Effects of hydrolytic and freeze-thaw aging on the performance of spruce wood

Abstract

Wood is susceptible to various degradation mechanisms when exposed to dynamic environmental conditions, including hydrolysis caused by the infiltration of water into the wood cell structure. This study aims to examine the differences between the effects of two types of accelerated aging on the long-term performance of white spruce wood samples to have a better understanding of the performance of spruce wood in real-world applications. Two separate sets of samples were employed in this experimental study. One set was placed in a hydrolytic aging chamber at 90 °C and 80% relative humidity while the other set was placed in a freeze-thaw cycling chamber with temperature variations from 25 °C to -18 °C at a rate of 6 cycles per day. The aged samples were tested at regular intervals, with a testing span of 3 months for the hydrolytically aged samples and 300 cycles for the freeze-thaw aged samples. The results obtained from characterization tests showed that both aging conditions caused a significant increase in the crystallinity index of the samples. This finding highlights the potential value of subjecting wood to these conditions as a pre-treatment to standardize crystallinity levels for experimental purposes. Ultimately, the hydrolytic aging conditions were found to be more detrimental to the spruce wood samples. The samples that underwent hydrolytic aging demonstrated higher water uptake levels, lower viscoelastic properties, and lower thermal degradation temperatures than the samples that were subjected to freeze-thaw cycling.