Bond dissociation energy and thermal stability of energetic materials
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Bond dissociation energy and thermal stability of energetic materials Guojun Bao1 · René Yo Abe1 · Yoshiaki Akutsu1 Received: 17 December 2018 / Accepted: 16 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Thermal stability of energetic materials is often screened by differential scanning calorimetry and accelerating rate calorimetry measurements. On the other hand, bond dissociation energies can explain reactivity or stability of chemical compounds. Here bond dissociation energy was derived from standard enthalpies of formation estimated by semi-empirical molecular orbital calculations using the MOPAC-PM7 package. The weakest bond dissociation energies of energetic materials and their onset temperatures in differential scanning calorimetry and accelerating rate calorimetry measurements correlated well, except for molecules where decomposition was favored by effects like intermolecular interactions. Bond dissociation energies derived from molecular orbital calculations have been found useful to roughly predict onset temperatures in the calorimetric measurements for energetic materials where data may sometimes not be available. Keywords Bond dissociation energy · DSC · Accelerating rate calorimetry · Molecular orbital package
Introduction Differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC) are widely used to evaluate the thermal stability and the potential hazard of fire and explosion of energetic materials [1, 2]. These calorimetric methods provide the so-called onset temperature of an exotherm decomposition among other information like rate of enthalpy change or presence of other processes like phase transitions. Here, this onset temperature is of interest, as it reflects the material’s thermal stability. Sometimes the calorimetric tests cannot easily be performed because the material of interest is difficult to obtain or handle in accordance to the analysis methods. In such a case, a method of estimating the thermal stability of a material from its chemical structure would be practical. Various structural parameters are also used to explain the sensitivity and the stability of energetic materials [3]. Bond dissociation energy (BDE) is useful for understanding the reactivity and characteristics of chemical compounds and seems a promising parameter to explain thermal stability. Here, we tried to clarify the relationship * Guojun Bao [email protected] 1
Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha 5‑1‑5, Kashiwa, Chiba 277‑8563, Japan
between the thermal stability of energetic materials and their BDE using DSC and ARC onset temperature data and semiempirical molecular orbital (MO) calculations. A correlation of the weakest BDE in a molecule to the onset temperature measured by DSC or ARC, which can be interpreted as an index of thermal stability [4], can be expected. The weakest BDE also indicates which bond in a molecule will dissociate in the initial stage of the pyrolysis of energetic materials. Here, the BDE has been estim
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