Improving stable anti-weathering performance of wood by impregnation with active aminated alkali lignin

Alkali lignin (AL), as a bio-based industrial byproduct, has certain potential in improving the photostability of wood in outdoor applications based on its UV absorption feature. The present study developed aminated low molecular weight depolymerized AL for wood impregnation, and evaluated the pre- and post-modification weathering resistance of the wood. The filling of aminated AL within the wood matrix was demonstrated using methods including scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and fluorescence microscopy. Compared with AL treated wood, modified poplar and Chinese fir showed a high weight gain rate increased by 251.8 and 320.9%, respectively, and a low loss resistance rate decreased by 39.9 and 32.5%, respectively. Free radicals exhibited a reduced generation during in situ irradiation. Changes in composition over the same period of weathering treatment were minimized, thereby delaying the structural and morphological alterations induced by weathering. Macroscopic photodegradation and morphological damage observed in the modified wood were substantially mitigated, with the integrity of the anatomical structure preserved. These findings substantiate the protective effect of aminated AL treatment on wood weathering behavior, which is beneficial for enhancing the stability of wood in outdoor applications.