How Weathering Affects Lignocellulose Microstructure and Drives Brown-Rot Decay: Mechanistic Insights

Wood is widely utilized in outdoor applications; however, weathering and decay are unavoidable phenomena that significantly shorten the service life of wood products. There is a scarcity of research investigating the interplay between weathering and decay in wood as well as the degradation mechanisms when these factors occur simultaneously. In this study, the effect of weathering on brown-rot degradation of lignocellulose was evaluated. Specifically, the changes in morphology, thermal stability, wettability, and crystalline structure of lignocellulose during accelerated UV weathering were analyzed. Furthermore, the processes of weathered lignocellulose participating in nonenzymatic and enzymatic degradation of brown-rot decay were evaluated, and the mechanism was clarified. Weathering-induced fragmentation of cellulose and hemicellulose enhanced brown-rot decay with ∼8° initial contact angle reduction and a 7.8–38.9 °C Tg decline for hemicellulose. Additionally, weathered holocellulose contributed to the generation of increased destructive hydroxyl free radicals during nonenzymatic degradation. However, weathered lignin impeded brown-rot decay due to the progressively disrupted microstructures caused by weathering, which increased its barrier effect. The capacity of weathered lignin to scavenge free radicals during the nonenzymatic degradation, along with the enhanced nonproductive adsorption on enzymes during the enzymatic degradation, further amplified the inhibitory effect on brown-rot decay.