Abstract:A critical examination was made on the reliability of kinetic parameters of nonisothermal thermoanalytical rate measurement by the widely applied Coats-Redfern(CR) equation. For this purpose, simulated TGA curves were made for reactions with different kinetic models, including chemical, diffusion (Janders) and mixed mechanism at different heating rates. The results show that, for reactions controlled kinetically by one mechanism, all solid state reaction models show linear trends by use of CR method and this method can not distinct the correct reaction model. For reactions with mixed mechanism, the CR method shows nonlinear trends and the reaction models and kinetic parameters can not be extracted from CR curves. The overall conclusion from this comparative appraisal of the characteristics of the CR approach to kinetic analysis of TGA data is that the CR approach is generally unsuitable for determination of kinetic parameters.

Key words: kinetic analysis; Coats-Redfern equation; nonisothermal TGA; rate equation; Arrhenius parameters