Dynamic viscoelastic properties of wood and acetylated wood in nonequilibrium states swollen by water or organic liquids

Yuka Miyoshi,Yuzo Furuta,Ai Sakae,Keisuke Kojiro,Nao Arimura

doi:10.1186/s10086-020-1856-7

Abstract

To discuss the factors that greatly affect the stabilization and destabilization of the conformation of lignin caused by changes in temperature and/or swelling, the temperature dependence of the loss tangent (tanδ) of the sample given the different cooling rates and the changes in the storage elastic modulus (E′) and the loss elastic modulus (Eʺ) over time during the swelling process were measured using the untreated or the acetylated wood samples swollen by water or organic liquids. The difference in the glass transition temperature of lignin mainly affects the degree of the destabilization of the conformation of lignin caused by quenching in the untreated and acetylated wood samples. The changes in E′ and Eʺ during swelling process were significantly different between the liquids in the untreated wood sample. The differences of E′ and Eʺ in the different liquids were considered to be caused by the balance of the stabilization depending on the swelling amount and passage of time and the destabilization due to the rapid swelling.

Highlights

Wood subjected to short-term changes in temperature and/or swelling shows lower elastic modulus and greater fluidity compared with stable wood that has been exposed to a constant temperature and humidity for a long time [1,2,3,4,5,6,7,8]
The tanδ measured after quenching was higher than the tanδ measured after annealing due to the decrease in the storage elastic modulus (E′) and the increase in the loss elastic modulus (E′’) in the temperature range below the peak temperature of the tanδ
The maximum value of the tanδ measured after quenching (tanδQ)/ tanδ measured after annealing (tanδA) of the sample swollen by FA was the highest in all of the acetylated samples. These results indicate that the degree of instability caused by quenching is closely tanδQ / tanδA (%) tanδQ / tanδA (%) tanδQ / tanδA (%)

Summary

Introduction

Wood subjected to short-term changes in temperature and/or swelling shows lower elastic modulus and greater fluidity compared with stable wood that has been exposed to a constant temperature and humidity for a long time [1,2,3,4,5,6,7,8]. It has been reported that the glass transition temperature of lignin in the water-swollen wood with quenching and/or drying was lower than that in green wood [9, 10]. The glass transition temperature of lignin that was decreased by these histories was increased over time by water soaking [10]. These changes in the mechanical properties of wood. The stabilization and destabilization occur simultaneously during the process of changes in temperature and swelling, and the degree of the instability of wood

Methods

Results

Conclusion