Heat treatment is admittedly a significant value-adding step in wood processing. However, the decrease in mechanical properties of wood caused by heat treatment has always been an urgent problem to be solved. This study aimed to overcome this barrier by impregnating Balfour spruce (Picea likiangensis var. balfouriana) wood with low-molecular-weight lignin before heat treatment. The low-molecular-weight lignin impregnated more effectively and distributed uniformly in wood cell wall. The equilibrium moisture content of the heat-treated wood with lignin impregnation decreased significantly compared to those without lignin impregnation. The low-molecular-weight lignin impregnation combined with heat treatment improved the dimensional stability and humidity resistance effectively. The impregnated cell walls with lignin were integrated and seldom spoiled during heat treatment. The heat-treated wood impregnated with low-molecular-weight lignin showed an increased MOE, MOR, and compressive strength (CS) of 52, 177, and 25%, respectively, compared with the heat-treated wood without lignin impregnation. The indentation modulus of the secondary walls of heat-treated wood with impregnated low-molecular-weight lignin increased by 300%. These findings provide some insights into the relationship between lignin content and the strength of wood and show a way to enhance the mechanical properties of heat-treated wood without damage to its dimensional stability.

热处理无疑是木材加工中一个重要的增值步骤。然而，热处理引起的木材力学性能下降一直是亟待解决的问题。本研究旨在通过浸渍 Balfour 云杉 ( Picea likiangensis var. balfouriana) 热处理前含有低分子量木质素的木材。低分子量木质素更有效地浸渍并均匀分布在木材细胞壁中。与未浸渍木质素的热处理相比，浸渍木质素的热处理木材的平衡水分含量显着降低。低分子量木质素浸渍结合热处理有效提高了尺寸稳定性和耐湿性。用木质素浸渍的细胞壁是一体的，在热处理过程中很少变质。与未经木质素浸渍的热处理木材相比，浸渍低分子量木质素的热处理木材的 MOE、MOR 和抗压强度 (CS) 分别提高了 52%、177% 和 25%。浸渍低分子量木质素的热处理木材次生壁的压痕模量提高了300%。这些发现为木质素含量与木材强度之间的关系提供了一些见解，并展示了一种在不损害其尺寸稳定性的情况下提高热处理木材机械性能的方法。