Analysis of zone-melted ultra-pure organic compounds: a new quantitative differential thermal analysis method

A method for the rapid quantitative determination of impurities in ultra-pure organic compounds is described. It is based on the difference in slopes of the curves obtained when the difference in temperature between the sample and a reference shield is plotted against time. The results are compared with those obtained by thermal analysis.     

Applications of a new low temperature differential scanning calorimeter

A new low temperature differential scanning calorimeter is described which operates over the temperature range –150 °C to 700 °C. The equipment features a chromel heat flux DSC sensor plate located in a cobalt alloy heating chamber, enabling work to be carried out in oxidizing atmospheres to above 600 °C. Full data processing and programme control facilities are provided by an IBM compatible computer system. The performance of the instrument is illustrated by experiments on indium and poly (vinyl chloride).

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Zusammenfassung Ein neues Tieftemperatur-Differential-Scanning-Kalorimeter für den Bereich von –120 °C bis+700 °C wird beschrieben. Das Gerät enthält eine Wärmefluss-DSC-Sensorplatte aus Chromel in einer Heizkammer aus einer Kobaltlegierung, was Arbeiten in oxidierender Atmosphäre bis über 600 °C ermöglicht. Ein IBM-kompatibles Computersystem bietet alle Möglichkeiten der Datenverarbeitung und Programmregelung. Die Leistungsfähigkeit des Geräts wird an Hand von Experimenten mit Indium und Polyvinylchlorid demonstriert.

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, —150° 700°. , 600°. IBM . .

     

Quantitative thermal analysis,I Mathematical problems of quantitative differential thermal analysis

A highly simplified method for calculating heat of phase transitions from DTA data is presented. Two DTA curves are needed to calculate the heat of transition and the specific heat of the sample: one is for the original sample and one is for a sample prepared by mixing the original sample with some unreactive diluent the specific heat of which is known. The data of the DTA curves used in the calculations are the peak area, the rate of heating and the deviation of the DTA curve from the base line.

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Zusammenfassung Eine einfache Methode zur Errechnung der Werte der Phasenübergangswärme aus den DTA Daten wird besprochen. Die Kenntnis der spezifischen Wärme der betreffenden Substanz und zwei Thermogramme sind hierzu nötig, jenes der Originalprobe und jenes einer Mischung der zu prüfenden Substanz mit einem indifferenten Stoff von bekannter spezifischer Wärme. Die notwendigen DTA Daten sind die Spitzenflächen, die Erhitzungsgeschwindigkeit und die Abweichung der DTA Kurve von der Nullinie.

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Résumé On décrit une méthode simple pour caIculer les chaleurs des transitions de phase à l'aide des données d'analyse thermique différentielle. Il est nécessaire de connaître la chaleur spécifique et les thermogrammes de l'échantillon pur et en mélange avec une substance indifférente, de chaleur spécific connue. Pour les calculs, on se sert des données suivantes: surface des pics d'A. T. D., vitesse de chauffage et déviation de la courbe d'A. T. D. par rapport à la ligne de base.

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The application of low temperature differential scanning calorimetry to polymer blend analysis

The temperature regions in which glass transitions (Tg's) occur for a series of blends of polybutadienes with natural rubber and two styrenebutadiene copolymers of different styrene contents have been studied by differential scanning calorimetry. The resulting DSC curves may be used to categorize the polybutadiene, determine the bound styrene content of the styrenebutadiene copolymer and quantify the polybutadiene content of the blends.

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Zusammenfassung Die Temperaturbereiche, in denen bei einer Reihe von Gemischen von Butadien mit natürlichem Kautschuk und bei zwei Styrol-Butadien-Kopolymeren mit verschiedenem Styrolgehalt Glastransformationen erfolgen, wurden mittels DSC untersucht. Die erhaltenen DSC-Kurven können zur Kategorisierung des Polybutadiens und zur Bestimmung des Gehalts an gebundenem Styrol in Styrol-Polybutadien-Kopolymeren und des Polybutadiengehalts der Gemische verwendet werden.

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Thanks are due to the Board of MRPRA for permission to publish this paper.     

