Some methodological problems concerning the kinetic analysis of non-isothermal data for thermal and thermo-oxidative degradation of polymers and polymeric materials

The procedures used in some very recent works for evaluation of the kinetic parameters from non-isothermal data corresponding to thermal and thermo-oxidative degradation of polymers and polymeric materials are critically analysed. It is pointed out that only the use of a set of conversion degree vs. temperature curves recorded at different heating rates can give reliable information on the degradation mechanism and in some suitable cases, can lead to the true kinetic parameters. A general algorithm for evaluation of the kinetic parameters from the non-isothermal data is suggested. The application of this algorithm for a set of simulated non-isothermal data has been shown that when the activation energy is independent of the conversion, the invariant kinetic parameters method associated with the criterion of independence of kinetic parameters on the heating rate is recommended for evaluation of the kinetic triplet (activation energy, pre-exponential factor, conversion function).