Artificial weathering of tropical woods. Part 1: Changes in wettability

Abstract

Changes in the wettability of eight species of tropical woods during artificial weathering up to 600 h are discussed from the aspect of chemical and structural changes in their surfaces: Amnurana acreana, Acacia auriculiformis, Dipterocarpus spp., Eucalyptus marginata, Eucalyptus robusta, Shorea spp., and Tabebuia spp. with relatively high and low specific gravity. On the whole, the wettability of specimens decreased upon irradiation up to 20 h; above that they increased. Changes in wettability during artificial weathering differed according to wood species. The IR spectra suggest that the specimen surfaces after irradiation for 600 h result in a cellulose-rich layer, and therefore the increase in wettability during artificial weathering can be explained in terms of the increase in hydroxyl groups originating from both the exposed cellulose and adsorbed water. However, the difference in wettability exists between species even after the surface develops a cellulose-rich layer. The stereoscopic micrographs showed the development of cracks for all of the specimens after irradiation for 600 h, and differences in their magnitudes according to species. From these results, the differences in wettability between species were estimated to be due to the structural changes on the surface during artificial weathering, whereas the increase in wettability was due to the chemical changes.

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

“…Different structural and chemical changes that occur in wood surface in the effect of photochemical reactions during the weathering cause the reduction of contact angle and increasing the wettability of wood surface. Increased cellulose and hydroxyl groups in the effect of lignin degradation and its exit from wood surface are among the most important reasons (Kalinins andFeist 1993, Kishino andNakano 2004). Figure 8C and D show the wettability of oleothermally treated wood samples before and after the weathering for both beech and fir species.…”

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

“…For a comprehensive view of wood weathering, a number of studies on the general features of natural outdoor weathering, the accelerated natural weathering tests and the artificial weathering of untreated wood are available [4,41,42,[44][45][46][47].…”

“…Kishino and Nakano [45,101] investigated the changes in wettability of tropical woods for outdoor purposes during artificial weathering up to 600 h. On the whole, the wettability of specimens decreased upon exposure up to 20 h; above that, it increased. They found that the changes in wettability during artificial weathering differed depending on wood species.…”

“…The IR spectra for each treatment and artificial weathering time were transformed into absorbance spectra. All relative intensity ratios were normalized relative to the peak of the band at 2900 cm' 1 which is C-H stretching in methyl and méthylène groups [45]. In FTIR, it is very important to use a spectral band that does not change during the treatment process if quantitative analysis is to be performed.…”

“…They proposed that UV irradiation cleaned the wood surface, consequently, the wettability and surface free energy increased significantly after a specific exposure period to UV light. Changes in wettability of tropic woods due to artificial weathering were reported [45].…”