Limitations of the Isoconversional Principle in Thermal Analysis of Complex Reactions

This study explores the isoconversional principle by showing, through both inference and calculation on simulated reactions, that the conversion function of complex reactions may depend not only on the degree of conversion but also on temperature or thermal history. We demonstrate from mathematical perspective that the isoconversional principle can be considered accurate only when the isoconversional temperature interval () approaches zero, a condition not attainable in practice. Instead, the kinetic triplets—activation energy, pre‐exponential factor, and conversion function—derived by isoconversional methods are only approximations of their corresponding values at the mean isoconversional temperatures. Using both simulated reactions and the thermal decomposition of the polymer coating from a commercial optical fiber, we show that kinetic triplets are influenced by conversion degree, reaction temperature, and the applied temperature program.