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Abstract  

The decomposition of series of supramolecular compounds, namely inclusion compounds, was studied by means of different thermoanalytical methods, i.e., traditional thermogravimetry, quasi-equilibrium thermogravimetry, and thermomechanical analysis. The series of compounds included the intercalates on the base of fluorinated graphite C2F, the clathrates on the base of carbamide and on the base of coordination compounds and microporous inclusion compounds on the base of coordination compounds. Kinetic parameters of decomposition processes were estimated within the approaches of the non-isothermal kinetics (“model-free” kinetics, linear and non-linear regression methods for the topochemical equation detection). The kinetic stability of the inclusion compounds under heating, the flexibility of the matrix structure, and the thermodynamic stability of the intermediate phases are discussed.

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Abstract  

The change of properties of leather and gelatin after the treatment by poly(hexamethyleneguanidine) derivatives was studied. The study of thermal transformationwas performed by means of derivatograph Q-1500-D (MOM, Hungary). The dehydration process, melting of crystal areas of anhydrous collagen, the destruction of poly(peptides) chains proceed one after another in the range from 20 to 250C. The computer program TA 1B for the non-isothermal kinetics (on the basis of the integer method) was used for data processing. The best kinetic description for the thermal dehydration in all cases was the equations of diffusion processes. We believe that this process can be considered as inner chemical diffusion: the hindrance for water molecules removal from the sample because of alternate breaking and forming of hydrogen bonds with aminoacids chains on the contact surface of pores. Both the difference in water content, and the slight difference in values of kinetic parameters (E and A) are discussed; they are attributed to the structure difference between leather collagen and gelatin and processing effect.

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Summary Thermogravimetry was used to study the kinetics of isothermal degradation of an epoxy thermoset powder coating in a nitrogen atmosphere and in oxidizing atmospheres of air and pure oxygen. An integral isoconversional procedure was used to analyse how the activation energy varies depending on the degree of conversion and depending on the atmospheres used. In the case of degradation in a nitrogen atmosphere, in addition to the activation energy, the kinetic triplet was completed using an Avrami reaction model and the pre-exponential factor. With this atmosphere, the conclusion was reached that the isothermal and non-isothermal kinetics are equivalent. It was shown that the thermooxidative degradation process is more complex and consists of a two-stage process. The first stage of degradation is similar whether nitrogen, oxygen or air are present. Chain scission occurs and it seems that there is formation of thermally more stable compounds. The second stage of degradation, involving several phenomena, occurs only in the presence of oxygen or air and leads to the total disappearance of the organic material by thermooxidation. These stages are very similar under non-isothermal or isothermal conditions.

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Journal of Thermal Analysis and Calorimetry
Authors: M. Beneš, V. Pla?ek, G. Matuschek, A. A. Kettrup, K. Györyová, W. D. Emmerich, and V. Balek

Summary  

Thermal behavior of commercial PVC cable insulation both before and after extraction of plasticizers, fillers and other agents were tested by TG/DTG and DSC during heating in the range 20-800C in air. The ultrasound enhanced hexane extraction and dissolution in THF with subsequent precipitation of PVC were used to prepare 'extracted' and 'precipitated' samples. The total mass loss measured for the 'non-treated', 'extracted' and 'precipitated' PVC samples was 71.6, 66.6 and 97%, respectively. In the temperature range 200-340C the release of dioctylphthalate, HCl and CO2was observed by simultaneous TG/FTIR. From TG results measured at different heating rates (1.5, 5, 10, 15 K min-1) in the range 200-340C the non-isothermal kinetics of the PVC samples degradation was determined. Activation energy values of the thermal degradation processes calculated by ASTM E 698 method, for 'non-treated', 'extracted' and 'precipitated' PVC samples were 174.617 kJ min-1, 192.819 kJ min-1, 217.120 kJ min-1, respectively. These kinetic parameters were used for the lifetime simulation of the materials.

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Abstract  

Residual differences after model fitting were investigated in both isothermal and non-isothermal kinetics in order to make numerical comparisons between several models and various parameter-estimating methods. Data from two independent experimental series were evaluated. A large data set, collected earlier under isothermal conditions from decompositions and hydrothermal reactions of aluminium hydroxides and oxides, was processed first. It showed that mechanical activation of the starting gibbsite affected reactivity of samples in several subsequent reactions for all model equations tried. The relative residual deviation concept is introduced, and statistics were applied to find a model that fits a certain reaction in most of the cases. In the second study, the sulphate decomposition step of aluminium sulphate octadecahydrate was investigated. TG curves were measured using a constant heating rate. Dynamic models were fitted by three mathematical methods, including a new general purpose one. Fitting ability of the methods with various complexity were compared on the basis of residual deviations obtained after integration of the model equations. As well as evaluating the best fit, this new parameter-estimating method provides a statistical analysis of the reliability of the whole model fitting process.

