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all the samples. The nucleation activity and crystallization activation energy of PP/kaolin composites were computed using Dobreva and Kissinger methods, respectively. In this article, the samples were subjected to three different processing

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Augis and Bennett (J. Thermal Anal. 13 (1978) 283.) [6] recently proposed a modified Kissinger method for determining the activation energy of a transformation. It is shown that the proposed method was, in fact, based upon a modification to the equation for the rate of reaction under non-isothermal conditions. The apparent discrepancy between the proposed method and the original Kissinger method is therefore resolved. The modified rate equation appears to have, at best, only a limited application. However, if the equation should be appropriate for a particular transformation, it is demonstrated that Augis and Bennett's method would be the correct method for determining the activation energy.

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Abstract  

The dynamic heating rate method developed by TA Instruments (Hi-ResTM) is a kind of sample controlled thermal analysis in which a linear relationship between the logarithm of the heating rate and the rate of mass change is imposed. It is shown in this paper that the reacted fraction at the maximum reaction rate strongly depends on the parameters selected for the Hi-Res heating algorithm, what invalidates the use of the Kissinger method for analysing Hi-Res data unless that the reaction fits a first order kinetic law. Only in this latter case, it has been demonstrated that it is not required that a constant value of the reacted fraction at the maximum reaction rate is fulfilled for determining the activation energy from the Kissinger method. In such a case the Kissinger plot gives the real activation energy, independently of both the heating schedule used and the value of the reacted fraction, αm, at the maximum.

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In this research, the effects of zinc stearate addition on paraffin wax degradation were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). The apparent activation energies of wax decomposition in nitrogen and air atmospheres were determined as 76 and 37 kJ mol−1, respectively applying Kissinger method to TG data. The degradation rate constants of paraffin containing zinc stearate (0.1–0.5%) were found to be almost two times greater than that of paraffin only in air atmosphere. However, zinc stearate did not affect the rate constants in nitrogen significantly.

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The thermal behaviour of the complexes formed in situ between the aromatic diamine 1,10-phenanthroline and the Co(II) and Ni(II) ions intercalated between the layers of γ-zirconium phosphate was studied by simultaneous TG/DSC techniques. The obtained materials show similar thermal behaviour: after a multi-step dehydration process they showed an oxidative decomposition in only one step. The kinetic study of the decomposition process was performed using both the model-free methods of Ozawa-Flynn-Wall and Kissinger. The former method provides a negligible dependence of activation energy on the degree of reaction α for both materials. Activation energies derived by the Kissinger method show a good agreement with the mean values derived by the Ozawa-Flynn-Wall method. The Arrhenius rate constants determined using also the pre-exponential factor values demonstrate that their thermal stability can be considered comparable, within the experimental uncertainty. Finally, a reliable method was applied to determine the model function from the best fit between the numerical dependence of the integral function g(α) vs. α and several theoretical model dependencies reported in literature for the most commonly used models. A Mampel first-order reaction model was selected to describe the thermal decomposition in both the materials studied.

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Journal of Thermal Analysis and Calorimetry
Authors: J. Saiter, N. Delahaye, M. Liziard, and L. Podgorski

Abstract  

The rate of cure of different oxidative drying oil modified alkyd resins are investigated by DSC, when the cure is made under UV light or not. We determine, from the Kissinger equation, the apparent activation energy at different stages of the curing process. This activation energy depends on the curing conditions (temperature, illumination or not). These variations lead to the determination of a time constant, characteristic of the curing kinetics. Two particular values of the apparent activation energy are also defined. The first one called ΔE o is a characteristic of the varnish at the liquid state, the second one called ΔE inf characterizes the stability of the structural state of the final film.

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Traditionally, the kinetic treatment of adiabatic calorimetry data has been based on the results of one or more experiments, but always with the assumption of the kinetic model that the reaction follows to calculate the kinetic parameters. In this paper a method for the determination of the activation energy that uses a set of adiabatic calorimetry data is developed. To check the method, the thermal decompositions of two peroxides were studied.

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Alkyd-based-thermosetting resin

Calorimetric investigations of the curing process

Journal of Thermal Analysis and Calorimetry
Authors: J. Saiter, N. Delahaye, M. Liziard, and L. Podgorski

Abstract  

In this work, the rate of cure of different oxidative drying oil modified alkyd resins are investigated by DSC measurements. We determine, from the Kissinger equation, the apparent activation energy of the curing process. We show that this activation energy depends on the curing duration and that these variations lead to the determination of a time constant, characteristic of the material.

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