Identifying patterns in the resistance of thermally modified ash wood to weathering

Weathering of thermally modified wood negatively affects both the appearance of structures and their physical-mechanical characteristics, which further determines their service life. Given this, the object of the study was the resistance of ash wood varying degrees modification to abiotic environmental factors. It was found that the color stability of thermally modified wood samples is higher compared to untreated ones. A decrease in the value of the coordinate L from 68.4 to 33.6 indicates a decrease in lightness, that is darkening of the wood. Analysis of dimensional changes revealed increased swelling for untreated wood and amounted to 7.49 %, and for modified at a temperature of 200 °С – 1.75 %. The difference in shrinkage rates is much smaller – 2.09 % for wood of group III, which is 2 times less than untreated wood. The results confirm that thermal modification makes wood cell walls more hydrophobic by eliminating hydrophilic and hydroxyl groups of hemicelluloses. A linear dependence (R2≈1) of change in the physical characteristics of wood depending on its density due to the degree of modification has been established. Analysis of mechanical properties revealed that thermal modification increases the resistance of wood to compressive across the fibers by 2 times. Therefore, a comprehensive approach to analyzing the impact of weathering on the aesthetic, physical, and mechanical properties of thermally modified wood makes it possible to identify the principles of material stability depending on the treatment schedule. The identified mechanisms of transformation of material parameters contribute to the establishment of optimal parameters of thermal modification, which improve its characteristics. This creates the prerequisites for implementing new technological solutions focused on environmental friendliness and energy efficiency in production