Application of thermal analysis to carbon black-elastomer systems

In this study a relationship between the surface and textural properties of carbon blacks and the gasification process induced thermally in air is noted. A temperature jump method was used to follow the gasification in air and to establish the relevant Arrhenius parameters. This can be associated with the activity of ‘basal’ plane carbon atoms as well as ‘edge’ carbon atoms at the surface. This is based on a model of carbon black structure consisting of the irregular packing of small graphite carbon structures. The carbon black surface was measured using a single measurement of adsorption based essentially on the BET volumetric method. The carbon black surface had a rate of oxidation per unit are which clearly indicated that the lower area carbon blacks had a predominately active area of ‘edge’ atoms at the surface while the surface of the higher area carbon blacks had a predominate amount of ‘basal’ plane graphite carbon atoms.     

The use of thermal analysis to predict the thermal life of organic electrical insulating materials

Three different thermoanalytical methods are introduced as significant time-saving techniques in conventional life tests of some organic electrical insulating materials. DTA in cyclically alternated atmospheres of nitrogen and oxygen according to Randino and Andreotti, and TG analysis methods at different heating rates according to Flynn and Wall and to Broido were applied to two electrical insulations based on aromatic poly-imide and epoxy resin. The activation energies obtained are compared with those derived from the slopes of the life-lines produced via conventional life tests. The assumptions necessary for applying the thermal analyses in these cases are discussed.

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Zusammenfassung Drei verschiedene thermoanalytische Methoden werden als wesentlich zeitsparende Techniken bei der üblichen Prüfung der Lebensdauer einiger organischer elektrischer Isoliermaterialien beschrieben. DTA in zyklisch wechselnden Atmosphären von Stickstoff und Sauerstoff nach Randino und Andreotti und Methoden der TG-Analyse bei verschiedenen Aufheizgeschwindigkeiten nach Flynn und Wall und Broido wurden bei zwei elektrischen Isolierstoffen auf aromatischer Polyimid und Epoxyd-Harz Basis eingesetzt. Die erhaltenen Aktivierungsenergien werden mit den aus der Neigung der an Hand konventioneller Lebensdauertests erhaltenen Lebenslinien verglichen. Die nötigen Voraussetzungen zur Anwendung der Thermoanalyse in diesen Fällen werden erörtert.

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Résumé On présente trois méthodes thermoanalytiques différentes qui permettent de réaliser un gain de temps important lors de l'examen conventionnel de la durée de vie de quelques isolants électriques organiques. L'analyse termique différentielle en atmosphères cycliquement alternées d'azote et d'oxygène, suivant Randino et Andreotti, et la thermogravimétrie avec différentes vitesses de chauffage, suivant Flynn et Wall et Broido, ont été appliquées à deux isolants électriques à base de polyimide aromatique et de résine époxy. Les énergies d'activation obtenues sont comparées à celles déduites de la pente des lignes de vie, obtenues par des examens conventionnels de durée de vie. Les approximations nécessaires pour appliquer l'analyse thermique à ces différents cas sont discutées.

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Application of thermal analysis to study smelting reduction kinetics

A thermal analysis study on the reduction of iron oxide rich slags under different conditions is presented in this paper. The effects of important process variables such as time, temperature, lime-silica ratio, FeO level in slag etc. are discussed. It is shown that the mechanism of reduction by externally added graphite is different from that by a carbon saturated bath although the activation energy values are similar.     

Application of thermal analysis to the study of several Spanish peats

Thermogravimetry and differential thermal analysis have been applied to the study of peats from the main Spanish basements.The results obtained show that the degree of transformation of the organic matter increases as the depth of the peat increases.The intensity of the weight loss corresponding to the first exothermic effect (directly related to the carbohydrate content of the sample, and inversely related to the content of humic compounds) is, in the case of the peats with a high degree of transformation, strongly influenced by the nature of their humic acids.On the other hand, the displacement of this exothermic effect towards lower temperatures is directly related to the ash content of the samples.

