Wood densification is aimed at reducing wood porosity through compression to improve wood surface hardness and transverse shear strength (Navi and Heger, 2004). This method has generated a lot of interest as it has the potential to improve the properties of low-density wood species, making them suitable for high-end applications such as wooden flooring
(Tenorio, Moya and Navarro-Mora, 2021). However, the hygroscopic nature of wood results in densified wood capable of regaining its original shape when re-moistened, known as set-recovery(Navi and Heger, 2004). By examining individual components, we can better understand their contributions. Previous research showed that partial lignin removal and increased moisture content reduced set-recovery after water immersion from 100% to 70%(Kilumets et al., 2024). These high values prompted investigation into hemicelluloses, the most hydrophilic cell wall component, which contributes to reversible swelling. While thermal modification enhances dimensional stability, its effectiveness may be linked to hemicellulose degradation, as hemicelluloses are more thermally labile than cellulose or lignin (Shafizadeh and Chin, 1977). A key question is whether thermal modification and hemicellulose water extraction yield similar effects. Water extraction could enable more precise removal of hemicelluloses, helping to clarify their specific role in set-recovery.
Keywords: Wood densification, dimensional stability, hot water extraction, set-recovery
Authors
Catherine Kilumets
Laboratory of Wood Technology, Department of Material and Environmental Technology
J.Y. Zhu
USDA Forest Service, Forest Products Laboratory, Madison, WI 53726, USA
Christopher G. Hunt
USDA Forest Service, Forest Products Laboratory, Madison, WI 53726, USA
Heikko Kallakas
Laboratory of Wood Technology, Department of Material and Environmental Technology
Jaan Kers
Laboratory of Wood Technology, Department of Material and Environmental Technology
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