Facile Fabrication of Double-Shell PA-MEL@PU@CFO Microcapsules and Their Fire Suppression Performance in Confined Spaces

Novel double-shell PA-MEL@PU@CFO microcapsules were successfully prepared by further coating the as-prepared PU@CFO microcapsules with the outer shell of phytic acid-melamine salt (PA-MEL). The fire suppression performance was then investigated in a simulated confined space experimental device. Effects of the emulsification conditions on the morphology of microcapsules were investigated in detail. Systematic characterization results demonstrated that the double-shell structure was successfully constructed. PA-MEL@PU@CFO microcapsules fabricated under the optimal emulsification conditions exhibited regular spherical morphology with rough flocculent surface and uniform particle size. The introduction of the outer PA-MEL shell raises the release temperature of core material, thereby improving the low-temperature storage stability of the microcapsules and facilitating their storage and transportation. PA-MEL@PU@CFO microcapsules exhibited favorable storage stability overall, with a relatively high core content of 53.18%. PA-MEL@PU@CFO microcapsules demonstrated excellent flame retardant and fire-extinguishing performance for the fires in confined spaces at the incipient fire stage, reducing the maximum flame temperature by 238.6 °C, shortening the extinguishing time by 53 s, and effectively inhibiting flame re-ignition. PA-MEL@PU@CFO microcapsules achieved efficient fire suppression by a synergistic effect of physical cooling, chemical suppression and phosphorus–nitrogen synergistic flame retardancy. PA-MEL@PU@CFO microcapsules hold great practical application potential in practical application such as anti-flame coatings and lithium-ion batteries.