Porous Core–Shell Nanoparticles Enable Concurrent Flame Retardancy and Mechanical Reinforcement in Silicone Rubber

Abstract

Silicone rubber (SR) is widely employed in advanced applications but is intrinsically limited by high flammability and insufficient mechanical robustness. Conventional flame retardants and reinforcing fillers typically operate independently, resulting in persistent trade-offs between fire safety and mechanical performance. Herein, we report a core–shell nanoarchitectural strategy that decouples and simultaneously optimizes these competing properties via a non-solvent-induced self-assembly approach. A phosphorus–nitrogen flame-retardant core is encapsulated within a porous SiO2 shell, enabling integrated gas-phase (radical scavenging and inert gas release) and condensed-phase (barrier formation and char stabilization) mechanisms. The porous shell further serves as an interfacial scaffold that allows partial infiltration of polymer chains, generating a confined interphase governed by confinement–interlocking–interaction synergy. This architecture enables efficient stress transfer, regulated chain mobility, and enhanced energy dissipation. The composites exhibit significantly enhanced fire safety, with the limiting oxygen index increasing from 19.6% to 28.0%, the peak heat release rate decreasing by 66%, and the total smoke release being reduced by 53%. Meanwhile, the composite achieves simultaneous mechanical reinforcement. At a loading of 75 phr, the tensile strength and elongation at break are improved by 269% and 37%, respectively, overcoming the conventional strength–ductility trade-off.