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Water State Study of Wood Structure of Four Hardwoods Below Fiber Saturation Point with Nuclear Magnetic Resonance

Leandro Passarini, Cédric Malveau, Roger E. Hernández

Abstract


Nuclear magnetic resonance (NMR) is a useful, powerful, and noninvasive technique to study the dynamics of wood-water relations, both quantitatively and qualitatively. The main objective of this study was to use NMR to characterize the state of water below the FSP. Two tropical hardwood species, huayruro (Robinia coccinea Aublet) and cachimbo (Cariniana domesticata [C. Martius] Miers), a plantation-grown eucalyptus species (Eucalyptus saligna Smith), and a temperate species, red oak (Quercus rubra L.), were studied. These species were chosen for their diversity in terms of anatomical and physical properties. Desorption tests were carried out at 21°C in a single-step procedure from full saturation state for huayruro, cachimbo, and red oak and from green condition for E. saligna. Discrete T2 times were obtained for each species and equilibrium moisture content (EMC). The results showed that even under EMC, there was a region in the hygroscopic range in which the loss of bound water takes place before all liquid water was drained. This region varies according to wood species. Furthermore, variation in the fast T2 values among the different wood species gives an indication of how bound water is distributed and arranged in sorption sites.

Keywords


Nuclear magnetic resonance;T<sub>2</sub> relaxation;water state;water-wood relations;fiber saturation point

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