Untenable Linear Fitting Approach in Determination of Thermal Decomposition Kinetic Model with Flynn-Wall-Ozawa Equation: A Case Study of Pymetrozine Dihydrate Decomposition

The accurate determination of thermal decomposition kinetics plays a crucial role in understanding the degradation behavior of materials. Traditional model-based methods, such as those relying on the Arrhenius equation, often face challenges due to the complexity of the decomposition mechanisms, leading to the kinetic compensation effect. The Flynn-Wall-Ozawa (FWO) equation offers a model-free approach, providing greater flexibility by bypassing the need for an assumed reaction model. This study investigates the thermal decomposition kinetics of pymetrozine dihydrate using the FWO method and highlights the limitations of linear fitting approaches. Discrepancies between model-based and model-free methods are discussed. Results demonstrate that while high determination coefficients can be achieved, the selection of inappropriate reaction models leads to significant variation in activation energy values, emphasizing the importance of discretion in selection of kinetic models. This research underscores the need for caution when applying model-free methods and proposes further refinement for robust kinetic analysis.