Wood is a naturally hygroscopic material, and the atmospheric water molecules interact with sorption sites in the cell wall, causing changing moisture contents depending on the relative humidity of the air (Skaar, 1988). Many properties of wood, such as dimensional stability (Kong et al., 2018), mechanical properties (Wagner et al., 2015) and resistance towards biological degradation (Thybring et al., 2018) are affected by the moisture content in wood. Acetylation is an effective method to reduce the hygroscopicity of wood by substitution of hydroxyl groups with acetyl groups as well as by bulking of the cell wall (Popescu et al., 2014; Beck et al., 2017). Wood-water interactions are related to the biopolymer composition of the cell wall, as the number of accessible hydroxyl groups differ between cellulose, hemicellulose and lignin (Thybring et al., 2017), and we hypothesize that biopolymer composition also affects the acetylation result. The objective of this study is to change the relative biopolymer composition in wood prior to acetylation and investigate the effects of these changes on the moisture in acetylated wood as studied by low field nuclear magnetic resonance (LFNMR) and by measurements of hydroxyl accessibility.
Keywords: acetylation, wood-water interactions, biopolymer composition
Authors
Tiantian Yang
Beijing Forestry University, University of Copenhagen, Denmark
Emil Engelund Thybring
Maria Fredriksson
Erni Ma
Jinzhen Cao
Ramunas Digaitis
Lisbeth Garbrecht Thygesen
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