How much water can wood cell walls hold? A triangulation approach to determine the maximum cell wall moisture content

Abstract

Wood is a porous, hygroscopic material with engineering properties that depend significantly on the amount of water (moisture) in the material. Water in wood can be present in both cell walls and the porous void-structure of the material, but it is only water in cell walls that affects the engineering properties. An important characteristic of wood is therefore the capacity for water of its solid cell walls, i.e. the maximum cell wall moisture content. However, this quantity is not straightforward to determine experimentally, and the measured value may depend on the experimental technique used. In this study, we used a triangulation approach to determine the maximum cell wall moisture content by using three experimental techniques based on different measurement principles: low-field nuclear magnetic resonance (LFNMR) relaxometry, differential scanning calorimetry (DSC), and the solute exclusion technique (SET). The LFNMR data were furthermore analysed by two varieties of exponential decay analysis. These techniques were used to determine the maximum cell wall moisture contents of nine different wood species, covering a wide range of densities. The results from statistical analysis showed that LFNMR yielded lower cell wall moisture contents than DSC and SET, which were fairly similar. Both of the latter methods include factors that could either underestimate or overestimate the measured cell wall moisture content. Because of this and the fact that the DSC and SET methods are based on different measurement principles, it is likely that they provide realistic values of the cell wall moisture content in the water-saturated state.

Targeted acetylation of wood: a tool for tuning wood-water interactions

“…7b). This supports that even though the cell wall moisture content is underestimated in LFNMR-measurements at room temperature (Beck et al 2018b;Thybring et al 2020a), it is still possible to compare different groups of specimens. One difference between the results in the hygroscopic range and in water saturated state was, however, that a slight reduction in moisture content and thus moisture exclusion efficiency was seen also for interface modification 1 in the hygroscopic range (Fig.…”

“…This is most likely caused by a reduced lumen volume, primarily in latewood, because of the acetylation induced swelling of cell walls as observed by Sander et al (2003). Note that evaluation of cell wall moisture contents from LFNMR measurements above 0°C underestimates the absolute value of the cell wall moisture content (Beck et al 2018b;Thybring et al 2020a). Therefore, the absolute value of the cell wall moisture content in Fig.…”

Deswelling of microfibril bundles in drying wood studied by small-angle neutron scattering and molecular dynamics

“…5 Moisture content as a function of time measured by DVS and the normalized height of the azimuthal peak and A-term from the WoodSAS model (Eq. 2) as determined by SANS while the lumina are empty (Thybring et al 2020). However, FSP is a theoretical value usually measured at equilibrium, while the spruce sample measured is a macroscopic object and the drying rate is so fast that the system is nowhere near equilibrium.…”

Conservation of Waterlogged Wood—Past, Present and Future Perspectives

“…This will have the property of reducing the glass transition temperature of the wood cell wall matrix, resulting in a decrease in sorption hysteresis [143,144]; assuming that water molecules are able to penetrate the PEG-cell wall polymer void system. Higher MW PEGs do not enter the sound cell wall [145], but the extent of penetration of the pore structure of degraded wood by PEGs of different sizes is not known. Nanopores exhibit a partitioning effect on solutions of PEGs of different MW (and radius of gyration) and that changing the concentration of PEG in solution influences the radius of gyration [146].…”