Accelerated weathering performance of plantation-grown juvenile poplar and Chinese fir woods

Abstract Plantation-grown juvenile wood species are extensively used as raw materials in the Chinese wood industry. The weathering performances of the wood are crucial for outdoor application. Two of the most important plantation-grown juvenile woods, poplar (Populus × euramericana cv. ‘74/76ʼ) and Chinese fir (Cunninghamia lanceolata Hook), were sliced into thin veneers and compared in this study to observe their weathering performance during exposure to UV alone for 504 h and UV/water for 168 h. The color difference, weight loss, and tensile strength loss of both veneers all increased with exposure time. Scanning electron microscopy showed that the initial structural deterioration originates from the corner of the middle lamella and pit, followed by cell separation, cell wall thinning, deformation, and collapse. Fourier transmission infrared spectroscopy, electron resonance spectrometry and X-ray photoelectron spectroscopy revealed a decrease in lignin-based infrared absorption intensity and radical generation, as well as an increase in O/C ratio throughout the exposure. Water spray considerably accelerated deterioration by washing away the degraded fragments, thereby exposing the fresh substrate underneath. Compared to poplar wood, Chinese fir showed durable structural integrity but more darkening during weathering. These findings reveal the anatomically structural weak phase and photo-degradation performance of two plantation-grown woods during weathering. The results of this work may facilitate the proper external use and further photo-stabilization treatment of plantation-grown juvenile wood products.