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Zusammenfassung Die thermogravimetrische Analyse und die Differentialthermoanalyse wurden zum Studium von Torfen aus den wichtigsten spanischen Lagerstätten eingesetzt.Die erhaltenen Ergebnisse zeigen, daß der Umwandlungsgrad der organischen Substanz mit zunehmender Tiefe des Torfes zunimmt.Die Intensität des dem ersten exothermen Effekt entsprechenden Gewichtsverlustes (welcher dem Kohlenhydratgehalt der Probe direkt und seinem Huminverbindungsgehalt umgekehrt proportional ist) wird im Falle von Torfen von hohem Umwandlungsgrad durch die Beschaffenheit ihrer Huminsäuren stark beeinflußt.Andererseits ist die Verschiebung dieses exothermen Effekts in Richtung der niedrigeren Temperaturen dem Aschegehalt der Proben direkt proportional.

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Application of thermal analysis to the study of the kinetics of two-stage reactions

A method is suggested for studying the kinetic parameters of two-stage reactions from thermoanalytical experimental data. The method allows determination of the kinetic characteristics of the process on the basis of integral thermoanalytical data, without separation of the individual stages. Parallel, independent and successive reactions taking place under isothermal and non-isothermal conditions are considered.

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Zusammenfassung Eine Methode zur Untersuchung der kinetischen Parameter von Zweistufenreaktionen unter Verwendung experimenteller thermoanalytischer Daten wird vorgeschlagen. Die Methode ermöglicht, die kinetischen Kennwerte des Prozesses basierend auf integralen thermoanalytischen Werten ohne Trennung der individuellen Schritte zu bestimmen. Unter isothermen und nichtisothermen Bedingungen parallel, unabhängig voneinander und nacheinander verlaufende Reaktionen werden diskutiert.

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Application of thermal analysis to the study of lipidic prodrug incorporation into nanocarriers

Anti HIV molecules as numerous drugs cannot efficiently penetrate into the brain. Prodrug synthesis and encapsulation into pegylated nanocarriers have been proposed as an approach for brain delivery. Pegylated polymeric nanoparticles and liposomes were chosen to incorporate glycerolipidic prodrugs of didanosine. Differential scanning calorimetry experiments were performed on mixtures of prodrugs and lipids or polymer in order to study their interaction. The optimal incorporation ratios were determined for each prodrug and compared for both types of nanocarriers. All these results would be used to prepare optimised formulations of didanosine prodrugs loaded into pegylated nanocarriers for brain drug delivery.     

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.     

Application of thermal analysis in the study of alkyd-allyl moulding compounds

Alkyd-allyl moulding compounds containing diallyl orthophthalate as networking monomer and five other unsaturated polyester resins were investigated by DTA. Analysis of DTA curves allowed choice of the alkyds forming well-cured moulding compounds within the investigated monomer. The thermal resistance and acetone absorption of the cured sample confirmed the choice of the alkyd.The influence of 6 different powder fillers on the exothermic effect of curing of alkydallyl moulding compounds was evaluated by DTA.

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Zusammenfassung Mittels DTA wurde die HÄrtung von Alkyd-Allyl Pre\massen aus o-Diallylphthalat und fünf Polyestern untersucht. Anhand der DTA-Kurven konnten gut gehÄrtete Pre\massen ergebende Alkyde ausgewÄhlt werden. Thermische StabilitÄt (TG) und Acetonaufnahme bestÄtigen die ZuverlÄssigkeit dieser Auswahlmethode. Mit dieser Methode wurde auch der Einflu\ von sechs verschiedenen Füllstoffen auf die WÄrmeeffekte des HÄrtungsprozesses bestimmt.

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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.     

Application of thermal analysis to the cement industry

Methods involving heat measurements have been applied in the cement industry for a long time. Differential thermal analysis (DTA) is used to explain the clinkering reactions, but it is a dynamic method which thus does not allow measurements and calculations of the thermal balance of the reactions to be made. In contrast, high temperature microcalorimetry may be used to measure the enthalpy of the clinkering reactions of industrial raw materials. Results obtained by using this technique allow us to determine the thermal profile of clinkering reactions in the kiln and to quantify the heat exchange in the solid material during its burning.Low temperature conduction microcalorimetry gives information on the hydration mechanism of the cement pastes. In this paper, we review the applications of thermal analysis in the cement industry paying special attention to new methods such as high temperature microcalorimetry.

