Fabrication and characterization of a PDMS modified polyurethane/Al composite coating with super-hydrophobicity and low infrared emissivity

Polydimethylsiloxane (PDMS) modified polyurethane (PU)/Al composite coating with super-hydrophobicity and low infrared emissivity was prepared via glass rod scraping method using nano-SiO2, PDMS modified PU, and Al powders as micro-nano structural modifier, resin matrix, and functional pigments, respectively. The effects of curing temperature, Al powder addition, and the ratio of Al powder and nano-SiO2 on the coating performance has also been discussed. The results show that when the curing temperature of coating was 80 °C, the coating had lowest infrared emissivity and glossiness properties. The Al powder addition had an important effect on the coating performance. When the amount of Al powder was 50 wt%, the emissivity and glossiness of the coating were as low as 0.167 and 13.5, respectively, while, the water contact angle (WCA) of the coating reached 117°, which is significantly higher than that for traditional resin-based low emissivity coatings. The modification of coating with appropriate amount of nano-SiO2 led to clear mastoid micro-nano structures on the coating surface, so that the coating could achieve super-hydrophobic properties. When the ratio of Al powder and nano-SiO2 in the coating was 6:4, the WCA of the coating reached 151.5°, the sliding angle reached 9°, and the coating had outstanding self-cleaning performance. At the same time, the super-hydrophobic coating had relatively low emissivity (0.614) and extremely low glossiness (3.5) properties.