Thermal-Responsive Microcapsules with Tailorable Triggering Temperatures via Crosslinking Density Engineering for On-Demand Fire Suppression

The rapid spread of fire in its incipient stage remains a critical challenge, largely due to the scarcity of suppression technologies capable of an immediate and effective response. Perfluorohexane (PHF), with its low boiling point and high vaporization enthalpy, is an effective flame suppressant, and microencapsulation offers a controlled delivery strategy. However, the thermal response temperature of conventional PHF microcapsules (MCs) is primarily governed by the chemical composition of the shell material, leading to largely fixed release characteristics and limited tunability. Here, we develop a low-temperature in situ polymerization strategy in which melamine is introduced to regulate the crosslinking density of the shell network, enabling PHF MCs with three distinct tunable thermal response temperatures of 56, 130, and 169 °C, respectively. The resulting MCs exhibit excellent storage stability, retaining 98.64% of their initial mass after 180 days, together with a high encapsulation efficiency (82.92%) and yield (97.8%). When incorporated into polyurethane matrices, these MCs markedly enhance fire suppression and inhibit flame spread, underscoring their potential for versatile early-stage firefighting applications.