Polysilsesquioxane encapsulating polymerizable monomer and blowing agent mesoporous-particles enable WPU micro-foaming with the help of redox initiation

Thermal insulation coating is one of the key methods to mitigate energy consumption, while waterborne polyurethane (WPU) foaming coating is demonstrating great application potential in various thermal insulation fields due to its excellent flexibility, adhesion, and environmental friendliness. However, the inherent low viscosity and no crosslinking in WPU pose a mismatching problem between system viscosity and foaming rate to result in foaming difficult. To address this challenge, we propose a physical-chemical hybrid nano-microfoaming strategy, in which utilizing organic siloxane hydrolysis-condensation in situ generating polysilsesquioxane smoothly encapsulates polymerizable monomer and blowing agent and then is introduced into WPU. The nanocomposite particles serve as both foaming agent and viscosity enhancer, effectively aligning viscosity with foaming rate, and also act as a reinforcing filler, significantly improving the mechanical properties of the foaming coatings. Furthermore, a balance of viscosity and foaming rate is achieved with the aid of the optimized redox process and the nanoparticles synergistic effect, realizing a multi-faceted coating with thermal conductivity of 0.0318 W m −1  K −1 . This nano-microfoaming technology provides a new approach and design idea for developing thermal insulation multifunctional coatings.