Composite thin film of silica hollow spheres and waterborne polyurethane: Excellent thermal insulation and light transmission performances

Silica hollow spheres treated by 3-aminopropyltriethoxysilane (KH550) and hydrochloric acid showed good compatibility with polyurethane due to the improved functional group matching and charge matching between them. The resultant composite thin film exhibited excellent thermal insulation (0.05 W m−1 K−1) and light transmission (above 80%), which were quantitatively evaluated by thermo-resistance superposition method and UV–vis spectra, respectively. Moreover, finite element simulation was used to calculate thermal conductivity of the composite thin film. The simulated value was close to the experimental one, which confirmed the effectiveness of the modifications.