Wettability changes and mass loss during heat treatment of wood

Hakkou, Mohammed; Pétrissans, Mathieu; Bakali, Idriss El; Gérardin, Philippe; Zoulalian, André

doi:10.1515/hf.2005.006

Cited by 86 publications

(56 citation statements)

References 13 publications

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“…En este caso, el número de grupos -OH libres en la superficie de la madera disminuye produciendo enlaces de hidrógeno internos y fuertes enlaces cruzados (Oliveira et al 2010, Chen et al 2012. Cuando las temperaturas son más altas, las regiones amorfas de la madera sufren reordenamientos, y las regiones cristalinas aumentan (Hakkou et al 2005). Así, sus características de mojabilidad son afectadas, ya que el contenido de humedad de la madera disminuye después del tratamiento térmico (Lekounougou bajos en las maderas tratadas térmicamente, lo que indica que las maderas tienen comportamiento más apolar después del tratamiento térmico; es decir, son más hidrófobas y repelen más el agua como se discutió previamente.…”

Section: Determinación De La Energía Libre Superficialunclassified

Cambios en la mojabilidad en superficies de maderas tratadas térmicamente: Angulo de contacto y energía libre superficial

Santos

Gonçalves

2016

Maderas, Cienc. tecnol.

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RESUMENFueron determinados los ángulos de contacto de las maderas Pinus (Pinus taeda), Erisma (Erisma uncinatum), Araucaria (Araucaria angustifolia) e Hymenaea (Hymenaea stilbocarpa) en cuatro líquidos de pruebas (agua, diyodometano, formamida y etilenglicol). Los valores de energía libre superficial fueron calculados en las maderas sometidas al tratamiento térmico, teniendo en cuenta los cambios en sus componentes polares y apolares (dispersivas). De acuerdo con los resultados del ángulo de contacto, energía libre superficial y polaridad superficial, las maderas se mostraron poco mojables después del tratamiento térmico, transformándose en hidrofóbicas. Las maderas Pinus y Araucaria se mostraron más polares y presentaron bajos valores de ángulo de contacto y alta mojabilidad (más hidrofílicas). Los valores de energía libre superficial obtenidos a partir de las medidas de ángulo de contacto mostraron una dependencia por el uso de dos, tres o cuatro líquidos de prueba, produciendo diferentes perfiles de los componentes de la energía libre superficial. Las características superficiales de las maderas fueron definidas con base en sus valores de polaridad superficial, un parámetro importante para inferir cuales maderas son más apolares (más hidrofóbicas), o sea, de mayor interés tecnológico.Palabras clave: Adherencia, ángulos de contacto, maderas hidrofóbicas, mojabilidad, superficies de maderas. ABSTRACTThe contact angles for Pinus (Pinus taeda), Erisma (Erisma uncinatum), Araucaria (Araucaria angustifolia) and Hymenaea (Hymenaea stilbocarpa) woods were obtained using four test liquids (water, diiodomethane, formamide, and ethylene glycol). The values of surface free energy were calculated for the heat-treated woods in order to analyze their changes in polar and non-polar (dispersive) components. According to the results of contact angles, surface free energies and surface polarities, the woods showed reduced wettability after heating treatment and become hydrophobic. Pinus and Araucaria were by far the most polar samples, since they presented low values of contact angle and high wettability (more hydrophilic). The approach used to calculate the surface free energy from the measurements of contact angle depends on the use of two, three or four test liquids, since different profiles were obtained for their polar and non-polar components. The surface characteristics for the wood samples were mainly defined based on polarity, which is an important parameter aiming at inferring when they are more polar (more hydrophobic), i.e. of great technological interest.

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Section: Determinación De La Energía Libre Superficialunclassified

Cambios en la mojabilidad en superficies de maderas tratadas térmicamente: Angulo de contacto y energía libre superficial

Santos

Gonçalves

2016

Maderas, Cienc. tecnol.

