Abstract:
To explore a simple method to prepare a epoxy resin (EP)-silicone sealant-SiO
2 superhydrophobic composite coating with self-repairing property and capable of being applied to the surface of a structure like concrete, which can be self-repairing in the case of chemical and mechanical damage, The EP-silicone sealant-SiO
2 superhydrophobic composite coating with self-repairing property was prepared on the surface of concrete by one-step method. The specific steps were to dissolve the EP, silicone adhesive and nano-SiO
2 in anhydrous ethanol solution, and the compound solution would be obtained after 8 h magnetic stirring and 20 min ultrasonic dispersion. Then the superhydrophobic coating with self-repairing performance would be successfully prepared on the surface of concrete by spraying compound solution. When the content of epoxy resin is 2wt%, the content of silicone adhesive is 3wt% and the content of nano-SiO
2 is 3wt%, the coating could exhibit optimal superhydrophobic performance. The average contact angle (CA) of the coating is 156°±1.2° and the average slid angle (SA) is 6°±0.8°. After 8 m of abrasion length at a pressure of 2.66 kPa (Sandpaper: 1.7 µm) or 8 h of immerse time in saline (2 mol/L NaCl solution) or acidic environments (pH=3, acetic acid), the coating still maintain superhydrophobicity. The contact angle of the coating remains above 150° after 8 cycles of alkaline damage and self-repair (pH=12, NaOH solution) or 4 cycles of mechanical damage and self-repair. Moreover, the coating also displays excellent self-cleaning and waterproof performance according to the self-cleaning test and waterproof test. The experiments of mechanical and environmental corrosion damage show that the similar structure of the coating can ensure that the micro-nano rough structure of the lower layer maintain superhydrophobicity after the upper layer being damaged. The damage and self-repair experiments show that the coating can be repaired when the coating is heated. This is because the flow of silicone adhesive can promote the migration of low surface energy molecules and nano-SiO
2 particles in the coating during the heating process. The simple preparation method, good mechanical wear resistance and excellent self-healing properties of this coating offer the possibility of practical application of superhydrophobic coatings.