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Abstract  

The thermal characterization of polypropylene (PP) composites containing untreated and treated zeolite with different silane coupling agents was carried out using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) to investigate the effects of natural zeolite and surface modifiers on melting, crystallization and degradation behaviour of PP. 3-aminopropyltriethoxysilane (AMPTES), methyltriethoxysilane (MTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) were used as surface modifiers at four different concentrations (0.5–2.0 mass%). Thermal analyses indicated that silane treatment and 2–6 mass% zeolite addition have no significant effect on the melting and degradation temperatures of the composites. The crystallization temperatures of the composites were increased due to the nucleating effect of the zeolite. The influence of the modifiers on the interactions between PP and zeolite was determined by the activities of untreated and treated zeolite. The maximum interactions leading to good adhesion were observed in the AMPTES treated composites. Also, non-isothermal crystallization kinetics of the composites was analyzed using Avrami and Kissinger models.

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Journal of Thermal Analysis and Calorimetry
Authors: P. S. Epaminondas, K. L. G. V. Araújo, A. Lima de Souza, M. C. D. Silva, N. Queiroz, A. L. Souza, L. E. B. Soledade, I. M. G. Santos, and A. G. Souza

Abstract

Chemical and thermal analyses of golden and brown flaxseeds were carried out for raw and toasted seeds aiming at evaluating their nutritional and thermo-oxidative properties. Moisture, lipids, protein, soluble carbohydrates, and ash contents were quantified. Concerning lipids and proteins, in average, no meaningful differences were observed for the two varieties, being also equivalent to the literature data. The golden variety had a lower amount of fibers and a higher amount of soluble carbohydrates than the brown variety. The techniques of thermogravimetry and differential scanning calorimetry were applied for elucidating the thermal degradation process of the seeds. The toasted gold and brown seeds were more stable to thermal decomposition than the raw seeds, under oxidative conditions. Golden seeds seem to be more susceptible to oxidation than brown seeds, under toasting conditions. Finally, no meaningful advantages were observed for the golden seeds in comparison to the brown ones.

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Abstract  

The thermal degradation process of mineral base lubricating oils was studied in this work by means of thermal, spectroscopic and rheologic analysis. The lubricating oils were degraded at temperatures varying from 150 to 210C, and for degradation times from 1 to 48 h. After the degradation, the lubricating oils were characterized by X-ray fluorescence, IR and NMR spectroscopies, rheological properties and thermal analyses (TG/DSC). The spectroscopic analyses determined the oxidation reaction products. TG curves indicate that the thermal stability of lubricating oils is below 161C. TG curves in air present three mass loss stages, whereas in nitrogen there are only two mass loss steps. DSC analyses in air indicate two highly exothermic peaks related to hydrocarbon oxidation and combustion processes, while in nitrogen only two endothermic peaks were observed. The decrease in the degradation temperature led to a decrease of the lubricant viscosity.

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The dehydration of CoHPO4 · 1.5H2O has been followed by means of thermal analyses at quasi isothermal-isobaric conditions. The intermediates and products prepared in the course of the TA and by calcination of the starting hydrogen phosphate in electric ovens at various temperatures have been analyzed and identified by means of thin-layer chromatography, IR spectroscopy, X-ray diffraction analysis and electron microscopy.

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Abstract  

In the present study, the effect of primary processing route on the dissolution and precipitation reactions in a commercial Al−Si alloy (designated as A390) is investigated using differential scanning calorimetry (DSC). The Al−Si alloy selected for the present investigation was processed using conventional casting and spray atomization and deposition routes. The results of differential scanning calorimetry conducted on the as-processed samples indicated no significant dissolution reaction for the as-cast A390 alloy when compared to the similar results obtained for as-spray atomized and deposited samples. However, the thermal analysis conducted on the solutionized cast and spray deposited samples exhibited no significant difference in the kinetics of precipitation reactions. The results of the differential thermal analyses were finally rationalized in terms of observed microstructural features.

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Abstract  

A newly developed Micro-Thermal Analyzer affords images based on thermal properties such as thermal conductivity, thermal diffusivity, and permits localized thermal analyses on samples of a square micrometer area by combining the imaging ability of the atomic force microscope and the thermal characterization ability of temperature-modulated differential scanning calorimetry. Since thermal penetration depth depends on frequency, one can obtain depth profiles of thermal conductivity and thermal diffusivity by varying the modulation frequency. Also, the analyzer can be used to characterize phase-transition temperatures, such as glass and melting transitions, of small sample regions with a precision of about ±3 K. Heating rates can be varied between 1 and 1500 K min–1. Modulation frequencies can be applied in the range from 2 to 100 kHz. We applied this new type of instrument to characterize microscopic thermal and structural properties of various polymer systems. The operation principles of the instrument are described, application examples are presented, and the future of the technique is discussed.

