干燥处理材的动态粘弹性

Dynamic viscoelastic properties of drying treated wood.

该文采用高温干燥、低温干燥和真空冷冻干燥3种干燥方法分别对杉木人工林木材进行干燥处理。用动态力学分析仪测定了3种干燥处理材在温度-120～250℃,测量频率1、2、5、10 Hz的动态粘弹性。结果表明：①储存模量和损耗模量均表现为高温干燥处理材最大,真空冷冻干燥处理材最小。②高温干燥处理材和低温干燥处理材的损耗模量温度谱中,从高温至低温方向可依次观察到3个力学松弛过程,其分子运动归属分别是木材细胞壁非结晶区中聚合物的微布朗运动、木材细胞壁聚合物分子的扭转振动和木材细胞壁无定型区中伯醇羟基的回转取向运动。③真空冷冻干燥处理材的损耗模量温度谱可观察到4个力学松弛过程,新增加的松弛过程是由木素分子的微布朗运动引起的。这说明木材经过高温干燥或低温干燥处理,由于受到热的作用,木材细胞壁分子链之间可能发生了一定程度的交联,从而限制了木素分子的微布朗运动。

In this study,Chinese fir（Cunninghamia Lanceolata（Lamb.）Hook.） plantation wood was treated by high temperature drying（HTD）,low temperature drying（LTD） and freeze vacuum drying（FVD）,respectively.The dynamic viscoelastic properties of dried wood were investigated.The measurement was carried out in the temperature range of-120 to 250℃ at four different frequencies（1,2,5,10 Hz） using a Dynamic Mechanical Analysis（DMA）.The following results are be concluded： 1） The storage modulus E′ and loss modulus E″ are the highest for HTD wood and the lowest for FVD wood.2） Three mechanical relaxation processes were detected in the HTD and LTD woods.They are attributed to the micro-brownian motion of the cell wall polymer in the non-crystalline region,the torsional oscillations of the cell wall polymer and the motions of the methylol groups of the cell wall polymer in the non-crystalline region in the order of the decreasing temperature at which they occurred.3） As for FVD wood,four mechanical relaxation processes were observed.The newly added relaxation is attributed to the micro-brownian motion of lignin.This study suggests that both HTD and LTD restrict the micro-brownian motion of lignin to some extent by the crosslinking of chains due to the heating history.