Quantitative characterization of chemical degradation of heat‐treated wood surfaces during artificial weathering using XPS

Abstract

The X-ray photoelectron spectroscopy (XPS) study of three heat-treated North American wood species (jack pine, birch and aspen) was carried out to evaluate chemical modifications occurring on the wood surface during artificial weathering for different times. The results suggest that the weathering reduces lignin content (aromatic rings) at the surface of heat-treated wood, consequently, the carbohydrates content increases. This results in surfaces richer in cellulose and poorer in lignin. Heattreated wood surfaces become acidic due to weathering, and the acidity increases as the weathering time increases. Three possible reasons are given to account for the increase of acidity during weathering. The lignin content increases, whereas the hemicelluloses content decrease due to heat treatment. Heat-treated woods have lower acidity to basicity ratios than the corresponding untreated woods for all three species because of the decrease in carboxylic acid functions mainly present in hemicelluloses. The wood composition changes induced by weathering are more significant compared to those induced by heat treatment at wood surface. Exposure to higher temperatures causes more degradation of hemicelluloses, and this characteristic is maintained during weathering. However, the wood direction has more effect on chemical composition modification during weathering compared to that of heat treatment temperature. The heat-treated jack pine is affected most by weathering followed by heat-treated aspen and birch. This is related to differences in content and structure of lignin of softwood and hardwood. The use of XPS technique has proved to be a reliable method for wood surface studies.

Torréfaction de la biomasse lignocellulosique dans les liquides ioniques: Analyse comparative par spectroscopies de surface

“…[10,31,32] ionique. [27] Les largeurs à mi-hauteurs des pics (FWHM) ont et e fix ees à la même valeur pour chaque pic des spectres de carbone C1s et d'oxygène O1s, car les r esultats physicochimiques et statistiques ont montr e qu'il y avait une signification coh erente et acceptable. Enfin, pour tous les spectres du bois brut et des bois torr efi es, l'incertitude des energies de liaison est estim ee à AE 0.2 eV.…”

“…[27,42] Pour nos echantillons de bois brut, ce rapport (O/C ¼ 0.29) est proche de celui de la lignine (Table 4) et suggère que la surface du bois brut est riche en lignine et en extractibles. [27] Favoris ee par le traitement thermique, les pertes sous forme d'eau, et d'espèces oxyg en ees (condensables et gazeuses) à partir de l'h emicellulose et de la cellulose contenues dans le bois contribuent à faire baisser le rapport O/C et donc à augmenter la teneur en lignine. Au contraire, l'enlèvement partiel pendant le traitement thermique d'extractibles riches en carbone (acides gras, terpènes et ph enoliques) et pr esents de façon abondante à la surface du bois contribue à faire croître le rapport O/C.…”

Chemical Analysis of Densification, Drying, and Heat Treatment of Scots pine (Pinus sylvestris L.) through a Hot-Pressing Process

“…High temperature treatment as a physical modification is achieved through the heat treatment of wood under high temperatures (160 to 250 °C) with lumber pyrolysis in shielded gas environments (Inari et al 2006;Boonstra et al 2007;Korkut et al 2008;Kocaefe et al 2013). This method effectively enhances the dimensional stability by relieving internal stress and improves the decay resistance (Park et al 2014).…”

Chemical and ultrastructural changes in compound middle lamella (CML) regions of softwoods thermally modified by the Termovuoto process

“…The changes in the gross chemistry after TM were also extensively studied as reviewed by Esteves and Pereira (2009). Microredistribution of wood components caused by TM was observed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), and ultraviolet microspectrophotometry (UMSP) (Sivonen et al 2002;Tjeerdsma and Militz 2005;Kocaefe et al 2012;Mahnert et al 2013). However, these methods also have limitations concerning changes at the cellular level, particularly on individual cell wall layers.…”