Abstract
Fabrication of binderless boards by compressively molding with high-pressure steam has been developed recently. The purpose of this study is to clarify its binding mechanism. The significant improvement in the physical properties of boards by converting its raw material from sawdust to wood-fiber suggests that fabric entanglement is deeply involved in its binding mechanism. Physical properties of boards made from extractive-free sawdust indicates that the presence of extractives in wood plays a role of supporting its dimensional stability, but this may not be a major binding factor. Furthermore, structural stability of fabricated boards by removal of hemicelluloses and lignin with hot water extraction and dioxane extraction indicates that the main binding factor in board fabrication is cellulose, even though lignin and hemicelluloses contribute to the additional strength. The increase in cellulose crystallinity and reconstruction of its crystal structure by high-pressure steaming creates entanglement of sawdust in the board. In addition, the successful fabrication of binderless boards with sufficient strength from the materials which contain infinitesimal amount of lignin, such as paper, cotton and fabric emphasizes that cellulose plays a major role in the binding mechanism of binderless boards.
