Surface hydrophobic modification of TiO₂ and its application to preparing PMMA/TiO₂ composite cool material with improved hydrophobicity and anti-icing property

A white functional methyl methacrylate film filled with titanium dioxide for building roof and exterior wall is introduced. The film has excellent cooling performance, sunlight reflection performance and anti-icing performance. In our study, hydrophobic modification was carried on titanium dioxide (TiO₂) to prepare functional composite films based on poly (methyl methacrylate) (PMMA). Herein, the nature of TiO₂ successfully changed from hydrophilic to hydrophobic with the assistance of 3 wt% stearic acid, which was acknowledged by Fourier transform infrared spectroscopy and thermogravimetric analysis. Compared with unmodified TiO₂, the contact angle of the modified TiO₂ powder was increased from 27° to 132°, and the freezing delay time was significantly enhanced from 6 s to 1284 s at −10 °C. In addition, the contact angle, solar reflectivity and cooling performance of PMMA/TiO₂ composites with different content of modified TiO₂ were investigated. Compared with PMMA/TiO₂ composite film introduced with 50 wt% unmodified TiO₂, the contact angle of that with 50 wt% modified TiO₂ raised from 85° to 115°, while the freezing delay time enhanced from 184 s to 555 s at −10 °C. Contrast with pure PMMA film, the solar reflectance and cooling performance of PMMA/TiO₂ composite film with 50% TiO₂ were ameliorated greatly. The reflectivity ascended by 57.3% and 42.4% in the visible and near infrared regions, respectively. Simultaneously, the final temperature of the corresponding sample was decreased by 6.3 °C in outdoor temperature test in comparison with PMMA, performing great cooling property. The as-prepared cool material is expected to be widely applied in construction for its improved hydrophobicity and anti-icing character.