Simultaneous thermogravimetry and mass spectrometry in polymer characterization

The assembly and operation of a simple, directly coupled thermobalance and quadrupole mass spectrometer are described. Usefulness of the method and ease of operation are illustrated by the decomposition of TDI and MDI polyurethanes, ABS plastic and a capped and uncapped polyester.     

Coupled thermogravimetry/photometry for polymer ignition studies

Evaluation of the ignition properties of a polymeric system is difficult due to the large number of properties that must be measured and correlated. This problem is complicated by the fact that these properties are often measured using different test under widely varying conditions. We have developed an attachment for a commercial thermogravimetric analyzer that detects ignition and measures smoke generation. Since thermogravimetry provides information concerning the char yield and the decomposition kinetics, four important measures of polymer ignition are thus simultaneously obtained. The use of this apparatus is illustrated on polymeric systems.     

Analysis of polymer blends and copolymers by coupled thermogravimetry and automatic titration

A technique coupling automatic titration to thermogravimetry is described. The amount of a selected component in the volatiles produced under precise heating conditions in a DuPont 951 thermogravimetric analyzer is quantitatively determined with a Radiometer recording titration system. With the combined information on temperature, weight loss and chemical compositional changes, the stability and degradation mechanism of a sample are conveniently studied. Of particular interest is the use of such a technique to analyze polymer blends and copolymers in complex systems. Examples will be given to illustrate the various features of this application.     

Non-isothermal thermogravimetry, differential scanning calorimetry and chemiluminescence in degradation of polyethylene, polypropylene, polystyrene and poly(methyl methacrylate)

The degradation of pure polymers such as polyethylene, polypropylene, polystyrene and poly(methyl methacrylate) in nitrogen and oxygen was characterized by means of non-isothermal thermogravimetry, chemiluminescence and differential scanning calorimetry. The link between the results of the different methods based on Bolland Gee scheme of polymer oxidation is described. From the set of parameters determined from the thermogravimetry, the rate constants based upon the sum of several temperature dependent first-order processes were calculated and compared with those obtained by an iso-conversional method derived for several heating rates. Competition between propagation of oxidation and depolymerisation to monomer is proposed to explain the differences in kinetic behaviour of the examined polymers.     

Nonisothermal thermogravimetry of polymers

The decomposition of polyethylene and ethylene-vinyl acetate copolymers in composites with Al(OH)₃ and Mg(OH)₂ (60% by wt.) has been estimated from the aspect of the extent of synchronization of the two fundamental processes, the release of water and flammable volatiles from a polymer and the effect of this on the resulting polymer flammability. An attempt has been made to implement the peculiarities of decomposition observed for each system to the fire behaviour of these materials.     

High resolution thermogravimetry

A new thermogravimetric instrument is introduced, Hi-Res^TM TGA 2950. The Hi-Res^TM TQA gives a significant improvement to TG results. The instrument control parameters are varied as a function of the sample's rate of weight change. This novel feature improves resolution and reduces analysis time. The maximum heating rate and resolution index are user selectable.Data presented demonstrate improved resolution for survey TG thermal curves and very high resolution for difficult to resolve complex materials. Results are demonstrated for many types of samples including: homopolymers, polymer blends, inorganic reference materials, and complex organic mixtures.Hi-Res trademark and patent applied for by TA Instruments, Inc.

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Zusammenfassung Es wird das neue thermogravimetrische Gerät Hi-Res^TMTGA2950 vorgestellt. Mit Hilfe von Hi-Res^TMTGA2950 ergibt sich eine eindeutige Verbesserung der TG-Resultate. Die Kontrollparameter des Gerätes werden als eine Funktion der Massenänderungsgeschwindigkeit der Probe geändert. Diese neue Eigenschaft verbessert die Auflösung und verringert die Analysenzeit. Maximale Aufheizgeschwindigkeit und Auflösungsindex können vom Anwender bestimmt werden.Die dargelegten Daten zeigen eine verbesserte Auflösung der TG-Kurven und eine sehr hohe Auflösung für schwer aufzulösende komplexe Substanzen. Es werden Ergebnisse für zahlreiche Beispiele gegeben: Homopolymere, Polymergemische, anorganische Referenzsubstanzen und komplexe organische Gemische.Das Warenzeichen Hi-Res und das Patent wurde von TA Instruments,Inc. beantragt.

