Historical review on research of kinetics in thermal analysis and thermal endurance of electrical insulating materials

In 1925 a paper on kinetic analysis of data obtained with thermobalances for isothermal mass loss of some natural products for electrical insulation was published. This is the first theoretical and experimental approach to accelerated test of electrical insulating materials and also to kinetic analysis of thermal analysis data at isoconversional points. In succeeeding papers, change in chemical composition and kinetics under temperature change were dealt with. A historical review of these two topics is described in this review article, especially on the basic concept commonly induced for these two fields.     

Historical review on research of kinetics in thermal analysis and thermal endurance of electrical insulating materials

Thermal analysis techniques, such as thermogravimetry, differential thermal analysis and evolved gas analysis, have been applied to thermal endurance evaluation of electrical insulating materials of high polymers, which are used for a long time at a relatively high operating temperature. Various attempts have been made to estimate the life time of the materials at the operating temperature by thermal analysis and a calorimetric method. These are critically described in this review paper.     

Effect of electrical charging on scanning electron microscopy-energy dispersive X-ray spectroscopy analysis of insulating materials

We investigated the conditions under which we can obtain reasonable qualitative results in scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analysis of trace elements in insulating materials using a diluted ionic liquid (EMI-CH₃COO) and changing probe current. Below 100 nA, electrical charging of insulating materials was prevented. The probe current of 10 nA was suitable for qualitative analysis because the intensities of peaks from these materials were strong enough to detect trace elements at the concentration of 0.1 wt.% in the sample without interference by sum peaks. Diluted EMI-CH₃COO can also be used for SEM-EDX quantitative analysis of insulating materials as discharging agents. In contrast, when insulating materials were electrically charged, the obtained spectra contained characteristic X-rays of the insulating materials with low energies and of materials other than the samples such as the sample stage and the collimator in the X-ray detector. This is because electrons from the electron beam were decelerated by and deflected from the insulating materials. By coating the insulating materials with the diluted EMI-CH₃COO, the deceleration and deflection of the electron beam were prevented.     

Application of thermal analysis to study the causes of disintegration in insulating systems

In the procduction of high-voltage insulating systems, disintegration and non-homogeneity occur in some cases and these factors can lead to the deterioration and even the breakdown such systems. In research into the causes of these phenomena DTA and TG were applied to study the course of hardening of the systems and to quantify the leaking substances. The results demonstrate the great value of thermal analysis in this field.     

The use of thermal and spectroscopic methods to study chemically modified materials

The application of thermal and spectroscopic techniques in the characterisation of chemically modified materials is illustrated with several examples: ethylene vinyl acetate (EVA) copolymers which had been hydrolysed under alkaline conditions, amosite asbestos fibres which had been reacted with alkyldimethylchlorosilanes, and a polymeric composite material which had been affected by moisture.The authors acknowledge the following for assistance in the project: Rhona MacBeth, Conservator, Courtauld Institute of Art and presently at the Boston Museum of Fine Arts, for the TMA measurements, conditioning of composite samples, and useful discussions. PL-Thermal Sciences (John Gearing for the DETA measurements on EVA). PL-Thermal Sciences (Epsom Laboratories) for the use of Dynamic Mechanical Thermal Analysis equipment.     

The use of thermal analysis to study thermal processing effects on polypropylene

The thermal stability of a polypropylene copolymer has been examined at several stages during the processing of the material into its final product in order to obtain information on the influence of processing steps such as grinding and thermal heating on the expected lifetime of the material. Mass loss kinetics in an inert atmosphere were able to detect differences in thermal stability, but oxidative differential scanning calorimetry studies proved to be a more sensitive techiique. A comparative study of a specially prepared series of samples revealed the importance of additives on measured thermal stability and indicated that both mechanical and thermal processing can cause reduction in measured thermal stability.     

