Abstract

This study aimed at a better understanding of the wood-water interaction, in particular the role of the hydroxyl accessibility during the humidity-dependent change in moisture content. Thin sections (80 µm) of never-dried Norway spruce sapwood that contained early- and latewood were used for the experiments. Sorption isotherm measurements confirmed the humidity-dependent moisture content changes and the effect of the first drying of the wood sections. Changes in hydroxyl accessibility were then determined by deuteration of the sections using deuterium oxide, followed by their re-protonation in water (H₂O) vapor at different relative humidity: 15, 55 or 95%. The deuteration and re-protonation of the wood sections were quantified by dry mass changes as well as by changes in the OH and OD stretching vibrations in the Fourier transform infrared spectra. The results showed that the deuterated sections could be almost completely re-protonated in H₂O vapor, nearly irrespective of the applied relative humidity. Therefore, changes in hydroxyl accessibility were not the driving force for the humidity-dependent changes in moisture content. However, a slow re-protonation rate at low relative humidity had to be considered. Nonetheless, a small quantity of OD groups persisted the re-protonation in H₂O vapor and liquid H₂O, which was not related to the drying of the wood.

Graphic abstract

中文翻译：

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挪威云杉木材中羟基可及性的湿度依赖性

摘要

这项研究旨在更好地了解木材与水的相互作用，特别是在水分含量随湿度变化时，羟基可及性的作用。实验使用了未干燥的挪威云杉边材的薄切片（80 µm），其中包含早材和晚材。吸附等温线的测量结果证实了湿度相关的水分含量变化以及木材第一次干燥的影响。然后通过使用氧化氘对切片进行氘化，然后在水中重新质子化（H ₂O）在不同相对湿度下的蒸气：15、55或95％。通过干燥质量的变化以及傅立叶变换红外光谱中OH和OD拉伸振动的变化来量化木材的氘代和质子化。结果表明，氘化段几乎可以在H ₂ O蒸气中完全重质子化，几乎与施加的相对湿度无关。因此，羟基可及性的变化不是湿度随湿度变化的驱动力。但是，必须考虑在低相对湿度下较慢的重质子化速率。尽管如此，少量的OD基团仍在H ₂ O蒸气和液体H ₂ O中保持了质子化，这与木材的干燥无关。

图形摘要