Influence of Different Modifications on Bending Strength of Wood

Despite intensive research in wood protection, no simple wood treatment method is available for satisfactory wood protection that could ensure appropriate strength and bio-resistance of wood products during their service life. The present study is a part of a project that is aimed to improve wood service properties by combining wood thermal treatment and impregnation with copper containing preservatives. The objective of the present study was to investigate the effect of conventional modifications (thermal modification at relatively mild temperature range (150 - 180°C) and impregnation) and double-treatments (impregnation after thermal treatment and vice versa) on the bending properties of birch (Betula spp.) and pine (Pinus sylvestris L.) wood. Bending strength considerably decreased after thermal modification of wood, however MOE values generally did not significantly change. Moreover, impregnation had no effect on the bending properties for both unmodified and thermally modified wood specimens. For double-treatment in which impregnation was carried out before thermal modification no changes in bending strength were observed comparing to thermally modified wood. However, MOE values of these specimens were 10 % for birch and 19 % for pine smaller comparing to just thermally modified wood. The results of double-treatment tests imply that, regarding wood bending properties, wood impregnation after thermal modification is more appropriate.