Thermal properties,induction period,interfacial energy and nucleation parameters of solution grown benzophenone

The kinetic parameters (reaction order, n, activation energy, E, pre-exponential factor, A, constant rate, k) for the dehydration step due to elimination of osmotic water and hydrogen-bounded water with the carboxylic groups, and for the anhydrifying step owing to the dehydration of two neighboring (-COOH) groups, were determined under non-isothermal conditions for some carboxylic resins with acrylic-divinylbenzene (DVB) matrix. The kinetic parameters were evaluated by means of isoconversional methods from (TG/DTG) thermal analysis data. The results show a dependence of the apparent kinetic parameters on the cross-linking degree, granulation, gel/macroporous matrix nature, exchange capacity and heating rate.     

Thermokinetic parameters and thermal hazard evaluation for three organic peroxides by DSC and TAM III

The thermokinetic parameters were investigated for cumene hydroperoxide (CHP), di-tert-butyl peroxide (DTBP), and tert-butyl peroxybenzoate (TBPB) by non-isothermal kinetic model and isothermal kinetic model by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III), respectively. The objective was to investigate the activation energy (E _a) of CHP, DTBP, and TBPB applied non-isothermal well-known kinetic equation to evaluate the thermokinetic parameters by DSC. We employed TAM III to assess the thermokinetic parameters of three liquid organic peroxides, obtained thermal runaway data, and then used the Arrhenius plot to obtain the E _a of liquid organic peroxides at various isothermal temperatures. In contrast, the results of non-isothermal kinetic algorithm and isothermal kinetic algorithm were acquired from a highly accurate procedure for receiving information on thermal decomposition characteristics and reaction hazard.     

Thermal decomposition studies. Part XII. Kinetics of dehydration of calcium oxalate monohydrate. Multiple correlation with heating rate and sample mass

The kinetic parameters (energy of activation, E, and pre-exponential factor, A) from non-isothermal TG data have been correlated, for the first time, with simultaneous variations of both the procedural factors (heating rate and sample mass) by multiple regression analysis. The unique equation based on the mechanism of the reaction as well as three general mechanism-non-invoking integral equations were used to calculate E and A from the TG data for the dehydration of CaC₂O₄ · H₂O. The kinetic parameters calculated using all four equations showed a systematic trend and the results can be expressed as E(or log A) = $\text{constant}\text{heating rate}$ + $\text{constant}\text{mass}$ + constant     

Kinetic Analysis of Single or Multi-Step Decomposition Processes; Limits introduced by statistical analysis

A kinetic study on decomposition processes of some penicillin and some commercial drugs was carried out. As expected by the complex structures of penicillins, several steps with different activation energies occurred in their decomposition processes. Model-fitting and model-free kinetic approach were applied to non-isothermal and isothermal data. In the model-fitting methods the kinetic triplets (f(α), A and E _a) that defines a single reaction step resulted in being at variance with the multi-step nature of penicillins decomposition. The model-free approach represented by isothermal and non-isothermal isoconversional methods, gave dependences of the activation energies on the extent of conversion. The complex nature of the multi-step process of the studied compounds was more easily revealed using a broader temperature range in non-isothermal isoconversional method. The failure in the model fitting method did not allow calculating storage times. Model-fitting and model-free methods, both isothermal and non-isothermal, showed that F1 mechanism is able to describe decomposition processes for drugs (having Phosphomycin salts as active component) for which a single decomposition process occurs. Statistical analysis allowed us to select reliable kinetic parameters related to the decomposition processes for these last compounds. This procedure showed that the values obtained by extrapolation, outside the temperature range where the processes occurred must be used with caution. Indeed half-life and shelf-life values, commonly extrapoled at room temperature, seemed to be unrealistic. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kinetic Analysis of Thermal Decomposition of Ca(OH)2 Formed During Hydration of Commercial Portland Cement by DSC

In this paper, evaluation of kinetic parameters (the activation energy – E,the pre-exponential factor – A and the reaction order – n) with simultaneous determination of the possible reaction mechanism of thermal decomposition of calcium hydroxide (portlandite), Ca(OH)₂ formed during hydration of commercial Portland-slag cement, by means of differential scanning calorimetry (DSC) in non-isothermal conditions with a single heating–rate plot has been studied and discussed. The kinetic parameters and a mechanism function were calculated by fitting the experimental data to the integral, differential and rate equation methods. To determine the most probable mechanism, 30 forms of the solid-state mechanism functions, f(α_c) have been tried. Having used the procedure developed and the appropriate program support, it has been established that the non-isothermal thermal decomposition of calcium hydroxide in the acceleratory period (0.004<α_c<0.554) can be described by the rate equation: d α_c/dT=A/βexp(−E/RT)f(α_c), which is based on the concept of the mechanism reaction:f(α_c)=2(α_c)^1/2. The mechanism functions as well as the values of the kinetic parameters are in good agreement with those given in literature. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal decomposition study of bismuth (III) trichloride complex with 1,10-phenanthroline as the ligand

