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

Vidholdová, Zuzana; Slabejová, Gabriela

doi:10.3390/polym13193373

Cited by 6 publications

(5 citation statements)

References 32 publications

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“…There were also confirmed significant impacts for wood species, lacquer/coating system type, lacquer modification, and wood surface pre-treatment with pigment and stain mordants on colour change during accelerated ageing. The better colour resistance of transparent surface-finished wood confirms the already recognised fact that darker wood surfaces are more stable [28][29][30]46]. In addition, it may be affected by the type and amount of topcoat applied [47,48].…”

Section: Beforesupporting

confidence: 64%

“…Photo-oxidative degradation and yellowing or discolouration in polyurethane coatings upon UV irradiation is a general phenomenon. In our previous study [ 30 ], discolouration of a finishing system based on polyacrylic, and aldehyde resin resulted mainly from the photo yellowing of underlying untreated and HTT-treated wood due to sunlight and increased with irradiation time. Furthermore, the results of the study [ 46 ] showed that an accelerated ageing process with simulation of indoor conditions induced significant discolouration of surface-treated wood, both coated with solvent-based polyurethane and water-based lacquers.…”

Section: Resultsmentioning

confidence: 99%

“…But we know from practice that not always the entire surface of a wood product (e.g., floor, shelf, table) is exposed to light. Many scientific works deal with the change in wood colour [ 22 , 23 , 24 , 25 , 26 , 27 ] or the change of surface finishes on wood in the interior due to the influence of light [ 17 , 28 , 29 , 30 ] or after accelerated weathering [ 9 , 13 , 31 , 32 , 33 , 34 , 35 , 36 ]. However, the effect of visible light from short waves (violet-blue) and the thermic effect of the infrared components of natural light passing through window glass [ 36 , 37 , 38 ] have to be considered as indoor ageing factors [ 25 , 39 , 40 ].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Two Different Ageing Exposures on the Colour Stability of Transparent Polyurethane Finishing

2023

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This paper deals with the influence of dark and light exposure on the colour change of a transparent two-component polyurethane surface finish. The surface finish with polyacrylic and aldehyde resin was applied to the surfaces of untreated and hydrothermally treated European beech, alder, Norway maple, and Paper birch wood. The test specimens were deposited indoors for 60 days. The colour values (lightness L*, redness + a*, yellowness + b*, chroma C*, hue angle h°) were expressed in the CIELAB system. The results showed that the colour difference of the finish surfaces of all hydrothermally treated wood species was 27–50% lower after the dark than when exposed to light. In the case of finished untreated wood, the colour difference was 51–73% lower after the dark than light exposure. Only the finished untreated and hydrothermally treated Norway maple wood surfaces showed similar and significant changes after both dark and light exposure. The lower value of the colour difference of the finished hydrothermally treated wood was due to the fact that steaming wood with saturated water steam has a positive effect on the overall colour stability of the finish and partial resistance to the initiation of photolytic reactions caused by light.

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Section: Beforesupporting

confidence: 64%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Two Different Ageing Exposures on the Colour Stability of Transparent Polyurethane Finishing

2023

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“…In particular, there are no reports on the technological properties of thermally modified wood in nitrogen atmosphere, especially finished with different coatings. The colour stability of thermally modified wood in overheated steam and covered with various types of coatings was widely analysed [37,38]. The influence of wood heat treatment and coatings on hardness, scratch resistance [39], abrasion resistance [40] was investigated.…”

Section: Introductionmentioning

confidence: 99%

Influence of Thermal Modification in Nitrogen Atmosphere on Physical and Technological Properties of European Wood Species with Different Structural Features

et al. 2022

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The wood of five European species: black poplar (Populus nigra L.), European beech (Fagus sylvatica L.), European ash (Fraxinus excelsior L.), European oak (Quercus robur L.), and Scots pine (Pinus sylvestris L.) was subjected to thermal modification in nitrogen atmosphere at 190 °C during 6 h. Native and modified wood was varnished and oiled in industrial conditions. Thermally modified (TM) wood was characterized by a greater absorption of varnish and oil when applying the first layer to the surface, which finally resulted in higher application values compared to native wood. In particular, after varnishing, there was a significant increase in gloss and radical change of colour. Regardless of the wood species, finishing process (varnishing, oiling), the ΔE values were close to or higher than 6, which proves high colour changes. Modified poplar, ash, and oak after varnishing had a different colour (ΔE higher than 12). The surface colour changes as a result of UV photoaging was individual, depending on the wood species and the method of finishing. In the case of the thickness of varnish coatings, the wood structure was important, i.e., on ring-porous hardwood and softwood they were thicker. In the case of wood species with a lower density, i.e., black poplar and pine, the thermal modification in nitrogen atmosphere process did not reduce the resistance of the varnish coat, and in the case of species with a higher density (oak, ash, beech) it decreased by one level. Thermal modification reduced the Brinell hardness of wood with wide rays (oak and beech) by 11%. The applied process of surface finishing by double varnishing or oiling did not significantly change the hardness of tested wood.

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“…In a study by Vidholdová et al [4] TM spruce wood lost individual hemicelluloses in this order: arabinose > mannose~glucose > xylose~galactose due to their depolymerisation, creation of internal ethers, and other rearrangement products, and finally, decomposition into volatile compounds [18][19][20]. Changes in the molecular level of TM wood have also been observed through infrared spectroscopy [21,22], and indirectly through colour changes [23,24], or creation of splits and cracks [25,26]. Details of the brittle behaviour of TM wood were revealed by means of images of fracture surfaces at the ultrastructural level.…”

Section: Introductionmentioning

confidence: 99%

SEM Analysis of Glued Joints of Thermally Modified Wood Bonded with PUR and PVAc Glues

2022

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This study deals with the scanning electron microscopy (SEM) analyses of the phase interfaces in the glued joints between Norway spruce wood elements thermally modified at 160, 180, 200, and 220 °C/4 h and polyurethane (PUR) and polyvinyl acetate (PVAc) glues with the aim of evaluating various anatomical influences of wood on the quality of joints. Due to cracked regions created in the surface of spruce wood at severe thermal modifications, the penetration depth of glues doubled from 140 to 241 μm for PUR glue, and from 100 to 200 μm for PVAc glue. The thickness of glue lines in joints was apparently higher for PVAc glue, mainly in earlywood regions; however, in joints from thermally modified (TM) woods it increased more apparently for PUR glue from 16.6 to 44.4 μm, probably in connection with formation of micro-bubbles in its structure. The SEM analyses corresponded well with the previous knowledge about lower shear strength of glued joints formed from the more intensively TM spruce elements and mentioned types of glues.

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

Cited by 6 publications

References 32 publications

Effect of Two Different Ageing Exposures on the Colour Stability of Transparent Polyurethane Finishing

Effect of Two Different Ageing Exposures on the Colour Stability of Transparent Polyurethane Finishing

Influence of Thermal Modification in Nitrogen Atmosphere on Physical and Technological Properties of European Wood Species with Different Structural Features

SEM Analysis of Glued Joints of Thermally Modified Wood Bonded with PUR and PVAc Glues

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