Fabrication of BS/FEVE-g-PDMS composite radiative cooling coatings and the synergistic mechanism of optical-mechanical properties

The development of radiative cooling (RC) coatings with superior optical properties, weather resistance, self-cleaning capability, strong substrate adhesion and high hardness is crucial for advancing their large-scale outdoor applications. In this study, barium sulfate (BS) was employed as the reflective pigment, isocyanate-functionalized propyltrimethoxysilane (SCA) as the coupling agent and auxiliary crosslinker, and polydimethylsiloxane-grafted fluorocarbon resin (FEVE-g-PDMS) as the binder. A high-performance BS/FEVE-g-PDMS radiative cooling coating was successfully fabricated via conventional coating preparation processes. The coating demonstrates a high solar reflectance (SR) of 94.02%, together with infrared emissivity (IE) of 96.00% in 8–13 μm and 93.78% in 16–25 μm, corresponding to the first and second atmospheric transparent windows, respectively. A maximum radiative cooling temperature drop of 3.78 °C was achieved under peak solar irradiance of 804 W·m⁻². The coating surface exhibits an advancing contact angle (ACA) of 158.3° and a hysteresis contact angle (HCA) of only 8.1°, enabling effective resistance to contamination and dust deposition and thus preserving long-term optical stability. Benefiting from the coupling and supplementary crosslinking effects of SCA, the coating achieves Grade 2 adhesion and a pencil hardness up to 6H. Furthermore, the coating exhibits stable optical and superhydrophobic performances under weathering and abrasion, indicating promising potential for long-term outdoor service. Energy simulation results reveal that applying this coating to building envelopes in New Delhi, Chengdu and Osaka can reduce building energy consumption by more than 20%. Through rational component design, this work overcomes the bottleneck of balancing multiple properties in radiative cooling coatings. The as-prepared BS/FEVE-g-PDMS coating provides a practical, high-performance cooling strategy for building energy conservation, with significant theoretical significance and engineering application value.