Influence of poly(vinylidene fluoride) coating layer on exothermic reactivity and stability of fine aluminum particles

Highlights: • Poly(vinyliedene fluoride) (PVDF) is coated onto fine Al particles instead of surface oxide. • The PVDF shows hydrophobic behavior and remarkably improved exothermic enthalpy energy. • The PVDF layer shows high stability to sudden explosion regardless of humidic atmosphere. Simultaneous achievement of both reactivity and stability to oxidation is crucial in practical applications of reactive aluminum (Al) powders, which can be used for propellant and explosives. In this study, we introduce a poly(vinylidene fluoride) (PVDF) coating layer a few tens of nanometers thick onto the surface of fine Al particles instead of alumina (Al₂O₃). The PVDF-coated Al particles exhibited hydrophobic surface behavior and a characteristic interface where Al fluorides were spontaneously formed. The exothermic enthalpy of PVDF-coated Al particles was approximately two times higher than that of the uncoated particles owing to the synergetic effect of the active formation of Al-F and Al-O reactions. Furthermore, the accelerated oxidation test revealed that the enhanced reactivity was retained even under high humidity. Thus, the PVDF coating layer protects pure Al core material from explosively reacting with external oxygen, simultaneously increasing exothermic enthalpy.