Effects of RDX and HMX on the thermal stability properties of modified double-base propellants

To investigate the thermal stability of RDX-CMDB propellant and HMX-CMDB propellant, the behavior of thermal decomposition was assessed using differential scanning calorimetry. The thermal safety characteristic parameters were calculated by the Ozawa method, and flame sensitivity and mechanical sensitivity tests were conducted to obtain the 50% ignition height, critical impact energy, and critical friction load. Molecular dynamics simulations were employed to analyze the trigger bond length and cohesive energy density (CED) of NC/NG, NC/NG/RDX, and NC/NG/HMX systems. The experimental results showed that as the contents of RDX and HMX increased, the first exothermic peak temperature of propellants was shifted to a higher temperature, and the second decomposition peak temperature of HMX-CMDB propellant was increased by 18.90 °C, thermal safety was increased. The flame sensitivity decreased by 0.74 cm and 1.32 cm, respectively, the friction sensitivity increased from 73 N to 96 N and 108 N, respectively, and the impact sensitivity remained almost unchanged. The simulation results showed that with the increase of the content of HMX and RDX, the trigger bond length of the system gradually decreased. The CED gradually increased, and the thermal stability of the system was enhanced.