Energy transferred to energetic materials during impact test at reaction threshold: Look back to go forward

Impact sensitivity of energetic material is considered to be not an intrinsic property of the compound, but to depend on multiple variables, including, in addition to chemical nature of the substance, both the powder and the instrument-depending factors. Therefore, the comparison of the sensitivity data obtained using different impact machines and measurement protocols, and even by the same ones but in the different laboratories is difficult. Based on the works carried out almost 90 years ago, we propose a relatively simple but versatile technique using the modified standard fallhammer to measure the drop weight speed in downward and upward directions. The combination of the tests without sample and with sample of energetic material (both for the “triggered” and “not-triggered” cases) allows obtaining the energy transferred to and absorbed by the sample at the weight-height load, corresponding to the reaction threshold. An energy balance during the impact event is calculated to show the importance and the maintenance-dependency of the energy losses stored in test machine, and to illustrate the difference between the full energy value and the actual energy absorbed by the sample. One of the outputs of the suggested procedure are the values of energy absorbed by the sample at reaction threshold. These values are obtained in the course of standard testing protocol, in addition to the nominal drop energy value, corresponding to 50% probability of the reaction initiation. The suggested “real” energy values represent more relevant measure of mechanical hazard than usually reported nominal drop energy values.