Multilayer Polyurethane/Silver Nanowire Composite Coatings for Simultaneously Achieving Low Infrared Emissivity and High Optical Transparency

Low-emissivity and highly transparent coatings are of considerable interest for applications requiring simultaneous infrared radiation control and optical transparency. However, transparent polymer matrices typically exhibit relatively high intrinsic infrared emissivity, while the incorporation of low-emissivity fillers often leads to a loss of optical transparency, making it difficult to balance these properties. In this work, a highly transparent polyurethane (PU) matrix was prepared via a prepolymer method, and a multilayer PU/silver nanowire/PU (PU–AgNW–PU) composite coating was fabricated by introducing AgNWs to simultaneously regulate infrared emissivity and optical transmittance. The PU film (40 μm) exhibited an infrared emissivity of 0.65 (8–14 μm) at 80°C. After incorporation of AgNWs, the composite coating showed a reduced infrared emissivity of 0.45 while maintaining visible-light transmittance above 80% (400–700 nm) and haze below 20%. This multilayer structural design provides an effective strategy to balance low infrared emissivity and high optical transparency in PU-based coatings.