Investigations into the influence of two different wood coatings on water diffusion determined by means of neutron imaging

Abstract

The diffusion of water into spruce wood coated with an acrylate/polyurethane and with a silica-based coating system is investigated by varying the humidity conditions. Thereby, the change of moisture content (MC) is measured and analysed with the non-destructive method of neutron imaging. For the acrylate/polyurethane based coating system, the barrier effect of the coating on wood sorption in direct water contact and the influence of surface defects on this barrier effect are also tested. On changing the humidity conditions, the specimens with silica-based coating initially show a clear deceleration of the sorption process, whereas after 10 days the MC gradient is nearly similar to the uncoated reference specimens. In contrast, the specimens with acrylate/polyurethane based coating show a strong barrier effect against water sorption into wood over the whole measurement period when changing the humidity conditions and in direct water contact. As can be expected, a defect in the coating strongly reduces its barrier effect. Thereby, the kind of defect (saw kerf or blade cut) is rather irrelevant.