Accurate estimation of the kinetic triplets of solid-state reactions

This study introduces a new isoconversional method for estimating kinetic triplets in simple and complex solid-state reactions under isothermal or nonisothermal conditions. The approach is based on factorization of the reaction rate into a temperature-dependent rate constant and a conversion function. The conversion function is represented using discrete cosine transform (DCT) or Chebyshev series expansion (CSE) models, while the rate constant is described by a CSE-based temperature polynomial. The degree of temperature polynomial is optimized through an F-test, avoiding overfitting and ensuring stable solutions. The method was validated using simulated reactions, where the estimated kinetic triplets closely matched exact values, and further demonstrated on experimental data for the thermal degradation of a blend of poly(methyl methacrylate) and cyclic olefin copolymer, revealing two distinct degradation stages. To promote practical use, GNU Octave/MATLAB codes are provided, enabling reliable application of the methodology to experimental kinetic studies.