Use of thermal analysis to predict the conditions for thermal explosion to occur: application to a Ce triethanolamine complex

Journal of Thermal Analysis and Calorimetry - Thermal energy storage (TES) has been identified as a breakthrough concept in development of renewable technologies. However, the main challenges are...     

The analysis of synthetic organic materials—A review

Synthetic organic materials consist of polymers, low-molecular-weight additives, and fillers. The review deals with the characterization of the polymer portion in the solid state by inelastic interactions with X-rays and by mass spectrometry (MS). Field desorption MS, secondary ion MS, fast atom bombardment MS, and plasma desorption MS have been used in a molar mass range up to 50000 g/mol. Electrospray or laser desorption MS enable samples of even higher molar mass to be investigated.     

Heat capacity measurement of organic thermal energy storage materials

The heat capacities of tris(hydroxymethyl)aminomethane (TRIS), 2-amino-2-methyl-1,3-propanediol (AMPL), and neopentylglycol (NPG) are measured from (193.15 to 473.15) K by modulated differential scanning calorimetry (MDSC). The heat capacities of the low temperature layered or chain ordered phases, high temperature orientationally disordered phases, and the liquid phases are reported for these compounds. The low temperature heat capacities (193.15 to 280) K of AMPL are reported for the first time. The heat capacities obtained from our MDSC experiments are in good agreement with adiabatic calorimetry measurements.     

Paper sludge functionalization for achieving fiber-reinforced and low thermal conductivity calcium silicate insulating materials

Paper sludge generated from the paper industry is classified as solid waste, comprising primarily wood fiber and calcium carbonate with low thermal conductivity. This paper is concentrated on the comparison of wood fiber and paper sludge from the structural strength and insulation property of calcium silicate insulating materials (CSIM). Test specimens with wood fiber and two different types of paper sludge were prepared by the compression molding and autoclaved curing, and DSC-TG analysis was used to compare the components and characteristic of different paper sludge. Based on the experimental results, detailed discussions on the strength, water absorption, dry density, correlation and thermal conductivity of CSIM are given. It is noted that the flexural strength of CSIM increases gradually within the increasing amount of two paper sludge from 0 to 7.5% and goes up to the highest value of 16.1 MPa and 15.1 MPa and increases about 14.2% and 7.1%. In addition, paper sludge can replace 0–0.4% of wood fiber under the requirement of the mechanical strength, and the dry density of CSIM with wood fiber is much larger than that with paper sludge. Furthermore, the addition of paper sludge in the CSIM notably decreases the thermal conductivity due to the low thermal conductivity of wood fiber and calcium carbonate. Finally, it can be concluded that the utilization of paper sludge presents a great potential to develop fiber-reinforced and low thermal conductivity CSIM and benefits to the development of waste management in producing sustainable CSIM.

     

The differential thermal analysis behavior of lead zirconate titanate materials

Differential thermal analysis has been used to examine the reactions involved in the formation of lead zirconate titanate and related materials. The reaction of PbO and TiO₂ produced an exothermic peak near 600°C, while mixtures of PbO and ZrO₂ gave endothermic peak at 760°C. Lead titanate and lead zirconate mixtures showed no evidence of reaction below 900°C. Evidence is presented which suggests that PbO and PbTiO₃ react in the vicinity of 750°C. For ternary mixtures of PbO, titanate, the thermograms indicate a complicated behavior between 600–800°C, depending on the ratios of the reactant materials. The results suggest that the calcination reaction to form lead zirconate titanate is a more complex process than has been recognized. Data on the various phase transitions for the lead zirconate titanate materials are also presented.     

Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants

The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (E_α). The increased E_α indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased E_α after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the E_α of fire-retarded cellulose thermal insulation compared with the KAS and FWO methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

     

Certified reference materials for thermal analysis

Eight inorganic substances recommended by ICTA as temperature standard reference materials for DTA and DSC were studied: KNO₃, KClO₄, Ag₂SO₄, K₂CrO₄, quartz, K₂SO₄, BaCO₃ and SrCO₃. The content of pure component in each of these substances was determined by classical chemical analysis. The temperatures and the heats of polymorphic transformations of these substances were measured with a Perkin-Elmer DSC-2 differential scanning calorimeter, and DTA studies were performed on a MOM 1500 D Q-derivatograph. The plot heat of transformation by DSCvs. DTA peak area is advanced as a calibration line for the approximate estimation of quantitative DTA effects. The substances studied will be certified as temperature standard reference materials for use in DTA and DSC.

