Highly practical multifunctional radiative cooling films for multi-temperature applications

Abstract

Passive daytime radiative cooling is a green, sustainable technology, however there are challenges in incorporating multifunctional radiative cooling technologies. In this paper, a biomimetic structure (PTP, porous tetra-needle zinc oxide whisker polydimethylsiloxane) with a needle-like structure on the surface and a porous structure in the interior is prepared by a simple process using inexpensive tetra-needle zinc oxide whiskers (T-ZnOw) as the filler particles and polydimethylsiloxane (PDMS) as the binder, which possesses the desired radiative cooling properties, and at the same time, it combines the anti-aging, thermal control flame retarding, and superhydrophobic properties. PTP film exhibits ideal reflectance (0.91) and emissivity (0.99), with an average temperature difference of 15.5 °C compared to Al, and maintains good radiative cooling performance under UV irradiation for 1000 h. The thermal conductivity of the PTP film is 0.931 W m^-1 k^-1. In the outdoor cooling test with a heat source, the average temperature difference is 13.3 °C compared to Al. The surface water contact angle (WCA) is 153.25° and the superhydrophobicity is maintained after more than 1400 h of aging. As a result, the PTP film has large potential in multi-temperature applications, such as buildings, factory sheds, and electrical appliances.