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Licensed Unlicensed Requires Authentication Published by De Gruyter September 4, 2012

Compressive-torsion DMA of yellow-poplar wood in organic media

Sudip Chowdhury and Charles E. Frazier
From the journal Holzforschung

Abstract

This work continues the introduction of the dynamic mechanical analysis (DMA) of wood in a novel stress mode, compressive-torsion. The glass/rubber transition in yellow-poplar (Liriodendron tulipifera) wood was measured under saturation in four organic solvents: N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), ethylene glycol, and glycerol. Systematic measurement of the linear viscoelastic response (LVR) revealed a complex relationship of LVR with grain orientation, temperature and solvent. This indicates that special care is required when analysis within the LVR is critical. Glass transition temperatures (Tgs) of swollen wood showed an inverse relationship with solvent induced volumetric swelling. DMF and NMP both caused volumetric swelling of ≥25%, and the corresponding Tgs were near 50°C. Ethylene glycol and glycerol caused volumetric swelling <25% and the corresponding Tgs were ≥100°C. Glycerol showed significantly higher solvolytic power than ethylene glycol. Glycerol plasticized wood underwent irreversible swelling when heated beyond the Tg, causing a reduction in the effective crosslink density and in the Tg. Consistent with the literature, the observed Tg grain dependency was highly varied. The weakest plasticizer, glycerol, produced a prominent Tg grain dependency, whereas grain dependency was variable in the stronger swelling agents. This study demonstrates the importance of researching lignocellulose rheology in a greater variety of organic liquids, to achieve new perspectives into the structure/property relationships of lignocellulose, and aspects of processing in organic media.


Corresponding author Macromolecular Science and Engineering Sustainable Biomaterials Virginia Tech, 230 Cheatham Hall Blacksburg, VA 24060, USA

Received: 2011-8-17
Accepted: 2012-8-3
Published Online: 2012-09-04
Published in Print: 2013-02-01

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