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Zusammenfassung Acht von der ICTA als Temperaturstandard-Referenzmaterialien für DTA und DSC empfohlene und im Lande verfügbare Substanzen wurden untersucht: KNO₃,KClO₄, Ag₂SO₄, K₂Cr₂O₄, Quarz, K₂SO₄, BaCO₃ und SrCO₃. Der Gehalt der Substanzen an diesen Verbindungen wurde klassisch chemisch-analytisch bestimmt. Temperaturen und Enthalpien der polymorphen Umwandlungen wurden mit dem Gerät DSC 2 (Perkin-Elmer) bestimmt, DTA-Untersuchungen erfolgten mittels Derivatograph Q 1500 D (MOM). Eine Darstellung (Umwandlungsenthalpie aus DSC-Messung) über der DTA-peak-Flä-che wird als Eichgerade für die näherungsweise quantitative Bewertung der DTA-Effekte vorgeschlagen. Die genannten Substanzen sollen als Temperaturstandards für DTA und DSC geprüft werden.

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The use of data center recorders in thermal analysis

The application of a Data Center recorder to the thermal analysis techniques of TG, DTA and dilatometry is described. The recorder used is essentially an eight-channel data acquisition system that multiplexes and converts up to ± 10 V analog data into 12-bit digital data which are stored on a floppy disk. The stored data be recalled at the convenience of the operator and mathematically manipulated before they are replotted on the integral X–Y or Y—time plotter.     

The use of thermal analysis in medical science with special reference to nephroliths

The applications of thermal methods in medical science have been summarized, with special regard to kidney stones. Complex thermal analysis can be used successfully for examination of human and animal urinary calculi, bones, odontoliths biological tissues (proteins, skin, callus, nail) etc.

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Zusammenfassung Es wurden die Anwendungen der Thermoanalyse auf medizinischem Gebiet unter besonderer Berücksichtigung von Nierensteinen zusammenfassend behandelt. Komplexe thermoanalytische Methoden eignen sich zur Prüfung von menschlichen und tierischen Harnsteinen, Knochen, Zahnstein, biologischem Gewebe (Proteine, Haut, Nägel, usw.)

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Résumé Revue des applications des méthodes thermoanalytiques dans le domaine médical avec mention particulière pour les calculs rénaux. L'emploi des méthodes d'analyse thermique mixtes donnent de bons résultats pour l'examen des calculs rénaux animaux et humains, du tartre dentaire et des tissus biologiques (protéines, peau, ongles), etc.

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Investigation of complete oxidation of organic materials with thermal analytical measurements

The complete oxidation of styrene-divinylbenzene has been examined with complex thermoanalytical methods by derivatograph and thermogastitrimeter. With the combined application of combustion catalyst and postcatalytic method the oxidation of the styrene-divinylbenzene is complete.

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Zusammenfassung Die vollständige Oxydation von Styrol-Divinylbenzol wurde mittels einer komplexen thermoanalytischen Methode unter Verwendung eines mit einem Gastitrimeter kombinierten Derivatographen untersucht. Eine vollständige Oxydation wird bei Anwendung eines Verbrennungskatalysators und der postkatalytischen Methode erreicht.

