Nanocomposite coating superhydrophobicity recovery after prolonged high-impact simulated rain

Abstract

Polyurethane/fluoroacrylic/organoclay superhydrophobic nanocomposites were exposed to high-flux, high-speed 1 mm drops traveling at 25 m s⁻¹ (more than 10⁵ droplet impacts at Weber numbers exceeding 10⁴), which is equivalent to decades of rainfall impacting a moving surface. After dry-out from this simulated rain exposure, high contact angles and reasonable roll-off were generally recovered for samples oriented both normally and tilted to the impacting droplets, though some microscale osmotic swelling was noted. After refunctionalizing the vertically impacted surface with fluoroacrylic, an increase in performance was observed.