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Fibrous textiles constitute a class of porous media in which moisture transport is strongly affected by finite-size effects and by non-linear couplings between fluid state, pore structure and material swelling. During wetting and drying processes such as washing, drying or perspiration transport, the dynamics cannot be described solely in terms of capillary flow in the pore space.
In bio-based fibrous materials, a significant fraction of water is absorbed within the fibres themselves, where it is bound to amorphous regions. This bound water may represent up to 30% of the dry mass and induces swelling and non-linear moisture transport behaviour [1,2]. We hypothesize that the partitioning of water between free water, pore-confined water and fibre-bound water governs both imbibition and drying dynamics in textiles.
To test this hypothesis, we use 1H NMR relaxometry to monitor moisture evolution in time and to discriminate water populations according to their molecular mobility (cf Figure). This approach allows us to quantify and localize bound and free water during transient wetting and drying [3]. A comparative study of cotton, wool and acrylic textiles reveals that bound water plays a dominant role in controlling transport kinetics when present in significant amounts, leading to competing transport pathways at the fibre and pore scales. Accordingly, bio-based fibrous materials exhibit complex and non-linear moisture dynamics, particularly wool due to its hydrophobic yet highly hygroscopic nature.
These results demonstrate that moisture transport in bio-based textiles is governed by non-linear interactions between water state and material structure. Accounting explicitly for bound water is therefore essential for modelling wetting and drying in textiles, with implications for the broader understanding of flow and transport in specialized porous systems.
Figure: Evolution of the probability density function (PDF) of the NMR signal during the transport of a drop in a wool textile from impregnation (a) to drying (b).
| References | [1] X. Ma et al., Vapor-sorption Coupled Diffusion in Cellulose Fiber Pile Revealed by Magnetic Resonance Imaging, Physical Review Applied 17 (2022). [2] C. Duprat, Moisture in Textiles, Annual Review of Fluid Mechanics 54, 443–467 (2022). [3] B. Maillet et al., Dynamic NMR Relaxometry as a Simple Tool for Measuring Liquid Transfers and Characterizing Surface and Structure Evolution in Porous Media, Langmuir 38, 15009−15025 (2022). |
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| Country | France |
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