Tensile ice adhesion of bulk water ice on flat and microstructured hydrophobized polymer surfaces vs. reference materials

• Tensile ice adhesion measurements of large bulk water ice cylinders (D = 4 mm), corresponding to large water drops in static icing conditions • Microstructured (superhydrophobic) and flat (hydrophobic) Polyurethane (PU) films vs. reference surfaces • Low surface energy, high material elasticity and large microcracks enable low ice adhesion • Nanostructures enhance ice adhesion on microstructured surfaces, but not on flat surfaces • Ice adhesion is highest on microstructured superhydrophobic PU films and lowest on flat hydrophobic PU films in static icing conditions To validate the de-icing effectiveness in static icing conditions, we measured the tensile ice adhesion on durable, hydrophobic (flat) and superhydrophobic (microstructured by hot embossing, D > 35 µm) polyurethane (PU) films, coated with thin fluorocarbon or silicone-like plasma polymers, in comparison to conventional metal and polymer reference surfaces. Bulk water ice cylinders (4 mm in diameter) were removed from the samples at -20°C, and the influence of material elasticity, microcracks resulting from local stress, surface chemistry, micro- and nano-roughness was investigated. The tensile ice adhesion was lowest on flat, hydrophobic PU films, due to high material elasticity and the presence of microcracks, whereas it was highest on superhydrophobic surfaces, because of mechanical interlocking from mixed wetting states. The impact of nanoscale roughness on ice adhesion is negligible on flat surfaces, whereas it significantly enhances adhesion on microstructured surfaces due to the hierarchical roughness. Condition-adapted surface design is of crucial importance for effective de-icing.