Simulation of Heat Flow Curves of NC‐Based Propellants – Part 1: Determination of Reaction Enthalpies and Other Characteristics of the Reactions of NC and Stabilizer DPA Using Quantum Mechanical Methods

Abstract

AbstractThe heat flow curves of nitrocellulose (NC)‐based propellants are now an important assessment quantity for their quality and safety in storage and service. The measurable heat flow is the summarized effect of the rates of all the reaction heats of the reactions going on in the material. To get a detailed assessment instead the only global one requires knowing the heat flow parts caused by NC and by stabilizer reactions. For this, in turn, one needs to find the reaction enthalpies of the essential NC decomposition reactions and the stabilizer reactions at the temperature of the measurement of the heat flow. These data are not available in the literature. To get meaningful data it was necessary to use quantum mechanical calculations, here so‐called DFT (density functional theory) methods, to screen the possible reactions by transition states and the energetic situation between educts and products. For the calculation of the reaction enthalpies and the transition states, the reactants were embedded in a polarizable continuum, which simulates the NC environment for the reactants in NC and for the stabilizer reactions. In addition, to calculate bond dissociation enthalpies of NC and of nitroglycerine a type of shell model was used called ONIOM (‘Our own N‐layered Integrated molecular Orbital and molecular Mechanics’ model). The results from the determinations of reaction enthalpies are used in the second part of the publication.