Impact response characteristics of a cyclotetramethylene tetranitramine based polymer-bonded explosives under different temperatures

The temperature-impact safety correlation of a cyclotetramethylene tetranitramine (HMX) based polymer-bonded explosive (PBX) was investigated. Matrix of tests was determined by projectile velocities in the range of 160 m/s-370 m/s and five temperature cases of 28 degrees C (room temperature), 75 degrees C, 105 degrees C, 160 degrees C, and 195 degrees C. The safety performance under thermal-impact combined environment was evaluated by high speed camera and air over-pressure gauges. The samples before and after impact were compared by the scanning electron microscope. The mechanical performance and thermal decomposition under different temperatures were also studied by mechanics machine and the thermo gravimetric analysis technique. The phase transition of PBX-2 is investigated by XRD spectrograph. The results show that the reaction threshold of unheated explosive is between 263.5 m/s and 269.9 m/s. While heated to 75 degrees C and 105 degrees C, the values are increased to 316 m/s-367 m/s and 286 m/s-298.3 m/s, respectively. However, the threshold is less than 176 m/s at 160 degrees C and the threshold at 195 degrees C is even lower, which is less than 166.7 m/s. According to the temperature histories, the pictures of wreckages, the over-pressures, the mechanical performance, the thermal decomposition, and phase transition properties, some conclusions can be drawn. First of all, compared with unheated case, the impact safety of PBX-2 is improved at both 75 degrees C and 105 degrees C by a softened, easy-flowing, and energy absorbing mechanical properties. Secondly, at 160 degrees C, the impact safety becomes worse due to the thermal decomposition. Thirdly, when the temperature reaches or exceeds the beta -> delta phase transition range, the impact safety of PBX-2 becomes significantly worse. (C) 2013 AIP Publishing LLC.