This dissertation investigated the influence of various weathering factors on the durability of differently durable wood species, modified and protected wood. Confocal microscopy was used to determine the surface roughness of the weathered samples and their colonisation with blue stain fungi. The changes in the wettability of the wood due to weathering could be explained to a certain extent by the roughness at the microscopic level, which was determined at 50x magnification. According to Wenzel's theory, an increase in the roughness of thermally modified wood led to a decrease in the contact angle, as is typical for hydrophilic surfaces. In contrast, the contact angle on the hydrophobic surface of wax-treated, thermally modified wood increased with increasing roughness. In addition, the resistance to some decay fungi and the resistance to wetting of the weathered and control samples were determined. Both parameters were used to calculate the relative resistance dose of the tested materials. For most of the durable or moderately durable materials, the mass losses caused by fungi (T. versicolor, G. trabeum and R. placenta) increased with weathering. The deterioration in inherent durability coincided with the reduced extractives content. Weathering also had a negative effect on the wetting ability, which was reflected in the reduction of the relative resistance dose of all tested materials. Durability was best preserved in the heartwood of black locust, which even after 40 years of outdoor use contained a comparable or even slightly higher concentration of extractives than fresh wood. On the other hand, the resistance of Scots pine heartwood deteriorated the most.
|
