Effects of Prolonged Exposure to UV and Water on Super-Hydrophobic Surfaces at Ambient and Icing Conditions 2015-01-2160
The surfaces that shed drops helps with mitigation of icing. Shedding of drop depends on surface hydrophobicity, which becomes affected when exposed to water and/or UV. The hydrophobicity degradation of six (Spray SHS, Etched Al SHS, Hydrobead, Neverwet, Waterbeader, and WX2100) different super-hydrophobic surfaces (SHS), exposed to water or UV, were studied from the drop shedding perspective. Two methods were adopted for the hydrophobicity analysis. Among them, one is to study the contact angles (CA) and contact angle hysteresis (CAH) change at static state (i.e., no airflow) compared to the untreated surface. The other one is to analyze the change in critical air velocity (Uc) for a given drop exposed to airflow, on water/UV treated surfaces at room temperature (22 °C) and icing conditions (−1 and −7 °C). For the water/UV treated surfaces, the static CAH and Uc (for all temperatures tested) for drops on Etched Al SHS, Hydrobead, and Neverwet, were found to be less than the specified value for a surface to deem as under performing. Hence, from the overall analysis, Etched Al SHS, Hydrobead, and Neverwet, are considered retaining their performance fairly well at both room temperature and icing conditions after exposure.