     

Nonisothermal thermogravimetry of polymers

The model of weight loss taking place in each step of a scheme of consecutive reactions was applied to nonisothermal thermogravimetric records of bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide). The release of HBr was found to be faster in air than in nitrogen. A significant reduction in the apparent activation energy of dehydrobromination as compared with decomposition of the nonbrominated polymer was ascribed not only to a reduction in the activation energy of the initiation reaction, but also to an increase in the order of the termination reaction (from 1 for the nonbrominated polymer to 2 for the highly brominated polymer).     

Volatility rate by thermogravimetry

ASTM Committee E37 on Thermal Measurements published a new test method 'Standard Test Method for Volatility Rate by Thermogravimetry' in June 1999 with the designation E 2008. This approach to assessing volatility utilizes an extension of the pinhole technology previously employed by E37 for vapor pressure determinations using differential scanning calorimetry (ASTM E 1782). After publication of the test method E 2008, an Interlaboratory Study was undertaken to develop a 'Precision and Bias' statement to be assigned with the test method. This paper provides some background data that supports the claim that E 2008 is generally insensitive to experimental conditions other than temperature. The Interlaboratory Study showing the statistical review is also discussed.     

Cleaning validation using thermogravimetry

The health authorities require that equipment used in the pharmaceutical industry is clean prior to use. The main raison is to prevent any contamination of the drug products. This article demonstrates that thermogravimetry (TG) can be used for the determination of the residual impurities during the cleaning validation of the equipment of pharmaceutical production plants. The accuracy and the recovery rate of this method are comparable with those of the classical analysis method (determination of the distillation residue using a rotary evaporator). The fully automation of the testing equipment even allows its utilization around the clock by plants operators, leading to a significant reduction of the time necessary for the cleaning validation and to an increase of the plant capacity.     

Thermal standards in thermogravimetry

Comparisons of thermogravimetric data from different instruments have often led to controversy because of lack of appreciation that the values are influenced by the apparatus used. Consequently, it is suggested that various compounds be employed as thermal standards for comparing data from different sources. The paper also discusses the variables to be considered when attempting to devise such standards and includes a list of suggested thermal standards covering the ranges 100-400 degrees and 1050-1060 degrees.     

Reference materials for thermogravimetry

The thermobalances available commercially have a wide range of heater-sample-temperature sensor relationships. Because of the differences, relating data from one apparatus to another has been imprecise. The International Confederation for Thermal Analysis has certified a set of magnetic reference materials for thermogravimetry. Analysis of the test data from eighteen instruments shows that, whereas data from several models of a single instrument show spans of measured temperatures from 3–15°, the spans for all instruments were 17–39°. The differences are systematic, not only between balance types but also for the same model of instrument in different laboratories. The use of these certified reference materials enables correlation between instruments.

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Zusammenfassung Die handelsüblichen Thermowaagen verfügen über eine breite Skala von Heizkörper-Probe-Temperaturfühler-Beziehungen. Wegen dieser Unterschiede waren die Angaben von einem Gerät zum anderen ungenau. Die Internationale Konföderation für Thermoanalyse hat eine Reihe magnetischer Referenzsubstanzen für die Thermogravimetrie bestätigt. Die Analyse der Prüfdaten von achtzehn Geräten zeigt, daß während die Angaben verschiedener Modelle in einem einzigen Instrument eine Spanne gemessener Temperaturen von 3 bis 15° zeigen, die Spannen für sämtliche Instrumente 17 bis 39° betragen. Die Differenzen sind systematisch, nicht nur zwischen Waagentypen, sondern auch für dasselbe Gerätemodell in verschiedenen Laboratorien. Der Gebrauch dieser geeichten Referenzsubstanzen gestattet die Korrelation zwischen Geräten.

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Résumé Les thermobalances en vente ont une large gamme de dispositions respectives de l'ensemble chauffage — échantillon — détecteur de température. A cause de ces différences le rapprochement des données fournies d'un appareil à l'autre est imprécis. Le Confédération Internationale d'Analyse Thermique propose une série de substances de référence magnétiques certifiées pour la thermogravimétrie. L'analyse des données d'essais fournies par dixhuit instruments montre que le données fournies par les différents modèles d'un même instrument restent comprises dans un intervalle de températures mesurées de 3 – 15° tandis que l'intervalle peut être de 17 à 39° si les valeurs fournies par tous les instruments sont prises en compte. Les différences sont systématiques, non seulement entre les différents types de balances, mais aussi pour le même modèle d'instrument dans des laboratoires différents. L'utilisation de ces substances de référence certifiées permet de corréler les divers instruments.

