Kissinger Akahira Sunose Method Research Articles

Kinetic study on the thermal degradation of ethylene–norbornene copolymers under the effect of Fe and Mn stearates

A kinetic study on the thermal degradation of ethylene–norbornene cyclic olefin copolymers (COCs), pristine and formulated with iron and manganese stearate, was performed. Three different COCs with cyclic structure (norbornene) contents of 30 mol% (COC30), 38 mol% (COC38), and 55 mol% (COC55) were analyzed. The thermal degradation order (n), activation energy (E a), and pre-exponential factor (A) were evaluated using multiple heating rates based on three different “model-free” methods: Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose (KAS) and Friedman (FR). The thermal stability of virgin and formulated COC films with ferric and manganese stearates were calculated using a non-isothermal thermogravimetric analysis (TGA) and derivative thermogravimetric analysis. The reaction order of the thermodegradation of the tested copolymers was close to unity according to the KAS and FR methods. The calculated E a for pristine copolymers increased from 232 to 254 kJ mol−1 when the content of cyclic norbornene units in the pure copolymers was diminished from 55 to 30 mol%. The calculated E a for the stearate-formulated COC copolymers had values between 214 and 238 kJ mol−1. TGA curves of the thermal degradation in a nitrogen atmosphere show a one-step reaction in the range of temperatures between 30 and 600 °C. It was found that manganese stearate is more efficient than ferric stearate in initiating the thermodegradation of COC38 and COC55 copolymers.

Investigation of crystallization kinetics and deformation behavior in supercooled liquid region of CuZr-based bulk metallic glass

Abstract In this paper, a systematic study of crystallization kinetics and deformation behavior is presented for (Cu50Zr50)94Al6 bulk metallic glass in the supercooled liquid region. Crystallization results showed that the activation energy for (Cu50Zr50)94Al6 was calculated using the Arrhenius equation in isothermal mode and the Kissinger–Akahira–Sunose method in non-isothermal mode. The activation energy was quite high compared with other bulk metallic glasses. Based on isothermal transformation kinetics described by the Johson–Mehl–Avrami model, the average Avrami exponent of about 3.05 implies a mainly diffusion controlled three-dimensional growth with an increasing nucleation rate during the crystallization. For warm deformation, the results showed that deformation behavior, composed of homogeneous and inhomogeneous deformation, is strongly dependent on strain rate and temperature. The homogeneous deformation transformed from non-Newtonian flow to Newtonian flow with a decrease in strain rate and an increase in temperature. It was found that the crystallization during high temperature deformation is induced by heating. The appropriate working temperature/strain rate combination for the alloy forming, without in-situ crystallization, was deduced by constructing an empirical deformation map. The optimum process condition for (Cu50Zr50)94Al6 can be expressed as T∼733 K and ε . ${\rm{\dot \varepsilon }}$ ∼ 10−3 s−1.

Analysis of pyrolysis characteristics and kinetics of sweet sorghum bagasse and cotton stalk

The pyrolysis kinetic behavior of sweet sorghum bagasse (SSB) and cotton stalk (CS) samples was investigated in this work. Thermogravimetric analysis of two samples at five heating rates (15, 25, 35, 45 and 55 °C min−1) in nitrogen atmosphere was performed. Results show that the pyrolysis trends of SSB and CS in their respective five heating rates are similar. The thermal decomposition process of the SSB and CS can be divided into four stages. With the heating rate increasing, the main pyrolysis stage appeared thermal hysteresis phenomenon, the whole TG and DTG curves shifted to the higher temperature area, and the maximum pyrolysis rate increased too. For the kinetic analysis, fifteen degrees of conversion (α) were selected between 10 and 80% using the two isoconversional methods of Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO). The average activation energies for SSB and CS were found to be between 154.61 and 142.93 kJ mol−1 by KAS method and 155.61 and 145.39 kJ mol−1 using FWO method, respectively. Also, the variation of activation energy with the degree of conversion shows the apparent activation energies changed with the conversion degree, rising in an irregular jagged trend. The apparent activation energy value of SSB is also seen to be higher than that of CS at the same degree of conversion (α) except when it is 80% which gives lower value. The works therefore provide useful information for understanding energy requirement in pyrolysis process of biomass and in pyrolysis system design.

