Isoconversional methods: The many uses of variable activation energy

In this review article, the author briefly shares his personal experience of exploring the phenomenon of variable activation energy. Isoconversional methods frequently yield variable activation energy, E_α, which depends on conversion, α. It is emphasized that isoconversional kinetic analysis should not be limited to simply evaluating and reporting the E_α dependencies. Deeper insights into the thermal kinetics are gained by exploiting the intrinsic properties of the E_α dependencies. These properties can be defined as diagnostic, exploratory, predictive, modelistic, and intermediary. Thanks to them one can generate mechanistic hypotheses, test the validity of assumed temperature dependencies of the process rates, forecast the kinetics beyond experimental conditions, determine parameters of kinetic models, and evaluate the preexponential factors and reaction rate constants. The article provides a practical overview of these properties of the E_α dependencies and illustrates their usage by instructive examples.