All-Polymer Superhydrophobic Radiative Cooling Coating Based on Polytetrafluoroethylene/Polydimethylsiloxane Composites

In the present work, a polytetrafluoroethylene/polydimethylsiloxane (PTFE/PDMS) composite coating was fabricated using a simple brushing method. The PTFE/PDMS coating has both superhydrophobic self-cleaning property and radiation cooling function. The contact angle (CA) for water of the composite coating is 159.3°, and the sliding angle (SA) for water is 6.3°. Furthermore, the solar reflectivity of the coating in the wavelength range of 200–2500 nm is close to 92%, and the infrared emissivity in the 8–13 μm middle-infrared band is about 0.93. When the maximum daytime temperature in summer is 39 °C, the PTFE/PDMS coating could achieve an average radiation cooling temperature of 4.73 °C under direct sunlight from 10:00 a.m. to 16:00 p.m. Under the same conditions, covering the PTFE/PDMS coating on the electric vehicle seat cushion could realize the temperature drop of the seat cushion by 19.41 °C. After continuous washing and corrosion of 50,000 mL of simulated acid rain, 10 cycles of ultraviolet (UV) aging experiments, or 25 cycles of sandpaper abrasion, the superhydrophobicity and radiation cooling function of the PTFE/PDMS coating remained unchanged. In particular, the PTFE/PDMS coating lost the radiative cooling ability after the surface is contaminated. However, with the help of natural rainfall, its radiation cooling coating could recover rapidly. Therefore, the PTFE/PDMS coating developed in this work makes the radiative cooling coating more practical.