Non-isothermal kinetics of epoxy resin curing reaction under compressed CO2

The non-isothermal curing kinetics of epoxy resin system consisting of diglycidyl ether of bisphenol A (DGEBA) and m-xylylenediamine (MXDA) were investigated by high-pressure differential scanning calorimetry at different heating rates of 5, 10, 15 and 20 K min−1 under compressed carbon dioxide (CO2) of 0.1–8 MPa. The activation energies were determined by isoconversional Kissinger–Akahira–Sunose method and Vyazovkin numerical method, and the average values decreased from 53.5 to 46.8 and 54.1 to 44.5 kJ mol−1, respectively, when the CO2 pressure increased from 0.1 to 8 MPa. It is indicated that the curing reaction of epoxy resin occurs more easily under higher-pressure CO2 due to the promoted molecular movement, especially in the supercritical state. The non-isothermal curing kinetics were investigated by nth-order model and two-parameter autocatalytic model (Sestak–Berggren model), and the latter one analyzed by Malek method exhibited good agreement with the experimental data except the initial and final stages of the curing reaction.

Non-isothermal Crystallization Kinetics and Isothermal Crystallization Kinetics in Supercooled Liquid Region of Cu–Zr–Al–Y Bulk Metallic Glass

The crystallization kinetics of Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 bulk metallic glasses in non-isothermal and isothermal conditions was studied by differential scanning calorimetry. In the non-isothermal and isothermal modes, the average activation energy of (Cu43Zr48Al9)98Y2 is larger than that of Cu43Zr48Al9, meaning the higher stability against crystallization of (Cu43Zr48Al9)98Y2. In addition, the average activation energies for Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 calculated using Arrhenius equation in isothermal mode are larger than the values calculated by Kissinger–Akahira–Sunose method in non-isothermal mode, indicating that the energy barrier is higher in isothermal mode. The Johnson–Mehl–Avrami model was used to analyze the crystallization kinetics in the non-isothermal and isothermal modes. The Avrami exponent n for Cu43Zr48Al9 is above 2.5, indicating that the crystallization is mainly determined by a diffusion-controlled three-dimensional growth with an increasing nucleation rate, while the Avrami exponent n for (Cu43Zr48Al9)98Y2 is in the range of 1.5–2.5 in the non-isothermal mode, implying that the crystallization is mainly governed by diffusion-controlled three-dimensional growth with decreasing nucleation rate. Finally, the Avrami exponents n for Cu43Zr48Al9 and (Cu43Zr48Al9)98Y2 are different in the non-isothermal and isothermal conditions, which imply different nucleation and growth behaviors during the crystallization processes.

Characteristics and kinetics study of simultaneous pyrolysis of microalgae Chlorella vulgaris, wood and polypropylene through TGA

Thermal decomposition behavior and kinetics of microalgae Chlorella vulgaris, wood and polypropylene were investigated using thermogravimetric analysis (TGA). Experiments were carried out at heating rates of 10, 20 and 40°C/min from ambient temperature to 600°C. The results show that pyrolysis process of C. vulgaris and wood can be divided into three stages while pyrolysis of polypropylene occurs almost totally in one step. It is shown that wood can delay the pyrolysis of microalgae while microalgae can accelerate the pyrolysis of wood. The existence of polymer during the pyrolysis of microalgae or wood will lead to two divided groups of peaks in DTG curve of mixtures. The results showed that interaction is inhibitive rather than synergistic during the decomposition process of materials. Kinetics of process is studied by the Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The average E values obtained from FWO and KAS methods were 131.228 and 142.678kJ/mol, respectively.

