Investigation of thermal degradation of polystyrene with the aid of thermal analysis

When the DTA of polystyrene is carried out in air in a platinum sample holder, an anomalously high endothermic effect is observed. This effect was found to be related to gas-phase catalytic styrene oxidation occurring on the surface of both operating and reference platinum sample holders. Methodological recommendations are given concerning the DTA procedure for organic substances, making it possible to avoid this type of anomaly.     

Prize of the Government of the Russian Federation

Chronicle

Prize of the Government of the Russian Federation     

Prize of the Government of the Russian Federation

Chronicle

Prize of the Government of the Russian Federation     

Application of stable isotopes in Russian Federation

The increased use of enriched stable isotopes in Russian Federation resulting from the demand of medical diagnostic techniques, fundamental physical research, and the development of new materials is considered. The most perspective technology for producing wide spectrum isotopes of middle and heavy masses seems to be the gas centrifuge.     

Investigation on the thermal degradation of acrylic polymers with fluorinated side-chains

The thermal degradation of poly-2,2′,3,3′,4,4′,5,5′,6,6′,7,7′,7″-tridecafluoroheptylacrylate and poly-2,2′,3,3′,4,4′,5,5′,6,6′,7,7′-dodecafluoroheptylmethacrylate has been studied in isothermal conditions at 450-750 °C using pyrolysis-gas chromatography. The type and composition of the pyrolysis products give useful information about mechanism of thermal degradation. It was shown that the main thermal degradation process for both polymers is random main-chain scission. The major degradation products for fluorinated polyacrylate are monomer, dimer, saturated diester, trimer, and corresponding methacrylate. The fluorinated polymethacrylate gives monomer as the main product of thermal destruction. As a result of side-chain reaction, the thermal degradation of the fluorinated polyacrylate also produces remarkable amounts of alcohol. On the other hand, the respective alcohol is only a minor component among the pyrolysis products of the fluorinated polymethacrylate. For both polymers, the main nontrivial degradation product coming from the alkyl ester decomposition is the corresponding fluorinated cyclohexane. The formation of the fluorinated cyclohexanes may be accounted for a nucleophilic bimolecular substitution pathway.     

Investigation of the thermal degradation process of polystyrene brominated on the ring

The results of investigation of the degradation process of polystyrene brominated on the ring via an ionic route have been presented. Using thermogravimetric (TG) and differential thermal analysis (DTA) methods, the course of degradation of polymer samples with different bromine content has been described. Introducing of bromine on the aromatic ring influenced the initial decomposition temperature (IDT) and the temperature corresponding to the maximum of decomposition rate (T _m). The samples have been pyrolyzed at 300°C and some pyrolysis products were identified by means of gas chromatography/mass spectrometry. Finally, the possible mechanism of degradation was presented.     

Investigation of thermal degradation of polymers containing chlorine by thermogravimetry

The thermal degradation of chlorine-containing polymers used in a rubber technology has been investigated in a nitrogen atmosphere. The characteristics of degradation have been compared on the basis of thermogravimetry, carbon residues and chlorine elimination. The observed structure-dependent differences in degradation of the investigated polymers are discussed.

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Zusammenfassung Die thermische Zersetzung von in der Kautschuk-Technologie verwendeten chlorhaltigen Polymeren wurde unter Stickstoff untersucht.Die Charakteristika der Zersetzung durch die Thermogravimetrie, Kohlenrückstand und Chlorabspaltung wurden verglichen. Die in der Zersetzung der untersuchten Polymere in Abhängigkeit von ihrer Struktur beobachteten Unterschiede wurden diskutiert.

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Résumé On a étudié, en atmosphère d'azote, la dégradation thermique des polymères contenant du chlore, utilisés dans la technologie du caoutchouc.On a comparé les caractéristiques de la dégradation par thermogravimétrie, formation d'un résidu de carbone et élimination du chlore. On discute les différences observées dans la dégradation des polymères étudiés suivant leur structure.

