Dynamic viscoelastic behavior of wood under drying conditions |
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Authors: | Jiali Jiang Jianxiong Lu |
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Institution: | (1) 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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Abstract: | In this study heartwood from a Chinese fir Cunninghamia lanceolata (Lamb.) Hook] plantation was treated using a high-temperature drying (HTD) method at 115°C, a low-temperature drying (LTD)
method at 65°C, 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°C 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.
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Translated from Journal of Beijing Forestry University, 2008, 30(3): 96–100 译自: 北京林业大学学报] |
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Keywords: | high-temperature drying low-temperature drying freeze vacuum drying viscoelasticity relaxation processes micro-Brownian motion |
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