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Published on: April 26, 2017
Preparation of Superhydrophobic P-TiO2-SiO2/HDTMS Self-Cleaning Coatings with UV-Aging Resistance by Acid
Le Zhang1, Ying Liu2, Xuefeng Bai1
1Engineering Research Center of Ministry of Education for Geological Carbon Storage and Low Carbon Utilization of Resources, Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Xueyuan Road, Haidian District, Beijing 100083, China.
Abstract:
The superhydrophobic coatings for outdoor use need to be exposed to sunlight for a long time; therefore, their UV-aging resistances are crucial in practical applications. In this study, the primary product of titanium dioxide (P-TiO2) was used as the raw material. Nano-silica (SiO2) was coated onto the surface of P-TiO2 by the acid precipitation method to prepare P-TiO2-SiO2 composite particles. Then, they were modified and sprayed simply to obtain a superhydrophobic P-TiO2-SiO2/HDTMS coating. The results indicated that amorphous nano-SiO2 was coated on the P-TiO2 surface, forming a micro-nano binary structure, which was the essential structure to form superhydrophobic coatings. Additionally, the UV-aging property of P-TiO2 was significantly enhanced after being coated with SiO2. After continuous UV irradiation for 30 days, the color difference (ΔE*) and yellowing index (Δb*) values of the coating prepared with P-TiO2-SiO2 increased from 0 to 0.75 and 0.23, respectively. In contrast, the ΔE* and Δb* of the coating prepared with P-TiO2 increased from 0 to 1.68 and 0.74, respectively. It was clear that the yellowing degree of the P-TiO2-SiO2 coating was lower than that of P-TiO2, and its UV-aging resistance was significantly improved. After modification with HDTMS, the P-TiO2-SiO2 coating formed a superhydrophobic P-TiO2-SiO2/HDTMS coating. The water contact angle (WCA) and water slide angle (WSA) on the surface of the coating were 154.9° and 1.3°, respectively. Furthermore, the coating demonstrated excellent UV-aging resistance. After continuous UV irradiation for 45 days, the WCA on the coating surface remained above 150°. Under the same conditions, the WCAs of the P-TiO2/HDTMS coating decreased from more than 150° to 15.3°. This indicated that the retention of surface hydrophobicity of the P-TiO2-SiO2/HDTMS coating was longer than that of P-TiO2/HDTMS, and the P-TiO2-SiO2/HDTMS coating's UV-aging resistance was greater. The superhydrophobic P-TiO2-SiO2/HDTMS self-cleaning coating reported in this study exhibited outstanding UV-aging resistance, and it had the potential for long-term outdoor use.