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The effect of fullerene on the resistance to thermal degradation of polymers with different degradation processes

Investigations were made about the effect of fullerene (C₆₀) on the resistance to thermal degradation of high density polyethylene (HDPE), polypropylene (PP), polymethyl methacrylate (PMMA), and bisphenol A polycarbonate (PC) matrix by using thermogravimetric analysis coupled to Fourier transform infrared spectroscopy. The results showed that the influences of C₆₀ on the resistance to the thermal degradation of different polymers were dependent on their thermal degradation mechanism. The resistance to the thermal degradation of HDPE, PP, and PMMA were improved with the addition of C₆₀, especially for HDPE matrix, which indicated that the radical trapping played a dominant role. PP and PMMA released more gaseous products at high temperature by the random scission of C–C backbone; owing to the lower bond dissociation energy of C–C in the backbone for the existence of side chains. Meanwhile, the steric hindrance of side chains also made the radicals hard to recombine with each other and accelerated the random scission, leading to the less effect on the resistance to the thermal degradation of PP and PMMA. However, few changes of resistance to the thermal degradation were found in PC matrix with the addition of C₆₀ for its non-radical degradation mechanism.     

A comparative study of the degradation of different starches using thermal analysis

Four starches obtained from different sources were treated to thermal analysis and their mechanisms of degradation were deciphered using a rising temperature method of evaluation. A comparison of the solid state reactivity between the four starches was made, using a method known as the alpha(s)-alpha(r) method. By this method, it was possible to differentiate between four starches of completely different plant origin. Potato starch and rice starch were found to have the highest reactivity.     

Investigation of the thermal degradation of the aged pyrotechnic titanium hydride/potassium perchlorate

In previous works, the effects on the devitrification mechanism of a certain composition calcium phosphate with additives of TiO₂, SiO₂, Al₂O₃, CeO₂ have been studied. It was found that some metal oxide additives played a key role as the nucleation agent in calcium phosphate glass-ceramics, and the devitrification mechanism of calcium phosphate glass system was changed drastically by addition such as metal oxide. Hydroxyapatite (HAp), tricalcium phosphate (TCP) and β-calcium phosphate (β-CaP₂O₆) whisker are the three most biologically compatible materials to human bone in bio-ceramics field. In this work, the effect on devitrification mechanism and the physical properties of certain composition calcium phosphate glass with three above additives were investigated, and the result shown that although no fine crystalline was induced in the certain composition of calcium phosphate glass when a large amount of additive was added, but such additives play a catalyst role by lowering the activation energies of devitrification. It would supplement the mechanical properties and the biocompatibility for the calcium phosphate glasses.     

Investigation of the thermal degradation of alkyl isocyanate polymers by direct pyrolysis mass spectrometry

Thermal degradation mechanisms of alkyl isocyanate homo- and copolymers were studied using TGA and DP–MS. Both analyses showed that these polymers begin decomposing at around 190°C under inert or vacuum conditions. DP–MS analysis showed the formation of trace quantities of monomer from poly(butyl isocyanate) only and none from higher homologs. All polymers studied produced trimers as their principal decomposition product, implying that intramolecular cyclization is the dominant mechanism of decomposition.     

Investigation of water influence on coal based on thermal oxidative degradation kinetics

Journal of Thermal Analysis and Calorimetry - In order to further understand the effect of the water content on spontaneous combustion of coal, the thermal oxidative degradation kinetics of coals...     

Investigation of hexabromocyclododecane thermal degradation pathways by gas chromatography/mass spectrometry

The decomposition products of hexabromocyclododecane (HBCD), a widely used brominated flame retardant, were investigated by gas chromatography/mass spectrometry (GC/MS). HBCD thermal degradation was conducted under a moderate heating rate (10 degrees C/min) in a batch reactor using both inert and oxidizing atmospheres. GC/MS analysis allowed the identification of substances derived from the primary pyrolysis process at the moderate heating rates used. The presence of oxygen seems to have a negligible influence on the degradation products obtained in HBCD decomposition, at least at moderate heating rates. Based on the identified products, the main pathways of HBCD thermal degradation were assessed and a mechanism for HBCD decomposition was proposed. The results obtained indicate that hexa-, penta- and tetrabrominated polyaromatic structures seem not to be primary products of HBCD decomposition, and may only be obtained by secondary bromination reactions.     