The complex BiCl₃·L (L = 1,10-phenanthroline) was synthesized and characterized by elemental analysis and infrared spectroscopy (IR). Infrared spectroscopy data suggested that the nitrogen atom of the aromatic ring is bonded to the bismuth atom. The kinetic study of thermal degradation was determined by non-isothermal thermogravimetry. Two methods based on integral equation of Coats-Redfern, were necessary for determining the kinetic trip: the fitting method, known as the checking model and an iso-conversional method. The latter gives the activation energy for each degree of conversion and the first, the kinetic model gives activation energy and the pre-exponential factor for thermal decomposition processes that occur through a single simple mechanism. The kinetic parameters, E _a and log A for the heating rates of 5, 10, and 15 min K⁻¹, were determined considering the decomposition model denoted by F0/R1 in the range of degree of conversion between 0.065 and 0.71.     

Two novel algorithms for the thermogravimetric assessment of polymer degradation under non-isothermal conditions

Two novel algorithms are presented for processing thermogravimetric (TG) data obtained during the degradation of a polymer in a single step mechanism under non-isothermal conditions. The first algorithm assesses three characteristics computed from the TG profile against a theoretical data set, and identifies likely kinetic models to fit the experimental data. The second algorithm provides an iterative arithmetic method to extract the apparent activation energy, E_a, and Arrhenius A-factor, A, from TG data without simplifying assumptions. The algorithms are validated using model data and applied to data for the non-isothermal degradation of poly(ethylene adipate), poly(lactic acid) (PLA) and a food packaging PLA composite formulation containing kenaf, a natural fibre. The analysis of poly(ethylene adipate) produced E_a = 137 kJ mol⁻¹ and log₁₀A = 8.71 (first-order kinetic model). The kenaf fibre destabilizes PLA, lowering its E_a from 190 kJ mol⁻¹ to 150 kJ mol⁻¹ (contracting volume model).     

Application of model-free and multivariate non-linear regression methods for evaluation of the thermo-oxidative endurance of a recent manufactured parchment

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 E _FR  = E _FR (α) (E _FR 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, E _iso , 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.     

Kinetic model of poly(3-hydroxybutyrate) thermal degradation from experimental non-isothermal data

The non-isothermal data given by TG curves for poly(3-hydroxybutyrate) (PHB) were studied in order to obtain a consistent kinetic model that better represents the PHB thermal decomposition. Thus, data obtained from the dynamic TG curves were suitably managed in order to obtain the Arrhenius kinetic parameter E according to the isoconversional F-W-O method. Once the E parameters is found, a suitable logA and kinetic model (f(α)) could be calculated. Hence, the kinetic triplet (E±SD, logA±SD and f(α)) obtained for the thermal decomposition of PHB under non-isothermal conditions was E=152±4 kJ mol⁻¹, logA=14.1±0.2 s⁻¹ for the kinetic model, and the autocatalytic model function was: f(α)=α^m(1−α)ⁿ=α^0.42(1−α)^0.56.     

Non-isothermal kinetic study on the decomposition of Zn acetate-based sol-gel precursor

The paper presents a non-isothermal kinetic study of the decomposition of Zn acetate-based gel precursors for ZnO thin films, based on the thermogravimetric (TG) data. The evaluation of the dependence of the activation energy (E) on the mass loss (Δm) using the isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) has been presented in a previous paper. It was obtained that the sample dried at 125°C for 8 h exhibits the activation energy independent on the heating rate for the second decomposition step. In this paper the invariant kinetic parameter (IKP) method is used for evaluating the invariant activation parameters, which were used for numerically evaluation of the function of conversion. The value of the invariant activation energy is in a good agreement with those determined by isoconversional methods. In order to determine the kinetic model, IKP method was associated with the criterion of coincidence of the kinetic parameters for all heating rates. Finally, the following kinetic triplet was obtained: E=91.7 (±0.1) kJ mol⁻¹, lnA(s⁻¹)=16.174 (±0.020) and F1 kinetic model.     

A kinetic analysis of thermal decomposition of polyaniline/ZrO<Subscript>2</Subscript> composite

Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO₂ composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression method. The results show that the kinetic models for the decomposition process of PANI/ZrO₂ composite and PANI are all D₃, and the corresponding function is ƒ(α)=1.5(1−α)^2/3[1−(1-α)^1/3]−1. The correlated kinetic parameters are E _a=112.7±9.2 kJ mol⁻¹, lnA=13.9 and E _a=81.8±5.6 kJ mol⁻¹, lnA=8.8 for PANI/ZrO₂ composite and PANI, respectively.     