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Zusammenfassung Seit langer Zeit werden in der Zementindustrie Verfahren mit Wärmemessung angewendet. Zur Erforschung der Verschlackungsreaktionen wird DTA verwendet, was jedoch ein dynamisches Verfahren ist und keine Messungen und Berechnungen bezüglich des thermischen Gleichgewichtes erlaubt. Im Gegensatz dazu kann Hochtemperatur-Mikrokalorimetrie zur Messung der Enthalpie von Verschlackungsreaktionen industrieller Rohstoffe dienen. Mit Hilfe der durch diese Methode erlangten Resultate kann das thermische Profil von Verschlackungsreaktionen im Kiln und der Wärmeaustausch im Festmaterial beim Brennen bestimmt werden.Niedertemperatur-Konduktions-Mikrokalorimetrie liefert Informationen über den Hydratationsmechanismus von Zementleim. Unter spezieller Beachtung neuer Methoden, wie z.B. der Hochtemperatur-Mikrokalorimetrie, wird in diesem Artikel ein Überblick über die Anwendungen der Thermoanalyse in der Zementindustrie gegeben.

     

Application of thermal analysis to study the macroredox polymerization of styrene with hydroxy-terminated polybutadiene

Ceric ammonium nitrate-hydroxy-terminated polybutadiene macroredox initiator has been investigated for the polymerization of styrene in nitric acid medium at 35 °C. Water inhibited the polymerization of styrene using this macroredox system. The products obtained were crosslinked and insoluble in water and organic solvents. A probable mechanism for the copolymerization reaction has been inferred from differential scanning calorimetry. Kinetic parameters for thermal degradation have been calculated by thermogravimetry (TG).     

Application of thermal analysis to the study of anti-tuberculosis drug compatibility. Part 1

Worldwide Brazil is among one of the 22 countries with high rates of tuberculosis placing this disease as a priority for the Government Health Policies in this country. Studies with the main tuberculostatic drugs rifampicin, isoniazid, pyrazinamide, and ethambutol, aiming the development of fixed-dose combination formulations (FDCs) have been performed. The aim of this study was to evaluate the thermal behavior of these drugs by DSC, TG/DTG, and DTA in order to predict possible physical and chemical interactions between tuberculostatics. DSC and DTA curves suggested incompatibility and/or interactions among drug preparations resulting from new thermal events, as well as the disappearance and shift of the melting point of the drugs. TG/DTG curves of drug mixtures presented different profiles from those observed for the individually tested drugs, supporting the evidence of drug incompatibility and indicating that mixtures are less stable when compared to the drugs alone.     

Application of thermal analysis to study of phase composition changes in blast furnace sinters

Application of thermal analysis to determine a quantity portion of iron oxides in symmetric blast furnace sinters is presented. In the multicomponent sample, calcium ferrites and many silicate phases beside doped iron oxides phases were observed. The dependence of sinter phase composition from basicity and relation with physicochemical properties is defined.     

Application of thermal analysis to the investigation of catalysts

A short review of the possibilities of application of thermal analysis to the investigation of catalysts is given: analysis of catalysts, investigation of the processes during the preparation of catalysts, desactivation of catalysts, and interaction of reactants or catalytic poisons with the catalysts. Several examples are mentioned.

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Zusammenfassung Eine kurze Übersicht über die Möglichkeiten des Einsatzes der Thermoanalyse zur Prüfung von Katalysatoren wird gegeben: Analyse der Katalysatoren, Prüfung der Vorgänge während der Herstellung von Katalysatoren, Inaktivierung von Katalysatoren, Wechselwirkungen zwischen Reagenzien oder Katalysatorengiften und den Katalysatoren. Eine Anzahl von Beispielen wird erwähnt.

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Résumé On piésente une rapide vue d'ensemble sur les possibilités d'application de l'analyse thermique à l'étude des catalyseurs: l'analyse des catalyseurs, l'étude des processus ayant lieu lors de la préparation des catalyseurs, la désactivation des catalyseurs, l'interaction de réactifs ou de poisons sur les catalyseurs. Plusieurs exemples sont mentionnés.

