Preparation and study of the flame retardant properties of C₆₀/PMMA microspheres

In this paper, highly flame retardant C₆₀/PMMA composites were prepared using an in situ polymerization method by introducing fullerene (C₆₀) into polymethyl methacrylate (PMMA) to improve its combustion characteristics. The apparent morphologies of PMMA and C₆₀/PMMA microspheres were observed by scanning electron microscopy (SEM), and the structure was characterized by infrared spectroscopy (FT-IR). The thermal stability and flame retardancy were characterized using a synchronous thermal analyzer, a cone calorimeter and an oxygen index tester. The results show that the maximum initial decomposition temperature of C₆₀/PMMA-2 (prepared using C₆₀ with a concentration of 2 mg mL^-1) is 234.89 °C, which is about 59.89 °C higher than that of PMMA, and the thermal stability is the best. The limiting oxygen index of the C₆₀/PMMA-2 composite is 21.8, which is 28.2% higher than that of pure PMMA. In addition, the peak heat release rate (PHRR) of C₆₀/PMMA is reduced by 630.4 kW m^-2 when compared with pure PMMA, which means that the flame retardant property is improved. Meanwhile, the mechanical properties of the PMMA are also improved by adding C₆₀.