Large-area fabrication of colorful superhydrophobic coatings with high solar reflectivity

In the present work, the colorful superhydrophobic coating with high solar reflectivity was prepared using WPC (White Portland cement), color pigments, Polymethylhydrosiloxane and water as raw materials. The superhydrophobicity of the coating surface comes from the combination of the micron/sub-micron rough structure formed by the accumulation of cement hydration products and pigment particles and the low surface energy provided by PMHS (Polymethylhydrosiloxane). The superhydrophobic coating exhibits excellent resistance to corrosion of aggressive solutions, pollution of liquid foods, and accumulation of dust. The SR (Solar reflectance) of superhydrophobic coatings was optimized by changing the type, content and collocation of pigments. The results show that the superhydrophobic coating filled WP (with white pigment) and YP (yellow pigment) has the best performance. The optimized coating is yellowish brown with IR reflectance of 0.8191 and SR of 0.6569, which meets the building energy saving standard. The results of solar radiation experiments show that the surface temperature of the yellow–brown superhydrophobic coating is reduced by 5.7 °C compared with the ordinary Portland cement coating, which has a significant cooling effect. The colorful superhydrophobic coatings also possessed excellent weatherability and high mechanical robustness. Therefore, the coating developed in this work can be used on the exterior wall and roof of the building to reduce the energy consumption of the building in summer.