Fabrication of HMX/Fluororubber composite microspheres with enhanced mechanical and safety properties via channel assembly technology

The microstructure of composite explosives is crucial to the improvement of their safety performance. In this paper, HMX/fluororubber microspheres were prepared by channel assembly technology (CAT). SEM, EDS, micro-CT, bulk density and contact angle test results confirmed that the microspheres had regular morphology, controllable particle size, uniform fluororubber coating and dense aggregation structure. The phase transition temperature of HMX crystal was delayed from 183 °C to 195 °C due to the uniform coating of fluororubber in the microsphere sample, which had better chemical and physical stability. The maximum bearing capacity (121.52 N) and compressive strength (6.20 MPa) of HMX/5 %F microspheres are higher than those of PM(Physical mixture)-HMX/5 %F (99.44 N, 4.39 MPa), which have better mechanical properties and stronger interface bonding force. In terms of safety, the characteristic drop height (H50) increases with the increase of fluororubber content. At the same fluororubber content, the H50 of the uniformly coated HMX/5 %F microspheres (H50: 48.5 cm) is much higher than that of PM-HMX/5 %F(H50: 36.5 cm). In addition, the ignition reaction evolution of the composites was monitored by visual drop hammer test. At the same height, the order of hot spot formation time is always: HMX/5 %F > PM-HMX/5 %F > raw HMX. The results show that the fine regulation of the characteristic structure of the composite material can enhance the interface synergy and inhibit the heat transfer between the components, thus delaying the formation of hot spots or accelerating the disappearance of hot spots and improving the safety performance. This paper can provide experimental basis and reference for the study of microstructure regulation and safety performance influence mechanism of composite explosives.