COMPRESSIVE-MOLDING OF WOOD BY HIGH-PRESSURE STEAM-TREATMENT - PART 2- MECHANISM OF PERMANENT FIXATION

Permanent fixation of the compressively transformed shape of Harigiri (Kalopanax pictus Nakai) specimens was attempted by steaming them, com pressively transforming their shapes, and processing them with high-pr essure steam again. Also, the mechanism of the shape fixation was exam ined. The results are summarized as follows: (1) Compressively transfo rmed Harigiri specimens, after being processed with high-pressure stea m, did not recover to their original shape with heat and moisture, thu s achieving permanent fixation of compressed shape. (2) The conditions under which the fixed specimens would not recover to their original s hape were found to be steaming with saturated steam at 200 degrees C f or 4 min or longer or at 180 degrees C for 8 min or longer, within the scope of the current experiment. (3) Hemicellulose and lignin do not affect the fixation of compressive transformation. (4) The fixation of compressive transformation is caused by a structural change of cellul ose. (5) The mechanism of fixation of compressive transformation is su pposed to be that the inner stress is released because the paracrystal line region of cellulose, which is distorted by compressive transforma tion, is partially hydrolyzed. Further, steam-rearrangement of hydroly zed constituent into crystalline region occurs, keeping the transforme d shape intact.