首页|Dynamic viscoelastic behavior of wood under drying conditions
Dynamic viscoelastic behavior of wood under drying conditions
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In this study heartwood from a Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115℃, a low-temperature drying (LTD) method at 65℃, and freeze vacuum drying (FVD), respectively. The dynamic viscoelastic properties of dried wood specimens were investigated. The measurements were carried out at a temperature range of -120 to 250℃ at four different frequencies (1, 2, 5, and 10 Hz) using dynamic mechanical analysis (DMA). We have drawn the following conclusions: 1) the storage modulus E' and loss modulus E" are the highest for HTD wood and the lowest for FVD wood; 2) three relaxation processes were detected in HTD and LTD wood, attributed to the micro-Brownian motion of cell wall polymers in the non-crystalline region, the oscillations of the torso of cell wall polymers, and the motions of the methyl groups of cell wall polymers in the non-crystalline region in a decreasing order of temperatures at which they occurred; and 3) in FVD wood, four relaxation processes were observed. A newly added relaxation is attributed to the micro-Brownian motions of lignin molecules. This study suggests that both the HTD and the LTD methods restrict the micro-Brownian motion of lignin molecules somewhat by the cross-linking of chains due to their heating history.
Key Laboratory of Wood Science and Technology of the State Forestry Administration, Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China
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