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 degrees 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 degrees, 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 degrees, the sliding angle reached 9 degrees, 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.