Effect of thermal modification on mechanical properties of Canadian white birch (<i>Betula papyrifera)</i>

Lekounougou, S.; Kocaefe, Duygu; Oumarou, Noura; Kocaefe, Yasar S.; Poncsák, Sándor

doi:10.1179/2042645311y.0000000016

Cited by 22 publications

(15 citation statements)

References 16 publications

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“…While the MOE increases slightly between 190 and 200°C and decreases slightly at 210°C. Similar results were found in the literature with other species (Bekhta and Niemz 2003, Pavlo et al 2003, Poncsák et al 2006, Metsa-Kortelainen and Viitanen 2010, Lekounougou et al 2011). They found that the MOR decreases when the thermal modification temperature increases, while the MOE does not appear to be significantly affected by temperature.…”

Section: Resultssupporting

confidence: 92%

Effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of black spruce (Picea mariana)

Lekounougou

Kocaefe

2014

Wood Material Science & Engineering

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This study was aimed at evaluating the effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of Picea mariana. The boards were thermally modified at different temperatures 190, 200 and 210°C. The results indicated that the thermal modification of wood caused a significant decrease in the modulus of rupture (MOR) after 190°C, while the modulus of elasticity (MOE) seemed less affected with a slight increase up to 200°C and slight decrease with further increase in temperature. The hardness of the thermally modified wood increased in the axial direction. This increase was also observed in tangential and axial directions but at a lesser extent. The final value was slightly higher in axial direction and lower in radial and tangential directions compared to those of the untreated wood. Dimensional stability improved with thermal modification in the three directions compared to the dimensional stability of unmodified wood. The fungal degradation results showed that the decay resistance of thermally modified wood against the wood-rotting fungi Trametes versicolor and Gloephyllum trabeum improved compared to that of the untreated wood. By contrast, the thermal modification of P. mariana had a limited effect on the degradation caused by the fungus Poria placenta.

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Section: Resultssupporting

confidence: 92%

Effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of black spruce (Picea mariana)

Lekounougou

Kocaefe

2014

Wood Material Science & Engineering

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“…In the closed system the decrease in MOE is directly correlated to the CML, but in the open system modification there was an increase of the MOE ratio until 200°C reaching 1,2 (CML 15%), after that point it started to decrease but without showing a direct relation between the CML and the MOE. Similar peaks of MOE have been reported in other species, such as Canadian white birch (Lekounougou et al 2011), Picea abies (Norway spruce) (Borrega and Kärenlampi 2008) and other eucalypt species, such as E. grandis and E. regnans (de Cademartori et al 2015), and E. globulus (Santos 2000), although no type of treatment was mentioned in the latter.…”

Section: Static and Dynamic Mechanical Propertiessupporting

confidence: 80%

“…In both species, MOE and MOR reduced with rising modification temperature. However, other authors showed that MOE of thermally modified wood can de higher than the reference values increased in certain thermal modifications (Borrega and Kärenlampi 2008, Kubojima et al 2000, Lekounougou et al 2011, Rautkari and Hill 2014, Santos 2000. The structural integrity of wood is also affected by the thermal modification, as the degradation of hemicelluloses (Alen et al 2002, Boonstra and Tjeerdsma 2006, Sundqvist et al 2006 can cause an increased brittleness of the material (Phuong et al 2007, Weigl et al 2012.…”

Section: Introductionmentioning

confidence: 97%

Relation of chemical and mechanical properties ofEucalyptus nitenswood thermally modified in open and closed systems

Wentzel

Fleckenstein

Hofmann

et al. 2018

Wood Material Science & Engineering

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Eucalyptus nitens is a fast growing plantation species that has a good acclimation in Chile. It is commonly used for pulp and paper, but there is a growing market for solid wood products made from this species and an interest on producing high quality material. Thermal modification technology have been used to obtain high quality product out of fast growing plantation species. In this study we modified Eucalyptus nitens to analyse the influences of the process conditions and evaluated its mechanical properties under several process conditions. The material was modified in a closed system under elevated pressure and controlled relative humidity (30 and 100% relative humidity) at temperatures between 150 and 170°C, and in an open system with a standard thermal modification procedure between 160 and 230°C. Modulus of elasticity, modulus of rupture, deflection and work in bending (in elastic and inelastic proportions) and the resistance to impact milling in high energy multiple impact tests were determined. Mass loss after each modification was also measured and correlated with the mechanical properties. Anatomical properties of selected modifications were analysed. There were no significant differences between open and closed system modifications in both mechanical and anatomical properties.

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“…Although several investigations were carried out to study the heat treatment effects on the mechanical properties of jack pine and birch [170][171][172], there is no publication available in the literature on the discoloration taking place due to the artificial weathering of the heat-treated and untreated specific wood species considered in this study. Hence, the effect of accelerated weathering on color changes of different heat-treated woods is investigated in more detail.…”

Section: Generalmentioning

confidence: 99%

Study on the degradation mechanism of heat-treated wood by UV light /

Huang

2012

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Heat-treated wood is a wood product thermally treated at high temperatures in the range of 180°C and 240°C for its preservation without using any additional chemicals. Heat treatment modifies wood both chemically and physically. Amorphous polysaccharide content (hemicelluloses) decreases, condensation and demethoxylation of lignin take place, and certain extractives are removed. Consequently, heat-treated wood possesses new physical properties such as reduced hygroscopy, improved dimensional stability, better resistance to degradation by insects and micro-organisms, and attractive darker color. These new beneficial and attractive properties make heat-treated wood popular for indoor as well as outdoor applications.However, similar to untreated wood, heat-treated wood is also susceptible to degradation due to environmental conditions. Weathering results in poor aesthetics for heat-treated wood because of the discoloration and surface checking when exposed to UV radiation. However, investigations on the wettability changes, chemical changes, and microscopic changes of heat-treated wood after exposure to artificial weathering are very limited; and there is no publication available in the literature on the degradation taking place due to the weathering of heat-treated North American jack pine, aspen, and birch used in this study.This work was undertaken to study the weathering degradation mechanisms of the three North American regional species (jack pine (Pinus banksiana), aspen (Populus tremuloides\ and birch (Betula papyrifera)) heat-treated under different conditions to understand the chemical and physical changes taking place and to compare these changes with those of untreated controlled samples when they are exposed to artificial weathering with and without water spray for various periods. Several techniques and tools were used such as color measurement, contact angle test for wettability analysis, Fourier transforms infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) for chemical analysis, florescence microscopy (FM), and scanning electron spectroscopy (SEM) for microscopic structural analysis. These provide a great deal of insight into the degradation process.The results show that color changes occurring during weathering of heat-treated woods are due to the increasing lignin condensation and decreasing extractives content on wood surfaces caused by heat treatment. Changes in wettability during weathering of heattreated wood are induced by the combination of surface structural and chemical modifications. Lignin in heat-treated woods is more sensitive to weathering than other components. It is proposed that the weathering mechanism of heat-treated woods consists of the degradation of lignin matrix and extractives, which lightens the wood color. As a result, the color difference between the color of heat-treated wood before weathering and the color of the same wood during weathering increases with exposure time. Then, the leaching of other polymers present on wood surface takes place...

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Effect of thermal modification on mechanical properties of Canadian white birch (Betula papyrifera)

Cited by 22 publications

References 16 publications

Effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of black spruce (Picea mariana)

Effect of thermal modification temperature on the mechanical properties, dimensional stability, and biological durability of black spruce (Picea mariana)

Relation of chemical and mechanical properties ofEucalyptus nitenswood thermally modified in open and closed systems

Study on the degradation mechanism of heat-treated wood by UV light /

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