Isothermal and non-isothermal measurements can yield different activation energies from thermoanalytical data

Thermal measurements employing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are frequently utilized in the study of chemical reactions and phase transformations involving the solid state. Given that these techniques typically involve heating (and occasionally cooling), it is essential to comprehend how the kinetics are influenced in comparison to isothermal measurements obtained using the same instrumentation. This matter has recently re-emerged due to an article published in the thermoanalytical literature that provided substantial evidence of unexpected linear correlations between the activation energy, E , and the reaction temperature, T , across diverse classes of conversions investigated with non-isothermal kinetic methods. This work provides a rationalization for the physical origin of that finding and proposes why, under isothermal conditions, the corresponding E values should remain temperature-invariant. In contrast to the Kissinger method, isoconversional methods are anticipated to remain unaffected when processing non-isothermal kinetic data.