Detailed high temperature pyrolysis mechanisms of stabilized hybrid HMX crystals by intercalation of 2D energetic polymer

Abstract

The two-dimensional high nitrogen insensitive triaminoguanidine glyoxal energetic polymer (TAGP) has been used as intercalating material for HMX crystals, resulting in novel hybrid energetic crystals (so called qy-HMX) with better stability and higher density. In this paper, the molecular dynamic simulations based on a reactive force field (ReaxFF) have been implemented to illustrate the stabilization and decomposition mechanisms of TAGP on HMX crystals, which were verified by TG-DSC and Pyro-GC/MS experiments. Six types of qy-HMX models with different TAGP contents have been constructed. The results suggest that the conformation of HMX molecule could be changed under the strong constraint of TAGP layers, which could hinder the decomposition of qy-HMX under lower temperature due to enhanced intramolecular interactions, resulting in more complete solid-state decomposition reactions than β-HMX. The TAGP and HMX would decompose simultaneously if the TAGP content is low enough, whereas the TAGP decomposes earlier than HMX molecules, if its mass content reaches over 50%. The isothermal decomposition activation energies also prove that the qy-HMX crystal is more stable and decomposes faster that raw β-HMX. Besides, the Pyro-GC/MS experiments show that there is little change for the major decomposition pathways for HMX under the effect of TAGP, but there has been strong interaction between the intermediate of their thermolysis products. The gaseous products differ only in relative content, depending on the pyrolysis temperature. Some products such as the HCN, H2O and NH3 are more dominant under temperature of 350 °C, whereas the CO2, HNO and NO2, are much less than β-HMX. which agree well with the simulated results.