Abstract
The influence of hygrothermal condition on dynamic viscoelasticity of Chinese fir (Cunninghamia lanceolata) during the moisture desorption (MDes) process was investigated. The ambient hygrothermal environments were set up as a series of constant temperatures and two relative humidity (RH) modes (RHramp-down and RHisohume). The MDes provided space for the rearrangement of the hydrogen bonds (Re-HB) and caused a mechano-sorptive (MS) effect. The enhancement of the Re-HB effect negatively correlated with the increment of loss modulus, while the elevation of the MS and the heating effects intensified the loss modulus. Lower values of RHc, determining the plateau area of loss modulus, were obtained at higher temperatures or greater RH ramping rates. The residual instability in the wood cell wall was quantitatively characterized by the extent of the MS effect. Residual instability was inversely proportional to the RHisohume level during the MDes process. The study of time dependent viscoelastic properties under moisture changing process provided insight into the condition of adsorbed water in the cell wall and optimized the manufacturing technique involved in the thermo-hygro-mechanical treatment of wood.
Acknowledgment
This work was financially supported by the National Natural Science Foundation of China, Funder Id: 10.13039/501100001809, (No. 31700487), the Natural Science Foundation of Jiangsu Province (CN) (No. BK20170926), the Innovation Fund for Young Scholars of Nanjing Forestry University (CX2017002), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Employment or leadership: None declared.
Honorarium: None declared.
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The online version of this article offers supplementary material (https://doi.org/10.1515/hf-2017-0130).
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