<p>Wood is often combined with other materials such as thermoplastics, adhesives and coatings. In general, combinations of wood and polymers especially in outdoor exposure have poor long-term durability. This behaviour can be related to an insufficient wood-polymer adhesion due to the low intrinsic compatibility between the wood substance and the polymers used. Another source for woodpolymer de-bonding is the high hygroscopicity of wood and great difference in hygro-thermal properties between the components.</p><p> The basic conceptual idea related to this work is to reduce the hygrosensitivity of wood by applying different wood modification methods, in particular, acetylation, furfurylation and heat treatment. The effects of such chemical modifications of wood, also accompanied with ageing effects, on its adhesion properties with commonly used synthetic polymers are, however, not well understood. In this context, the over-all purpose of this thesis is to achieve a better understanding of wood-polymer adhesion and interfacial forces which also may guide us to tailor the interaction between modified wood and e.g. thermoplastics and adhesives. The main focus of this thesis is therefore to apply contact angle analysis based on the Chang-Qin-Chen (CQC) Lewis acid-base model in order to estimate the work of adhesion (<i>W</i><i>a</i>) between the wood, modified wood and certain polymers. Contact angle measurements on wood samples were performed based on the Wilhelm plate principle. Related to this, an effort was also made to characterize the studied modified wood surfaces according to morphology and chemical composition. The methods that have been used are low vacuum scanning electron microscopy (LV-SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). </p><p>Results show that so-called interaction parameters can be successfully estimated for prediction of <i>W</i><i>a</i> between wood and polymers using the applied CQC model. Furthermore, such wetting analysis was successfully related to spectroscopic findings of the chemical composition of the wood samples surface. Ageing effects, i.e. the time after preparation of the wood surface, play a central role for the surface characteristics. In most cases, ageing resulted in a significant decrease of <i>W</i><i>a</i> between wood and water and a moderate decrease between wood and thermoplastics. The surface characteristics of acetylated wood were, however, more stable over time compared to unmodified, furfurylated and heat treated wood. The predicted <i>W</i><i>a</i>with the adhesives for heat treated and acetylated wood was increased due to ageing. Future work is planned to involve studies in order to relate such predicted adhesion properties with the actual performance of various wood-polymer systems.</p>

Wood is often combined with other materials such as thermoplastics, adhesives and coatings. In general, combinations of wood and polymers especially in outdoor exposure have poor long-term durability. This behaviour can be related to an insufficient wood-polymer adhesion due to the low intrinsic compatibility between the wood substance and the polymers used. Another source for woodpolymer de-bonding is the high hygroscopicity of wood and great difference in hygro-thermal properties between the components. The basic conceptual idea related to this work is to reduce the hygrosensitivity of wood by applying different wood modification methods, in particular, acetylation, furfurylation and heat treatment. The effects of such chemical modifications of wood, also accompanied with ageing effects, on its adhesion properties with commonly used synthetic polymers are, however, not well understood. In this context, the over-all purpose of this thesis is to achieve a better understanding of wood-polymer adhesion and interfacial forces which also may guide us to tailor the interaction between modified wood and e.g. thermoplastics and adhesives. The main focus of this thesis is therefore to apply contact angle analysis based on the Chang-Qin-Chen (CQC) Lewis acid-base model in order to estimate the work of adhesion (Wa) between the wood, modified wood and certain polymers. Contact angle measurements on wood samples were performed based on the Wilhelm plate principle. Related to this, an effort was also made to characterize the studied modified wood surfaces according to morphology and chemical composition. The methods that have been used are low vacuum scanning electron microscopy (LV-SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Results show that so-called interaction parameters can be successfully estimated for prediction of Wa between wood and polymers using the applied CQC model. Furthermore, such wetting analysis was successfully related to spectroscopic findings of the chemical composition of the wood samples surface. Ageing effects, i.e. the time after preparation of the wood surface, play a central role for the surface characteristics. In most cases, ageing resulted in a significant decrease of Wa between wood and water and a moderate decrease between wood and thermoplastics. The surface characteristics of acetylated wood were, however, more stable over time compared to unmodified, furfurylated and heat treated wood. The predicted Wa with the adhesives for heat treated and acetylated wood was increased due to ageing. Future work is planned to involve studies in order to relate such predicted adhesion properties with the actual performance of various wood-polymer systems. / QC 20101108

