木質材料 厚さ方向の小片結合ネットワークを強化した低密度パーティクルボード 基礎物性および単板オーバーレイによるその補強

Abstract

To improve mechanical properties and dimensional stabilities of low-density particleboards, a new mat forming and pressing technique was applied. An extruded mat which consists of splint-shape particles (2mm by 2mm by 50mm) was rotated by right angle and then pressed flat with the movement of all mat sides constrained. Particleboards with a density ranging 0.2-0.5g/cm3 and with isocyanate resin as binder were manufactured both in the above method (E-board) and a conventional method (C-board). E-boards showed the constructive characteristics such as more enhanced particle bond network and less particle compressive strain in the panel thickness direction than C-boards, in addition to the strong orientation to one axis on the panel plane. As a result, E-boards exhibited much smaller thickness swelling (TS) and higher residual internal bond strength after boiling than C-boards, and were given better bending properties, inter-lamina shear strength and dimensional stability (linear expansion; LE) along the axis particles oriented on the panel plane. Veneer overlaying improved bending properties and LE in the direction perpendicular to it, which provided E-boards with those basic properties equal or better than C-boards, keeping much less TS than C-boards. Furthermore, cross-lapped two-layer veneer overlaying was found to provide E-boards with better bending properties than C-boards.