Heat transfer errors in quantitative differential thermal analysis

A DTA apparatus has been built to examine some of the errors neglected in present quantitative DTA. The heat transfer characteristics within DTA systems were found to limit in situ measurements of powder thermal conductivity. It was also demonstrated that the negligence of heat lost to the DTA block from the sample cell during an exothermic reaction and heat gained from the DTA block by the sample cell during endothermic reactions lead to large errors in quantitative estimations. A modified double differential thermocouple DTA was designed to take these heat losses into account. The apparatus was calibrated with CaCO₃ and kaolinite endotherms and the kaolinite exotherm and tested on the SrCO₃ rhombic trigonal inversion endotherm. The result was found to be in good agreement with accepted literature values.

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Zusammenfassung Ein DTA-Apparatur wurde gebaut um einige in der gegenwärtig üblichen quantitativen DTA vernachlässigte Fehler zu prüfen. Es wurde gefunden, daß die Wärmeübertragungscharakteristika in DTA-Systemen die in situ Messungen der Wärmeleitfähigkeit von Pulvern begrenzen. Es wurde ebenfalls gezeigt, daß die Vernachlässigung von Wärmeverlusten der Probezelle an den DTA-Block bei exothermen Reaktionen und vom Wärmegewinn der Probezelle vom DTA-Block bei endothermen Reaktionen zu bedeutenden Fehlern in den quantitativen Bestimmungen führt. Ein DTA-Gerät mit doppeltem Differentialthermoelement wurde entworfen um diese Wärmeverluste zu berücksichtigen. Der Apparat wurde mittels der endothermen Reaktionen von CaCO₃ und Kaolinit, bzw. mittels der exothermen Reaktion von Kaolinit geeicht und an der Inversion von rhombischem zu trigonalem SrCO₃ erprobt.

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Résumé On a réalisé un appareil ATD pour étudier certaines erreurs négligées jusqu'à présent en ATD quantitative. On a trouvé ainsi que les caractéristiques du transfert de chaleur limitent la mesure in situ de la conductivité thermique des poudres. On montre également que le fait de négliger les échanges de chaleur entre la cellule renfermant l'échantillon et le bloc ATD (pertes ou gains de chaleur suivant que les réactions sont exothermiques ou endothermiques) conduit à des erreurs considérables dans les dosages. Un double thermocouple différentiel a été conçu pour tenir compte de ces pertes. L'étalonnage de l'appareil a été ré alisé à l'aide des réactions endothermiques de CaCO₃ et de la kaolinite et contrôlé avec la transition endothermique de SrCO₃ (rhomboédrique-trigonal).

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DTA , DTA. , DTA . , , DTA DTA . , . CaCO₃ SrCO₃.

     

A new differential thermal analysis method

A new differential thermal analysis method has been developed which allows fast and accurate determinations of phase equilibria in condensed systems between 400 and 1100°. In this method the temperature is increased stepwise, heat effects being determined by analysis of the transient thermoelectric effects after each step. Between steps the temperature is kept constant until equilibrium is attained. The method has been tested in measurements of displacive solid-state transformations and melting points.

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Zusammenfassung Eine neue Methode der Differentialthermoanalyse wurde entwickelt, welche rasche und genaue Bestimmungen von Phasengleichgewichten in kondensierten Systemen zwischen 400° und 1100° ermöglicht. Bei dieser Methode wird die Temperatur stufenweise erhöht und die Wärmeeffekte durch Analyse der thermoelektischen Übergangseffekte nach jeder Stufe bestimmt. Zwischen den Stufen wird die Temperatur bis zum Erreichen des Gleichgewichts konstant gehalten. Die Methode wurde bei Messungen von Verschiebungsumsetzungen in festem Zustand und von Schmelzpunkten erprobt.

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Résumé Une nouvelle méthode d'analyse thermique différentielle a été mise au point. Elle permet de déterminer de façon rapide et exacte les équilibres de phases dans des systèmes condensés, entre 400 et 1100°. Selon cette méthode, on augmente graduellement la température en déterminant les effets thermiques par analyse des effets thermoélectriques intermédiaires après chaque palier. A chaque palier, on maintient la température constante jusqu'à ce que l'équilibre soit atteint. On a contrôlé la méthode par l'étude de changements de phases displacifs dans l'état solide et par mesure de points de fusion.

