Thermal analysis of ammonium dinitramide (ADN)

Abstract

Kinetic constants of decomposition were determined for ADN and prilled ADN by DSC and TG. Pressure DSC at 550 psi air or helium had similar kinetic constants for prilled ADN, namely 29 kcal/mol activation energy and a log frequency factor of ∼14.0 min −1. These values were similar to those found in sealed sample pans in which the decomposition gases were confined. DSC and TG runs in open sample pans in nitrogen or helium had higher activation energies and frequency factors, namely 40–43 kcal/mol and 18–20 min −1, respectively. Thus, it appears that confinement of the ADN decomposition gases either under pressurization or a sealed environment accelerates the decomposition of prilled ADN. Kinetics of decomposition of unprilled ADN at atmospheric pressure in nitrogen or helium by DSC and TG were E a=37 kcal/mol and log A=17 min −1. Unprilled ADN had lower activation energies and frequency factor for decomposition than prilled ADN which contained stabilizers. The effect of sample containment (i.e. aluminum, coated aluminum, gold, and glass ampoules) on the shape of the DSC curve of ADN was investigated. Isothermal TG in vacuum of ADN in the 45–75°C region and the DSC analysis of the TG residues showed unusual results in the 60°C region. The rate and enthalpy of decomposition of four dinitramide salts and their dielectric relaxation were related to the basicity of the cation.