Mechanisms of liquid imbibition in Douglas-fir inferred from 1H Nuclear Magnetic Resonance methods

Dang-Mao Nguyen (1) , Sabine Caré (1) , Denis Courtier-Murias (1) , Meng Zhou (1) , Philippe Coussot (1)

1 NAVIER UMR 8205 - Laboratoire Navier

This study aims at identifying the mechanisms of oil and water imbibition in heartwood and sapwood of Douglas-fir through a combination of original experiments with Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) relaxation measurements for oil and free water, and deformation measurements for bound water. Experiments by weighing are performed to verify whether the imbibition process is also consistent with Washburn law. All the results are discussed taking into account the structure of wood (tubular tracheids closed at their tips, but possibly connected to each other via open pits on the side faces) and the preparation of samples. The observation of relatively fast oil flow imbibition confirms that sapwood exhibits a connected hydraulic network through which a liquid can a priori flow and climb along the structure. However, the spontaneous water imbibition is strongly damped by its very poor wetting when in contact with cell-walls only partially saturated with bound water, so that the diffusion of bound water control the uptake dynamics. However, due to preferentially closed pits, the heartwood does not exhibit a continuous hydraulic network and water essentially penetrates into wood by diffusion through the cell walls.

Mots clés: Washburn.; softwood; Free and bound water; Magnetic Resonance Imaging; Nuclear Magnetic Resonance Relaxation; oil; permeability

Domaines: Mécanique des matériaux [physics.class-ph]

Dang-Mao Nguyen, Sabine Caré, Denis Courtier-Murias, Meng Zhou, Philippe Coussot. Mechanisms of liquid imbibition in Douglas-fir inferred from 1H Nuclear Magnetic Resonance methods. Holzforschung, 2021, 75 (3), pp.225-236. ⟨10.1515/hf-2020-0051⟩. ⟨hal-02878893⟩