Abstract
The optimal conditions of compression processing in a short time and with low energy using hot-pressing to improve surface hardness of Sugi (Cryptomeria japonica) was investigated. In this study, after boards of Sugi of sapwood and heartwood were conditioned to approximately 10 and 25% of moisture content (MC) and compressed at temperatures of 20 to 140°C with 6 cycles of compression processing including 5 minutes pressing and 1 minute unloading, they were evaluated by recovery of compressive deformation by springback, density profile in the radial direction, observation by Scanning Electron Microscope (SEM) and Brinell hardness. From these results, the optimal condition of compression processing in this study was approximately 10% of MC, and pressing temperatures above 100°C for sapwood and at 100°C for heartwood. Density and hardness of the surface on compressed woods were kept at a high level after planer treatment. Since boards generally contain both sapwood and heartwood, the optimal condition of compression processing is considered approximately 10% of MC and at 100°C of pressing temperature. Long-term dimensional stability was not considered because compressed board is assumed to be painted right after compression processing.
