Analysis of hygrothermal recovery of tension wood induced by boiling at 50–80 °C

Abstract

Abstract Hygrothermal recovery (HTR) is an irreversible dimensional change that occurs when green wood is heated under wet conditions. Reaction wood presents a substantial dimensional change owing to HTR. In this study, the HTR of reaction wood was examined to understand the mechanisms of HTR. This study aimed to elucidate the HTR of tension wood, and particularly its temperature dependency. Two types of analyses were applied to the data measured, namely the two-phase exponential model and the time-temperature superposition analysis. The two-phase model was well fitted to the data and showed that the evolution of HTR could be divided into initial recovery and subsequent continuum contraction. The intensity of the initial recovery increased with increasing temperature. Continuum contraction was not well characterized in this study. Time–temperature superposition analysis provided an apparent activation energy of 326 kJ/mol, which suggests that HTR is a lignin-related phenomenon. A simulation based on the analysis also simulated HTR behavior at ambient temperature in a standing tree.