Enhancing Thermally Modified Wood Stability against Discoloration

Cīrule, Dace; Sansonetti, Errj; Andersone, Ingeborga; Kuka, Edgars; Andersons, Bruno

doi:10.3390/coatings11010081

Cited by 15 publications

(4 citation statements)

References 46 publications

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“…The findings in this research agree with the publications of other authors for native wood surfaces (e.g., [ 15 , 32 , 33 , 34 , 42 ]), the surfaces of thermally modified wood [ 21 , 35 ], and clear coated wood, although most of the reported research [ 21 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 43 , 44 ] used simulated indoor sunlight exposure or other accelerated weathering methods. In these studies, the dependence curves showing the colour change had an initial period of severe increase that was maintained at a practically constant value with further exposure.…”

Section: Resultssupporting

confidence: 93%

Colour Stabilisation of Surface of Four Thermally Modified Woods with Saturated Water Vapour by Finishes

Vidholdová

Slabejová

2021

Polymers

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This paper deals with the influence of the type of transparent surface finish on the change of colour of the surfaces of native wood, and thermally treated wood, with saturated water vapour. In the experiment, alder, European beech, Paper birch, and Norway maple wood were thermally treated at a temperature of 135 °C under saturated water vapour for six hours. Three various types of surface finishes (acrylic-polyurethane, polyacrylic and aldehyde resin, and alkyd resin) were applied onto the wood surfaces. The colours of the surfaces in the system, CIE L*a*b* (lightness, coordinates a* and b*, chroma and hue angle), were measured during finishing and natural ageing behind glass windows in an interior, over a period of 60 days. The results show that the changes in the yellowness index, and the total colour differences after the application of individual surface finishes to wood species, changed because of sunlight exposure. Moreover, it is clear that different wood finishes behaved differently on all of the wood species. An analysis is presented in this paper.

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Section: Resultssupporting

confidence: 93%

Colour Stabilisation of Surface of Four Thermally Modified Woods with Saturated Water Vapour by Finishes

Vidholdová

Slabejová

2021

Polymers

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“…The lightness L*, the chromatic coordinate on the red-green axis a*, and the chromatic coordinate on the yellow-blue axis b* were determined. The CIE L*a*b* model is one of the most frequently used to specify the colour of wood [42][43][44][45]. Wood colour parameters were measured in two points on the surface, in two sections (radial and tangential) for 15 samples from each modification.…”

Section: Determination Of Wood Colour Parametersmentioning

confidence: 99%

Temperature, Time, and Interactions between Them in Relation to Colour Parameters of Black Poplar (Populus nigra L.) Thermally Modified in Nitrogen Atmosphere

Bytner¹,

Drożdżek²,

Laskowska³

et al. 2022

Materials

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Thermal modification of wood in nitrogen atmosphere permits its usability value to be improved. The aim of the research was to determine the impact of technological modification parameters at different levels on the colour of black poplar (Populus nigra L.). Black poplar was thermally modified in nitrogen atmosphere at a range of temperatures from 160 °C to 220 °C, at times between 2 h and 8 h. The parameters of wood colour were measured according to the CIE L*a*b* colour space model. The changes in a* and b* had a non-linear profile. The maximum value of a* for black poplar wood was achieved after a modification at the temperature of 200 °C, while the maximum value of the b* parameter was achieved after modification at 190 °C. Colour changes in the ΔE of black poplar after modification at 160 °C and 170 °C were similar, and the dynamics of changes increased after modification at the temperature of 180 °C. The highest value of ΔE, around 40, was observed after modification at the temperature of 220 °C and time of 8 h. There were no statistically significant differences between the ΔE for radial and tangential sections. Statistical analysis showed that modification temperature was responsible for the variability of the L* value in 90%, and in ca. 70% for the changes in parameters a* and b*. The influence of the modification time on the colour parameters was minor—below 4%. The influence of the interaction between modification temperature and time on the colour parameters was below 10%. As a consequence, in the case of ΔE of black poplar wood, the influence of temperature was at a level of ca. 80%. On the other hand, the influence of time and the interaction between temperature and time of modification was low—below 3%.

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“…In addition to the temperature and time of thermal treatment, the change in the color of the wood is also influenced by the environment in which the thermal modification of the wood takes place. Thermally modified wood acquires a dark-brown caramel shade in its entire cross-section, while more intense color changes of wood occur in response to higher modification temperatures and prolonged thermal modification time (Sailer et al 2000;Bekhta and Niemz 2003;Srinivas and Pandley 2012;Cirule et al 2021). A darkening of wood exposed to higher temperatures is generally attributed in particular to the decomposition of hemicelluloses and the chemical changes in extractives (Sundqvist and Morén 2002;Sehlstedt-Persson 2003;Esteves et al 2008).…”

Section: Color Of the Peg-thermally Treated Beech Woodmentioning

confidence: 99%

Beech wood thermally modified in the melt of polyethylene glycol

Reinprecht

Repák

2021

BioRes

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Various techniques of wood thermal modification in air, liquids, or melts at temperatures above 160 °C improve its resistance to biological damage and water. In this experiment, the European beech (Fagus sylvatica L.) wood was held for 1 to 4 hours in the melt of polyethylene glycol 6000 (PEG 6000) and during a given time either heated at 100 °C or thermally modified at 190 or 210 °C. Its decay resistance improved – maximally at using the more intense modification mode 210 °C/4h – to Poria placenta by 60.3% and to Trametes versicolor by 62.8%. The soaking and volume swelling in water of the PEG-thermally treated beech wood usually was significantly reduced, after 336 h maximally by 60% and 34.6%, respectively. The presence of PEG during the thermal modification processes caused darkening of beech wood – a decoratively interesting and more pronounced effect than what occurs in traditional air-thermal modifications – at which the Eab* was also great from 13.1 to 52.6. However, since the mechanical properties of the PEG-thermally modified beech wood worsened – impact bending strength maximally by 34% and Brinell hardness maximally by 43.3% – its application for structural elements would be limited.

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Enhancing Thermally Modified Wood Stability against Discoloration

Cited by 15 publications

References 46 publications

Colour Stabilisation of Surface of Four Thermally Modified Woods with Saturated Water Vapour by Finishes

Colour Stabilisation of Surface of Four Thermally Modified Woods with Saturated Water Vapour by Finishes

Temperature, Time, and Interactions between Them in Relation to Colour Parameters of Black Poplar (Populus nigra L.) Thermally Modified in Nitrogen Atmosphere

Beech wood thermally modified in the melt of polyethylene glycol

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