Effect of Resin Content on the Creep Behavior of OSB under Adsorption

用膠量對定向粒片板吸濕潛變之影響

葉民權(Min-Chyuan Yeh) ； 唐潤秋(R. C. Tang)

《林產工業》 17卷4期 (1998/12) Pp. 671-680

摘要

本研究之目的在探討定向粒片板在吸濕環境下，同時承受長期載重之潛變行為，以及分析不同用膠量的影響。長薄片形粒片所採用之樹種為南方松，酚樹脂膠合劑之用量分別為4.5%及6.5%，定向粒片板之厚度為0.5吋（12.7 mm），平均比重為0.625。試材以相對濕度65%調濕後，在95% RH下以中央集中載重方式進行潛變試驗三個月，載重大小為靜曲強度值之20%，40%以及循環施予20%至40%之載重等三種，其中循環載重為每7天增或減一次20%之載重。靜曲潛變之測定方向為定向粒片板平行長度方向，結果顯示部分試材在較大載重及吸濕條件下提早破壞，此現象在低佈膠量試材尤為明顯，其餘試材在解除20%及40%之載重後，定向粒片板的瞬間彈性回復值比初施予載重時的瞬間彈性變位量分別增大27.2%及66.2%。循環載重條件下之定向粒片板的潛變量則介于20%及40%之兩種載重條件之間。用膠量為4.5%時，在20%及40%載重條件下定向粒片板之相對潛變值分別為3.94及6.45；用膠量為6.5%時，在20%及40%載重條件下之相對潛變值分別為3.74及6.12。在吸濕狀態下，循環載重處理的試材每次在載重量由20%增加至40%時所提高的瞬間彈性變位量以第一週為最高，在第二次以後則呈依次遞減之趨勢。經過長期吸濕載重試驗後，定向粒片之殘留靜曲強度及靜曲彈性係數分別為未處理試材之70%及75.2%。

關鍵字

定向粒片板 ； 潛變 ； 用膠量

並列摘要

The effect of resin content on the creep behavior of oriented strand boards (OSB) subjected to various loading conditions was investigated. OSB specimens, fabricated with southern pine (Loblolly) flakes and liquid phenol formaldehyde resin of 4.5% and 6.5% resin content (RC), were preconditioned and equilibrated under constant 65% RH and 75 of (23.8°C) and then tested in bending with concentrated load applied at the middle span under an adsorptive condition of 95% RH. The duration of creep test was three months followed by a 3-week recovery with load removed. Loading conditions selected were constant low load (equal to 20% of static bending strength: MOR), constant high load (equal to 40% of MOR), and load cyclically changed between 20% and 40% MOR with a 7-day duration at each level. Creep deformation was measured from specimens with flakes parallel to the length axis. The instantaneous recoveries of specimens measured after loads removed were 23.2% and 66.2% higher than the instantaneous deflections for those subjected to constant low and high loads, respectively. The magnitude of creep deflection of cyclically loaded specimens was between that of groups subjected to constant loads. Under the adsorption, the instantaneous deflection in the cyclic load group, due to the application and removal of the second loads, increased after the first week and then leveled off during the following weeks. Relative creep values of specimens prior to unloading was 3.94 and 6.45 for the 4.5% RC groups subjected to constant low and high loads respectively while values of 3.74 and 6.12 were observed in the 6.5% RC groups. After 3-week recovery, residual mechanical properties of specimens were evaluated and compared to those of specimens without load applications.

並列關鍵字

OSB ； creep ； resin content