Academic literature on the topic 'Thermal decomposition (TG, DTG, SDTA)'

The thermal decomposition of brominated butyl rubber under air atmosphere was investigated by thermogravimetry (TG) and derivative thermogravimetry (DTG) at various heating rates. The kinetic parameters were evaluated by TG and the isoconversional method developed by Ozawa. One prominent decomposition stage was observed in the DTG curves at high heating rates, while an additional small peak was observed at low heating rates. The apparent activation energy determined using the TG method ranged from 219.31 to 228.13 kJ·mol−1 at various heating rates. The non-isothermal degradation was found to be a first-order reaction, and the activation energy, as determined by the isoconversional method, increased with an increase in mass loss. The kinetic data suggest that brominated butyl rubber has excellent thermal stability. This study can indirectly aid in improving rubber pyrolysis methods and in enhancing the heat resistance of materials.

The thermal behavior and thermal decomposition kinetic parameters of podophyllotoxin (PPT) and 4-demethypodophyllotoxin (DMPPT) in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for leading stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analysis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of both decomposition reactions in differential form was (1-α) 2. The values of Ea indicated that the reactivity of PPT was higher than that of DMPPT in the thermal decomposition reaction. The values of the entropy of activation ΔS≠, enthalpy of activation ΔH≠ and free energy of activation ΔG≠ of the reactions were estimated.

This work investigates kinetics and thermal decomposition behaviors of pentaerythritol tetranitrate (PETN) and two polymer-bonded explosive (PBX) samples created from PETN (named as PBX-PN-85 and PBX-PP-85) using the vacuum stability test (VST) and thermogravimetry (TG/DTG) techniques. Both model-free (isoconversional) and model-fitting methods were applied to determine the kinetic parameters of the thermal decomposition. It was found that kinetic parameters obtained by the modified Kissinger–Akahira–Sunose method (using non-isothermal TG/DTG data) were close to those obtained by the isoconversional and model-fitting methods that use isothermal VST data. The activation energy values of thermal decomposition reactions were 125.6–137.1, 137.3–144.9, and 143.9–152.4 kJ·mol−1 for PBX-PN-85, PETN, and PBX-PP-85, respectively. The results demonstrate the negative effect of the nitrocellulose-based binder in reducing the thermal stability of single PETN, while the polystyrene-based binder seemingly shows no adverse influence on the thermal decomposition of PETN in our presented PBX compositions.

The thermal behavior and thermal decomposition kinetic parameters of podophyllic acid and picropodophyllic acid in a temperature-programmed mode have been investigated by means of DSC and TG-DTG. The kinetic model functions in differential and integral forms of the thermal decomposition reactions mentioned above for leading stage were established. The kinetic parameters of the apparent activation energy Ea and per-exponential factor A were obtained from analysis of the TG-DTG curves by integral and differential methods. The most probable kinetic model function of the decomposition reaction in differential form was 2/3•α-1/2 for podophyllic acid and 1/2• (1-α)-1 for picropodophyllic acid. The values of Ea indicated that the reactivity of picropodophyllic acid was highter than that of podophyllic acid in the thermal decomposition reaction. The values of the entropy of activation ΔS≠, enthalpy of activation ΔH≠ and free energy of activation ΔG≠ of the reactions were estimated.

:The thermal behavior and thermal decomposition kinetic parameters of ethane-1,2-diamine copper (II) chloride (EDCC) in a temperature-programmed mode have been investigated by mean of TG-DTG. There are four stages in the thermal decomposition process. The kinetic parameters of the apparent activation energyEa(130.2, 143.6 and 158.9 KJ·mol–1) and per-exponential factorA(1011.80, 1012.18and 1011.83s–1) in II, III and IV stages were obtained from analysis of the TG-DTG curves by Kissinger method. The values ofEaindicated that the difficulty coefficient of pyrolysis in II, III and IV stages was increased in the order: II < III < IV. The values of the entropy of activation ΔS≠, enthalpy of activation ΔH≠and free energy of activation ΔG≠of the reaction were estimated.

Abstract The paper presents the results of thermal analysis of polymer material in the form of starch derivatives in the form of sodium carboxymethyl starch (CMS–Na) with degree of substitution (DS) in the range 0.2–0.9 for the preparation of foundry binder. In this work, the thermal behavior of the modified starch and qualitative assessment of degradation products released during pyrolysis were determined and comprised. The analysis of the course of progressive decomposition of the starch material under controlled heating in the range of 25–1000 °C in anaerobic atmosphere was based on the results of thermal analysis methods (TG–DTG–DSC) in combination with the results of pyrolysis–gas chromatography–mass spectrometry (Py–GC/MS). The detailed TG–DTG–DSC analysis allowed to determine and compare the temperature at which the process of decomposition of carboxymethyl starches sodium salts with different degrees of substitution begins and to determine the course of its degradation under conditions corresponding to the contact of the foundry binder in the form of starch material with liquid metal (conditions like in foundry mold). Thermogravimetric analysis shows that decomposition processes are multistage, and dehydration is the first step of decomposition. Moreover, TG–DTG–DSC analyses indicate that the thermal stability and the decomposition path of tested compounds depend on the DS. Results of Py–GC/MS studies showed that the formation of decomposition products (including cyclic and aromatic hydrocarbons) in a predetermined temperature range is lower in the case of CMS–Na with high DS.