Im Rahmen des Forschungsprojektes wurden zwei Verfahren zur Herstellung thermisch modifizierter Furniere entwickelt. Nach Verfahren 1 erfolgt die Herstellung von Furnier durch Messern von thermisch modifizierten Blöcken, wobei der Hauptanteil der Untersuchungen an längs gemesserten Furnieren durchgeführt wurde. Ein Industrieversuch belegt die Machbarkeit der Herstellung thermisch modifizierter Furniere aus modifizierten Blöcken durch quer messern, also nach dem üblichen Verfahren zur Herstellung dekorativer Furniere. Nach Verfahren 2 erfolgt die Herstellung von thermisch modifizierten Furnieren durch thermische Modifizierung handelsüblicher dünner Messerfurniere (d=0,5...0,6 mm). Parameter für eine thermische Modifikation sind im Wesentlichen die Dauer der Behandlung sowie die Temperatur. Die Temperatur wurde im Bereich zwischen 170°C und 210°C variiert, die Dauer der Hochtemperaturbehandlung zwischen 2 h und 4 h. Als Holzarten wurden Rotbuche, Ahorn, Birke, Pappel und Esche untersucht. Die hergestellten Furniere wurden hinsichtlich verschiedener mechanischer Eigenschaften, farblicher Eigenschaften sowie verarbeitungstechnischer Eigenschaften untersucht und bewertet.

Bestimmte Extraktstoffe aus thermisch modifizierter Buche weisen fungizide Eigenschaften auf. Methanol-Extrakte aus thermisch modifizierter Buche, die in Propanon wieder aufgelöst wurden, wiesen eine leichte pilzwachstumshemmende Wirkung auf. Die getränkten Prüfkörper aus Buche erreichten eine Zuordnung zur Dauerhaftigkeitsklasse 4, d. h. nicht dauerhaft. Prüfkörper, die mit anderen Extrakten aus thermisch modifizierter Buche getränkt wurden, dabei insbesondere Wasser-Extrakte, weisen dagegen keine signifikante Resistenzverbesserung auf. Die Analyse der Methanol-Extrakte mittels Gaschromatografie mit Massenspektrometrie-Kopplung (GC-MS) ließ einen erhöhten Anteil bestimmter phenolischer Verbindungen erkennen, die teilweise Resistenz fördernde Wirkungen haben. Das Vorhandensein dieser Verbindungen kann somit als Begründung der Verbesserung der Resistenz entsprechend imprägnierter Prüfkörper herangezogen werden. Die Endfassung des Artikels ist auf www.holztechnologie.de verfügbar. / Certain extractives from thermally modified beech have fungicidal properties. Methanol extracts, resolubilized in propanone, caused a significant retardation of fungal growth on native beech specimen. Beech specimen impregnated with these extractives could be assigned to the durability class 4, i. e. not permanent. Other extracts of thermally modified beech, in particular water extracts, did not show significant improvement in resistance. The analysis of methanol extracts using gas chromatography coupled with mass spectrometry (GC-MS) showed an increased amount of phenolic compounds known to increase resistance. Their presence in organic extracts of thermally modified wood may explain the improvement of the resistance of the impregnated specimen. The original publication is available at www.holztechnologie.de.

Bestimmte Extraktstoffe aus thermisch modifizierter Buche weisen fungizide Eigenschaften auf. Methanol-Extrakte aus thermisch modifizierter Buche, die in Propanon wieder aufgelöst wurden, wiesen eine leichte pilzwachstumshemmende Wirkung auf. Die getränkten Prüfkörper aus Buche erreichten eine Zuordnung zur Dauerhaftigkeitsklasse 4, d. h. nicht dauerhaft. Prüfkörper, die mit anderen Extrakten aus thermisch modifizierter Buche getränkt wurden, dabei insbesondere Wasser-Extrakte, weisen dagegen keine signifikante Resistenzverbesserung auf. Die Analyse der Methanol-Extrakte mittels Gaschromatografie mit Massenspektrometrie-Kopplung (GC-MS) ließ einen erhöhten Anteil bestimmter phenolischer Verbindungen erkennen, die teilweise Resistenz fördernde Wirkungen haben. Das Vorhandensein dieser Verbindungen kann somit als Begründung der Verbesserung der Resistenz entsprechend imprägnierter Prüfkörper herangezogen werden. Die Endfassung des Artikels ist auf www.holztechnologie.de verfügbar. / Certain extractives from thermally modified beech have fungicidal properties. Methanol extracts, resolubilized in propanone, caused a significant retardation of fungal growth on native beech specimen. Beech specimen impregnated with these extractives could be assigned to the durability class 4, i. e. not permanent. Other extracts of thermally modified beech, in particular water extracts, did not show significant improvement in resistance. The analysis of methanol extracts using gas chromatography coupled with mass spectrometry (GC-MS) showed an increased amount of phenolic compounds known to increase resistance. Their presence in organic extracts of thermally modified wood may explain the improvement of the resistance of the impregnated specimen. The original publication is available at www.holztechnologie.de.