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1,10-phenanthroline (phen), 2,2′-bipyridyl (bipy), pyridine (py) and 4-picoline (4-pic) complexes of dibutyltindichloride (Bu2SnCl2) and dimethyltindichloride (Me2SnCl2) were synthesized. The complexes were characterized with the help of elemental analyses, IR spectra and thermal analyses. The complexes were found to have the compositions [Bu2SnCl2·phen], [Bu2SnCl2·bipy], [Me2SnCl2·phen], [Me2SnCl2·bipy], [Me2SnCl2·2py] and [Me2SnCl2·2(4-pic)]·H2O. All these complex compounds appeared to posses octahedral structures. Thermodynamic parameters, such as activation energyE a * enthalpy change ΔH and entropy change ΔS, for the dehydration and sublimation of the complexes were evaluated using some standard methods.

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Abstract  

Fourteen organic compounds, 1-pentene, 2-methylbutane, 2-methyl-1,3-butadiene (isoprene),n-pentane, 2-chloropropane, ethyl alcohol, 2,2,4-trimethylpentane,n-hexane,n-hepatane, 1,3-difluorobenzene, 1,2-dichloroethane, hexafluorobenzene, cyclohexane and diphenyl ether, as new reference materials for energy and temperature calibrations of differential thermal analysers (DTA) and differential scanning calorimeters (DSC) in the temperature range 100–300 K, were investigated. The purities, triple point and transition temperatures, fusion and transition enthalpies of these compounds were measured using a low-temperature DTA apparatus developed by the CTM of the CNRS in Marseille. The results obtained were compared with those produced by adiabatic precision calorimetry. Our data are in good agreement with literature values. Enthalpies of fusion and transition, triple point and transition temperatures are reproduced within ±1% and ±0.1K, respectively.

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Abstract  

The influence of thermal process for indium hydroxoformate, In(OH)(HCO2)2, used as one of the precursor material of ITO transparent conducting films, has been successfully investigated in some controlled atmospheres by unique thermal analyses equipped with a humidity generator, which are thermogravimetry - differential thermal analysis (TG-DTA), thermogravimetry in conjunction with evolved gas analysis using mass spectrometry (TG-MS) and simultaneous measurement of differential scanning calorimetry and X-ray diffractometry (XRD-DSC). The thermal process in dry gas atmosphere by linear heating experiment was indicated through a single-step reaction between 200 and 300C, while the thermal process in the atmosphere of controlled humidity proceeded through two-step reactions and the formation of crystalline indium oxide (In2O3) was effectively promoted and completed at the lower temperatures with introducing water vapor in the atmosphere. The thermal process changed dramatically by introducing water vapor and was quite different from that in dry gas atmosphere. Pure In2O3 was synthesized in inert atmosphere of controlled humidity and could be easily formed at temperatures below 260C. The XRD-DSC equipped with a humidity generator revealed directly the crystalline change from In(OH)(HCO2)2 to In2O3 and the formation of the intermediate during the thermal decomposition. A detailed thermal process of In(OH)(HCO2)2 and the effect of heating atmosphere are discussed.

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Abstract  

Co(II), Ni(II), Cu(II) and Cd(II) chelates with 1-aminoethylidenediphosphonic acid (AEDP, H4L1), α-amino benzylidene diphosphonic acid (ABDP, H4L2), 1-amino-2-carboxyethane-1,1-diphosphonic acid (ACEDP, H5L3), 1,3-diaminopropane-1,1,3,3-tetraphosphonicacid (DAPTP, H8L4), ethylenediamine-N,N′-bis(dimethylmethylene phosphonic)acid (EDBDMPO, H4L5), O-phenylenediamine-N,N′-bis(dimethyl methylene phosphonic)acid (PDBDMPO, H4L6), diethylene triamine-N,N,N′,N′,NN″-penta(methylene phosphonic)acid (DETAPMPO, H10L7) and diethylene triamine-N,N″-bis(dimethyl methylene phosphonic)acid (DETBDMPO, H4L8) have been synthesised and were characterised by elemental and thermal analyses as well as by IR, UV–VIS, EPR and magnetic measurements. The first stage in the thermal decomposition process of these complexes shows the presence of water of hydration, the second denotes the removal of the coordinated water molecules. After the loss of water molecules, the organic part starts decomposing. The final decomposition product has been found to be the respective MO·P2O5. The data of the investigated complexes suggest octahedral geometry with respect to Co(II) and Ni(II) and tetragonally distorted octahedral geometry with respect to Cu(II). Antiferromagnetism has been inferred from magnetic moment data. Infrared spectral studies have been carried out to determine coordination sites.

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