The thermal reaction kinetics of fly ash cement pastes were studied by Differential Scanning Calorimetry (DSC) and Thermal Gravity Analysis-Differential Thermal Gravity (TG-DTG) method, the kinetics parameters such as apparent activation energy was calculated by the Kissinger method, and the physical parameters were obtained. The result show that the fly ash cement pastes performance three endothermic reaction stages at different heating rates, peak temperatures of each stage at the range of 91.85~121.08°C, 453.93~496.48°C, and 680.21~751.62°C. TG-DTG show there were three thermal decomposition stages, thermal dehydration reaction apparent activation energy of fly ash cement pastes in each stage were 47.23kJ/mol, 128.84kJ/mol, and 134.07kJ/mol.

Magnesium hydroxide sulfate hydrate (MHSH) whiskers were prepared using brine, sodium hydroxide and sodium sulfate as raw materials by one-step hydrothermal process. X-ray powder diffraction (XRD), thermal analysis (TG-DTG) and scanning electron microscope (SEM) were employed to characterize the MHSH whiskers. It was shown that the MHSH whiskers were MgSO4•5Mg(OH)2 •2H2O with a diameter of 0.2–0.3 μm and a length of 20–30 μm . The thermal decomposition of MHSH whisker was demonstrated a three-step scheme based on the TG-DTG data. The utilization ratio of magnesium in brine was above 80%.

Actived carbon can be widely used as adsorbent, catalyst and catalyst support for many chemical reactions. At present, the research on thermal analysis Kinetics of actived carbon is quite few.Studing on it,is helpful for disclosing the decomposition reaction process and thermodynamic law of actived carbon. By thermal analysis, thermal decomposition Characteristics of actived carbon is studied. The TG and DTG eurves of actived carbon were obtain ed using multiple heating rate method.The test data were processed by iso-conversional method to obtain the kinetic parameters.The results showed that, with the improving of heating rate , the startimg reaction temperature of TG and the peak temperature of DTG shifted to the high temperature zone, postponement phenomena occurred.Based on the collected experimental data, it proved that had better linear relations with . The activation energy E of decomposition reaction of actived carbon, which was determined by measurements of slope, was 96.59kJ/mol. The plot of vs was drew and a straight line was obtained. .The mechanism function was defined as ,so according to the slope and intercept of the line,it can be obtained that n=3.585,A=40189.85984.

Copper malonate crystals were grown using silica gel as the growth medium. The grown crystals were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT Raman). The thermal decomposition of the compound was investigated using thermogravimetry (TG) and derivative thermogravimetry (DTG) measurements.

Este trabalho tem por objetivo a caracterização comparativa do comportamento de degradação e/ou decomposição térmica da esponja sintética dupla face, base poliuretana (parte amarela e parte verde), e da palha de aço, a partir das técnicas termoanalíticas. As esponjas sintéticas para limpeza doméstica, em substituição à palha de aço, apesar da vantagem econômica, podem apresentar restrições de descartes para o meio ambiente ou expor o usuário a riscos de contaminação. Amostras de esponja sintética dupla face (verde e amarela) e de palha de aço foram caracterizadas por análise térmica (TG/DTG, DTA e DSC) empregando atmosfera dinâmica de ar e de N2. Essas amostras foram estudadas por métodos cinéticos por termogravimetria isotérmica e não isotérmica. Os parâmetros cinéticos obtidos permitiram estimar os tempos necessários para a decomposição de ambas as partes da amostra da esponja sintética e também da palha de aço sob atmosfera de ar. Os resultados evidenciaram claramente que a matriz polimétrica da esponja sintética para ser degradada completamente exige um tempo muito longo, acima de 20.000 anos. Por outro lado, os resultados indicaram comportamento similar entre as amostras de esponja sintética e de palha de aço considerando apenas o efeito temperatura e tipo de atmosfera. Contudo, no cotidiano sabe-se que a palha de aço se oxida muito facilmente sob atmosfera de ar na presença de umidade.
This work aims at a comparative characterization of degradation behavior and/or thermal decomposition of synthetic double-face sponge, polyurethane base (yellow part and green part), and steel wool, from thermoanalytical techniques. Synthetic sponges for household cleaning, replacing steel wool, despite the economic advantage, may have restrictions on discharges to the environment or expose the user to risks of contamination. Samples dual synthetic sponge face (green and yellow) and steel wool were characterized by thermal analysis (TG/DTG and DTA DSC) employing an atmosphere of air and N2. These samples were studied by kinetic methods isothermal and non-isothermal thermogravimetric analysis. The kinetic parameters obtained allowed the estimation necessary for decomposition of the sample both sides of the synthetic spomge and also of steel straw times under air atmosphere. The results clearly showed that polymetric matrix of synthetic sponge to be degraded completely requires a very long time, over 20,000 years. Moreover, the results showed similar behavior among synthetic sponge and steel wool sample considering only the effect of temperature and type of atmosphere. However, in daily life it is known that the steel wool oxidizes very easily under air atmosphere in the presence of moisture.

