Aesthetic changes of coated thermally modified wood after artificial weathering

IRG/WP 17-40819

R Herrera, J Sandak, E Robles, J Labidi

The thermal modification process affects the chemical configuration of the wood matrix improving some physical properties and durability. In addition, the distinctive dark tones of thermally modified timber increase the economic value of several light-coloured species. However, heat-treatment alters the substrates and it could influence in the application of coating products, necessaries to maintain the surface features in certain end-use sectors. Ash wood (Fraxinus excelsior L.) samples industrially treated at 212 ÂșC were coated with decorative and industrial coatings. Afterwards, the samples were subjected to accelerated weathering test and estimated the aesthetical response compared to untreated wood. The surface topography was monitored with a 3D scanner and a profilometer, showing slight visual changes although finding dissimilar roughness where irregularities in modified -samples increased with waterborne product but not with UV-curable; remarkable the changes in roughness below 5% in modified samples. The colour changes were calculated by hyperspectral information of the visible range, generating the profile map of L*, a*, b* parameters. The results point out an acceptable photostability of coated thermally modified wood. Heat-treated wood could be an appropriate substrate with similar conditions as unmodified wood; nevertheless the interaction with water-base products could vary depending on the treatment temperature and the layer thickness.


Keywords: 3D surface profile, hyperspectral image, colour stability, roughness-gloss

Conference: 17-06-04/08 Ghent, Belgium


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