Oil Shale Pyrolysis: Conversion Dependence of Kinetic Parameters

Oil can be recovered from kerogen in oil shale by pyrolysis. The devolatilization kinetics of the pyrolysis of oil shale from the Irati Formation in Brazil was studied. Kinetic parameters were determined from dynamic thermogravimetric analysis over the temperature range 323–1173 K, using different model-free methods. Evaluation and validation were performed by pyrolysis at 673 K for 3 hours. It was found that the activation energy depended on the extent of conversion. Activation energy increased over the range 215–255 kJ/mol for conversion in the range 0.15 ≤ α ≤ 0.55, where α = 1 for pyrolysis at 1173 K. When the reaction rate was high, the conversion calculated using kinetic parameters derived by the Friedman method was more accurate than those calculated from the Flynn–Wall–Ozawa and the Kissinger–Akahira–Sunose methods. The latter two methods performed better when the reaction rate was lower, i.e., at higher conversion. Isothermal kerogen pyrolysis approached an incomplete conversion limit that could ...

Synthesis and characterization of methacrylamide-acrylic acid-N-isopropylacrylamide polymeric hydrogel: degradation kinetics and rheological studies

Methacrylamide-acrylic acid-N-isopropylacrylamide terpolymeric hydrogels have been prepared via free radical polymerization using diammonium-peroxo-disulphate initiator system and ethylene glycol-di-methacrylate as a cross-linker. The hydrogels were characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Molar mass was determined by viscometric method. Rheological profiling of the hydrogels was carried out by rheological measurements at various temperatures and methacrylamide contents in hydrogels. Thermogravimetric data were analyzed to assess the kinetic triplet by iso-conversional method. The values of apparent activation energy (E a) figured out from TG data were measured for each step by Kissinger–Akahira–Sunose method. On the findings of results, the decomposition reaction of terpolymeric hydrogels has been analyzed as a slow reaction, which is evident from the low-frequency factor values (A), i.e., 3 × 106, 2 × 1010, and 4 × 1015 s−1, respectively. The master plot method was used to predict the mechanism for degradation of MANIPAM-7. Flow curve and frequency sweep tests at different temperatures showed temperature dependency with shear rate indicating the pseudo-plastic nature of the synthesized samples. The rheological parameters were analyzed using various models. Out of these methods, the Ostwald, modified Bingham, and Herschel–Bulkley models were established to provide better fit to experimental data. Dynamic moduli measured as a function of angular frequency showed viscoelastic nature of all the samples. Frequency sweep studies indicated that storage (G′) and loss modulus (G″) showed an increase with increasing concentration of methacrylamide. Composition dependency of crossover frequency directed an increase in relaxation time with methacrylamide contents in the hydrogel.

Thermal stability and non-isothermal crystallization kinetics of Pd82Si18 amorphous ribbon

Rapidly quenched Pd82Si18 ribbon was prepared by melt spinning. The thermal stability and non-isothermal crystallization kinetics of Pd82Si18 amorphous ribbon were investigated by differential scanning calorimeter measurements. Its structure was investigated by X-ray diffraction and transmission electronic microscopy. The activation energy was calculated by the Kissinger method, and the nucleation and growth during non-isothermal crystallization were investigated by the local activation energy and local Avrami exponent. The average activation energy for Pd82Si18 amorphous ribbon based on the Kissinger method is 330.672 kJ/mol, indicating that it has high thermal stability. The local activation energy of the glass ribbon was determined by the Kissinger–Akahira–Sunose method, and the local Avrami exponent was obtained based on the Johnson–Mehl–Avrami model. The calculated local activation energy increases to a maximum when the crystallization column fraction reaches 0.3, and it then decreases, which shows that crystallization is a multistep process. The local Avrami exponent indicates that the crystallization process of Pd82Si18 amorphous ribbon is controlled by volume nucleation with three-dimensional growth at various nucleation rates.

