Novel methods of unified evaluation of two (or more) thermogravimetric curves have been worked out on the basis of known non-linear
parameter estimating procedures (Gauss-Newton-Marquardt-type regression and the direct integral method of Valkó and Vajda
were adapted). Their ability to provide estimate for common kinetic parameters of several TG (m−T) or DTG (dm/dt-T) curves were tested for pairs of curves of different heating rates, and for repeated curves of the same heating rate, obtained
for the decomposition of CaCO3 in open crucible. In these cases the Arrhenius terms and then-th order model functions were assumed. The fitting ability of estimations made for single curves and for pairs of curves
sharing different number of parameters, was judged on the base of residual deviations (Sres) and compared to the standard deviation of the measurements.
In the case of different heating rates, the two curves could not be described with the assumption of three common parameters,
because of the minimum residual deviation was very high. However, sharing of activation energy and preexponential term only,
and applying different exponents for the two curves, provided a satisfactory fit by our methods. Whilst in the case of repeated
curves, we could find such a common three-parameter set, which has a residual deviation comparable with the standard deviation
of the measurements.
Because of their flexibility (taking into account the variable number of common parameters and the versatile forms of model
equations), these methods seem to be promising means for unified evaluation of several related thermoanalytical curves.