The Viscoelastic Properties of Chinese Fir During Water-Loss Process Under Hydrothermal Conditions

Abstract

In this paper, the viscoelastic properties of water-swollen Chinese fir during water-loss process under different hydrothermal conditions (30 -90 °C, 40 -80 % RH) were investigated. After the 300min hydrothermal process at 70 or 90 °C, the moisture contents (MCs) of the specimens were well below the MC value at the fiber saturation point (FSP).During the hydrothermal process, normalized E′ increased at first, and then leveled off at temperatures above 50°C. The wood specimens were softened due to the hydrothermal effect. The glass transition of hemicellulose appeared at 50 °C. The lignin transition was observed at 70 and 90 °C. Superposition of transitions of lignin and hemicellulose moved to low storage modulus E′ with the increasing temperature and RH level. † These authors contributed equally to this work

Moisture-dependent orthotropic viscoelastic properties of Chinese fir wood in low temperature environment

“…Generally, the α-relaxation process higher than 20 °C was considered as the glass transition of hemicellulose [16,26,28,29]. The β-relaxation process at around − 90 °C was assigned to the reorientation of the methylol groups in amorphous wood cell walls and the reorientation of adsorbed water molecules in wood by many investigators [16,30,31].…”

On the applicability of the Flory–Huggins and Vrentas models for describing the sorption isotherms of wood

“…Hemicelluloses are known to have a lower softening temperature compared with lignin (Salmén 1984). In Chinese fir the T g of hemicellulose was reported as 323 K and that of lignin as 353-373 K in the presence of sorbed moisture (Zhan, Jiang and Lu 2015). The major glass transition temperatures of dry wood components have been reported to occur in the region of 473-523 K for amorphous cellulose, 423-493 K for hemicellulose and 478 K for lignin (Horvath, Peralta, Frazier and Peszlen 2011).…”