Thermal degradation of poly(lactic acid) and acrylonitrile-butadiene-styrene bioblends: Elucidation of reaction mechanisms

Square plates (nominal tickness: 3mm, nominal width: 100mm) of diferent rheolgically modified PLA/acrylonitrile-butadiene-styrene (ABS) blends were manufactured through injection molding process. During processing, the properties of the melt were stabilized and enhanced by the addition of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent (SAmfE). The general analytical equation has been used in order to evaluate the kinetic parameters of the thermal degradation of PLA-REX, ABS and its bioblend with a weight content of 70/30. Various empirical and theoretical solid-state mechanisms have been tested to elucidate the best kinetic model. In order to reach this goal, activation energy values were calculated by means of the Kissinger–Akahira–Sunose method. On the other hand, the standardized conversion functions have been constructed. Given that it is not always easy to visualize the best accordance between experimental and theoretical values of standardized conversion functions, a recently proposed index has been determined to quantitatively support our findings relative to the best reaction mechanisms. It has been demonstrated that the best mechanism for the thermal degradation of PLA-REX and ABS was the random scission of macromolecular chains. The bioblend thermal degradation occurred in two steps: the first step (α<60%) took place through an R2 mechanism whereas the second step (α>75%) did it according an F3 mechanism. Moreover, y(α) master plots have also been used in order to confirm that the selected reaction mechanisms were adequate.

Thermal and Kinetic Behaviors of Fallen Leaves and Waste Tires Using Thermogravimetric Analysis

Thermal decomposition characteristics and kinetic parameters of fallen leaves (FLs), waste tires (WTs), and their blends (1:1 weight ratio) were investigated. Pyrolysis experiments were conducted with four different heating rates of 5 °C/min, 10 °C/min, 20 °C/min, and 40 °C/min from 35 °C to 800 °C in a nitrogen atmosphere using a thermogravimetric analysis (TGA). The thermogravimetry/derivative thermogravimetry (TG/DTG) curves indicated that the three samples were mainly degraded in a wide temperature range of 350 °C to 450 °C, and that a greater weight loss rate corresponded to a higher heating rate. An elemental analysis demonstrated that FLs/WTs blends embraced a maximum calorific value that reached 25.24 MJ/kg. Two model-free methods, iso-conversional Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) were applied on the TGA data of samples to calculate the activation energies. The results showed that the average activation energies of the same feedstock based on KAS and FWO methods were approximately the same, with the highest error within 1.6%. Then, the activation energies obtained were introduced in the Coats/Redfern (CR) model-fitting method to derive the pre-exponential factors, based on first order rate of reaction.

Thermal Degradation of Flame Retarded Polyvinylchloride Cable Sheath in Air Atmosphere

A series of thermogravimetric experiments from 10 K/min to 50 K/min was performed to analyse the pyrolysis behaviours and reaction kinetics of typical old flame-retarded PVC cable sheath in air atmosphere. Two model-free methods of Flynn-Wall-Ozawa (FWO) method and Kissinger-Akahira-Sunose (KAS) method were used to estimate the activation energy, as well as the model-fitting method called Coats-Redfern (CR) method. Three peaks can be observed in mass loss rate profiles and the first peak value is much larger than the other two. Due to the oxidation of carbon or others, the first and third peak values in air atmosphere are significantly larger, and the final residue mass fraction in air atmosphere is around 62% the one in Nitrogen atmosphere. FWO method predicts the activation energy of 223.1kJ/mol while KAS model estimates the one of 223.7kJ/mol in air atmosphere, and both have the deviation of 0.27%. By CR method, the most probable reaction mechanism is [1 − (1 − α)−2]/(− 2) for current fire retarded PVC cable sheath. Moreover, it estimates the activation energy of 237.6 kJ/mol, which is well agreeable with those from FWO and KAS methods.

Pyrolysis Kinetics and Emission Characteristics of Waste Disposable Paper Cups Using the Thermogravimetric-FTIR Technique

