Model-free and model-fitting approaches to kinetic analysis of isothermal and nonisothermal data

The model-free and model-fitting kinetic approaches have been applied to da ta for nonisothermal and isothermal thermal decompositions of HMX and ammon ium dinitramide. The popular model-fitting approach gives excellent fits fo r both isothermal and nonisothermal data but yields highly uncertain values of the Arrhenius parameters when applied to nonisothermal data. These valu es cannot be meaningfully compared with the values derived from isothermal measurements, nor they can be used to reasonably predict the isothermal kin etics. On the other hand, the model-free approach represented by the isocon versional method yields similar dependencies of the activation energy on th e extent of conversion for isothermal and nonisothermal experiments. The de pendence derived from nonisothermal data permits reliable predictions of th e isothermal kinetics. The use of the model-free approach is recommended as a trustworthy way of obtaining reliable and consistent kinetic information from both nonisothermal and isothermal data. (C) 1999 Elsevier Science B.V . All rights reserved.