Influences of particle size and content of RDX on burning characteristics of RDX-based propellant

Research on the burning characteristics of propellants prepared with cyclotrimethylenetrinitramine (RDX) has not yet provided sufficient systematic experimental data. In this study, the thermal decomposition behaviors and the burning characteristics of RDX/hydroxyl-terminated polybutadiene (HTPB) propellants prepared with five series of RDX with weight mean diameters of 41 μm41 μm, 80 μm80 μm, 145 μm145 μm, 300 μm300 μm, and 515 μm515 μm and at various RDX contents of 50–80% were investigated.The thermal decomposition behavior of the RDX propellants was not affected by the particle size of RDX. RDX and HTPB decomposed almost separately in propellant matrices. The flame structure and the burning surface of propellants became more heterogeneous with increasing particle diameters of RDX. The burning rates of RDX propellants increased with increasing RDX content. The increasing ratio of the burning rate with increasing RDX content was not dependent on the mean particle diameter of RDX, but incremented with higher combustion pressure. The pressure exponents increased at higher RDX content and did not have particle size dependence below 145 μm145 μm of mean particle diameter of RDX. The burning rates of propellants increased with decreasing mean diameter of RDX particles. The relations between the burning rate and the mean particle diameter of RDX were expressed by a linear regression line on a double logarithmic plot. The RDX particle size dependence of the burning rates became smaller with higher RDX content. The interparticle distances of RDX particles in the propellant matrix played a key role in determining the particle size dependence on the burning rate.