Chemical modification is an efficient strategy for improving wood quality; however, for some fast-grown wood species unwanted shrinkage occur upon treatment with alkaline solution. This study was devised to reveal the shrinkage behavior of poplar and radiata pine woods treated with 5, 10, 15 and 20 % alkaline sodium silicate (SS) solutions. Wood treated with sodium hydroxide (SH) solution adjusting to the same pH as the specific SS solution was used as a reference sample. The weight loss, chemical components analysis, and confocal microscopy revealed that treatments with SS caused considerable reductions in hemicellulose and acid-insoluble lignin (AIL) of poplar wood up to 51 % and 21 %, respectively. In contrast, such reductions of the SS-treated radiata pine wood were only 13 % and 2 %, respectively. Consequently, shrinkage of poplar wood in the tangential- and radial-directions reached up to 22 % and 11 % respectively. However, such shrinkage for radiata pine was less than 2 % in either direction. The crystallinity index of poplar and radiata pine woods after treatment increased up to 35.3 % and 4.8 %, respectively, attributable to removal of the amorphous fraction. The scanning electron microscopy displayed that treatments had minor effect on the cell structure of radiata pine, but brought about significant collapse of poplar cells. The above results show that radiata pine is more chemically stable to alkaline treatment than poplar.

中文翻译：

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杨木和辐射松木材经水玻璃和氢氧化钠处理后的收缩率

化学改性是提高木材质量的有效策略；然而，对于一些快速生长的木材品种，用碱性溶液处理后会出现不必要的收缩。本研究旨在揭示用 5%、10%、15% 和 20% 碱性硅酸钠 (SS) 溶液处理的杨树和辐射松木材的收缩行为。使用氢氧化钠 (SH) 溶液处理的木材，调节至与特定 SS 溶液相同的 pH 值，作为参考样品。重量损失、化学成分分析和共聚焦显微镜显示，SS 处理导致杨木的半纤维素和酸不溶性木质素 (AIL) 显着减少，分别高达 51% 和 21%。相比之下，经 SS 处理的辐射松木材的减少量分别仅为 13% 和 2%。因此，杨木的切向和径向收缩率分别达到22%和11%。然而，辐射松的收缩率在任一方向上均小于 2%。处理后杨树和辐射松木材的结晶度指数分别增加至35.3%和4.8%，这归因于无定形部分的去除。扫描电镜结果显示，处理对辐射松细胞结构影响较小，但对杨树细胞造成明显破坏。上述结果表明辐射松对碱处理的化学稳定性比杨树更好。