Cement based superhydrophobic coating with excellent robustness and solar reflective ability

Abstract

In the process of outdoor use, building exterior wall coating inevitably undergoes the effects of temperature change, ultraviolet radiation, mechanical contact, dust pollution and so on, which reduces the solar reflectivity. Therefore, improving the durability of the solar reflective coating is the premise to ensure the long-term stable use of the solar reflective coating. In this study, white Portland cement (WPC) was used as the matrix, room temperature vulcanized silicone rubber (RTV) was used as the hydrophobic agent, and titanium dioxide was used as the solar reflective filler, so as to realize the self-cleaning, durability and solar reflection function of the coating. The cement based coatings were prepared using a simple one-step brushing method. The coating exhibited superhydrophobicity after cured at ambient condition for 24 h. The self-cleaning property, mechanical robustness and the resistance against temperature variation and ultraviolet radiation were studied. The results indicated that the cement based superhydrophobic coating can not be dirtied by dust or smudged by commonly used liquid foods. In addition, the surface superhydrophobicity was maintained after 10 cycles of peeling tests or 2 m length of abrasion test. The superhydrophobic coating can withstand repeated temperature variation (from −40 °C to 100 °C) and prolonged UV radiation (100 h). Therefore, the as-prepared cement based superhydrophobic coating exhibited excellent robustness. Furthermore, the infrared reflectance and solar reflectance of the superhydrophobic coating were 0.867 and 0.67, respectively. Both of them decreased by less than 3% after abrasion test or peeling test. Therefore, the cement-based superhydrophobic solar reflective coatings developed in this work has potential applications in long-acting building cooling coatings.