Evaluation of the thermo-mechanical and explosive properties of bimodal and hybrid polymer bonded explosive (PBX) compositions based on HNS and HMX

In the present paper, a series of bimodal PBX compositions containing coarse (90 μm) and fine (<1 μm) HNS (2,2’4,4’6,6’-hexanitrostilbene) and hybrid PBX compositions based on HNS and HMX (1,3,5,7-tetranitro-1,3,5,7- tetraazacyclooctane) in varying mass ratios, along with the fluoropolymer Viton-A, a vinylidene fluoride and hexafluoropropylene copolymer, as a binder (5%), have been prepared on the lab scale. In order to observe any effect of incorporating fine HNS particles with coarse ones and the effect of replacing HNS with HMX in all types of bimodal and hybrid PBX compositions, the samples were characterized for composition analysis, thermal behavior and morphological analysis as well as evaluated for their mechanical and explosive properties including sensitiveness tests and detonic properties. The data showed that incorporation of fine HNS into coarse particles of HNS in the bimodal PBX resulted in an increase in mechanical strength and a decrease in friction and impact sensitivity, as well as an enhanced performance compared to PBXs based on coarse HNS alone. Viton-A based hybrid PBX compositions provided better mechanical and sensitivity properties as compared to conventional explosive compositions based exclusively on HMX or HNS and the performance of the PBX compositions increased with increasing HMX content.