Flexible and Mechanically Enhanced Polyurethane Composite for γ-ray Shielding and Thermal Regulation

Microencapsulation of paraffin with lead tungstate shell (Pn@PWO) shows the drawbacks of low wettability and poor leakage-proof property and thermal reliability, restricting the application of phase change microcapsules. Herein, a novel paraffin@lead tungstate@silicon dioxide double-shelled microcapsule (Pn@PWO@SiO₂) has been successfully constructed by the emulsion-templated interfacial polycondensation and applied in the waterborne polyurethane (WPU). The results indicated that a SiO₂ layer with controlled thickness was formed on the PbWO₄ shell. The Pn@PWO@SiO₂ microcapsules have exhibited superior leakage-proof properties and thermal reliability through double-shelled protection, and the leakage rate decreased by at least 54.11% compared to that of Pn@PWO microcapsules. The SiO₂ layer with abundant polar groups ameliorated the wettability of microcapsules and the interfacial compatibility between microcapsules and the WPU matrix. The tensile strength of WPU/Pn@PWO@SiO₂-2 composites reached 10.98 MPa, which was over 7 times greater than that of WPU/Pn@PWO composites. In addition, WPU/Pn@PWO@SiO₂-2 composites with a latent heat capacity of over 41 J/g exhibited efficient phase change stability and γ-ray shielding properties. Also, the mass attenuation coefficients reached 1.38 cm²/g at 105.3 keV and 1.12 cm²/g at 86.5 keV, respectively. These properties will greatly promote the application of WPU/Pn@PWO@SiO₂ composites into γ-ray-shielding devices with thermal regulation.