Perfluorohexanone Fire-Extinguishing Microcapsules Prepared with Double Layer: Urea-Formaldehyde Resin and Poly(methyl methacrylate)

Self-igniting fire-extinguishing microcapsules have garnered increasing attention for protecting valuable equipment from fires within seconds. In this study, C 6 F 12 O fire-extinguishing microcapsules with a urea-formaldehyde (UF) single shell and a UF-poly(methyl methacrylate) (PMMA) double shell were synthesized. Thermogravimetric analysis (TGA) indicated that microcapsules with a UF shell dried at 25 °C had a core content of 56.9 ± 0.6 wt %, which was higher than the 23.8 ± 0.2 wt % observed for microcapsules dried at 50 °C. Conversely, microcapsules with a UF-PMMA double shell exhibited excellent thermal stability, maintaining a core content of 48.0 ± 0.5 wt % at 50 °C. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed the successful integration of UF and PMMA. SEM images revealed that PMMA particles adhered to the UF shell, forming a second layer with a thickness of 0.87 μm. The mixture of coating and microcapsules with a double layer retained fluidity, whereas the mixture with a UF layer solidified gradually unless the microcapsules were wet. The coating modified with 20 wt % of C 6 F 12 O fire-extinguishing microcapsules maintains thermal stability even at 100 °C and can extinguish fire within 10 s, indicating significant potential for practical application.