Affiliation:
1. School of Fashion and Textiles The Hong Kong Polytechnic University Kowloon Hong Kong SAR 999077 P. R. China
2. State Key Laboratory of Fire Science University of Science and Technology of China Hefei 230026 P. R. China
3. Jiangsu Key Laboratory of Hazardous Chemicals Safety and Control College of Safety Science and Engineering Nanjing Tech University Nanjing 211816 P. R. China
4. School of Mechanical and Manufacturing Engineering University of New South Wales Sydney NSW 2052 Australia
5. College of Materials Science and Engineering State Key Laboratory of Bio‐fibers and Eco‐textiles Shandong Collaborative Innovation Center of Marine Biobased Fibers and Ecological Textiles Qingdao University Qingdao 266071 P. R. China
Abstract
AbstractThe aesthetic demand has become an imperative challenge to advance the practical and commercial application of daytime radiative cooling technology toward mitigating climate change. Meanwhile, the application of radiative cooling materials usually focuses on the building surface, related tightly to fire safety. Herein, the absorption and reflection spectra of organic and inorganic colorants are first compared in solar waveband, finding that iron oxides have higher reflectivity in NIR region. Second, three kinds of iron oxides‐based colorants are selected to combine porous structure and silicon‐modified ammonium polyphosphate (Si‐APP) to engineer colored polyurethane‐based (PU) coating, thus enhancing the reflectivity and flame retardancy. Together with reflectivity of more than 90% in near‐infrared waveband and infrared emissivity of ≈91%, average temperature drops of ≈5.7, ≈7.9, and ≈3.8 °C are achieved in porous PU/Fe2O3/Si‐APP, porous PU/Fe2O3·H2O/Si‐APP, and porous PU/Fe3O4·H2O/Si‐APP, compared with dense control samples. The catalysis effect of iron oxides in the cross‐linking reaction of pyrolysis products and dehydration mechanism of Si‐APP enable PU coating to produce an intumescent and protective char residue. Consequently, PU composite coatings demonstrate desirable fire safety. The ingenious choice of colorants effectively minimizes the solar heating effect and trades off the daytime radiative cooling and aesthetic appearance requirement.
Funder
Innovation and Technology Fund
National Natural Science Foundation of China
Natural Science Foundation of Anhui Province