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The thermal stability and non-isothermal kinetics of the decomposition of alkali metal bifluorides were studied using a derivatograph. The removal of hydrogen fluoride from LiF · HF and NaF · HF takes place before melting and their decomposition occurs in a single stage; however, potassium, rubidium and cesium bifluorides at first undergo polymorphous transformation and melting on heating, and their decomposition proceeds stepwise. The thermal stability of alkali metal bifluorides has been found to increase with increasing ionic radius of the cation, reflecting its correlation with the hydrogen bond strength in these compounds.

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Science of Heat and Thermophysical Studies A Generalized Approach to Thermal Analysis by Jaroslav Šestk Hardbound, ISBN: 0-444-51954-8, 486 pages, publication date: Elsevier, Amsterdam 2005, price 175 Euro Jaroslav Šestk has been a leading figure of thermal analysis for decades. He was a founding member of Thermochimica Acta and he is a member of editorial board of Journal of Thermal Analysis and Calorimetry. He is author/ coauthor of nearly 300 papers that have received approximately 2500 citations. He was presented by several scientific awards, including an ICTAC award in 1992. His present book summarizes his extensive, comprehensive knowledge on the science of heat and the book is dedicated to the 40th anniversary of ICTAC. The term ‘thermophysical studies‘ in the title is used in a generalized sense, as the chapters of the book reveals: 1. Some Philosophical Aspects of Scientific Research. 2. Miscellaneous Features of Thermal Science. 3. Fire as a Philosophical and Alchemical Archetype. 4. Concept of Heat in the Renaissance and New Age. 5. Understanding Heat, Temperature and Gradients. 6. Heat, Entropy and Information. 7. Thermodynamics and Thermostatics. 8. Thermodynamics, Econophysics, Ecosystems and Societal Behavior. 9. Thermal Physics of Processes Dynamics. 10. Modeling Reaction Mechanism: The use of Euclidian and Fractal Geometry. 11. Non-Isothermal Kinetics by Thermal Analysis. 12. Thermometry and Calorimetry. 13. Thermophysical Examinations and Temperature Control. 14. Afterward (including a brief history of ICTA creation) 15. Literature: 700 citations 16. Appendix: short characteristics of some selected individualities of the general history and recent thermal analysis as related to the book contents. There is a particularly careful exploration of the philosophical and historical background of the treated subjects. The science history involves early Greek philosophical views, medieval alchemy, Renaissance upgrading as well as the recent and modern scientific achievements of the 18–20th Centuries. The author has also included views on the present and future aspects of the subject (caloric as entropy, information and organization, non-stationary heat diffusion, quantum diffusion and self-organization, thermal radiation and the modern concept of vacuum, etc.). However, in the present short book review there is no space to list all the subjects included in the book, accordingly I try to illustrate the broad spectrum of the work by two examples. The first chapter includes, among others, a few pages on the author’s view on scientific publications in a world where approximately one million publications appear in each year in roughly ten million pages. The second chapter includes, among others, a brief review on the energy resources and their durability, sustainable protection of our environment, the greenhouse effect caused by the CO2 emission, and the corresponding options of mankind. The modern theory of the heat science is outlined using a pertinent level of mathematical apparatus of so called ‘near-equilibrium‘ thermodynamics (heating rate and the effect of temperature changes, non-equilibrium phenomena paying attention to nucleation and related kinetic and T-T-T phase diagrams, equilibrium background and the kinetic degree of transformation, variant and invariant processes, thermodynamics of glass transition). An unique separate chapter deals with the applicability of the thermodynamic theory for the description of social and economic phenomena (thermodynamic laws and human feelings, strategy of survivals). Two chapters treat in details the kinetics and mechanism of the thermal reactions (suitability of various models) and a relatively brief chapter of 35 pages reviews thermometry (mainly theory and practice of DSC and DTA) and calorimetry. Keeping in mind the broad subject area of the book, one cannot expect truly comprehensive reviews in a single volume of around 500 pages. The author, however, has obviously employed a thoughtful weighing and selection of the information available and provided a generalized outlook useful to the readers and their better orientation in modern sciences. Gbor Vrhegyi Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences E-mail: varhegyi@chemres.hu

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through various workers [ 7 – 13 ], but the detailed study of the crystalline to smectic A transition of the 8CB have not been found in the literature so far. Here, this report presents the non-isothermal kinetics of the crystalline to smectic A transition

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International Congress on Thermal Analysis and Calorimetry (ICTAC) kinetic project, Isoconversional methods can be used extensively [ 33 ]. In Non-isothermal kinetics, KAS [ 19 – 21 ] and FWO [ 17 , 18 ] methods are the most popular representatives of the

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2 O with controlled morphologies via solid-state reaction at low heat [ 20 , 21 ] and to study the kinetics and thermodynamics of the decomposition of MnV 2 O 6 ·4H 2 O using DSC technique. Non-isothermal kinetics of the decomposition process of MnV

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