A note on the influence of extractives on the photo-discoloration and photo-degradation of wood

Pandey, Krishna K.

doi:10.1016/j.polymdegradstab.2004.09.007

Cited by 190 publications

(141 citation statements)

References 15 publications

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“…Only the colour changes of samples treated with an oil-based coating (C) were significantly lower compared to untreated oak after 3 weeks of artificial weathering ( Figure 2). As mentioned above, high colour changes indicate a degradation of the protective coating layer and leaching of extractives [29] and lignins decomposed using UV light [16]. This result therefore showed that this type of coating provides sufficient protection for oak wood in the initial phase of the weathering test, wherein it prevents the wood from leaching degraded extractives and lignin-see also the initial decrease of L* values (darkening) associated with the increase of a* values (reddening) and b* values (yellowing) after 1 week of weathering ( Figure 2, Table 4).…”

Section: Resultsmentioning

confidence: 88%

“…The use of hydrophobic layers instead of traditional coating systems has the advantage of easier application (only 1 layer of hydrophobization is sufficient). However, hydrophobic coatings only prevent damage caused by water and do not protect the underlying wood against UV and visible (VIS) spectra causing decomposition of lignin and extractives [28,29], and they are associated with chemical and colour changes [30,31]. For wood stabilization, it is possible to use protective pigments which are used as parts of coatings [25], as well as nanoparticles [32][33][34][35], UV stabilizers [36], and HALS applied in the penetration protective layer [37][38][39].…”

Section: Introductionmentioning

confidence: 99%

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Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

et al. 2017

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Abstract:The durability of transparent coatings applied to an oak wood exterior is relatively low due to its anatomic structure and chemical composition. Enhancement of the protection of oak wood against weathering using transparent hydrophobic coatings is presented in this study. Oak wood surfaces were modified using UV-stabilizers, hindered amine light stabilizer (HALS), and ZnO and TiO 2 nanoparticles before the application of a commercial hydrophobic topcoat. A transparent oil-based coating was used as a control coating system. The artificial weathering test lasted 6 weeks and colour, gloss, and contact angle changes were regularly evaluated during this period. The changes in the microscopic structure were studied with confocal laser scanning microscopy. The results proved limited durability against weathering of both tested hydrophobic coatings. The formation of micro-cracks causing the leaching of degraded wood compounds and discolouration of oak wood were observed after 1 or 3 weeks of the weathering test. Until then, an oil-based coating film had protected the wood sufficiently, but after 6 weeks the wood was fully defoliated to its non-homogenous thickness, which was caused by the presence of large oak vessels, and by the effects of specific oak tannins. Using transparent hydrophobic coatings can prolong the service life of the exteriors of wood products by decreasing their moisture content. Without proper construction protection against rainwater, the hydrophobic coating itself cannot guarantee the preservation of the natural appearance of wood exteriors.

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Section: Resultsmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

et al. 2017

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“…These are then responsible for the color change of wood. The extractives in wood are also sensitive to light irradiation (Pandey 2005b;Nzokou and Kamdem 2006;Zahri et al 2007;Chang et al 2010;Fan et al 2010). Živković et al (2014) investigated the effect of wavelength on photodegradation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Air Relative Humidity and Temperature on Photodegradation Processes in Beech and Spruce Wood

Tolvaj¹,

Popescu²,

Molnár³

et al. 2015

BioResources

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Spruce and beech samples were irradiated by UV light in humid (100% air humidity) and dry conditions to clarify the effects of vapor on photodegradation. UV-irradiated samples were also soaked in distilled water for comparison. The color change and the IR absorption spectra were measured. The wet condition generated considerably greater discoloration than did the dry condition. The intensity of the color change was higher at elevated temperature (53 °C) than at 32 °C. The results showed that the presence of water as vapor increased the degradation of lignin. The nonconjugated carbonyl groups absorbing around 1760 cm -1 were found not to be stable, and the number of these chemical groups decreased in the presence of vapor when compared against the dry condition. The rising temperature amplified this degradation effect.

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“…According to the results, the gradient of changes in ΔE value in fir samples was more than beech ones (except oleothermally treated beech wood coated with PDMS which had a relatively large color change in the first 30 days that is related to the changes observed for coordinate L * in the samples (Table 1). In general, the type of wood species (hardwood or softwood) as well as the amount of extractives migrated from innermost of the wood, affect the rate of photochemical reactions and the intensity of color change (Pandey 2005a). As Pandey 2005b, explained because of differences in the structural units of softwood and hardwood especially in lignin and hemicelluloses, the color changes due to the weathering are not the same.…”

Section: Color Changesmentioning

confidence: 99%

Effects of oleothermal treatment and polydimethylsiloxane (PDMS) coating on natural weathering of beech and fir woods

Saei

Mohebby

Abdeh

2015

Maderas, Cienc. tecnol.

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Effects of natural weathering on oleothermally treated wood and coated with an organic silicone compound were studied. Slats of beech and fir woods were cut in sizes of 20×10×1 cm. The slats were treated by soybean oil at 230˚C for 1 h. Then, the half of the untreated and oleothermally treated slats were coated with polydimethylsiloxane (PDMS) and the rest of them were considered as control. All slats were hanged in 45˚ angle at the southwest (SW) direction for 90 days. They were analyzed for color changes, roughness, and contact angle properties at 30-day intervals. Results showed that the oleothermal treatment of wood reduced discoloration of fir samples against natural weathering; however, the reducing effect was lower in the Beech samples. This treatment also reduced the surface roughness of the fir samples during weathering while it increased the surface roughness of beech. Wettability of the samples in both species, before and after weathering, was reduced by the oleothermal treatment. Results also revealed that coating of the wood surface with PDMS does not prevent the discoloration and surface roughness against weathering. Nevertheless, the coating could considerably decrease the hydrophilicity of the woods even after weathering.

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A note on the influence of extractives on the photo-discoloration and photo-degradation of wood

Cited by 190 publications

References 15 publications

Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

Efficacy of Hydrophobic Coatings in Protecting Oak Wood Surfaces during Accelerated Weathering

Effects of Air Relative Humidity and Temperature on Photodegradation Processes in Beech and Spruce Wood

Effects of oleothermal treatment and polydimethylsiloxane (PDMS) coating on natural weathering of beech and fir woods

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