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Application of thermal analysis to mineral synthesis

Differential thermal analysis (DTA) and thermogravimetry (TG) are applied to various fields of mineral science. The present work illustrates the importance of the application of thermal analysis to mineral synthesis, to the determination of the mechanism and optimum temperature of synthesis and the thermal behaviour of minerals and starting materials. Selected examples of applications in this field are given. These include DTA studies of the synthesis of topaz, cryptohalite, wulfenite, perovskite, scheelite and the refractory materials, baddeleyite and corundum. Thermal analysis is proved to be an important and valuable tool in mineral synthesis.     

Application of thermal analysis in study of binary mixtures with metformin

Thermal analysis is an essential analytical tool in development of new formulations as well as to study the interaction between drugs and excipients. This work aims to investigate the possible interactions between metformin and excipients as microcrystalline cellulose (Microcel MC101®), starch sodium glycolate (Explosol®), sodium croscarmellose (Explosel®), PVP K30, magnesium stearate, starch and lactose, usually employed in pharmaceutical products. TG, DSC and DTA techniques were used for the thermal characterization to track if the thermal properties of the drug substance were modified in the mixture. Disregard of the starch and lactose systems, no changes in thermal behavior of mixtures were found. Thermogravimetric studies (TG) of metformin and its binary mixtures showed different thermal behavior.     

Application to polymer characterization by thermal analysis

The measured results of thermal analysis depend on experimental conditions. The international and national organizations have constituted a series of methods to characterize the physical and chemical properties for substances. The applications to physical transition, chemical reaction, and characteristic parameters of substances are given in the article as examples.     

The study of 'DSP' binding systems by thermogravimetry and differential thermal analysis

The so-called DSP (Densified Systems containing homogenously arranged Particles) systems represent a high-performance class of inorganic binders. The hydration and hardening processes of some DSP systems, based on calcium silicates (C₃S and C₂S) or Portland cement/clinker with silica fume additions, were assessed, in this paper, using the thermogravimetry (TG) and differential thermal analysis (DTA). These data permit a qualitative and quantitative study of the formed hydrates as well as the estimation of hydration process kinetics. This revised version was published online in August 2006 with corrections to the Cover Date.     

The application of differential thermal analysis technique to the study of single,binary and ternary oxide catalyst systems

The authors have reviewed the salient features of the thermal behavior of the following systems:

1. Single oxide systems: (i) Cr₂O₃, (ii) Fe₂O₃, (iii) Al₂O₃, (iv) MnO₂, (v) ZrO₂, (vi) NiO, (vii) ZnO, (viii) TiO₂, (ix) SiO₂, (x) ThO₂.
2. Binary oxide systems: (i) Cr₂O₃-Al₂O₃, (ii) Cr₂O₃-Fe₂O₃, (iii) Cr₂O₃-ZnO, (iv) Al₂O₃-SiO₂, (v) Al₂O₃-Fe₂O₃, (vi) MnO-Cr₂O₃, (vii) Cu-Al₂O₃, (viii) ZrO₂-Cr₂O₃, (ix) NiO-Cr₂O₃, (x) ZrO₂-NiO, (xi) ThO₂-Al₂O₃.
3. Ternary oxide systems: (i) NiO-Cr₂O₃-ZrO₂, (ii) Fe₂O₃-Cr₂O₃-Al₂O₃.
4. Vanadates: (i) tin vanadate, (ii) copper vanadate, (iii) lead vanadate, (iv) cobalt vanadate and (v) silver vanadate.

Excellent correlations have been obtained in most of the systems between the thermal characteristics of the solids, as revealed by DTA, and their specific surface areas and catalytic activity.     

Application of thermal analysis to study of the synthesis of K0.5Bi0.5Tio3 ferroelectric

Synthesis of potassium bismuth titanate ferroelectric by heating of mixtures prepared using oxide precursors, i.e. Bi₂O₃, TiO₂ and K₂CO₃ was investigated. DTA, TG, XRD and SEM methods were used to study the formation of intermediate compounds and the final product. Usage of associated homogenization and grinding of precursors mixture permits to decrease the temperature of formation of K_0.5Bi_0.5TiO₃. This revised version was published online in July 2006 with corrections to the Cover Date.