Kinetic modelling of the stabilizer consumption and of the consecutive products of the stabilizer in a gun propellant

Diphenylamine (DPA) is used for the stabilization of solid propellants based on nitrocellulose. It reacts with the autocatalytically acting decompn. product of nitrocellulose and forms consecutive products, which also stabilize. The kinetics of these stabilizing reactions are described by 4 reaction models. With respect to DPA and the DPA consecutive products the models have 1, 2, and 4 steps. The 4-step model contains the DPA consecutive products up to trinitro-DPA. By approxns. an anal. equation for the stabilizer decrease was derived, which describes the stabilizer consumption very well. The other equation systems were integrated numerically by a Runge-Kutta procedure and their reaction rate consts. were obtained by a non-linear least squares fit parameter calcn. This allows an evaluation of the reaction kinetic models. Relative reactivities of the DPA consecutive products with respect to DPA are calculable with the obtained reaction rate consts. and an effective DPA concn. can be e stablished. The different reactivities of mixed stabilizers as N-methyl-p-nitroanaline (MNA) and 2-NO2-DPA can be described with the presented method of modeling.