydrolysis as the main mechanism of cellulose depolymerization. Analysis of the iron distribution using ICP AES shows that iron is most abundant in the surface of the timbers and decreases as the concentration of oxalic acid increases. Experimental work also shows that some iron species (rust) in the Vasa neutralize oxalic acid, thereby protecting the surface wood from acid hydrolysis.

  • 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.
    Iversen, Tommy
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Degradation reactions in vasa wood2011In: Shipwrecks 2011, 2011, p. 114-116Conference paper (Refereed)
  • 4.
    Dedic, Dina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Iversen, Tommy
    Sandberg, Teresia
    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.
    Chemical analysis of wood extractives and lignin in the oak wood of the 380 year old Swedish warship Vasa2011Conference paper (Refereed)
    Abstract [en]

    In order to map the source of oxalic acid in the interior wood of the Vasa ship, an analysis of wood extractives (tannins) was conducted. Samples used for analysis were PEG-impregnated dry Vasa wood, waterlogged Vasa wood and a reference material (fresh oak). The wood material was ground and extracted with an acetone/water-mixture. In the reference sample, several types of tannins were found such as the isomers castalagin/vescalagin and grandinin and their dimmers roburin A/D and roburin B/C respectively. The results have been confirmed by NMR spectroscopy and MALDI-TOF. The interior of the waterlogged Vasa wood contained small amounts of monomers, whereas the dry, PEG treated Vasa revealed no discernible amounts of hydrolysable tannins or other easily soluble compounds. Furthermore, an analysis of lignin was made by means of chemical degradation (thioacidolysis). A decrease in the amount of β-O-4 bonds in the lignin structure would imply a formation of easily oxidized free phenolics. The products were analyzed by GC-MS, which revealed no dramatic differences between the Vasa samples and the reference. The results were confirmed by CP/MAS NMR by analyzing the differences in the aromatic region (150∼160 ppm) as well as the carbonyl region (190∼200 ppm).

  • 5.
    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.

  • 6.
    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.))
1 - 6 of 6
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  • apa
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