Im Rahmen des Forschungsprojektes wurden zwei Verfahren zur Herstellung thermisch modifizierter Furniere entwickelt. Nach Verfahren 1 erfolgt die Herstellung von Furnier durch Messern von thermisch modifizierten Blöcken, wobei der Hauptanteil der Untersuchungen an längs gemesserten Furnieren durchgeführt wurde. Ein Industrieversuch belegt die Machbarkeit der Herstellung thermisch modifizierter Furniere aus modifizierten Blöcken durch quer messern, also nach dem üblichen Verfahren zur Herstellung dekorativer Furniere. Nach Verfahren 2 erfolgt die Herstellung von thermisch modifizierten Furnieren durch thermische Modifizierung handelsüblicher dünner Messerfurniere (d=0,5...0,6 mm). Parameter für eine thermische Modifikation sind im Wesentlichen die Dauer der Behandlung sowie die Temperatur. Die Temperatur wurde im Bereich zwischen 170°C und 210°C variiert, die Dauer der Hochtemperaturbehandlung zwischen 2 h und 4 h. Als Holzarten wurden Rotbuche, Ahorn, Birke, Pappel und Esche untersucht. Die hergestellten Furniere wurden hinsichtlich verschiedener mechanischer Eigenschaften, farblicher Eigenschaften sowie verarbeitungstechnischer Eigenschaften untersucht und bewertet.