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, 400° 1100°. , . . .

     

Evaluation of heats and entropies of fusion by quantitative differential thermal analysis method

The technique of dynamic differential calorimetry is discussed as a method for the quantitative determination of several thermodynamic properties of crystals. Some results on heats and entropies of fusion of binary tetrahedral semi-conductors are reported.     

A new apparatus for simultaneous differential thermal analysis and gas evolution analysis

A new apparatus is described which permits the simultaneous recording of the differential thermal analysis and gas evolution curves for a given sample from ambient to 900°. The sample is pyrolyzed in a dynamic helium gas atmosphere using a conventional DTA furnace and sample holder assembly. The evolved decomposition products are detected in the helium gas stream by means of a thermistor thermal conductivity cell. From a knowledge of the GE curve and an analysis of the decomposition products, a more accurate interpretation of the DTA curve can be made.     

The application of differential thermal analysis to investigation of thermoplastics

The courses of phenomena occurring in investigated plastics during heating were studied. The plastics specimens have been subjected to investigation before and after heating. Two kinds of plastics being applied in machine constructions Tarnamid T-27 (polyamide 6) and Tarnoform 300 (polyacetale) have been chosen to investigation. The specimens have been subjected to heat treatment in turbine oil at minimum temperature of crystallization: polyamid 6 at 170°C and polyacetal at 140°C. It has been found that during heating in tested plastics endo- and exothermic effects take place and there are some differences for plastics before and after heating. It is possible to calculate the grade of crystallinity on the base of DTA curves. In polyamid 6, in which the polymorphic transformation takes place, the known methods of calculation of degree of crystallinity proves ineffective. Plastics after heating characterize the higher degree of crystallinity grade.     

Critical temperature measurements of liquids by means of differential thermal analysis

When studying crytalline substances and liquids in sealed off glass ampoules by differential thermal analysis the melting ranges but not the heat of evaporation of the liquids and fused substances are found, because inside the glass ampoule, there will always be the vapour pressure equillibrium which corresponds to the temperature. With liquids undergoing decomposition, it is possible to measure the range and heat of decomposition. Given a suitable quantity inside the ampoule the critical temperature, e.g., of water of ethanol can be measured for non-decomposing liquids. The measuring effect is based on the pronounced change of the liquid's specific heat at the critical temperature.Fundamental studies of the measurement of critical temperatures of liquids were carried out by the turn of the century. One the methods reported is the meniscus method, optimal measurement of the critical temperature, which comprises a liquid being filled into a glass tube which is then sealed by melting. The glass tube is heated while observing the meniscus. Its rise means that the critical volume has been exceeded, while a drop means that it has not yet been reached. The conditions are only met when that volume of liquid has been filled into the tube at which the meniscus neither rises nor falls on heating but rather remains, e.g. at mid level of the tube until it disappears. The tube contains the critical volume at the critical density when the critical temperature is reached. The critical pressure is then present. These conditions are obtained when the meniscus disappears and the liquid completely goes over into the vapour phase.The melting range (and the latent heat of fusion) are found when investigating a crystalline material under normal pressure by differential thermal analysis. Given a suitable arrangement the boiling temperature and, in rough approximation, the heat of evaporation are also found (Fig.1). The latent heat of fusion is found again when carrying out the same measurement in a closed system (glass tube sealed by melting). The heat of evaporation can no longer be measured since the vapour pressure equilibrium coresponding to the given temperature is present in the glass tube.     

The apparatus function of quantitative differential thermal analysis,including heat convection and radiation

The apparatus function, i.e. the response of the equipment to a heat pulse, is derived for DTA instruments where, besides heat conduction, convection and radiation are considered. The solution of the heat-balance equation is described by a superposition of two exponential functions, which leads to the dependences of the calibration factor and the time constants on the heat capacity, the heating rate and the temperature. For the experimental determination, the relations are transformed into expressions which can easily be obtained from the calibration measurements.

