An experimental study of the combustion characteristics of novel Al/MO_X/PVDF metastable intermixed composites

The combustion of metastable intermixed composites (MICs) containing fluoropolymers is yet still not well understood. In this study, five new Al/MO_X/PVDF nanocomposites (MO_X: WO₂, WO₃, CuO, Fe₂O₃, Bi₂O₃) are prepared using a high-energy ball milling method. The thermal decomposition behaviors, combustion characteristics, and combustion products of the MICs are compared using TG-DSC, laser ignition test, and a multifunctional combustion diagnostic system. It is proved that PVDF efficiently promotes the energy release of conventional thermites. All five composites show a higher heat of reaction than Al/MO_X in an argon environment by over 30%. Al/WO₃/PVDF has the fastest combustion propagation speed in the confined combustor (72.5 mm⋅s⁻¹). Due to the low boiling temperature and low thermal conductivity of the product, Al/Bi₂O₃/PVDF exhibits the lowest ignition delay (62 ms), the best pressure output performance (27.5 MPa⋅s⁻¹), and the least product agglomeration (D₄₃ = 15.2 μm). Due to the highest heat of reaction (3829 J⋅g⁻¹), Al/CuO/PVDF has the highest flame temperature (2544 °C). The combustion flame temperature of Al/MO_X/PVDF nanocomposites is suggested to be controlled by the heat of reaction, the ignition delay is mainly controlled by the thermal conductivity of the material, and the main factor affecting the high pressure output is the boiling point of the combustion products. This study can provide a theoretical basis for the development and application of MICs.