Recent progress in superhydrophobic rubber coatings

Under the extreme climate, the demand for surface protection from wetting and icing has increased extensively. Many studies focused on developing superhydrophobic coatings from elastic rubbers because of their excellent wear resistance properties. This review not only compares the specific strategies developed to produce superhydrophobic rubber coatings but also analyses the characteristics and applications of superhydrophobic rubber coatings. The common reinforcing agent (SiO2 nanoparticles) and the filler (CaCO3) of rubber products were used to create nano- and microroughness for capturing air on the superhydrophobic surface. Hydrophobic agents were further incorporated to reduce the surface energy of rubber coatings. Besides inorganic nanoparticles, superhydrophobic rubber coatings have been successfully produced using carbonaceous materials, namely multi-walled carbon nanotubes, carbon black and carbon nanofibers. Without nanoparticles, a rough surface could be created through anodizing, laser treatment, plasma jet treatment, chemical etching, or templating. Besides showing large water contact angles (>150°) and low sliding angles (<10°), superhydrophobic rubber coatings showed anti-icing properties on glass insulators. Superhydrophobic rubber coatings were applied on fabric, concrete and asphalt pavement to prevent wetting. Future development should concentrate on the improvement of coating durability. More superhydrophobic natural rubber coatings with improved sustainability should be developed as well.