Forced wetting of hydrophobic flocked pile fabrics.

The hydrophobicity of a material is enhanced by introducing a multi-scaled roughness on its surface. When a liquid droplet deposited on such a surface is submitted to a stress, a wetting transition is observed. This transition is abrupt for model rigid surfaces. The case of textile materials is very different since they are highly deformable and the liquid may penetrate the structure. In this paper, we focus on hydrophobic pile textile fabrics. Firstly, their wetting properties are characterized by the contact angle, the contact angle hysteresis and the roll-off angle. Then, we study the influence of an external pressure applied to a drop deposited on the surface. The contact angle after squeezing is studied vs. the pressure and vs. the lateral deformation of the fabrics. The results are discussed according to the geometrical parameters of the piles and the microscopic organization of the structure. [ABSTRACT FROM AUTHOR]