Experimental Study on the Evolution of Contact Angles with Temperature Near the Freezing Point

Measurements of the water contact angle as a function of temperature down to freezing gives valuable information for the development of anti-icing coatings. Advancing (ACA) and receding (RCA) contact angles were measured by depositing drops of water oil different material surfaces for temperatures ranging from room temperature to 0 degrees C. No changes in the contact angles as a function of temperature have been observed for polished silicon, polished aluminum, roughened silicon, gold, high density polyethylene, PTFE (polytetrafluoroethylene), and PMMA (poly(methyl methacrylate)) for the entire temperature range. However both the ACA and RCA decrease and the hysteresis increases at temperatures below 5 degrees C for all nanostructured materials used in this Study, Such as nanopatterned PMMA, PTFE nanoparticles film, and HIREC-100 (a super water-repellent coating blended with TiO(2); developed by NTT Advanced Technology Corporation (http://www.ntt-at.com)). This behavior was attributed mainly to the condensation from the vapor phase of the water drop for temperatures below 5 degrees C. The resulting thin water film decreases the contact angles, especially for the receding, contact, enhancing the hysteresis and water drop adherence. These experimental results Could explain the adherence of ice on superhydrophobic nanostructured Surfaces.