The Effect of Coating Additives on the Properties of Hydrophobic Coatings with Low Infrared Emissivity

In order to further reduce the emissivity of hydrophobic low infrared emissivity composite coating and improve its mechanical properties, a dispersant, adhesion enhancer, and defoamer were used to improve the dispersion state of the fillers, the interface structure, and the surface state of a hydrogen silicone oil-modified polyurethane/Al composite coating. The influences of dispersant, adhesion enhancer, and defoamer on the microstructure, emissivity, glossiness, hydrophobic property, adhesion strength, and impact strength of the coating were systematically studied. The results indicate that polycarboxylate anionic dispersant can improve the dispersion state of Al powder and nano-SiO2 in the coating, so that the infrared emissivity of the coating can be reduced, and the coating can have greater hydrophobic and mechanical properties. The bonding strength between the resin and the substrate of the coating can be improved by the adhesion enhancer through a bridging action, so that the mechanical properties of the coating can be significantly improved. The defoamer can significantly reduce the pores in the coating, resulting in a substantial improvement in the surface condition, and the mechanical properties can be significantly improved. The coating exhibits superior characteristics, including an emissivity value of 0.527, glossiness of 4.3, adhesion strength of grade 1, impact strength of 40 kg·cm, and hydrophobic property (the water contact angle (WCA) is 140°) when the amount of dispersant, adhesion enhancer, and defoamer is 5 wt%, 4 wt%, and 1 wt%, respectively.