Analysis of Chemical Reaction Process after Pentaerythritol Tetranitrate Hot Spot Ignition

Abstract

In this paper, ReaxFF force field combined with molecular dynamics method was used to study the ignition, deflagration, and detonation of pentaerythritol tetranitrate (PETN) induced by hot spots. The hot spot is 5.6% of the total volume. When the hot spot temperature is 1000 K, the deflagration and detonation of PETN cannot be observed in the simulation time of 200 ps. When the hot spot temperature is 2000 K, it corresponds to the heating time of 20 to 50 ps, deflation and detonation were observed. During hot spot ignition, the products of decomposition of the condensed phase PETN are dominated by NO2 and HONO. The energy required for the C–C bond and C–ONO2 bond cleavage in PETN is high, resulting in only a small amount of CH2O and NO3 during the reaction. Small nitrogen-containing molecules (such as NO2, NO3, HONO, HNO3, etc.) mainly exist during thermal equilibrium, while the number of N2 increases sharply during the thermal runaway stage, and a small amount of NH3 and NH2 are also produced. H2O molecules are formed before CO2 and N2 are produced, and the number always dominates. During the thermal runaway, the entire system can maintain a spontaneous reaction, resulting in a sharp rise in temperature of about 2500 K in 20 ps. During this phase, the catalytic effect of H2O accelerates the formation of CO2 and N2 due to the near Chapman–Jouguet point in the crystal. PETN is a weak oxygen balance explosive that results in a small amount of CO and H2 production during the thermal instability phase. When the reaction is balanced, the relative molecular mass is close to or exceeds that of PETN. The product is only less than 1% of the total mass fraction, while the small molecule product is as high as 78%, and some relative molecular masses are [75,225]. The intermediates account for about 21%. Rapid and complex reaction events make it difficult to accurately predict the structure of these intermediates by existing experiments and calculations, which will be the focus of future research.

Chemical Evaluation and Performance Characterization of Pentaerythritol Tetranitrate (PETN) under Melt Conditions

“…The degradation of PETN has been studied extensively, , with detailed investigations on decomposition by acid, metal oxides, , impurities, and radiation − and biological, , explosive, and thermal − insults. The O–NO 2 bond in the nitrate ester of PETN is the weakest in the molecule, and it is generally accepted that this bond is the first to break during both slow decomposition − and fast decomposition found in detonations .…”