Susceptibility of wood to fungal degradation shortens service life and is one of the primary factors limiting the use of wood in constructions today. Traditionally, biodegradation has been mitigated by treatments with biocides, but the use of these chemicals is increasingly restricted due to environmental and health concerns. Alternatively, resistance to fungal decay can be improved by chemical modification which provides a nontoxic mode of action (Hill 2006). Although commercial chemical modification processes such as thermal modification, acetylation and furfurylation are gaining market share (Jones et al. 2018), growth is constrained by higher production costs compared to traditional wood preservation methods. Thus, a low- cost wood protection system with a non-toxic mode of action is needed. Polyesterification of wood with sorbitol and citric acid appears to be a promising technique. Larnøy et al. (2018) showed that polysorbitol (PS) modified wood cured at 140°C was resistant to leaching of reactant chemicals and provided increased decay protection against brown-rot and white-rot fungi. The exact mechanism behind the increased durability in chemically modified wood remains unclear, but it is generally acknowledged that a critical factor contributing to enhanced decay resistance is moisture content reduction (Thybring 2013, Ringman et al. 2019). This study assesses the moisture content in wood modified with sorbitol and citric acid. Various reactant concentrations provided different levels of modification and the modified samples were assessed for volumetric swelling and measured with low-field NMR (LFNMR).
Keywords: polyesterification, sorbitol, citric acid
Authors
Greeley Beck
Norwegian Institute of Bioeconomy Research, Ås, Norway
Andreas Treu
Erik Larnøy
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