Liquid water absorption in small specimens of acrylic coated cladding was investigated before and after one year of outdoor exposure, and before and after 3000 h of exposure in a QUV chamber. Regarding the specimens exposed outdoors, water absorption was measured until more than 3000 hours, and desorption was measured as well. Statistical analysis was performed on amount of absorbed water after 72 and 672 h. Regarding the QUV exposed specimens, water absorption was measured after 72 hours only. In both experiments the specimens absorbed less water after exposure. Origin had effect in both experiments; samples from high productive sites with young trees had a higher water uptake than those from low productive sites with old trees. Horizontal orientation of the specimens (inner/outer board) had influence on the results both before and after outdoor exposure, but this effect was not found in the QUV exposed specimens. Regarding wood properties, no significant effect of density or annual increment width was found. In specimens exposed outdoors, heartwood content had large influence on water uptake. Outdoor exposure apparently had a smaller effect on water absorption in outer boards than in inner boards, causing the difference between outer and inner boards to be smaller after exposure.
Keywords: acrylic coating, natural weathering, QUV, service life, water uptake
Authors
Sivertsen M.S.
Mycoteam AS, Blindern, Norway
Vestøl G.I.
Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, Ås
Hundhausen U.
Norwegian Institute of Wood Technology (TRETEKNISK), Blindern, Oslo
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