In principle, the kinetic analysis of thermal effects has limitations when based on a single measurement. Using a simulated
example and the dehydration of Ca(OH)2 , it will be shown that, through the simultaneous application of non-linear regression to several measurements run at different
heating rates (multivariate non-linear regression), the difficult problem of determining the probable reaction type can be
Thermal behavior of nitroguanidine (NQ) has been investigated by TG/DSC-MS-FTIR simultaneous analysis performed under both
isothermal and nonisothermal conditions. The isothermal test at 230 °C indicated that the release of gas products can be divided
into several stages. The processing of the non-isothermal data, namely 5, 10, 15, and 20 K/min, was performed by using Netzsch
Thermokinetics. The dependence of the activation energy evaluated by Friedman’s isoconversional method on the conversion degree
shows that the investigated process is complex one, and can be divided into three parts. The mechanism of the process and
the corresponding kinetic parameters were determined by Multivariate Non-linear Regression Program. The kinetic results was
used to simulate the thermal decomposition of NQ under isothermal condition at 210 °C. The simulated curve is in agreement
with the tested curve. The obtained results were also used for prediction of the thermal lifetime of NQ corresponding to a
The thermo-oxidative degradation of a parchment recent manufactured from a goat skin has been investigated by TG/DTG, DSC
simultaneous analysis performed in static air atmosphere, at six heating rates in the range 3–15 K min−1. At the progressive heating in air atmosphere, the investigated material exhibits three main successive processes occurring
with formation of volatile products, namely the dehydration followed by two thermo-oxidative processes. The processing of
the non-isothermal data corresponding to the first process of thermo-oxidation was performed by using Netzsch Thermokinetics—a
Software Module for Kinetic Analysis. The dependence of activation energy, evaluated by isoconversional methods suggested
by Friedman, and Ozawa, Flynn and Wall, on the conversion degree and the relative high standard deviations of this quantity
show that the investigated process is a complex one. The mechanism and the corresponding kinetic parameters were determined
by Multivariate Non-linear Regression program. Three mechanisms, one consisting in four successive steps and two others in
five successive steps, exhibit the best F-test Fit Quality for TG curves. It was also used the previously suggested criterion, according to which the most probable
process mechanism correspond to the best agreement between EFR = EFR (α) (EFR is the activation energy evaluated by isoconversional method suggested by Friedman; α is the conversion degree) obtained
from non-isothermal experimental data and activation energy values, Eiso, obtained by applying the differential method to isothermal data simulated using non-isothermal kinetic parameters. According
to this last criterion, the most probable mechanism of parchment oxidation consists in four successive steps. The contribution
of the thermo-oxidation process in the parchment damage by natural aging is discussed.
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.
Authors:G. Xu, L. Zhang, L. Liu, G. Liu, and D. Jia
Thermal behaviors of two mixed-ligand complexes, [Ni(PMPP-SAL)(Py)3] and [Cu(PMPP-SAL)Py]·MeOH, (PMPP-SAL=1-phenyl-3-methyl-4-(salicylidene hydrazide)-propenylidene-pyrazolone-5, Py=pyridine),
were studied by TG-DTG-DTA in dynamic air atmosphere. The complexes show the loss of pyridine molecule is followed by the
decomposition of the PMPP-SAL anion and give respective metal oxides as residues. Meanwhile, the Ozawa-Flynn-Wall model-free
analyses and multivariate non-linear regressions were applied to perform single and overall steps optimization. Kinetic parameters
were given and the most probable mechanism functions were suggested in this study.
Kinetics of exothermal decomposition of 2-nitrophenylhydrazine (2-NPH) and 4-nitrophenylhydrazine (4-NPH) was investigated
by differential scanning calorimetry. The isoconversional methods, Friedman and Flynn-Wall-Ozawa, were applied to determine
the activation parameters from the common analysis of multiple curves measured at different heating rates. For the processes
involving two-step reactions the multivariate non-linear regression was used. A good agreement between the experimental and
the fitted data was found.
Authors:F. M. Cabrera, A. Khamlichi, I. Losilla, and I. Hanafi
Considering the increasing prospective regarding the various applications of Poly Ether Ether Ketone reinforced with 30% carbon fibres (PEEK CF30), there is a crucial need to investigate its machinability. In this work, focus is centered on non-linear regression based models that can be built to predict roug hness parameters Ra and Rt associated to turning of PEEK CF30 when using TiN coated cutting tool. Attention was paid to one-variant models that can be proposed to represent the effect of the cutting speed on the surface finish parameters. A broad class of non-linear interpolation models was considered. Their aptness to be used in modelling this particular application was assessed. The identification of the various mathematical models was performed by using experimental results that were obtained from CNC turning of PEEK samples. Based on statistical analysis, all the considered non-linear regression models proved to be highly significant and succeeded to fit adequately the experimental results.
Authors:Jeanina Pandele Cusu, Adina Magdalena Musuc, and Dumitru Oancea
validated by means of a multivariate non-linearregression analysis. The activation energy was also determined using two equation based on the variable heating rate method, by differential Kissinger [ 17 ] and integral Ozawa [ 18 ] isoconversional methods
Authors:V. Logvinenko, V. Bakovets, and L. Trushnikova
dehydroxylation are shown in Fig. 7 .
Data processing for Ni(OH) 2 dehydroxylation. TG curves (5 and 10 K min −1 ) fitting of non-linearregression, simulated with Fn equations for all three steps. Experimental
Authors:Yujiao Xie, Chang Liu, Hanbing He, and Xiaohua Lu
, multivariate non-linearregression (Netzsch Thermokinetics) was used to obtain the dehydration mechanism and corresponding kinetic parameters [ 21 ]. Considering the dehydration process of S1, the initial reversible step was omitted because of the small mass