From the Kissinger equation to model-free kinetics: reaction kinetics of thermally initiated solid-state reactions
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Recently the term, “model-free kinetics” has increasingly been used in thermoanalytical studies. It is noteworthy that even without knowledge of the concrete reaction mechanism of a material transformation, “model-free kinetics” can be used to determine relevant kinetic parameters such as activation energy ΔEa, preexponential factor A, and reaction rate constant k. An obvious thought that comes to mind is to combine techniques of the thermal analysis with the classical chemical reaction kinetics. Concerning the investigation of classical reaction kinetics, a series of isothermal experiments is necessary to take the time-to-yield ratio of any chemical reaction into account. Based on an introduced mechanism of the chemical reaction, the reaction rate constant k is determined for a series of temperatures T, i.e. k becomes a function of temperature; k = k(T). Generally, the examined substances are solids (e.g. polymers, plastics) and their thermal conversions are heterogeneous reactions at an interface. Would it, therefore, not be simpler to use non-isothermal procedures of thermal analysis for the kinetic analysis of solid state reactions?
KeywordsSolid-state Non-isothermal kinetics Model-free kinetics Thermal analysis
I would like to thank PD Dr. Richard Thede, University of Greifswald, for his critical review of the manuscript and the discussion of the basic equation, Eq. (6). I extend my thanks to my daughter Julia Koenig, Cologne Academy of Media Arts, and to Mr. Roger Skarsten, University of Applied Sciences and Arts, Hildesheim, for the translation of the German version into English.
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