Determination of activation energy during the thermal degradation of Polyamide 66/glass fiber composites

The objective of this study was to clarify the mechanical properties and the non-isothermal degradation kinetics of Polyamide 66 (PA 66)/glass fiber (GF) composites. The non-isothermal degradation behavior of the samples was studied by thermal gravimetric analysis under nitrogen purge. The perfect compatibility of GFs with polymer matrix in composites was studied by scanning electron microscopy. It was found that with increasing content of GFs in samples due to good distribution of fibers in PA 66, the degradation temperature and calculated activation energy in composites increased in all heating rates. The activation energy was calculated by the Flynn–Wall–Ozawa method (isoconversional method). It was concluded that the model-free methods can be a reliable way to determine the kinetic parameters. Furthermore, the isokinetic relationship was used to estimate a model-independent pre-exponential factor (ln A) corresponding to a given degree of conversion.

A Study on the Kinetics and Mechanism of the One-Pot Formation of 3,4,5-Substituted Furan-2(5H)-Ones in the Presence of Lactic Acid: Effect of Different Substituents

The kinetics of the reaction between para-substituted anilines and dimethyl acetylenedicarboxylate (DMAD) with derivatives of benzaldehyde for the one-pot formation of 3,4,5-substituted furan-2(5 H)-ones in the presence of lactic acid as a catalyst have been studied spectrophotometrically at different temperatures. A mechanism involving four steps was proposed for the reactions, all of which followed second-order kinetics. The partial orders with respect to substituted aniline and DMAD were one and one and the reactions revealed zero-order kinetics for benzaldehyde and its derivatives. Changing of substituents on benzaldehyde left rates of reaction unaffected. However, various substituents on aniline showed that para electron-withdrawing groups decreased the rate of reaction. According to investigation of an isokinetic relationship, a common mechanism exists for all studied substituents and a general mechanism can be formulated. Kinetic values ( k and Ea) and associated activation parameters (Δ G‡, Δ S‡ and Δ H‡) of the reactions were determined.

High thermodynamic stability study of PLA/LCNF composite

Thermal degradation behaviors of one composite constituted by poly(lactic acid) (PLA), cellulose nanofibrils (CNF), and lignin–cellulose nanofibrils (LCNF) in a nitrogen atmosphere were studied using thermogravimetric analysis (TGA). It was found that the thermal degradation stability of the PLA/LCNF composite was improved when compared to PLA and PLA/CNF. The Flynn–Wall–Ozawa method was used to determine the apparent activation energy of the composite samples which was based on a set of TGA data obtained at different heating rates. It was shown that the conversion functions calculated by means of the Coats–Redfern method depend on a set of kinetic models, which could be concluded that using the model-fitting methods couldn’t reveal the complexity of the thermal degradation process and the isokinetic relationship method was used to estimate a model-independent pre-exponential factor (ln A) corresponding to a given degree of conversion.

Kinetics of Carbothermic Reduction of Ilmenite

The reduction kinetics of ilmenite was investigated. Phase evolution during the reduction process was identified by XRD and morphology change was observed using SEM. Kinetic parameters of the activation energy and pre-exponential factor were determined by Kissinger-Akahira-Sunose (KAS) method and Coast-Redfern method&artificial isokinetic relationship (IKP) respectively. Results showed that when the reaction of titanium suboxides makes a growing contribution, the conversion dependence of activation energy has an ascending trend. When the conversion exceeded 0.7, the reactants almost consumed, and the process was controlled by diffusion.

Solvent Effect of Oxygen in the Thermolisys Decomposition of the Acetone Diperoxide

In this paper, the kinetics of the thermal decomposition reaction of 3,3,6,6-tetramethyl-1,2,4,5 tetroxane (ACDP) is investigated in various oxygen solvents at different temperatures. Linear relationships are observed between the enthalpy and entropy of activation of the unimolecular reactions of those diperoxides. The isokinetic temperature calculated by Leffler’s treatment is 527.2K, which is consistent with the proposed Exner correlation between the logarithm of the rate constant values for the same reaction in each solvent at two temperatures, where the corresponding ß value was 523.5K. A true “isokinetic relationship” for the ACDP thermolysis indicates that their reactions constitute a reaction series with similar interaction mechanisms. This can be related to the capacity for hydrogen bonding between the solvent and the diperoxide molecules. The solvanting properties of the media help the peroxidic bond rupture these molecules.

Meso-tetraphenylporphyriniron(iii) chloride catalyzed oxidation of aniline and its substituents by magnesium monoperoxyphthalate in aqueous acetic acid medium

The catalytic properties of the first generation catalyst meso-tetraphenylporphyriniron(III) chloride and magnesium monoperoxyphthalate (MMPP) as oxidant have been studied in the oxidation of aniline and its substituents in acetic acid medium. The thermodynamic parameters for the oxidation have been determined and discussed. It confirms the Exner relationship (only at the low range of temperatures) and also some of the activation parameters to the isokinetic relationships. The magnesium monoperoxyphthalate oxidation with 18 ortho- meta- and para-substituted anilines fulfills with isokinetic relationship but not to any of the linear free energy relationships. The reaction mechanism and the rate law were proposed.