Structure–Property Evolution of Chinese Fir Induced by Controlled KOH Impregnation for Biomimetic Archaeological Wood Preparation

This study presents a controllable alkaline degradation strategy for preparing biomimetic archaeological Chinese fir through potassium hydroxide (KOH) impregnation, addressing the limitations of scarce and heterogeneous authentic archaeological wood for conservation research. Four KOH concentrations (5%, 10%, 20%, and 30%) combined with different treatment cycles (2–6 cycles) were applied to induce controlled degradation states under laboratory conditions. The results demonstrated that KOH concentration and treatment cycles effectively controlled the structure–property evolution of Chinese fir. Mass loss increased to 42.14%, while maximum water content reached 427.35%, accompanied by reductions in oven-dry and basic densities. X-ray diffraction analysis revealed a decrease in cellulose crystallinity from 34.10% to approximately 24%–26%, indicating partial disruption of cellulose crystalline domains, while Fourier transform infrared spectroscopy confirmed preferential degradation of hemicellulose through alkaline hydrolysis and relative preservation of lignin structures. Scanning electron microscopy further demonstrated tracheid deformation, lumen collapse, and enhanced pore connectivity after severe treatment. Based on the combined evaluation of physical, chemical, mechanical, and microstructural parameters, a three-level biomimetic archaeological wood grading system was established to correlate KOH treatment conditions with different degradation states. This study provides a reproducible approach for fabricating standardized biomimetic archaeological wood models and offers a reliable platform for conservation material evaluation and degradation mechanism studies.