Design and thermal performance analysis of solar reflective paints using BaSO₄-PTFE composite for passive radiative cooling

Passive radiative cooling (PRC) has emerged as a promising strategy to reduce building energy consumption and mitigate global warming. However, high humidity and persistent cloud cover often limit its effectiveness in tropical climates. In this study, a novel cooling paint formulation based on barium sulphate (BaSO₄) and polytetrafluoroethylene (PTFE) was developed. The optical properties of the coatings were systematically characterized using UV-Vis-NIR spectroscopy (250-2500 nm) and Fourier-transform infrared (FTIR) analysis to evaluate solar reflectance and infrared emissivity. The results demonstrate that BaSO₄-based composites exhibit a solar reflectance in the UV-Vis-NIR region of 89.94%. The optimized coating achieved high broadband solar reflectance along with excellent emissivity of 96.43% within the atmospheric transparency window. Field tests conducted under both daytime and nighttime conditions revealed a maximum temperature reduction of 16 °C relative to a reference metal substrate during daytime, and 2.5 °C below ambient temperature during nighttime. The water contact angle was 115°, and the maximum cooling power was approximately 110 W/m² under tropical outdoor conditions. These findings highlight the strong potential of the developed composite coatings for efficient thermal management and energy savings in buildings.