Superhydrophobic poly-4-methyl-1-pentene/polyvinylidene fluoride coating with excellent passive daytime radiation cooling performance

Passive daytime radiation cooling (PDRC) materials have attracted more and more attention due to their low energy consumption, no pollution and energy saving potential. However, current PDRC materials face many challenges in practical applications, such as expensive raw materials, complex manufacturing processes, and performance degradation due to surface contamination by dust. Herein, we prepared a poly-4-methyl-1-pentene/polyvinylidene fluoride (TPX/PVDF) superhydrophobic PDRC coating by a simple scraping method. By optimizing the amount of TPX in the scraping solution, the surface contact angle (CA) of the coating can reach 153.5 degrees and the sliding angle (SA) is 8.9 degrees, showing good self-cleaning properties. At the same time, the solar reflectance (Rs) can reach 91.6%, and the infrared emissivity (E-IR) is larger than 0.97. Under direct sunlight in hot summer months, the coating sample can achieve a radiative cooling effect of 7.5 degrees C below the ambient temperature on average. Additionally, the TPX/PVDF coating was used as the roof and exterior paint of a miniature house (MH), and the cooling performance of the TPX/PVDF coating under direct sunlight was studied. The result indicated that the mean interior temperature of the MH covered with TPX/PVDF coating is 13.5 degrees C lower than that of the unmodified MH. Importantly, once the radiative cooling ability of the TPX/PVDF coating degraded due to surface dirt accumulating, it can recover automatically via its self-cleaning function. The TPX/PVDF based superhydrophobic and radiative cooling coating has a broad application prospect in the field of building energy conservation.

Automated summary

Passive daytime radiation cooling (PDRC) materials are being increasingly studied due to their low energy consumption, pollution-free nature, and potential energy-saving capabilities. However, current PDRC materials face challenges in practical applications such as expensive raw materials, complex manufacturing processes, and performance degradation due to surface contamination. In this study, a superhydrophobic PDRC coating based on poly-4-methyl-1-pentene/polyvinylidene fluoride (TPX/PVDF) was prepared using a simple scraping method. The coating exhibited a high contact angle, good self-cleaning properties, high solar reflectance, and a significant radiative cooling effect. It was also successfully applied as a roof and exterior paint for a miniature house, demonstrating its potential for building energy conservation. Additionally, the coating's self-cleaning function allowed for the automatic recovery of its radiative cooling ability when dirt accumulated on its surface.