Decomposition of diphenylamine in nitrocellulose based propellants—I. Optimization of a numerical model to concentration-time data for diphenylamine and its primary degradation products determined by liquid chromatography with dual-amperometric detection

Abstract

The consumption of diphenylamine (DPA) in two nitrocellulose (NC) based propellants subjected to a heat storage test at 85° has been studied. A previously developed method based on reversed-phase liquid chromatography with dual-amperometric detection was used to monitor the concentrations of DPA, 2-nitro-DPA and 4-nitro-DPA during the test. A numerical model based on first order rate equations was fitted to the obtained analytical data with the use of a specially written curve fitting program. The model implemented in the program describes the initial nitrosation and nitration steps of DPA in aging NC propellants. The use of matrices in the calculation of concentration-time (CT) curves enables the introduction of a general algorithm which can be readily changed in order to simulate any system of first order reactions. The program can therefore be used in other applications such as mechanistic studies in organic synthesis. The general simulation algorithm allows inclusion of unknown (not analysed) components in the reaction mechanism. In this application, it was possible to simulate the course of N-nitroso-DPA which is not detectable by the amperometric principle.