Electrostatic repellent dispersion method for green and cost-effective aqueous radiative cooling paint

Abstract

Radiative cooling paint (RCP) serves as an effective energy-saving method for cooling of built infrastructure. Given that the synthesis of most RCPs contains volatile organic compounds (VOC) for binder dispersion, water-based systems have been preferred as cost-effective alternatives that can provide low/no emission of VOC for minimized environmental impact. However, development of cost-effective and robust water-based radiative cooling paint is still challenging. Moreover, there exists particle dispersion issues leading to structural non-uniformity when excess amount of water is used in paints with high particle volume concentration (PVC). Herein, we address these challenges by proposing a universal electrostatic-assisted dispersion method to tackle the dispersion challenge. With ultrahigh PVC (∼70 %), the derived radiative cooling paint exhibits dense and uniform surface while maintaining robust mechanical, chemical, and thermal stabilities, as well as universal adhesivity, significantly contrasting to the cracking and poor adhesivity observed in conventional water dispersed paint. Assisted by superfine dispersion and high PVC, our paint achieves excellent optical properties (R_solar∼ 97 %, E_LWIR> 95 %) for enhanced radiative cooling, and is effective under various climates. This work provides insights into more environmental-friendly and durable designs for radiative cooling paint.