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Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.ORCID iD: 0000-0002-9156-3161
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Technical Research Institute of Sweden.ORCID iD: 0000-0001-7014-6230
SP Technical Research Institute of Sweden.
2015 (English)In: Wood and Fiber Science, ISSN 0735-6161, Vol. 47, no 4, 410-420 p.Article in journal (Refereed) Published
Abstract [en]

The surface energy of unmodified and thermally modified spruce wood components was researched at dry and moist conditions using inverse gas chromatography. The results indicate a more pronounced heterogeneous nature of the thermally modified wood surfaces in terms of the dispersive (nonpolar) component of the surface energy, compared with that of the unmodified wood surfaces. The dispersive component of the surface energy of the thermally modified wood ranged between 44 and 38 mJ/m(2) corresponding to an increase in surface coverage from a low level and up to about 10%. Suggested explanations for the more distinct heterogeneity of the thermally modified wood sample are related to chemical changes of the wood substance which seem to result in certain micromorphological features observed by scanning electron microscopy as alternated fracture surfaces created in the grinding process; and also possible changes or redistribution of the wood extractives. An increase of the MC, representing a change from a dry condition of approximately 0% RH to ca 75% RH, of both the unmodified and thermally modified samples seemed to have a marginal influence on the dispersive component of the surface energy. Possible implications of the results in this study can be found in the tailoring of new compatible and durable material combinations, for example, when using thermally modified wood residuals as a component in new types of biocomposites.

Place, publisher, year, edition, pages
SOC WOOD SCI TECHNOL , 2015. Vol. 47, no 4, 410-420 p.
Keyword [en]
Thermally modified wood, inverse gas chromatography, humidity cycling, Norway spruce, dispersive surface energy, surface energy heterogeneity, BET-specific surface area
National Category
Materials Engineering
Research subject
Civil and Architectural Engineering
Identifiers
URN: urn:nbn:se:kth:diva-172956ISI: 000363992000011Scopus ID: 2-s2.0-84991704745OAI: oai:DiVA.org:kth-172956DiVA: diva2:851329
Funder
Swedish Research Council Formas, EnWoBio 2014-172
Note

QC 20151202

Forskningsfinansiärer: Stiftelsen Nils och Dorthi Troëdssons forskningsfond (Projektnr 793/12 Hydro-termo-mekanisk modifiering av trä). EcoBuild Institute Excellence Centre

Available from: 2015-09-04 Created: 2015-09-03 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Surface characterisation of thermally modified spruce wood and influence of water vapour sorption
Open this publication in new window or tab >>Surface characterisation of thermally modified spruce wood and influence of water vapour sorption
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Today there is growing interest within the construction sector to increase the proportion of biobased building materials made from renewable resources. By-products or residuals from wood processing could in this case be valuable resources for manufacturing new types of biocomposites. An important research question related to wood-based biocomposites is how to characterise molecular interactions between the different components in the composite. The hygroscopic character of wood and its water sorption properties are also crucial. Thermal modification (or heat treatment) of wood results in a number of enhanced properties such as reduced hygroscopicity and improved dimensional stability as well as increased resistance to microbiological decay.

In this thesis, surface characteristics of thermally modified wood components (often called wood fibres or particles) and influencing effects from moisture sorption have been analysed using a number of material characterisation techniques. The aim is to increase the understanding in how to design efficient material combinations for the use of such wood components in biocomposites. The specific objective was to study surface energy characteristics of thermally modified spruce (Picea abies Karst.) under influences of water vapour sorption. An effort was also made to establish a link between surface energy and surface chemical composition. The surface energy of both thermally modified and unmodified wood components were studied at different surface coverages using inverse gas chromatography (IGC), providing information about the heterogeneity of the surface energy. The water vapour sorption behaviour of the wood components was studied using the dynamic vapour sorption (DVS) method, and their surface chemical composition was studied by means of X-ray photoelectron spectroscopy (XPS). Additionally, the morphology of the wood components was studied with scanning electron microscopy (SEM).

The IGC analysis indicated a more heterogeneous surface energy character of the thermally modified wood compared with the unmodified wood. An increase of the dispersive surface energy due to exposure to an increased relative humidity (RH) from 0% to 75% RH at 30 ˚C was also indicated for the modified samples. The DVS analysis indicated an increase in equilibrium moisture content (EMC) in adsorption due to the exposure to 75% RH. Furthermore, the XPS results indicated a decrease of extractable and a relative increase of non-extractable compounds due to the exposure, valid for both the modified and the unmodified wood. The property changes due to the increased RH condition and also due to the thermal modification are suggested to be related to alterations in the amount of accessible hydroxyl groups in the wood surface. Recommendations for future work and implications of the results could be related to knowledge-based tailoring of new compatible and durable material combinations, for example when using thermally modified wood components in new types of biocomposites for outdoor applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xiii, 36 p.
Series
TRITA-BYMA, ISSN 0349-5752 ; 2015:4
Keyword
Thermally modified wood, Norway spruce, inverse gas chromatography (IGC), dynamic vapour sorption (DVS), X-ray photoelectron spectroscopy (XPS), surface energy, Värmebehandlat trä, gran, omvänd gaskromatografi (IGC), dynamic vapour sorption (DVS), röntgenelektronspektroskopi (XPS), ytegenskaper, ytenergi
National Category
Civil Engineering Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-172989 (URN)
Presentation
2015-09-25, B25, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas, EnWoBio 2014-172
Note

Forskningsfinansiärer och strategiska forskningsprojekt:

Nils och Dorthi Troëdssons forskningsfond (Projektnr 793/12 Hydro-termo-mekanisk modifiering av trä).

 KTH Royal Institute of Technology.

 COST Action FP0904.

 KK-Stiftelsen.

Stiftelsen för strategiskt forskning (SSF). QC 20150908

Available from: 2015-09-08 Created: 2015-09-04 Last updated: 2015-09-08Bibliographically approved

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Wålinder, MagnusSegerholm, Kristoffer

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