On the evaluation of the nonisothermal kinetic parameters of (GeS2)0.3(Sb2S3)0.7 crystallization using the IKP method

The isoconversional method suggested by Friedman and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the nonisothermal crystallization of (GeS₂)_0.3(Sb₂S₃)_0.7. The objective of the paper is to show the usefulness of the IKP method both for determining the activation parameters as well as the model of the investigated process. It was shown that the kinetic triplet [(E, A, f(α), where E is the activation energy, A is the preexponential factor, and f(α) is the differential function of conversion], which results through the application of the IKP method, depends on the set of kinetic models considered. For different sets of kinetic models, proportional values of f(α) are obtained. A criterion for the selection of this set, the use of which lead to the true kinetic triplet corresponding to the analyzed process (E = 163.2 kJ mol^?1; A = 2.47 × 10¹² min^?1 and the Avrami‐Erofeev model, A_m, for m = 2.5–2.6 was suggested. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 309–315, 2004     

Kinetics of the exothermic decomposition of 1-nitro-3-(β,β,β-trinitroethyl)-4,5-dinitroiminoimidazolidine-2-one

The kinetic parameters of the exothermic decomposition of the title compound in a temperatureprogrammed mode have been studied by means of DSC. The DSC data obtained are fitted to the integral, differential, and exothermic rate equations by the linear least-squares, iterative, combined dichotomous, and least-squares methods, respectively. After establishing the most probable general expression of differential and integral mechanism functions by the logical choice method, the corresponding values of the apparent activation energy (E _a), preexponential factor (A), and reaction order (n) are obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential form and the values of E _a and A of this reaction are (1 − α)^−4.08, 149.95 kJ mol⁻¹, and 10^14.06 s⁻¹, respectively. With the help of the heating rate and kinetic parameters obtained, the kinetic equation of the exothermic decomposition of the title compound is proposed. The critical temperature of thermal explosion of the compound is 155.71°C. The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal explosion rule of the title compound. The text was submitted by the authors in English.     

Kinetic Analysis of Nonisothermal Decomposition of Acetyl Ferrocene

The work deals with thermal decomposition of acetyl ferrocene in nitrogen atmosphere based on nonisothermal thermogravimetry. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetic parameters. Model free (integral isoconversional) methods are employed to analyze the thermogravimetric data. The decomposition is a multistep process. The activation energy E_α of decomposition is conversion (α) dependent. The average values of activation energy are E_α = 49.87, 106.28, and 183.35 kJ mol⁻¹ for three major steps of decomposition. The most probable reaction mechanism function, g(α), for thermal reactions has been identified by the master plot method, and the stepwise reaction mechanisms are found to be different for different steps. The estimated values of the activation energy E_α and g(α) have been utilized in the determination of the reaction rate A_α of thermal decomposition. The α‐dependent reaction rate values are determined and are found to lie in the range of 5.2 × 10⁵ to 3.2 × 10⁴ min⁻¹, 1.7 × 10¹⁵ to 7.8 × 10⁶ min⁻¹, and 3.8 × 10⁸ to 1.4 × 10⁷ min⁻¹ for three different steps. Based on the values of E_α, g(α), and A_α, the thermodynamic triplets (ΔS, ΔH, ΔG) associated with the decomposition reactions have been estimated. Estimated kinetic parameters have been used to construct the conversion curves, and those have been successfully compared with the experimentally observed ones.     

Synthesis,crystal structure,and thermal decomposition kinetics of complex [Nd(BA)<Subscript>3</Subscript>bipy]<Subscript>2</Subscript>

The complex of [Nd(BA)₃bipy]₂ (BA = benzoic acid; bipy = 2,2′-bipyridine) has been synthesized and characterized by elemental analysis, IR spectra, single crystal X-ray diffraction, and TG/DTG techniques. The crystal is monoclinic with space group P2(1)/n. The two–eight coordinated Nd³⁺ ions are linked together by four bridged BA ligands and each Nd³⁺ ion is further bonded to one chelated bidentate BA ligand and one 2,2′-bipyridine molecule. The thermal decomposition process of the title complex was discussed by TG/DTG and IR techniques. The non-isothermal kinetics was investigated by using double equal-double step method. The kinetic equation for the first stage can be expressed as dα/dt = A exp(−E/RT)(1 − α). The thermodynamic parameters (ΔH ^≠, ΔG ^≠, and ΔS ^≠) and kinetic parameters (activation energy E and pre-exponential factor A) were also calculated.     

