(240a) Metal Ion Modification Enabled Hydrophobic and Dimensionally Stable Wood

Wood is a hygroscopic material that responds to the moisture changes of the surrounding environment through swelling and shrinking, making it dimensionally unstable. This property is attributed to hydrophilic groups of wood's cellulose, hemicellulose, and lignin components. In this study, we introduce a facile metal-ion-modification (MIM) approach to enhance the dimensional stability of wood. The MIM process involved swelling the wood samples with aqueous metal ion solutions and drying. The high valent metal cations, such as Fe³⁺, Al³⁺, and Zr⁴⁺, interacted with the hydrophilic groups (e.g., OH, COOH) present in the wood fibers, limiting their access to water and moisture and thereby enhancing the wood's hydrophobicity and dimensional stability. Three wood species including southern yellow pine, poplar, and red oak were treated by MIM. The dimensional stability of wood samples was evaluated by measuring their full swelling ratios. The MIM treatment significantly decreased swelling in both the tangential and radial directions. For example, after Fe³⁺ treatment, the tangential swelling ratio of southern yellow pine decreased from 6% to 4%. Moreover, all the Fe³⁺-treated wood samples (southern yellow pine, poplar, and red oak) exhibited tangential anti-swelling efficiencies of 39.83%-57.14% and radial anti-swelling efficiencies of 34.74%-48.33%. Overall, our findings highlight the effectiveness of the MIM method in improving the dimensional stability of wood and providing a new route for wood property enhancement.