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Implications of chemical deterioration on mechanical performance of wood

Norbakhsh, Shahin (2014). Implications of chemical deterioration on mechanical performance of wood. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2014:17
ISBN 978-91-576-7982-6
eISBN 978-91-576-7983-3
[Doctoral thesis]

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Abstract

The oak wood of the 17th century warship Vasa has shown significant changes in the chemical and mechanical properties as compared to recent oak. The most important factors contributing to these changes are the incorporation of iron compounds during waterlogging and the uptake of polyethylene glycol (PEG) in the course of the preservation treatment. To investigate the effect of iron-dependent oxidative degradation reactions, samples of recent birch, pine and oak were impregnated with aqueous iron(II) chloride solution and thereafter exposed to air or pure oxygen at controlled relative humidity in long-term experiments, followed by tensile strength (TS) measurements. Iron-impregnated samples exposed to oxygen displayed significant effects already after one week and with a reduction in TS of ~50% after one year. Samples treated with additional PEG displayed less reduction in TS. The extent of oxidative degradation was monitored quantitatively following the O₂ consumption in closed vials with different relative humidity (RH), as a function of time. For oak, the initial O₂ consumption was high and declined with time. After 200 d, the accumulated O₂ consumption was 0.3-0.4 mmol∙(g wood)⁻¹. The formation of carbon dioxide and oxalic acid was positively correlated with RH. Samples kept for 1500 d at RH55% had accumulated 0.044 mmol oxalic acid∙(g wood)⁻¹, which equals the average oxalic acid content in the interior of Vasa oak. FT-IR analysis on iron(II) impregnated samples and on Vasa wood showed an increased signal intensity at 1710 cm⁻¹, assigned to carbonyl functions, in samples with reduced TS. The signal at 1710 cm⁻¹ is not primarily related to oxalic acid. The results show that chemical changes and mechanical performance of iron contaminated wood are strongly correlated and that the state of degradation is observable using IR spectroscopy. Overall, the results confirm that iron compounds have a detrimental effect in wood and indicate that PEG might act as an antioxidant in oxidative degradation processes. Concerning the Vasa, it may be concluded that most degradation related to iron compounds and oxidative processes has taken place during the first period of conservation when the wood was exposed to oxygen in a still very humid state. Thus, the current rate of oxidative degradation under the present relatively dry museum conditions should be relatively low.

Authors/Creators:Norbakhsh, Shahin
Title:Implications of chemical deterioration on mechanical performance of wood
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :March 2014
Volume:2014:17
Number of Pages:64
Papers/manuscripts:
NumberReferences
I.NORBAKHSH, S., BJURHAGER, I. & ALMKVIST, G. 2013. Mimicking of the strength loss in the Vasa: model experiments with iron-impregnated recent oak. Holzforschung, 67, 707-714.
II.NORBAKHSH, S., BJURHAGER, I. & ALMKVIST, G. 2014. Impact of iron compounds and oxygen on degradation of oak – modeling of the Vasa wood. (DOI: 10.1515/hf-2013-0197). Holzforschung, (in press)
III.NORBAKHSH, S., ALMKVIST, G., PERSSON I. 2014. Tensile strength depletion of hard and soft wood by iron compounds (manuscript).
IV.NORBAKHSH, S., BJURHAGER, I., ALMKVIST, G. 2014. FTIR analysis of chemically degraded wood - a comparison between recent oak and oak from the Vasa (manuscript).
Place of Publication:Uppsala
Publisher:Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-7982-6
ISBN for electronic version:978-91-576-7983-3
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:X Agricola extesions > X50 Chemistry
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Analytical Chemistry
(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Materials Chemistry
(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Inorganic Chemistry
(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Polymer Chemistry
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 204 Chemical Engineering > Corrosion Engineering
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 204 Chemical Engineering > Polymer Technologies
(A) Swedish standard research categories 2011 > 2 Engineering and Technology > 205 Materials Engineering > Paper, Pulp and Fiber Technology
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Wood Science
Agrovoc terms:wood, degradation, wood decay, iron, oxalic acid, oxidation, humidity, ethylene glycol, tensile strength, infrared spectrophotometry
Keywords:Wood, Fenton, Iron, Tensile strength, Oxalic acid, Infrared Spectroscopy, Multivariat data analysis
URN:NBN:urn:nbn:se:slu:epsilon-e-1816
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-1816
ID Code:11071
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Department of Chemistry and Biotechnology (140101-161231)
External funders:Swedish Agency for Innovation Systems
Deposited By: Shahin Norbakhsh
Deposited On:19 Mar 2014 13:37
Metadata Last Modified:02 Dec 2014 11:05

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