Abstract The present thesis exploits advanced liquid and gas NMR methods for the characterization of various interesting materials. The methods used to study the structural properties of thermally modified wood, ionic liquids, cements, shales, and porous organic cages include MRI, NMR cryoporometry, Laplace NMR, multidimensional Laplace NMR, as well as ¹²⁹Xe and ¹⁹F NMR. The commonality factor in all the studies is the usage of either inherent or introduced liquid or gas molecules to probe the topical materials. The MRI method was utilized to visualize the water absorption phenomena in the thermally modified pine wood. High-resolution images made it possible to observe the spatial distribution of free water and the changes in the rate of absorption of water in wood samples modified at different temperatures. The images also helped to resolve the individual resin channels. T₂ maps enabled us to observe the changes in the relaxation values of free water in thermally modified wood as compared to their unmodified reference wood samples. The multidimensional Laplace NMR methods were exploited to study the structural and dynamical properties of a novel halogen-free, boron-based ionic liquid (hf-BIL). NMR self-diffusion (D) experiments showed the presence of two coexisting dynamic phases in hf-BIL. Multidimensional D − T₂ correlation experiments made it possible to determine the T₂ relaxation times of the slow and fast diffusing phases. T₂ − T₂ relaxation exchange measurements allowed quantifying the exchange rates of anions and cations between the phases. Moreover, the theoretical modeling of the experimental data revealed that the slow diffusing phase was composed of anion-cation aggregates, while the fast diffusing phase was comprised of free anions and cations. ¹²⁹Xe NMR analysis of the xenon adsorbed in the cements and shales helped us to determine their porous structures. The method exploits the high sensitivity of the chemical shift of ¹²⁹Xe to its local environment. The chemical shift value of ¹²⁹Xe enabled us to estimate the size of the mesopores in the cement samples. The exchange spectroscopy (EXSY) measurements were used to determine the exchange rates between the free gas and mesopores of the cement samples. ¹²⁹Xe NMR spectra of the shale samples provided information about pore sizes and paramagnetic compounds. ¹H NMR cryoporometry measurements of the shale samples immersed in acetonitrile made it possible to analyze the pore size distribution ranging from 10 to over 100 nm. Moreover, T₂ − T₂ exchange measurements helped us to quantify the exchange rates of acetonitrile in the shale samples. Xenon and SF₆ were used as internal reporters to gain versatile information on adsorption phenomena in the cage and window cavities of the crystalline porous organic cages. ¹²⁹Xe NMR analysis of the adsorbed xenon helped us to determine the diffusion coefficients and activation energy of diffusion as well as thermodynamic parameters. With the help of T₂ relaxation time values, it was possible to estimate the exchange rates between cage and window cavities. Chemical exchange saturation transfer (CEST) experiments resolved a window cavity site, which arises from crystal defects in porous organic cages. In addition, ¹⁹F NMR analysis made it possible to estimate the relaxation rates and diffusion coefficients of SF₆ gas in porous organic cages. Modelling of the T₁, T₂ and diffusion data confirmed that the cage to window exchange is the completely dominating mechanism for ¹²⁹Xe T₂ relaxation. T₁ relaxation is dominated by diffusion modulated dipole-dipole relaxation (DDinter) and chemical shift anisotropy (CSA) relaxation due to local cavity mobility. Whereas, in case of SF₆ T₂ data, the dominating mechanism is diffusion modulated dipole-dipole relaxation and for T₁ the local tumbling of SF₆ in cage cavity is the key dynamics behind the dipole-dipole and CSA mechanisms. / Original papers The original publications are not included in the electronic version of the dissertation. Javed, M. A., Kekkonen, P. M., Ahola, S., &amp; Telkki, V.-V. (2015). Magnetic resonance imaging study of water absorption in thermally modified pine wood. Holzforschung, 69(7), 899–907. https://doi.org/10.1515/hf-2014-0183 Javed, M. A., Ahola, S., Håkansson, P., Mankinen, O., Aslam, M. K., Filippov, A., … Telkki, V.-V. (2017). Structure and dynamics elucidation of ionic liquids using multidimensional Laplace NMR. Chem. Commun., 53(80), 11056–11059. https://doi.org/10.1039/c7cc05493a http://jultika.oulu.fi/Record/nbnfi-fe2017102750335 Javed, M. A., Komulainen, S., Daigle, H., Zhang, B., Vaara, J., Zhou, B., &amp; Telkki, V.-V. (2019). Determination of pore structures and dynamics of fluids in hydrated cements and natural shales by various ¹H and ¹²⁹Xe NMR methods. Microporous and Mesoporous Materials, 281, 66–74. https://doi.org/10.1016/j.micromeso.2019.02.034 http://jultika.oulu.fi/Record/nbnfi-fe2019041712678 Komulainen, S., Roukala, J., Zhivonitko, V. V., Javed, M. A., Chen, L., Holden, D., … Telkki, V.-V. (2017). Inside information on xenon adsorption in porous organic cages by NMR. Chemical Science, 8(8), 5721–5727. https://doi.org/10.1039/C7SC01990D http://jultika.oulu.fi/Record/nbnfi-fe201709288804 Håkansson, P., Javed, M. A., Komulainen, S., Chen, L., Holden, D., Hasell, T., … Telkki, V.-V. (2019). NMR relaxation and modelling study of the dynamics of SF₆ and Xe in porous organic cages. Manuscript.

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Densification is a well-known method for improving the mechanical properties of wood. In the present study, unmodified and furfurylated wood samples were densified and submitted to cyclic water storage tests and cyclic alternating climate tests. Swelling coefficients and spring-back data were determined for the evaluation of the quality of densification. The study shows that results depend on the test method applied. Simple water storage tests do not reflect the behavior of densified wood in the high humidity range. The spring-back data of unmodified samples are more influenced by the testing method than those of the furfurylated ones.

This paper deals with the determination of the capillary pore-size distribution (CPSD) and equilibrium moisture content (EMC) of untreated and thermally modified (TM) Norway spruce [Picea abies (L.) Karst.] by means of the pressure plate technique (PPT). Desorption experiments were conducted at very high values of relative humidity (RH) in the range between 99.2% and 100%. The thermal modification of spruce results in an alteration of the CPSD, owing to the formation of intercellular cracks in the middle lamella, as a result of cell-wall compression. The desorption curves for both untreated and TM spruce show an extremely upward bend at 99.97% RH. This step reflects an EMC of 38.1% for untreated spruce and 33.8% for TM spruce. None of the samples shrunk during the PPT measurements. Following desorption experiments at 97.4% RH, all samples shrunk. This step reflects an EMC of 27.9% for untreated spruce and 21.7% for TM spruce.