The effects of surface energy and roughness on the hydrophobicity of woven fabrics

The wetting behavior of a hydrophobic rough surface is investigated on a surface fabricated by applying low surface tension materials such as silicone or fluoropolymer to polyester woven fabric consisting of multifilament yarns. The roughness factor of various woven fabrics can be calculated by Wenzel's and Cassie-Baxter's equations. For the fabrics treated with silicone or fluoropolymer, the Cassie-Baxter model was applied, showing a level of agreement for the fabric specimens non-textured filament fibers between the predicted contact angles and the measured values. More precisely, the fabrics treated with silicone or fluoropolymer represent the transitional state between the Wenzel type and the Cassie-Baxter type; that is, the fractional contact area between the water and air f(2) is greater than zero, and the sum of the fractional contact areas for solid-water f(1) and air-water f(2) is greater than 1. A surface with lower energy and higher roughness gave f(1) + f(2) close to 1 with smaller f(1) and larger f(2), which resulted in a high contact angle.