Study on anisotropic contact angle of rectangular convex structure on fluorine rubber surface

In order to study the anisotropic behavior of surface contact angle of fluorine rubber (FKM) with rectangular convex structure, firstly, FKM materials with rectangular convex structure were prepared by template method. Secondly, the contact angle of the FKM surface in the direction of 0–90° (the direction parallel to the pit is 0°) was tested. The contact angle data of different surface anisotropy of FKM and the contact diameter of water droplets are summarized. Finally, by using the theory of contact line density and the law of line roughness of FKM surface in different directions, the anisotropic contact angle mechanism of FKM surface structure was explained. The results show that the contact angle and contact diameter of FKM surface are in the observation range of 0 ∼ 90°, and the maximum differences are 9° and 162 µm, respectively. The contact angle has an extreme point in the 45° observation direction. The contact angle is inversely proportional to the contact diameter. Contact line density and line roughness are the main causes of anisotropic contact angle. In order to reduce the measurement differences caused by anisotropic contact angle, this paper puts forward a new test standard of anisotropic contact angle, which provides a certain theoretical basis and practical value for the future measurement of anisotropic contact angle.