Glass transition in polymers: (In)correct determination of activation energy

The possibility of applying Kissinger-type equations for the evaluation of apparent activation energy in the case of the glass transition phenomenon was investigated. Theoretically simulated data based on the generally accepted Tool–Narayanaswamy–Moynihan model were used to represent all possible cases of structural relaxation behavior. The values of apparent activation energy determined by Kissinger-type equations were in major disagreement with the original values of Δh∗ used as the input data for the simulations. In addition, a large dependence of the Δh∗ evaluations on the thermal history of the glass was found in the case of all tested equations. The latter points to a significant systematic error in the currently commonly accepted methodology, resulting in a fundamental contradiction with the principle/concept of activation energy as a physico-chemical quantity. In light of these facts, usage of Kissinger-type equations for the evaluation of the “glass transition activation energy” was shown to be incorrect.