湿式硬質繊維板の強度的性質に関する研究(第2報) : 予備圧締の効果について

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繊維間の空隙を減少させて接触面積を増加し,湿式硬質繊維板の強度的性質を向上させる手段としての予備圧締の効果を検討した.　予備圧締は Wet sheet の冷圧とし,繊維には熱可塑性を与えず,水可塑性のみに止めて圧締すれば,繊維は熱圧時よりも比較的変形し難いので水を潤滑剤として繊維間の空隙の充填のみが一方的に著しく進む.その後,熱圧すれば強度的性質は改良されると考えた.　Red lauan 材を原料とし, Table 1, 3 および4に示す条件でSIS硬質繊維板を製造して材質試験を行い次の結果を得た.　1) 予備圧締圧力の増加に伴い曲げ強さ,ヤング係数,ブリネル硬さおよび衝撃曲げ吸収エネルギは増加するが30kp/cm^2以上になると変化が見られず大体一定値を示すが,衝撃曲げ吸収エネルギでは低下する(Fig's.1～7).又,表面粗さは直線的に低下してより平滑になる(Fig.8).　2) 予備圧締速度の強度的性質に対する影響は本実験の範囲内では認められなかった(Fig's.1,3,5,7). 3) 予備圧締時間が比較的短時間(0,5min)の範囲内では,曲げ強さ,ヤング係数およびブリネル硬さに対して圧締圧力の増加は効果的で大きいが,長時間(10min)になると,反って低下させる傾向が見られる(Fig's.2,4,6). 4) 以上の結果からWetsheetの予備圧締は圧力約30kp/cm^2で約5min以内の短時間であれば,その材質向上には有効である事が明瞭となった.但し表面は圧締圧力の大きい程,平滑になる.In this study, we investigated the effects of prepressing on the decreasing gap and the increasing contact area between fibres as means improving strength properties of SIS hardboard. Our way of thinking are as follows : 1) Because the prepressing is carried out under room temperature, the fibre in the wet sheet have moisture-plasticity but less thermo-plasticity. 2) The gap filling progress mostly by the lubricant action of water exist on the surface of fibre, but the fibre deform slightly. 3) If the prepressed wet sheet is hot pressed after preressing, the strength properties of manufactured hardboard must be improved very much. We manufactured the SIS hardboards from Red lauan chip under the condition as shown in Table 1, 3 and 4, and tested those properties. The results of this investigation are as follows : 1) With the increase of specific pressure of prepressing until 30 kp/cm^2, the modulus of rupture, Young's modulus, Brinell hardness and absorbed energy in impact bending increase and then do not increase and keep constant values when the specific pressure increased more than 30 kp/cm^2, but the absorbed energy in impact bending decreases only (Fig's. 1～7). The surface of hardboard becomes more smooth therefore the surface roughness (P_<max>) decrease rectilinearly (Fig. 8). 2) In the range of condition of this investigation, prepressing speed do not effect to the strength properties of SIS hardboard (Fig's. 1, 3, 5, 7.). 3) There is a tendency to improve the modulus of rupture, Young's modulus, and Brinell hardness of SIS hardboard with increment of specific pressure, within the limis of relatively shorter prepressing time (0,5 min.) but to lower the value of those properties, when the prepressing time become longer than former cases (Fig's. 2, 4, 6,) . 4) From above-mentioned results, it became clear that the prepressing of wet sheet improve the strength properties of SIS hardboard at specific pressure of about 30 kp/cm^2 and in shorter time than about 5 minutes. The smooth surface of SIS hardboard become more smooth with increase of specific pressure of prepressing (Fig. 8).
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湿式硬質繊維板の強度的性質に関する研究(第2報) : 予備圧締の効果について

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