不同含水率速生杨木DMA图谱分析及应用

DMA Spectra Analysis of Fast-Growing Poplar with Different Moisture Contents

采用动态热机械分析仪对绝干、6%、12%、18%、30%、50%、100%和水饱和8种含水率速生杨木试件进行了动态黏弹性分析。动态力学分析参数为:温度扫描范围35～350℃,升温速度5℃.min-1,测量频率10Hz。储能模量的变化表明:各含水率试件在整个扫描温度范围内均出现2个明显的弹性转变过程,完成次级弹性转变的温度随含水率的增加先减小后增大,30%含水率时出现极小值;发生主弹性转变的温度随含水率的增加而增大。损耗模量的变化表明:除绝干试件外,在整个扫描温度范围内其他含水率试件均出现2个明显的黏性转变过程,发生和完成次级黏性转变过程的温度基本上随含水率的增大先减小后增大,极小值都出现在30%含水率时;所有含水率试样发生主黏性转变的温度基本上集中在225℃附近。通过损耗因子图谱准确地获得了不同含水率试件从玻璃态到高弹态,从高弹态到黏流态的转变温度。

The dynamic viscoelastic properties of fast-growing poplar samples with different moisture contents （ absolute dry, 6% , 12% , 18% , 30% , 50% , 100% , and water saturation） were studied by dynamic mechanical analysis （DMA）. Operating parameters of DMA were designed as temperature 35 to 350 degrees C, heating rate 5 degrees C per minute, and measuring frequency 10 Hz, The storage modulus results showed that two elastic changes occurred during the whole range of scanning temperature. The completion temperatures of secondary elastic transition first decreased and then increased with the increasing moisture content, and the minimum completion temperature was 125 degrees C at 30% moisture content. The temperature of the main elastic transition increased with increasing moisture content. The loss modulus indicated that two viscosity transitions took place as the scanning temperature increased, except the absolute dry sample. Both generaring and finishing temperatures of secondary viscosity transition first decreased and then increased with increasing moisture content, and the minimum of the two temperatures occurred at 30% moisture content. The temperature of main viscosity transition for all the samples was around 225 degrees C. The accurate transition temperatures from glassy to high-elastic state and from high-elastic to viscous flow state could be obtained through the loss factor spectra.