Estimation of the Pre-Exponential Factor and Conversion Function of Solid-State Reactions Using the Vyazovkin Isoconversional Method

<jats:p>The Vyazovkin isoconversional method is widely regarded as a reliable model-free approach for the kinetic analysis of solid-state reactions. However, its direct application is primarily limited to the determination of the activation energy, while the pre-exponential factor and conversion function generally require additional model-based analysis. In this study, a new methodology is proposed that combines the Vyazovkin isoconversional method with the Chebyshev series expansion (CSE) reaction model, and when required, with the compensation effect relationship, to estimate the pre-exponential factor and conversion function of simple or complex reactions. The proposed approach is applicable to both isothermal and nonisothermal kinetic datasets, including processes exhibiting either single or multiple peaks in their reaction-rate profiles. Moreover, the methodology enables estimation of the conversion function for processes exhibiting non-Arrhenian temperature dependence. The performance of the proposed method was first assessed using simulated kinetic datasets under both isothermal and nonisothermal conditions. Its applicability was subsequently demonstrated using experimental datasets for several processes, including the thermal degradation of poly(methyl methacrylate) and its blend with cyclic olefin copolymer, as well as the melt crystallization of poly(butylene 2,5-furandicarboxylate). GNU Octave/MATLAB codes were provided to facilitate application of the proposed methodology to experimental kinetic data.</jats:p>