The pyrolysis of waste disposable paper cups (WDPCs) was investigated using a thermogravimetric analyser coupled with a Fourier transform infrared spectrometer. The activation energies of the pyrolysis reactions were obtained by the Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods respectively. The kinetic model was determined by the master plots method. Thermogravimetric results showed that the highest weight loss rate occurred from 345 to 365 °C as the heating rate was increased from 10 to 30 °C min−1, indicating the pyrolysis of cellulosic material in the WDPC. The weight loss between 400 and 500 °C can be attributed to the decomposition of polyethylene. By analysing the FTIR spectra, it was found that the absorbance of all the evolved gaseous products had peaks at 360 °C due to the decomposition of cellulose fibres and the cracking of polyethylene at 485 °C led to the emergence of a second hydrocarbon peak. Ketones were the most abundant condensable organic products and CO2 was the dominating gaseous product, which can also be produced via secondary cracking of the small molecule organics above 400 °C. Kinetic analysis revealed that the average activation energy of the pyrolysis of the WDPC was 153.75 kJ mol−1 from the FWO method and 151.43 kJ mol−1 from the KAS method. The reaction mechanism can be described by the R3 model.

On the variation of activation energy for amorphous–crystallization phase transition in Se–Te–Sn chalcogenide glasses using iso-conversional analysis

ABSTRACTIn this paper, the variation of activation energy of amorphous–crystallization phase transition of as-Se85–xTe15Snx (x = 2, 4 and 6) chalcogenide glasses is investigated using iso-conversional analysis under non-isothermal conditions using differential scanning calorimetric (DSC) technique. The study is based on the variation of activation energy of crystallization with the degree of conversion and hence with temperature. The three iso-conversional methods of Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW) and Friedman are used to deduce the variation of activation energy with the extent of conversion and also with temperature. The KAS and OFW methods give the similar values while the Friedman method gives lower values of activation energy of crystallization for the investigated chalcogenide glasses.

Thermal degradation kinetics and reaction models of 1,3,5-triamino-2,4,6-trinitrobenzene-based plastic-bonded explosives containing fluoropolymer matrices

In this article, thermal degradation behavior of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)-based plastic-bonded explosives (PBXs) bonded with a different fluoropolymer matrices namely indigenous poly(vinylidene fluoride-chlorotrifluoroethylene) (FKM), FK 800, fluoroplastic F-32L and fluororubber SKF 32 was investigated through non-isothermal thermogravimetric analysis (TG) technique under nitrogen atmosphere. It was observed that the mass loss of PBXs containing FKM and FK 800 matrices occurred in three steps. The mass loss of PBXs containing fluoroplastic F-32L and fluororubber SKF 32 occurred in two steps. Kinetics were investigated through non-isothermal TG at different heating rates for the first step of degradation by means of model-free Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The activation energies calculated by applying FWO method are in good agreement and very close to those obtained by KAS method. The results revealed that the effect of the polymer matrices on the thermal degradation reaction of TATB was significantly observed especially different outcomes of kinetic parameters. The reaction models for degradation were also studied by Criado method. The reaction models are probably best described by the power law and diffusion models.

TG–FTIR study on pyrolysis of waste printing paper

Pyrolysis of waste printing paper was investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG–FTIR). The activation energies of pyrolysis reactions were obtained via the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods, respectively. The kinetic model was determined by the master plot method. TG results showed that the highest mass loss rate occurred increased from 618 to 638 K as heating rate increased from 5 to 20 K min−1, indicating the pyrolysis of cellulose fibers in WPP. The mass loss above 873 K can be attributed to the decomposition of calcite used as filler. By analyzing the FTIR spectra, it was found that the major generation temperatures of the evolving gaseous products ranged from 635 to 647 K during the pyrolysis of WPP at 20 K min−1. CO2 was the primary non-condensable product, and aldehydes, organic acids, ketones were the dominating condensable products, in addition to ethers. Kinetic analysis revealed that the activation energy of the pyrolysis reaction of WPP was 189.39 kJ mol−1 for the FWO method and 189.03 kJ mol−1 for the KAS method. The reaction model function was f(α) = (1 − α)1.95, and the frequency factor A = 3.66 × 1015 min−1. All of the findings would help further understanding of pyrolysis behavior of WPP and its thermochemical utilization for fuels and chemicals.

