Study of the decomposition of phase stabilized ammonium nitrate (PSAN) by simultaneous thermal analysis: determination of kinetic parameters

Abstract

Ammonium nitrate (AN) has been extensively used both in explosive and propellant formulations. Unlike AN, there is a lack of information about the thermal decomposition and related kinetic analysis of phase stabilized ammonium nitrate (PSAN). Simultaneous thermal analysis (DSC-TG) has been used in the thermal characterisation of a specific type of PSAN containing 1.0% of NiO (stabilizing agent) and 0.5% of Petro (anti-caking agent) as additives. Repeated runs covering the nominal heating rates range from 2.5 to 20 K min-1 allowed to conclude on the good reproducibility of the main features of the thermal behavior of PSAN, i.e., two phase transitions, melting and decomposition. Non-isothermal kinetic analysis has been used to estimated the Arrhenius parameters of the decomposition process by applying both a single curve method and two isoconversion methods to the TG data. The results are discussed considering the range of applicability of the methods as well as the influence of the experimental conditions and/or techniques in the kinetic analysis results in a broader sense. A systematic approach based on the isoconversion methods results and statistical tools has been adopted to obtain reliable estimates of the Arrhenius parameters for the thermal decomposition of PSAN. Under the condition of study, the values of 81.4±3.5 kJ mol-1 for the activation energy and (5.63±0.01)×105 s-1 for the pre-exponential factor were found as describing the process over a wide range of the kinetic analysis.