Research On Process Of Cast PBX Explosives With High Solid Content

Cast PBX(polymer bonded explosive) explosive is a mixing explosive, composed by explosive, continuous phase polymer binder, plasticizer and various additives, among which explosive as the dispersed phase, liquid as the continuous phase. Cast PBX explosive is widely used due to its high energy, low sensitivity and security. Since the hydroxyl-terminated polybutadiene(HTPB) is superior to other binders in sensitivity, HTPB widely used in cast PBX explosives. Detonation velocity and detonation pressure of explosive increase with the increasion of solid content, in order to improve the energy and density of explosives, solid content should be increased.The cast PBX explosive formulations with high solid contents have been determined through numerical simulation and experiments. Cast explosive with low molecular weight HTPB as binder has been prepared by method of casting, the use of reasonable size gradation increased the density of explosives. Detonation velocity and detonation heat are obtained through theoretical calculations and experimental and the experimental results match the theoretical calculations results well.By using Material Studio software to build the layer structure RDX(0 0 1) crystal surface with different molecular weights of HTPB, the interfacial bonding between different binder and explosive are simulated, and binding energy between RDX(0 0 1) crystal surface and HTPB binder with different molecular weights are calculated. Binding energy between class Ⅲ HTPB and RDX(0 0 1) is 1752.9k J/mol, and binding energy between HTPB with low molecular weight and RDX(0 0 1) is 305.3k J/mol.Surfactant Tween 80 and soybean lecithin can reduce the viscosity of the binder system with class Ⅲ HTPB, increase the viscous flow activation energy of binder system and the sensitivity to temperature. From the viewpoint of the viscosity, HTPB with low molecular weight can be used to prepare cast PBX slurry with high solid content.The results of curing experiments show that in terms of binder system with low molecular weight HTPB, curing agent MDI and IPDI with mass ratio of 4 and curing agent DDI can meet the requirement of pot life.With proper size gradation, the viscosity of slurry will be reduced, and the liquidity will get improved. When the coarse and grain solid mass ratio is 3:1, the slurry viscosity is minimum, slurry with low viscosity can be made when the coarse and grain solid mass ratio is 50:20.By combining experiments and numeral calculations, cast PBX explosive formulation with high solid content has been determined, and cast PBX explosive with 90% solid content has been prepared, its detonation parameters are obtained by theoretical calculation and its detonation velocity is 7.9km/s, blasting heat is 7806.4k J/kg, the results get by explosive performance test are close to the theoretical value.The results show that HTPB with low molecular weight and surfactants can reduce the viscosity of the binder system, the binder system containing HTPB of low molecular weight has the minimum viscosity. Simulation of binding energy between explosive and binder system provide a theoretical basis for screening binder system. Proper particle gradation can reduce the viscosity of the explosive slurry and increase the solid content of cast PBX explosive. The detonation velocity get improved with the increase of solid content.