Influence of artificial and natural weathering on water exclusion efficacy of wood

IRG/WP 15-20559

M ┼Żlahtič, M Humar

Water exclusion efficacy (WEE) is one of the most important properties of wood that contributes to the overall performance of naturally durable wood species in outdoor above ground applications. WEE is in strong correlation with moisture dynamics of wood, its hydrophobicity and can indicates susceptibility against wood decay fungi. Despite of the importance of this parameter, WEE is not completely understood. The main question was, how WEE changes within time, artificial or natural weathering, fungal exposure, etc. In order to elucidate this question Norway spruce (Picea abies), European larch (Larix decidua) and Scots pine (Pinus sylvestris) sapwood specimens were prepared. WEE of spruce wood was upgraded with thermal modification and/or with impregnation with cupper-ethanolamine, tung oil and montan wax suspension. Weathering was accelerated with different methods. After conditioning, specimens were exposed to blue stain fungi Aureobasidium pullulans and Sclerophoma pithyophila, wood decay fungi Schizophyllum commune and Gloeophyllum trabeum, artificially accelerated weathering and outdoor weathering. After weathering, mass loss and color changes were determined and compared to unexposed material. WEE was determined with surface sessile drop method, short term and long term water uptake. The results indicates that WEE can be considerably improved with proper hydrophobic treatment. Different ageing agents have ununiformed influence on the WEE. The highest decrease of WEE was determined after artificial and natural ageing. This is somehow expectable, as both ageing reflects synergistic effect of different factors.

Keywords: water exclusion efficacy, weathering, water uptake, performance, Norway spruce, European Larch, Scots pine

Conference: 15-05-10/14 Vina del Mar, Chile

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