Inserting Poly(ε-caprolactone) into Wood Cell Wall Structures for Dehydration and Consolidation of Waterlogged Scots Pine Wood

Archaeological wooden artifacts are buried in wet environments, leading to water absorption and waterlogged wood. In order to conserve these wooden cultural heritage items, dehydration and consolidation are critical steps. This study used nontoxic epsilon-caprolactone (CL) as the dehydration agent to replace the water in the simulated waterlogged wooden structures, inserting the poly(epsilon-caprolactone) (PCL) into the wood cell walls by oxalic acid catalysed CL ring-opening polymerization (ROP). The mechanical and chemical performance of the untreated and treated wood was evaluated. The weight gain percentage and dimensional stability of the treated wood were significantly improved. The polyester chains within the cell wall structures were analyzed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA-DTA), and scanning electron microscopy (SEM). FT-IR showed that the intensity of hydroxyl (-OH) absorption peaks decreased, and carbonyl (C=O) peaks attributed to the PCL addition were observed. Thermal analysis revealed that the degradation of PCL polymers was faster than that of wood components. The morphology characterization demonstrated that the treated wood was bulked with the PCL polymers.