Controlling FOX-7 crystal morphology via the emulsion method: monodisperse micron-sized spherical aggregates and enhanced safety performance

Abstract

The crystal morphology and particle size distribution of explosives are the decisive factors affecting their detonation characteristics and sensitivity. In this paper, the oil-in-oil emulsion method was used to study the effects of the type and amount of surfactants and the ratio of the discontinuous phase to the continuous phase on the stability of the emulsion with DMSO as the discontinuous phase and cyclohexane as the continuous phase. Spherical FOX-7 with dimensions of tens of microns was successfully prepared, which filled the technical gap in the preparation of mesoscale spherical FOX-7, and its morphology, specific surface area, fluidity, structure, thermal decomposition and safety were characterized. The results showed that the stable emulsion could be obtained when Tween-80 was selected as the surfactant, the dosage was 3 g L⁻¹, and the ratio of the discontinuous phase to the continuous phase was 1 : 3. The size of spherical FOX-7 was between 30–70 μm, the D₅₀ was 43.1 μm, the specific surface area was 1.502 m² g⁻¹, and the fluidity was greatly improved. The change of morphology did not cause the change of crystal form. Compared with the raw material FOX-7, the thermal stability of the sphere is better, and the apparent activation energy is reduced by 65.36 kJ mol⁻¹. The characteristic drop height (H₅₀) is increased by 22.77 cm, the friction sensitivity is reduced from 20% to 8%, and the safety performance is better. This study is expected to provide new ideas for the performance optimization of high-energy insensitive explosives.