OAK Wood Chemical Densification: Microstructure Changes and Perspectives

Wood is a versatile material used for various purposes due to its good properties, such as its aesthetic properties, acoustic properties, mechanical properties, and thermal properties, although its poor dimensional stability and low natural durability are the main obstacles that limit its use in mechanical applications. Therefore, modification is needed to improve these properties. Wood densification improves mechanical and physical properties by compressing the porous structure under steam, heat, and pressure. The wood's lignin, cellulose, and hemicelluloses are polymers that behave similarly to the artificial polymers and are bonded together in wood. However, lignin differs from the other two substances by its highly branched, amorphous, three-dimensional structure. Under appropriate conditions, the lignin incorporated in the wood softens at about 100 ℃, allowing its molecules to deform in the cell walls. This paper proposes an eco-friendly and cost-effective method based on the hydrothermal modification of wood, as potential substitute of conventional chemical techniques for the densification of wood. The chemical structure and mechanical properties of wood cell walls were modified by the traditional alkali method and new hydrothermal treatments and experimentally characterized. This study provides a facile strategy by means of the facile green hydrothermal method for the development of new wood nanotechnology and various functional wood-derived materials.