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Presented at the 6th ICTA Conference Bayreuth, G. F. R., 1980.     

Non-isothermal kinetics-current problems

The author presents some experimental and theoretical contributions in non-isothermal kinetics developed in the last years. Special emphasis is given on heterogeneous kinetics with the help of Q-derivatograph, kinetic indexes of thermal stability and on the classical non-isothermal change (CNC).

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Zusammenfassung Es werden einige, in den vergangenen Jahren entwickelte experimentelle und theoretische Beiträge zur nichtisothermen Kinetik dargestellt. Besonders betont werden heterogene Kinetik mittels Q-Derivatografie, kinetischer Index der thermischen Stabilität sowie klassische nichtisotherme Umwandlungen (CNC).

     

Non-isothermal kinetics of dyeing

This paper aims to present an essay to use the non-isothermal kinetic method in order to obtain the kinetic parameters of dyeing in a certain dye-fibre system. Some limitations of the model are discussed.     

Non-isothermal model-free predictions

Suitable thermal treatment of metal organic precursors is a key process to obtain oxide films. To this purpose, non-isothermal model-free predictions are specially suited. In this article we will explore the ability of these methods to provide an accurate prediction of the evolution of the decomposition of yttrium trifluoroacetate, a precursor used in the synthesis of YBaCuO superconducting thin-films. A good agreement has been obtained between the predicted and the measured reaction courses.     

Quantitative thermogravimetry of multicomponent zeolite-bearing rocks

A quantitative thermoanalytical determination of mixture compositions is extremely difficult if there is a partial or full overlapping of the temperature ranges of the thermal transformations, and a proximity of the quantitative characteristics of the weight changes is also observed. A method of quantitative analysis of such a system is offered, based on the calculation of differences in the regularity of rate variation of the thermal transformations of the separate mixture components. The principle of distinguishing temperature intervals with maximum differentiation of thermal effects and methods of calculation of the quantitative mixture composition is shown. Examples of determination of the mineral compositions of zeolite-bearing rock are given.

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Zusammenfassung Eine quantitative thermoanalytische Beschreibung der Zusammensetzung eines Gemisches ist äusserst schwer, wenn die Temperaturbereiche der thermischen Zersetzungen teilweise oder vollständig überlappen und auch die quantitativen Charakteristika der Gewichtsänderungen nahe bei einander liegen. Eine Methode der quantitativen Analyse eines solchen Systems wird gezeigt, die auf der Berechnung der Unterschiede der Regelmässigkeit der Geschwindigkeitsänderung bei der thermischen Umsetzung der einzelnen Komponenten des Gemisches beruht. Das Prinzip der Unterscheidung von Temperaturbereichen unter maximaler Differenzierung der thermischen Effekte, sowie die Methode zur Berechnung der quantitativen Zusammensetzung des Gemisches werden beschrieben. Beispiele zur Bestimmung der Zusammensetzung der Mineralstoffe in zeolithaltigem Gestein werden gegeben.

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Résumé La détermination quantitative de la composition d'un mélange est très difficile par les méthodes thermoanalytiques si les intervalles de température où s'effectuent les transformations se chevauchent partiellement ou totalement et si les variations pondérales sont proches les unes des autres. Pour effectuer l'analyse quantitative d'un tel système, on présente ici une méthode qui repose sur le calcul des modifications de la vitesse de transformation des composants individuels du mélange. On décrit le principe suivant lequel on effectue la distinction des intervalles de température avec une différenciation maximale des effets thermiques ainsi que les méthodes permettant de calculer la composition du mélange. Le dosage des constituants présents dans des roches à zéolites est donné comme exemple.

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Non-isothermal Crystallization of UHMWPE

Processing of Ultra High Molecular Weight Polyethylene (UHMWPE) parts involves non-isothermal cooling leading to crystallinity variations, which cause variations in the mechanical properties. Study of non-isothermal crystallization kinetics of UHMWPE forms the basis for process modelling. The crystallization of UHMWPE was studied at seven different cooling rates. The crystallization onset and peak temperatures were linearly related to the cooling rate. The crystallization of UHMWPE was concluded to be a nucleation dominated process with small contribution from growth of nuclei. Differences in ultimate crystallinity (≈11%) were produced due to different cooling rates. A significant portion of the change in ultimate crystallinity occurred at lower cooling rates (<6°C min⁻¹). At higher cooling rates (6–22°C min⁻¹) the change in ultimate crystallinity was insignificant. This revised version was published online in July 2006 with corrections to the Cover Date.