Experimental investigation of radiative cooling protective coatings for building materials

Abstract

The application of radiative cooling protective coatings on building roofs and exterior walls represents a new strategy for energy saving and emission reduction. This approach not only decreases reliance on air conditioning by improving thermal management but also enhances the durability of concrete structures, contributing to reduced carbon emissions in the cement production process. This study proposed a straightforward and facile method for fabricating radiative cooling coatings by incorporating vacuum ceramic microspheres (VCM) modified with polycatecholamine (PCA) into polyurethane (PU) matrix. VCM@PCA significantly enhanced the mechanical properties and thermal stability of PU composite coating, reduced the thermal conductivity, and simultaneously increased its infrared emissivity. The radiative cooling performance of this coating was systematically evaluated. In the xenon lamp radiation experiments, the PU/[email protected] coating demonstrated a remarkable cooling performance, with its bottom surface temperature showing a reduction of 17.1 °C compared to the ambient temperature. Infrared thermography further confirmed that this coating consistently exhibited the lowest temperature among the tested samples. In outdoor experiments, the model house coated with PU/[email protected] exhibited a maximum temperature reduction of 8.8 °C compared to the external ambient temperature. Additionally, this new kind of coating demonstrated excellent hydrophobicity (130.3°) and excellent resistance to chloride ion penetration (the rapid chloride ion migration (RCM) value of the cement specimen was reduced to 1.75 × 10^-12 m²/s). These findings underscored the potential of PU/VCM@PCA as a promising coating material for improving energy saving efficiency and durability in building materials, thereby paving the way for innovative applications in sustainable construction.