Changes in gas permeability and pore structure of wood under heat treating temperature conditions

Eun-Suk Jang,Chun-Won Kang

doi:10.1186/s10086-019-1815-3

Abstract

In this study, changes in gas permeability and pore structure of wood are evaluated after heat treatment with temperatures ranging from 190 to 230 °C for 6 h for both hardwood (yellow poplar: Liriodendron tulipifera) and softwood (Korean red pine: Pinus densiflora). The purpose of this study is to investigate changes in pore size, content of three pore types (through pore, blind pore, and closed pore), as defined by IUPAC, and gas permeability by increasing heat treatment temperatures in hardwood and softwood using capillary flow porometry and gas pycnometry. As the heat treatment temperature increased, only through pore porosity increased, causing an increase in gas permeability.

Highlights

Wood is a non-homogeneous hygroscopic material and swells or shrinks due to changes in the equilibrium moisture conditions
It was difficult to determine the difference of anatomical features in the surface pore morphology of the cross section by heat treatment in yellow poplar, similar to the findings in Kim et al [24]
Results of through pore diameter The maximum pore size and the mean pore size of through pores measured by the capillary flow porometry and the average value of each part are presented in Figs. 10 and 11

Summary

Introduction

Wood is a non-homogeneous hygroscopic material and swells or shrinks due to changes in the equilibrium moisture conditions. Heat treatment is a method for improving the quality of wood to overcome these demerits. It is generally recognized as an environmentally friendly method because it uses only high temperature or steam without chemical additives [2]. Due to high-temperature heat treatment, the properties of wood are changed as follows: increase in the durability against decay, decrease in hygroscopicity due to a decrease in hydrophilic OH groups, decrease in the equilibrium moisture content, increase in the dimensional stability, relief of the internal stress, change in the coloration, and decrease in the thermal conductivity [2,3,4,5,6].

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Conclusion