Atualmente, a participação da energia elétrica na matriz energética mundial é um assunto em evidência. O estudo do compósito isolante da barra estatórica, um dos componentes principais da máquina hidrogeradora, permite a obtenção de informações físico-químicas relevantes ao aperfeiçoamento do sistema, e também de estudos de comportamento térmico quando este é exposto à alta temperatura, por diferentes intervalos de tempo submetidos a estresses mecânicos, elétricos e/ou químicos. O sistema em estudo é o MICALASTIC®, desenvolvido pela empresa Siemens em 1960. Neste trabalho, as propriedades térmicas do compósito isolante, formado por uma fita de mica, resina epóxi (DGEBA), endurecedor (MHHPA) e acelerador naftenato de zinco (N-Zn) foram estudadas. Utilizando-se as técnicas termoanalíticas Calorimetria Exploratória Diferencial (DSC) e Termogravimetria e Termogravimetria Derivada (TG/DTG), o comportamento térmico de cada um dos materiais foi avaliado. As curvas DSC e TG/DTG também evidenciaram as possíveis interações químicas entre os componentes. Os estudos referentes à cura do material e da degradação térmica do compósito curado foram realizados. Observou-se claramente a influência da quantidade de acelerador na polimerização do sistema. A partir das curvas DSC, observou-se dois mecanismos de cura diferentes coexistentes, um com menor quantidade de N-Zn e outro com concentração maior, resultando em eventos de cura com início em temperaturas diferentes. Esse fato ainda não havia sido estudado desde a origem do sistema. Além disso, a perda de massa referente à evaporação do endurecedor no início do processo de cura foi confirmada a partir da caracterização do compósito por espectroscopia de absorção na região do infravermelho, comparando-se os espectros antes e após o fenômeno. Na prática, dois perfis de impregnação, o Homogêneo e o Heterogêneo, de barras condutoras são utilizados, e uma diferença significativa entre eles foi observada. Os estudos desenvolvidos devem ser associados a testes elétricos específicos para o melhor entendimento da relação entre a aplicação do material e suas propriedades teóricas termoanalíticas. Além disso, foi realizado o estudo cinético da decomposição térmica do compósito curado por métodos termogravimétricos, isotérmico e dinâmico.
Currently, the electric energy participation in the world energy matrix is a significant issue. The insulating composite in stator bars, which are one of the most important components in hydrogenerator machines, allows the attainment of relevant physical and chemical information to system optimization, in addition to study thermal behavior when the material is exposed to high temperatures, for different time intervals and mechanical, chemical and/or electrical stress. The studied system is MICALASTIC®, developed by Siemens Company in 1960. In this work, thermal properties of this insulating composite, composed by mica tape, epoxy resin (DGEBA), hardener (MHHPA) and zinc naphtenate (N-Zn) as accelerator, were studied. Using thermoananalytical techniques as Differential Scanning Calorimetry (DSC) and Thermogravimetry and Derivative Thermogravimetry (TG/DTG), thermal behavior of each material was evaluated. DSC and TG/DTG curves evidenced chemical interactions between components. The study relative to material curing and cured composite thermal degradation were described. It was clearly observed the N-Zn amount influence in the cure of system, and through DSC curves, it was possible to observe two distinct polymerization coexisting mechanisms, one with lower quantity of N-Zn and another one with bigger concentration, resulting in cure events starting in different temperatures. This fact has not been studied yet since the system has been originated. Besides that, the weight loss related to hardener evaporation starting with curing process was confirmed by composite characterization by FTIR spectra, before and after phenomenon. In practice, two impregnation patterns (Homogeneous and Heterogeneous) of conductive bars are used and a significant difference between them was observed. The developed studies have to be associated to electrical tests to a best understanding about material application and theoretical thermoanalytical properties. In addition, it was performed thermal decomposition of cured composite kinetic study by isothermic and dynamic thermogravimetric methods