Study of the decomposition of phase stabilized ammonium nitrate (PSAN) by simultaneous thermal analysis: determination of kinetic parameters P.N. Simo Äes a,* , L.M. Pedroso a , A.A. Portugal a , J.L. Campos b a Departamento de Engenharia Quõ Âmica, Laborato Ârio de Energe Âtica e Deto Ânica, Faculdade de Cie Ãncias e Tecnologia, Largo Marques de Pombal, Universidade de Coimbra, 3000 Coimbra, Portugal b Departamento de Engenharia Meca Ãnica, Laborato Ârio de Energe Âtica e Deto Ânica, Faculdade de Cie Ãncias e Tecnologia, Largo Marques de Pombal, Universidade de Coimbra, 3000 Coimbra, Portugal Received 17 February 1998; received in revised form 8 May 1998; accepted 22 May 1998 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 speci®c 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 in¯uence 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)10 5 s 1 for the pre-exponential factor were found as describing the process over a wide range of the kinetic analysis. # 1998 Elsevier Science B.V. Keywords: Ammonium nitrate (AN); Phase stabilized ammonium nitrate (PSAN); Kinetic parameters; Simultaneous thermal analysis; Thermal decomposition 1. Introduction Ammonium nitrate (AN) is a well-known oxidizer used for many years both in explosive and propellant formulations. Some reasons for this are its low cost, chemical stability, low sensitivity to friction and to shock, as well as its low polluting characteristics. Its use as a main propellant ingredient has been somewhat limited due to its high hygroscopicity, solid state phase transition characteristics, particle shape, low energy and low reactivity. Despite these drawbacks the AN has gained a new interest in the last years, namely because efforts are being made to overcome the environmental problems posed by the propellants based on ammonium perclorate (AP). In the view of the costs that would be involved in the search for new oxidizers the possible replacement of AP by AN for Thermochimica Acta 319 (1998) 55±65 *Corresponding author. Tel.: +351-39-828392; fax: +351-39- 841138; e-mail: pnsim@eq.uc.pt 0040-6031/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved PII S0040-6031(98)00386-4