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Zusammenfassung Die Apparatefunktion, das ist die Reaktion der Anordnung auf einen Heizimpuls, wird für eine Differential-Thermo-Anlage abgeleitet, wobei neben Wärmemeitung auch -Konvektion und-Strahlung zugelassen sind. Die Lösung der Wärmebilanzgleichung wird durch die Überlagerung zweier Exponentialfunktionen beschrieben, wobei sich die Anhängigkeiten des Gerätefaktors und der Zeitkonstanten von der Wärmekapazität, der Heizrate und der Temperatur ergeben. Zur experimentellen Bestimmung werden die Ausdrücke zu leicht aus den Kalibrierungsmessungen zugänglichen Größen aufbereitet.

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Applicability of the du pont 900 DTA apparatus in quantitative differential thermal analysis

Some problems of quantitative differential thermal analysis have been studied by means of a Du Pont 900 DTA instrument. Applying the equation of heat transfer the features of a thermogram (base line and peak surface) may be interpreted in terms of heat of transition, specific heat and thermal conductivity. Satisfactory results are obtained for substances with thermal conductivities lower than 10^-3 cal/sec deg.     

High pressure differential thermal analysis of the lanthanum nickel-hydrogen system

A high pressure differential thermal analysis apparatus is described which is capable of operation in the pressure range from 1–680 atm of hydrogen at temperatures from 20 to 900°C. This system has been used to investigate the LaNi₅H₂ system from 1–200 atm.     

Evaluation of the degree of hydration of synthetic alites by quantitative differential thermal analysis

The degree of hydration of synthetic alites has been determined by quantitative differential thermal analysis, using strong signals related to the polymorphic transformations of alites. The conditions suitable for noting the various reference signals, obtained with maximum apparatus sensibility, have been described and the data derived from differential thermal test with those obtained by analysis of the liquid phase in contact with the hydrating solid are correlated.     

A comparison of quantitative and qualitative superoxide dismutase assays for application to low temperature microalgae

Antioxidant enzymes such as superoxide dismutase (SOD) play a key role in the removal of reactive oxygen species produced during visible and ultraviolet irradiance stress in microalgae and plants. However, little is known about the enzymatic antioxidative stress responses in ecologically important Antarctic marine microalgae. SOD in particular is difficult to analyze, possibly due to problems in obtaining sufficient quantities necessary for reliable and reproducible enzymatic assays. The aim of the present work was to create a sensitive, easy-to-use and reliable method for SOD determination in Antarctic microalgal material by comparing and optimizing existing protein extraction procedures and SOD assays in the marine Antarctic diatom Chaetoceros brevis. Optimization was achieved in cell disruption (sonication) and protein extraction procedures, extraction buffers, SOD assay methods (xanthine/xanthine oxidase and NBT/riboflavin photometric quantitative methods and native gel electrophoresis qualitative method) and the assay temperature. Protein extraction was optimal at low sonication amplitudes after a few pulses, irrespective of the type of buffer used. Extraction efficiency varied highly between the tested buffers; most protein was extracted in the presence of 1% of Triton X-100. SOD activity was best quantified using the NBT/riboflavin method in combination with a buffer containing potassium phosphate and Triton X-100. Moreover, the NBT/riboflavin method was demonstrated to be the most reliable and sensitive method at low temperatures (5 degrees C).     

Non-isothermal kinetics of diffusion and its application to thermal analysis

Non-isothermal kinetics of diffusion are derived, extending the fundamental equation of diffusion to non-isothermal conditions, and the equation is solved for a few typical cases. From these theoretical considerations, two methods of analyzing thermoanalytical data of diffusion are proposed. One of the methods is applied to EGA curves of the volatilization of toluene from epoxy resin cured with ethylenediamine. The diffusion constants obtained as a function of temperature for two plate-specimens of different thicknesses at various heating rates are in good agreement with each other. The temperature dependence of the diffusion constant observed for a powdered sample is also in good agreement with those observed for the two plate-specimens.

