Sur des conditions d''amorçage par onde de choc de la détonation du nitrométhane

Results concerning the thermodynamic and mechanical properties of nitromethane (N.M.) at pressures up to 11 GPa are presented. The pressure is generated either by an incident shock wave or by a shock wave reflected within a medium prepressurized by a first shock wave. Calculation of the temperature behind these shock waves, based on the Walsh-Christian model, calls, in particular, upon the knowledge of the N.M. shock polar relative to normal temperature and pressure conditions, but also of those corresponding to prepressurized states.

Taking advantage of the phenomena of N.M. electric polarization under shock, we determine, on the one hand, the relation between pressure and particle velocity and, on the other hand, the influence of pressure conditions on induction delays of the explosive.

According to calculation, for a same pressure level the N.M. temperature behind a single shock is higher than that obtained by two successive compressions.

Experimentally, we observe that N.M. compressed at 11 GPa by means of two shock waves does not detonate (during the observation time of about 0,5 μs), while in the case of a single shock wave of the same amplitude the induction delay is lower than 0.1 μs. These results show the important role of temperature, as opposed to that of pressure.