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Colored Radiative Cooling and Flame-Retardant Polyurethane-Based Coatings: Selective Absorption/Reflection in Solar
Wei Cai1,2, Junling Wang3, Wei Wang4
1School of Fashion and Textiles, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, 999077, P. R. China.
Small (Weinheim an Der Bergstrasse, Germany)
|August 8, 2024
Summary
This study developed colored radiative cooling coatings using iron oxides and flame retardants. These coatings achieve significant daytime cooling while enhancing fire safety for broader applications.
Area of Science:
- Materials Science
- Nanotechnology
- Sustainable Energy
Background:
- Daytime radiative cooling is crucial for mitigating climate change.
- Aesthetic requirements and fire safety are key challenges for radiative cooling materials.
- Iron oxides show high reflectivity in the near-infrared (NIR) spectrum.
Purpose of the Study:
- To engineer colored polyurethane-based (PU) coatings with enhanced radiative cooling and fire safety.
- To investigate the effect of iron oxides as colorants on coating performance.
- To address the aesthetic demands for practical radiative cooling applications.
Main Methods:
- Comparative analysis of organic and inorganic colorant spectra in the solar waveband.
- Incorporation of iron oxides (Fe2O3, Fe2O3·H2O, Fe3O4·H2O) into porous PU structures with silicon-modified ammonium polyphosphate (Si-APP).
- Evaluation of reflectivity, emissivity, temperature drop, and fire safety characteristics.
Main Results:
- Iron oxide-based coatings achieved >90% reflectivity in the NIR region and ≈91% infrared emissivity.
- Average temperature drops of 3.8–7.9 °C were observed compared to control samples.
- The PU composite coatings demonstrated excellent fire safety due to intumescent char residue formation.
Conclusions:
- Iron oxide colorants effectively minimize solar heating while balancing cooling and aesthetics.
- The developed PU coatings offer a promising solution for practical daytime radiative cooling with improved safety.
- This research advances the commercial viability of radiative cooling technologies for climate change mitigation.
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