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Zusammenfassung Die nicht-isotherme Kinetik der Diffusion wird abgeleitet, indem die Grundgleichung der Diffusion auf nicht-isotherme Fälle erweitert und für einige typische Fälle gelöst wird. Von diesen theoretischen Erwägungen ausgehend werden zwei Methoden zur Analyse thermoanalytischer Diffusionsangaben vorgeschlagen. Eine der Methoden wird für die EGA-Kurven der Verflüchtigung von Toluol aus mit Ethyländiamin behandeltem Epoxyharz angewandt. Die an zwei Platten-Arten verschiedener Dicke bei verschiedenen Aufheizgeschwindigkeiten als Funktion der Temperatur erhaltenen Diffusionskonstanten stimmen gut überein. Die an einer pulverförmigen Probe beobachtete Temperaturabhängigkeit der Diffusionskonstante ist ebenfalls in guter Übereinstimmung mit der an den zwei Plattenkörpern erhaltenen.

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Résumé On étudie la cinétique de diffusion en régime non isotherme, en étendant l'équation fondamentale de la diffusion aux cas non isothermes et l'on donne la solution de l'équation pour quelques cas typiques. A partir de ces considérations théoriques, on propose deux méthodes pour analyser les données thermoanalytiques de la diffusion. On applique l'une d'elles aux courbes AGE de stabilisation du toluène à partir des résines époxy traitées à l'éthylène diamine. Les constantes de diffusion obtenues en fonction de la température pour plusieurs vitesses d'échauffement sur deux échantillons en forme de plaquette sont en bon accord, de même que pour des échantillons pulvérulents.

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A thermal analysis evaluation of the low temperature synthesis of BaBiO3

Thermal decomposition of metal-organic precursors for the mixed oxide BaBiO₃ was studied using TG and EGA. Precursors produced by polyesterification of bifunctional acids with ethylene glycol (Pechini process) decomposed about 100°C higher than those without the diol. BaCO₃ was identified by IR and XRD as a reaction intermediate. EGA proved that the amount of BaCO₃ was below 10% of the total barium, and that the barium exists mainly as a nitro-compound up to 650°C. Phase-pure BaBiO₃ with a moderately high surface area (1.4 m²/g) could be synthesised from a citrate precursor by the Pechini process at around 850°C.     

Simultaneous photothermal and differential thermal analysis

Simultaneous photothermal analysis (PTA), and differential thermal analysis (DTA) curves of inorganic compounds and organic polymers are presented. While the two techniques reinforce each other and provide complementary information, light emanating from the sample and detected by a photomultiplier tube provides features in the PTA thermograms not present in the DTA thermograms.     

Evaluation of the degree of hydration of tricalcium silicate pastes by quantitative differential thermal analysis

The hydration kinetics of C₃S pastes can be easily evaluated by DTA using the most intense and reversible transition of C₃S. Some modifications are proposed to Ramachandran's method concerning the measurement of this effect, the weight of the sample used for each experiment and the heating rate. The results of the hydration degree versus times of C₃S agree reasonably with those reported by Ramachandran, while still better agreement is observed with those of Locher who used X-ray quantitative analysis.

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Zusammenfassung Die Hydratisierungskinetik von C₃S Pasten kann mittels DTA leicht bewertet werden, falls der intensivste und am meisten reversible Übergang von C₃S genutzt wird. Einige Änderungen zur Methode von Ramachandran bezüglich der Messung dieses Effekts, des Gewichts der bei den einzelnen Messungen eingesetzten Proben und der Aufheizgeschwindigkeit werden vorgeschlagen. Die Ergebnisse des Hydratisierungsgrades von C₃S in Abhängigkeit von der Zeit sind in guter Übereinstimmung mit denen von Ramachandran, während eine noch bessere Übereinstimmung mit den Werten von Locher beobachtet werden kann, welcher sich jedoch der quantitativen Röntgenanalyse bediente.

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Résumé La cinétique de l'hydratation des pâtes de C₃S peut être facilement déterminée par ATD, en utilisant la transition de C₃S la plus intense, qui est réversible.On propose des modifications à la méthode de Ramachandran, concernant la mesure du phénomène, le poids des échantillons utilisés pour chaque expérience et le choix de la vitesse de chauffage. Les résultats donnant le degré d'hydratation de C₃S en fonction du temps sont en bonne concordance avec ceux publiés par Ramachandran tandis qu'une concordance encore meilleure est observée avec les résultats de Locher obtenus par analyse quantitative aux rayons X.

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Financial support by Consiglio Nazionale delle Ricerche (Italy).