Characterization of ice-phobic surfaces: Improvements on contact angle measurements

Abstract

One of the main problem for the aircrafts is the ice formation on a critical components that decrease reliability and safety of the flights. At present, methods which prevent or oppose the ice nucleation and growth are not effective and several studies are on going.In this work we focus the activity on passive methods to prevent the ice (ice-phobic surfaces).The factors characterizing the adhesion of water to the surfaces are analyzed, in particular we focused our studies on two performance indexes, wettability and surface free energy, which are strongly correlated with the ice-phobic properties. Surface Free Energy (SFE) and wettability are two properties which depend on the chemical state and the roughness of the surface material. Changing the chemical state or roughness, it is possible to change the surface behavior of the materials.It is evident that, to design ice-phobic surfaces, it is important to evaluate the behavior of supercooled water droplet which starts to be in contact with the surface of the component at real condition of pressure and temperature of flight. For this reason it is important to realize a characterization technique which allows to analyze the sample surfaces varying both pressure and temperature.In this work we have design, developed and validated a test room in order to determine wettability and surface free energy in flight condition (pressure until to 0.1bar and temperature until to −50°C). In this way it was possible to reproduce, in static condition, the behavior of a supercooled liquid drop on the surface component. This new method was validate on a standard material such as Polypropylene. Tests demonstrated that both temperature and pressure influence the shape of the drops, in particular reducing the pressure and temperature, the liquid spread on the surfaces much more than standard conditions (at ambient pressure and temperature).It was corroborated that this new test room is useful for the characterization of ice-phobic surfaces.