Comparative kinetic study of decomposition of some diazepine derivatives under isothermal and non-isothermal conditions

Thermal analysis is one of the most widely used methods for studying the solid state of pharmaceutical substances. TG/DTG and DSC curves provide important information regarding the physical properties of the pharmaceutical compounds (stability, compatibility, polymorphism, kinetic analysis, phase transitions etc.). The purpose of a kinetic investigation is to calculate the kinetic parameters and the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the diazepam, nitrazepam and oxazepam thermal decomposition was performed, under non-isothermal and isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 483, 498, 523, 538 and 553 K. The TG/DTG data were processed by three methods: isothermal model-fitting, Friedman’s isothermal-isoconversional and Nomen-Sempere non-parametric kinetics. In the model-fitting methods the kinetic triplets (f(α), A and E _a) that defines a single reaction step resulted in being at variance with the multi-step nature of diazepines decomposition. The model-free approach represented by isothermal and non-isothermal isoconversional methods, gave dependences of the activation energies on the extent of conversion. It is very difficult to obtain an accord with the similar data which resulted under non-isothermal conditions from a previous work. The careful treatment of the kinetic parameters obtained in different thermal conditions was confirmed to be necessary, as well as a different strategy of experimental data processing.     

Kinetic of decomposition of some complexes under non-isothermal conditions

Kinetics of thermal decomposition of three structurally similar complexes Co₂Cu(C₂O₄)₃ (R-diam)₂, where R is ethyl, 1,2-propyl or 1,3-propyl, was studied under non-isothermal conditions and nitrogen dynamic atmosphere at heating rates of 5, 7, 10, 12 and 15 K min⁻¹. For data processing the Flynn-Wall-Ozawa and a modified non-parametric kinetic methods were used. By both methods the activation energy are in the range of 97–102 kJ mol⁻¹. The formal kinetic is r=kα(1−α)². Also a compensation effect between lnA and E was evidenced. The kinetic analysis lead to the conclusion of an identic decomposition mechanism by a single step process.     

Non-isothermal kinetics of dehydration of equilibrium swollen poly(acrylic acid) hydrogel</o:p>

Summary Kinetics of dehydration of equilibrium swollen poly(acrylic acid) hydrogel was investigated using methods of non-isothermal thermal analysis. Methods of Kissinger, Coats-Redfern, Van Krevelen and Horowitz-Metzger were applied for determination the kinetics parameters: activation energy (E), pre-exponent (lnA) as well as the kinetics model ƒ(69) for the process of hydrogel dehydration under different heating rates. An existence of good agreement between determined values of kinetic parameters (Eand A), which were obtained applying different methods under the same heating rate. Functional relationship between changes of kinetic parameters of dehydration and changes of heating rate was established. An existence of compensation effect is accepted and explanation of compensation effect appearance during the hydrogel dehydration is suggested.     

Mechanism and kinetics of crystallization of α-Fe in amorphous Fe81B13Si4C2 alloy

The non-isothermal crystallization of α-Fe from Fe₈₁B₁₃Si₄C₂ amorphous alloy was investigated. The kinetic parameters of crystallization process were determined by Kissinger and Kissinger–Akahira–Sunose (KAS) methods. It was established that the kinetic parameters of transformation do not change with the degree of crystallization in the range of 0.1–0.7. The kinetic model of the crystallization process was determined using the Malek's procedure. It was established that the primary crystallization α-Fe phase from amorphous alloy can be described by Šesták–Berggren autocatalytic model with kinetic triplet E_a = 349.4.0 kJ mol⁻¹, ln A = 50.76 and f(α) = α^0.72(1 − α)^1.02.     

Comparative kinetic study of the non-isothermal thermal curing of <Emphasis Type="Italic">bis</Emphasis>-GMA/TEGDMA systems

The thermal polymerization kinetics of dimethacrylate monomers was studied by differential calorimetry using non-isothermal experiments. The kinetic analysis compared the following procedures: isoconversional method (model-free method), reduced master curves, the isokinetic relationship (IKR), the invariant kinetic parameters (IKP) method, the Coats-Redfern method and composite integral method I. Although the study focused on the integral methods, we compared them to differential methods. We saw that even relatively complex processes (in which the variations in the kinetic parameters were only slight) can be described reasonably well using a single kinetic model, so long as the mean value of the activation energy is known (E). It is also shown the usefulness of isoconversional kinetic methods, which provide with reliable kinetic information suitable for adequately choosing the kinetic model which best describes the curing process. For the system studied, we obtained the following kinetic triplet: f(α)=α^0.6(1−α)^2.4, E=120.9 kJ mol⁻¹ and lnA=38.28 min⁻¹.