High-Loading Temperature-Responsive Fire-Extinguishing Microcapsules via RAFT Suspension Polymerization

Temperature-responsive fire-extinguishing microcapsules (TFMCs) have garnered considerable attention due to their ability to autonomously release fire-extinguishing agents upon reaching a critical temperature, thereby mitigating the fire spread. The fire-extinguishing performance of TFMCs is determined by the loading capacity of the fire-extinguishing agents. However, conventional fabrication methods typically yield low loading efficiency (<40%), which impairs the fire-extinguishing performance of TFMCs. Herein, we propose a novel strategy to prepare high-loading TFMCs, involving poly-(methyl methacrylate-ethylene glycol dimethacrylate) (P-(MMA-EGDMA)) as the shell material and DMTP as the core material, via RAFT suspension polymerization for the first time. The results demonstrate that a well-defined core-shell structure and robust shell are beneficial to suppress diffusion and leakage of fire-extinguishing agents, thereby enabling high-loading TFMCs. RAFT polymerization markedly facilitates the formation of well-defined core-shell structures. Moreover, increasing EGDMA content and introducing methacrylic acid (MAA) as a functional comonomer improve the shell mechanical strength. However, excessive EGDMA content disrupts core-shell structure formation, and either an excessively high or low RAFT/ADVN mass ratio can result in the rupture of TFMCs. When the mass ratio of shell monomers (MMA/MAA/EGDMA) is 6/3/1 and that of RAFT/ADVN is 1/2, the resulting TFMCs display a well-defined core-shell structure and an approximately spherical morphology, with an average diameter of 946 nm and a particle size distribution of 1.05, achieving the highest loading efficiency and encapsulation efficiency of 70.6% and 94.3%, respectively. Fire-extinguishing tests show that these TFMCs reduced the extinguishing time from 58.5 to 11.6 s. This work provides a new approach to encapsulating fluorinated fire-extinguishing agents and lays the foundation for the industrial application of TFMCs.