Viscoelastic Properties of the Chinese Fir (Cunninghamia lanceolata) during Moisture Sorption Processes Determined by Harmonic Tests

Materials

Jianmin Chang¹  Hui Peng²  Anxin Li²  Jianxiong Lu²  Jiali Jiang²  Tianyi Zhan² 

[1] College of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China;State Key Laboratory of Tree Genetics and Breeding, Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China;

关键词: Chinese fir;    sorption;    viscoelasticity;    harmonic test;    mode of RH increment;    plasticization effect;    unstable state;   

DOI  :  10.3390/ma9121020

来源: DOAJ

【 摘 要 】

Measured by harmonic tests, the viscoelastic properties of Chinese fir during moisture sorption processes were examined under three relative humidity (RH) modes: RHramp, RHisohume, and RHstep. The stiffness decreased and damping increased as a function of the moisture content (MC), which is presumed to be the effect of plasticization and an unstable state. The increasing damping was associated with the breaking of hydrogen bonds and the formation of free volume within polymer networks. The changes of loss modulus ratio at 1 and 20 Hz, E″1Hz/E″20Hz, proved the changing trend of the unstable state. Higher ramping rates aggravated the unstable state at the RHramp period, and higher constant RH levels provided more recovery of the unstable state at the RHisohume period. Changes of viscoelastic properties were associated with RH (varied or remained constant), and the application of Boltzmann’s superposition principle is a good approach to simulate viscoelasticity development.

【 授权许可】

Unknown