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The use of thermogravimetric analysis technique for the characterization of construction materials

The thermogravimetric analysis (TG) technique is widely used in the characterization of diverse types of construction materials related to binders, such as plasters, limes and cements. For calcium sulphate dihydrate (gypsum) two serial dehydration steps are very near in temperature decomposition and overlapping in the thermogravimetric events is observed. The goal of this research is to develop new thermogravimetric analysis procedures that allow obtaining more precise information in the characterization of plasters. The resolution of both dehydration events has been increased using two different strategies: on one hand, the production in the experience of a water vapour self-generated atmosphere by the use of sealed aluminium pan with a pinholed lid. On the other hand, the use of high resolution thermogravimetric analysis (HRTG), based on the variation of the heating rate as a function of the rate of mass loss observed at once. The results obtained for both strategies of improvement of the TG curves, showed that they are two procedures that let to obtain a total resolution of the two dehydration steps for gypsum.     

Hydrogen-bonded network: An effective approach to improve the thermal stability of organic/polymer electro-optic materials

Preparation of PMMA-co-PHPMN-(4-hydroxyphenyl)maleimide was prepared according tothe literature [1]. The monomer mixtures, comprising of 0.6g N-(4-hydroxyphenyl)maleimide, 0.4 g MMA and 0.004 g , ′-azobisisobutyronitrile (AIBN) were dissolved in 2 mLDMF. Air above the monomers was swept out using thefreeze-pump-thaw procedure three times and filled with     

The use of complementary data in the application of thermal analysis techniques

The use of thermal analytical procedures to obtain both thermodynamic and kinetic parameters is outlined. The advantage of DTA techniques in establishing thermodynamic data is demonstrated. Kinetic data calculated from TG data is demonstrated. Kinetic data calculated from TG data leads to plots of the logarithm of the specific reaction rate constant against 1/T (whereT is the temperature in degrees Kelvin) and from this point onwards the calculation is the same to establish the kinetic parameters no matter whether the data was obtained from TG or isothermal studies. Information on changes in the density and surface area of solid residues in the decomposition process leads to the conclusion that the number of particles present changes significantly during the decomposition and it is pointed out that this factor is largely ignored in setting up kinetic models for the decomposition of solid materials.

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Zusammenfassung Der Einsatz thermoanalytischer Verfahren zur Bestimmung sowohl thermodynamischer als auch kinetischer Parameter wird beschrieben. Der Vorteil der DTA-Techniken bei der Ermittlung thermodynamischer Daten wird gezeigt. Die aus TG-Daten berechneten kinetischen Daten führen zu graphischen Darstellungen der Funktion des Logarithmus des spezifischen Reaktionsgeschwindigkeitskonstante gegen 1/T (wobeiT die Temperatur in Kelvin bedeutet). Hiervon ausgehend ist die Berechnung der kinetischen Parameter dieselbe, ungeachtet dessen, ob die Daten aus TG-Messungen oder aus isothermen Untersuchungen erhalten worden waren. Die Information bezüglich der Änderungen der Dichte und Oberfläche fester Rückstände von Zersetzungsprozessen führt zu der Folgerung, daß die Zahl der anwesenden Teilchen sich während der Zersetzung wesentlich ändert. Es wird betont, daß dieser Faktor bei der Entwicklung zur Zersetzung von Festkörpern in vielen Fällen ausser Acht gelassen wird.

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Résumé On donne un aperçu sur l'utilisation des procédés thermoanalytiques en vue d'obtenir les paramètres thermodynamiques et cinétiques. On montre les avantages des techniques d'ATD pour établir les données thermodynamiques. Les données cinétiques calculées à partir des courbes TG conduisent au tracé du logarithme de la constante spécifique de vitesse de réaction en fonction de 1/T, T étant la température en degrés Kelvin. A partir de là, le calcul pour établir les paramètres cinétiques est le même, que les données aient été obtenues par TG dynamique ou isotherme. Les données relatives aux changements de densité et de surface spécifique des résidus solides au cours des réactions de décomposition permettent de conclure que le nombre de particules présentes change d'une façon importante pendant la décomposition. On insiste sur ce fait qui reste souvent négligé lors de l'établissement des modèles cinétiques de décomposition des matériaux solides.

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