ESCA study of oxidized wood surfaces

Hon, David N.‐S.

doi:10.1002/app.1984.070290908

Cited by 64 publications

(59 citation statements)

References 7 publications

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“…Thus, extractives in non-extracted specimens were oxidized easily during artificial irradiation. Table 4 shows that the O/C ratios of extracted samples (U2, T2) were higher after 1008 h of weathering, with values close to 0.88 for the O/C ratio of cellulose and above 0.33 for lignin (Hon 1984). This data suggested that the surface of the extracted wood was richer in cellulose and poorer in lignin after weathering, which reflected the protective effect of extractives against lignin degradation.…”

Section: Xps Analysismentioning

confidence: 84%

“…C3 represents the C=O and O-C-O bonds; these groups come mainly from polysaccharides and extractives. The C4 peak corresponds to the O-C=O bonding of carboxylic derivatives (Hon 1984;Chang et al 2001;Sinn et al 2001;Fardim and Durán 2002;Shchukarev et al 2002;Nzokou and Kamdem 2005). For both nonextracted and extracted thermally modified wood, after weathering, the C1 peak shrank and the C2 peak became higher, suggesting a significant decrease in both lignin and extractive contents for the surface of the thermally modified wood during weathering.…”

Section: Xps Analysismentioning

confidence: 99%

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Influence of Post-extraction on Photostability of Thermally Modified Scots Pine Wood during Artificial Weathering

Shen¹,

Cao²,

Sun³

et al. 2016

BioResources

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The photo-stabilizing effect of post-extraction was evaluated for thermally modified wood. Extracted and non-extracted thermally modified Scots pine (Pinus sylvestris L.) samples were exposed in a xenon weather-ometer for 1008 h, and the surface color and chemical changes were characterized using a chroma meter, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). The results showed that: (1) the weight losses of thermally modified wood were higher than those of unmodified wood after extraction due to the leaching of some low molecular weight compounds that were generated during thermal modification; (2) the photodegradation of thermally modified wood during weathering was hindered by the presence of extractives; and (3) the color change during weathering was a little more severe in sapwood than in heartwood because more extractives were present in heartwood.

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Section: Xps Analysismentioning

confidence: 84%

Section: Xps Analysismentioning

confidence: 99%

Influence of Post-extraction on Photostability of Thermally Modified Scots Pine Wood during Artificial Weathering

Shen¹,

Cao²,

Sun³

et al. 2016

BioResources

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“…These studies generally have been made on untreated wood and often with Radiata pine or southern yellow pine. A number of researchers have examined the effect of weathering on the physical structure of wood [8,74,[79][80][81][82][83][84]. Microscopic studies showed characteristic ridges on the S3 wall layer, wall checking, ray and pit degradation, and middle lamella breakdown.…”

Section: Micro-structural Changes Of Untreated Wood During Weatheringmentioning

confidence: 99%

“…As long as the main reinforcing structural elements, the microfibrils, remain intact, the major properties of wood do not apparently undergo drastic changes [84]. Four hardwoods (red oak, white oak, yellow-poplar, and sweet gum) were exposed to outdoor weathering and to artificial UV light with wavelengths of X> 220 nm and X > 254 nm by Hon and his colleagues [81] and then they studied these using SEM. The results showed that all wood species exhibit surface deterioration after an exposure of 30 days to sunlight or 500 hours to UV light.…”

Section: Micro-structural Changes Of Untreated Wood During Weatheringmentioning

confidence: 99%

“…Study of Hon (1984) on the surface of wood exposed to outdoor weathering and UV irradiation showed that ESCA provides valuable information and insight into the manifestation of weathering and photo-oxidation. XPS studies of four hardwoods, which were exposed to outdoor weathering and artificial ultraviolet (UV) light, revealed a high oxygen content on the wood surfaces indicating severe oxidation of wood.…”

Section: Chemical Changes During Weatheringmentioning

confidence: 99%

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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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Kinetic studies on the accelerated aging of cellulosic materials

Selli

Beltrame

Testa³

et al. 1998

Angew. Makromol. Chem.

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SUMMARY: The natural aging of cellulosic materials (high purity paper, cotton, raw and bleached flax, viscose) was simulated by thermal oxidation in air at constant temperature (123 -192 8C). Also the synergetic effect of light was investigated at 50 -85 8C. The kinetics of polymer degradation was followed through intrinsic viscosity measurements and was correlated with the degree of crystallinity, determined by X-ray diffraction, and with the surface oxidation of the investigated samples, evaluated through XPS analysis. At least two constant rate stages were observed in kinetic runs. The acceleration factors and time necessary for simulating a 20-year thermal aging of the investigated cellulosic materials were obtained from the calculated activation parameters by extrapolation of the process rate coefficients to room temperature. Surface oxidation parallel to aging led to the formation of low-molecular-weight, easily removable products in pure cellulose materials, while in lignin-containing materials mainly lignin was involved.ZUSAMMENFASSUNG: Die natürliche Alterung von Zellstoffen (hochreines Papier, Baumwolle, ungebleichter und gebleichter Flachs, Viskose) wurde mittels thermischer Oxidation bei konstanter Temperatur (123 -192 8C) simuliert. Die synergistische Lichteinwirkung bei 50 -85 8C wurde ebenfalls geprüft. Die Kinetik des mit Hilfe von Viskositätsmessungen verfolgten Abbaus der Polymeren wurde mit dem durch Röntgen-diagramme ermittelten Kristallinitätsgrad sowie mit der durch XPS-Analyse bestimmten Oberflächenoxida-tion der untersuchten Proben korreliert. Mindestens zwei Abbauphasen mit konstanter Geschwindigkeit wurden bei den kinetischen Messungen festgestellt. Die Beschleunigungsfaktoren und die für die Simulation einer zwanzigjährigen Alterung der untersuchten Faserstoffe benötigte Behandlungszeit wurden aus den errechneten Aktivierungsparametern durch Extrapolation der Geschwindigkeitskoeffizienten auf Raumtemperatur ermittelt. Bei den reinen Zellstoffen führte die parallel zur Alterung verlaufende Oberflächenoxida-tion zur Bildung niedermolekularer, leicht zu entfernender Produkte, während bei den Lignin enthaltenden Faserstoffen hauptsächlich das Lignin in den Abbauprozeß einbezogen wird.

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ESCA study of oxidized wood surfaces

Cited by 64 publications

References 7 publications

Influence of Post-extraction on Photostability of Thermally Modified Scots Pine Wood during Artificial Weathering

Influence of Post-extraction on Photostability of Thermally Modified Scots Pine Wood during Artificial Weathering

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

Kinetic studies on the accelerated aging of cellulosic materials

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