The evaluation of nonisothermal thermoanalytical kinetics is simplified without the description of heat transfers, such as thermal inertia, which is not negligible, as indicated by Vyazovkin

Abstract

AbstractIn the field of thermoanalytical kinetics, which is widely used, basic questions arise regarding a possible description of the effect of heat transfer and subsequent thermal inertia. Current practice still uses a simplified interpretation of directly measured data for an inert sample at a constant temperature rise to describe the studied reaction, which leads to a simplified reaction conversion ratio, which is further used for various mathematical processing. The analysis of the introduced rectangular heat pulses and their indication by DTA clearly shows that the effect of thermal inertia is fundamental and not negligible. This is, after all, known from calorimetry, where the integral constant of inertia has historically been used to calibrate the descending temperature, but it cannot generally be applied to the whole temperature process due to its nonlinearity. In the case of parallel processing, for example by gradually increasing the heating rate, the effect of thermal inertia can be partially compensated for each other which have yet to be confirmed. However, for the kinetic analysis of a single peak, it is necessary to adapt to the effect of the thermal delay due to thermal inertia, which, similarly to the measured enthalpy, is tied to the sample size. Of course, it will be up to the researcher to find a solution that also includes the effect of heat transfer and dissipation, which should become the main principle of thermoanalytical methods of the future, as shown by current examples combining thermal processes with their specific kinetics.