Effect of tertiary amine accelerators with different substituents on curing kinetics and reactivity of epoxy/dicyandiamide system

Non-isothermal Differential Scanning Calorimetry and gel time measurements were employed to study the effects of four different tertiary amine accelerators with different molecular structure and substituents on the curing behavior and reactivity of epoxy/dicyandiamide (DICY) system. Results showed that the acceleration behavior depends on three factors: the bulkiness, the number of nitrogen atoms in molecular structure and the electron density of accelerator. Among these, the former two factors demonstrated stronger effect. The results of model fitting kinetic demonstrated that Šesták–Berggren model can well simulate the reaction rates especially for the samples accelerated by 2,4,6-tris(dimethylaminomethyl)-phenol and (Dimethylaminomethyl)phenol. The activation energy projected by Flynn-Wall-Ozawa and Kissinger–Akahira–Sunose methods exposed different amounts for each accelerator while both models revealed similar trends. Moreover, 1-methylimidazol-accelerated samples showed shortest storage life and gel time mainly due to the presence of two nitrogen atoms in a compact structure of accelerator.

β-Phase thermal degradation in Zr-added Cu–Zn–Al shape memory alloy

Small amounts of Zr, as a grain refiner, were added to the β Cu–Zn–Al shape memory alloy. The resulting microstructure was polycrystalline, with Zr-rich precipitates preferentially located in the grain boundary. An alloy of similar composition, without addition of Zr, was studied for comparison. The martensitic transformation and the stability of β-phase were studied by differential scanning calorimetry and optical microscopy. The activation energy of phase decomposition, within the β-phase metastability range, was determined by the Kissinger–Akahira–Sunose method, and values of 121 kJ mol−1 for Cu–Zn–Al(Zr) and 110 kJ mol−1 for Cu–Zn–Al were obtained. Furthermore, it was observed that the Zr-rich particles, responsible for controlling the grain size, were unstable during the heat treatments at temperatures within the β-phase stability range. The dissolution of precipitates leads to a gradual decrease in the volume fraction of the sample that transforms to martensite. Finally, after prolonged aging the martensitic transformation disappeared.

Thermokinetics of alkyl methylpyrrolidinium [NTf2] ionic liquids

The thermal degradation of two ionic liquids (ILs) was investigated using thermogravimetric analysis (TG) to establish a relationship between the thermokinetics and thermal stability. N-butyl, N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMPyrro][NTf2] and N-octyl, N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide[OMPyrro][NTf2] were subjected to thermogravimetric analysis at varying heating rates of 5, 10 and 20 °C min−1 in the temperature range of 50–600 °C. The data obtained were analysed for thermokinetics using Ozawa, Kissinger and Starink methods using differential thermogravimetric (DTG) techniques, and Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS) and Starink methods using TG techniques. The results produced very high regression coefficients (R 2 ) values around 0.996, which exhibited that they were best fitted by the kinetics equations. The average calculated activation energy (E a) of [BMPyrro][NTf2] using FWO, KAS and Starink methods was 128.6, 123.6 and 124 kJ mol−1, respectively, and 113.7, 107.8 and 108.2 kJ mol−1, respectively, for [OMPyrro][NTf2] using same empirical methods. This emphasizes that the activation energy is strongly related to the length of the side alkyl chain of a given IL. In other words, the longer the side alkyl chain, the lower the activation energy. The E a trends with degree of conversion (α) suggest that a single mechanism without formation of intermediates or short-life intermediates was followed by the pyrolysis kinetics. This study introduced thermokinetics as a tool to study the thermal stability of ionic liquids.

Characterization of lignocellulose biomass and model compounds by thermogravimetry

ABSTRACTIn this research, combustion characteristics of lignocellulose biomass (hazelnut shell) and three main components (cellulose, hemicellulose, and lignin) were investigated using thermogravimetry (TGA-DTG) technique at different heating rates. The ignition, peak, burn-out temperatures, and the heat liberation of lignocellulose biomass and three main components were also measured. Two different model-free kinetic methods, known as Ozawa–Flynn–Wall (OFW) and Kissinger–Akahira–Sunose (KAS), were used in order to determine the activation energy values. Throughout the study, it is observed that the activation energy values of the biomass compounds varied between 83.8 and 191.7 kJ/mol for OFW and KAS methods, respectively.