Preparation and characterization of hydrogen-containing silicone oil-modified polyurethane/Al composite coating with low-infrared emissivity

The goal of this research was to obtain a coating with low-infrared emissivity and both good hydrophobic and mechanical properties. Using nano-SiO₂ as the micro-nano structural modifier, a hydrogen-containing silicone oil (HCSO)-modified polyurethane (PU)/Al composite coating with super-hydrophobicity and low-infrared emissivity was prepared via a simple glass rod scraping method. Effects of the ratio of HCSO to PU, the total filler addition, and the ratio of Al powder and nano-SiO₂ on the coating properties are systematically discussed. The results show that as the ratio of HCSO to PU increases, the surface energy of the coating decreases, and this significantly increases the hydrophobicity of the coating. When the ratio is 2:8, the coating has outstanding hydrophobic properties, the adhesion strength of the coating reaches grade 1, and the water contact angle (WCA) reaches 152°. The total filler addition has a significant impact on the coating performance. With an increase in the filler addition, the emissivity of the coating increases, and the glossiness decreases. When the total filler addition is 50 wt%, the coating surface forms an obvious papillary micro-nano rough structure, so that the coating has outstanding hydrophobic properties. The ratio of Al powder to nano-SiO₂ obviously affects the emissivity and hydrophobic properties of the coating. When the ratio is 5.5:4.5, the coating has good overall performance. At this point, the emissivity of the coating is as low as 0.675; the glossiness and adhesion strength are 2.7 and grade 1, respectively; the WCA and sliding angle are 155° and 8°, respectively; and it has outstanding self-cleaning performance. Through the research in this paper, a low-infrared emissivity coating with outstanding super-hydrophobic properties and adhesion strength has been obtained and has important application value in the design and transformation of infrared stealth of various equipment.