Forced wetting of hydrophobic knitted fabrics analyzed with X-ray imaging

Understanding how water droplets penetrate a textile fabric under forced conditions is of considerable interest for sportswear comfort and protective clothing, but also for processes such as inkjet printing. Investigations on the role of geometrical morphology in liquid transport face difficulties in identifying the relevant geometrical parameters at play. Here, X-ray tomography was used to investigate how the liquid distributes inside knitted fabrics when a droplet is squeezed onto its surface using a specifically developed device. It makes it possible to visualize the dynamics of the droplet's penetration and to analyze the final liquid distribution after releasing the compression. The three-dimensional liquid zone can be reconstructed with a specific method and qualitatively analyzed. Variation in hydrophobicity and porosity, characterized by the cover factor, is the main contributor to changes in liquid distribution among samples, by influencing in-plane spread, that is, on the surface, and/or transplanar spread, that is, penetration into the thickness of the fabric.