BaSO4/TiO2 Microparticle Embedded in Polyvinylidene Fluoride-Co-Hexafluoropropylene/Polytetrafluoroethylene Polymer Film for Daytime Radiative Cooling

Radiative cooling is a new large-scale cooling technology with the promise of lowering costs and decreasing global warning. Currently, daytime radiative cooling is achieved via the application of reflective metal layers and complicated multilayer structures, limiting its application on a massive scale. In our research, we explored and tested the daytime subambient cooling effect with the help of single-layer films consisting of BaSO₄, TiO₂, and BaSO₄/TiO₂ microparticles embedded in PVDF/PTFE polymers. The film, consisting of BaSO₄/TiO₂ microparticles, offers a low solar absorbance and high atmospheric window emissivity. The solar reflectance is enhanced by micropores in the PVDF/PTFE polymers, without any significant influence on the thermal emissivity. The BaSO₄/TiO₂/PVDF/PTFE microparticle film attains 0.97 solar reflectance and 0.95 high sky-window emissivity when the broadly distributed pore size reaches 180 nm. Our field test demonstrated that the single-layer BaSO₄/TiO₂/PVDF/PTFE microparticle film achieved a temperature 5.2 °C below the ambient temperature and accomplished a cooling power of 74 W/m². Also, the results show that, when the humidity rises from 33% to 38% at 12:30 pm, it hinders the cooling of the body surface and lowers the cooling effect to 8%.