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“…An illustration of the hydroxyl groups' reduction is shown in Figure 1. Previous studies revealed that heat treatment reduces the equilibrium moisture content, water absorption, thickness swelling and wettability of wood (Pétrissans et al 2003, Hakkou et al 2005. Heat treatment at high temperature also induces darkening of wood (Brischke et al 2007).…”

Section: Introductionmentioning

confidence: 98%

“…Several studies have been conducted on the effects of heat treatment on wood color change, moisture sorption and dimensional stability, durability and mechanical properties (Rowell and Konkol 1987, Temiz et al 2006, Hakkou et al 2005, Korkut and Kocaefe 2009). However, research on the effects of heat treatment on the rheological behaviour and surface chemistry of Nigeria native trees is scanty.…”

Section: Introductionmentioning

confidence: 99%

Mid-infrared spectroscopy and dynamic mechanical analysis of heat-treated obeche (Triplochiton scleroxylon)wood

Fabiyi

Ogunleye

2015

Maderas, Cienc. tecnol.

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The chemical structure change and rheological behaviour of heat-treated Obeche (Triplochiton scleroxylon) wood were investigated. Wood samples were treated at 160 and 200°C for 30, 60 and 120 minutes. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and dynamic mechanical analysis (DMA) were employed to characterize the chemical structure and rheological property of the heat-treated wood, respectively. Infrared data showed that there was a reduction in the number of hydroxyl groups (one of the factors normally attributed to water absorption) of heat treated wood relative to the control samples. The relative cellulose crystallinity increased slightly which may be one of the factors contributing to the stiffness of the heat-treated wood. The latter increases with increasing treatment temperature and time. The rheological properties of the wood samples were tested while submerged in N-methyl-2-pyrrolidone solvent under saturated conditions. DMA results showed that the increasing heat treatment time caused an increase in the glass transition temperature relative to the control sample, irrespective of the treatment temperature. Therefore, heat treatment at moderately high temperatures (160 and 200 °C) showed an interesting potential which could be used to reduce water absorption and improve flexural modulus of Obeche wood.

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“…Vários trabalhos mostram que ocorre uma perda de massa progressiva, com o aumento do tempo e da temperatura de aquecimento (Hakkou et al, 2005;Garcia et al, 2012). Entretanto, a perda de massa e a redução da densidade e da resistência mecânica da madeira também dependem da espécie e do teor de umidade.…”

Section: Introductionunclassified

Propriedades físicas da madeira de teca termorretificada

et al. 2014

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RESUMOO objetivo deste estudo foi determinar o efeito de tratamentos termorretificadores nas propriedades físicas (densidade e teor de umidade) da madeira de teca (Tectona grandis L. f.), proveniente de plantios de diferentes espaçamentos. Amostras de madeira de cerne e alburno foram termorretificadas a 180°C e 200°C durante 2 horas e 30 minutos. A termorretificação afetou mais a densidade do cerne do que a densidade do alburno. As madeiras de cerne e alburno apresentaram uma redução média de 52% no teor de umidade de equilíbrio, após a termorretificação. O espaçamento entre árvores também afetou as propriedades físicas da madeira após a termorretificação.Palavras-chave: densidade, teor de umidade, termorretificação, Tectona grandis. Physical Properties of Heat-treated Teak Wood ABSTRACTThe objective of this study was to determine the effect of heat treatments on the physical properties (density and moisture content) of teak (Tectona grandis L. f.) wood from plantations of different spacings. Heartwood and sapwood samples were heat treated at 180 °C and 200 °C for 2 hours and 30 minutes. Heat treatment produced greater effect on heartwood density compared with sapwood density. Heartwood and sapwood presented an average reduction of 52% in equilibrium moisture content after heat treatment. Tree spacing also affected the physical properties of wood after heat treatment.

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Wettability changes and mass loss during heat treatment of wood

Cited by 86 publications

References 13 publications

Cambios en la mojabilidad en superficies de maderas tratadas térmicamente: Angulo de contacto y energía libre superficial

Cambios en la mojabilidad en superficies de maderas tratadas térmicamente: Angulo de contacto y energía libre superficial

Mid-infrared spectroscopy and dynamic mechanical analysis of heat-treated obeche (Triplochiton scleroxylon)wood

Propriedades físicas da madeira de teca termorretificada

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