Production and characterization of the biofuels obtained by thermal cracking and thermal catalytic cracking of vegetable oils

The thermal cracking and the thermal catalytic cracking of soybean oil were evaluated for the production of biofuels as an alternative to fossil fuels. The catalyst proposed for the cracking reaction was bauxite, a high-acidity and low-cost catalyst. The chromatographic profile of the biofuels obtained by cracking showed hydrocarbon compounds such as alkanes, alkenes and aromatics, as well as some oxygenated compounds such as carboxylic acids, ketones and alcohols. The products generated by the thermal catalytic cracking process showed better results than the thermal cracking products because of the low quantity of acids present. The catalyst used was thus shown to act in the secondary cracking process, in which the fatty acids decompose and generate hydrocarbons.     

Investigation of the influence of metal oxides on the thermal degradation of chlorine-containing polymers by thermogravimetry

The influence of oxides of zinc, magnesium, antimony and aluminium on the thermal degradations of polychloroprene, chlorinated polyethylene and epichlorhydrin homopolymer has been investigated. The investigations showed that these metal oxides can change the thermal stabilities and degradation processes of chlorine-containing polymers. A considerable acceleration of the dehydrochlorination of these polymers was found in the presence of zinc oxide.

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Zusammenfassung Es wurde der Einfluß von Zink-, Magnesium-, Antimon- und Aluminiumoxid auf den thermischen Zerfall von Polychloropren, chloriertem Polyäthylen und Epichlorhydrin-homopolymeren untersucht. Die Untersuchungen zeigen, daß diese Metalloxide die thermische Stabilität und die Zersetzungsprozesse von chlorhaltigen Polymeren verändern können. In Gegenwart von Zinkoxid wurde eine bedeutende Beschleunigung der Dehydrochlorierung dieser Polymere festgestellt.

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Investigation of peculiarities of sealant thermal degradation under conditions of high-temperature aging modes

Investigations on the relationship between the adhesive and thermal chemical properties of Viksint U-2-28NT sealant at high-temperature modes of adhesive joint aging are presented. It is shown that, under these conditions, if nonporous substrates are used, an abnormal thermal oxidative reaction takes place both in the volume of the adhesive, i.e., Viksint U-2-28NT sealant, and at the interphase boundary of the adhesive joint.     

The thermal degradation of polychloroprene-II study of the products of degradation

Studies have been made of the gaseous and liquid products and the involatile residue from the degradation of polychloroprene. Programmed heating was used; below 400° in addition to hydrogen chloride, small amounts of ethylene and a trace of chloroprene were detected in the volatile products. Above 400°, methane became a significant product; smaller amounts of hydrogen, ethylene and propylene were present. The liquid products were not fully characterized: the complex mixture contained products, which might be chloroprene dimers, and less volatile components containing aromatic structures. The involatile residue of partial degradation showed similarities to that obtained in PVC degradation, but differed in giving a clear indication of methyl groups. Conjugation was found to be much less extensive than in PVC after dehydrochorination; triene structures predominated, and there was little contribution from structures with 12 or more double bonds in conjugation.     

Investigation of thermal and thermooxidative degradation of some polyimides containing oxyphenylene groups in the main chain

Data for thermogravimetric analyses of some polymides synthesized from diamines and dianhydrides containing various amounts of oxyphenylene groups have been used to show the effect of the chemical structure of polyimide on its thermooxidative stability. Two polyimides were taken as examples demonstrating the possibilites of combining the methods of thermal analysis (TGA, DTA and TVA) for studying the transformations of polyamic acids and polyimides over the temperature range 20–800°.     

Investigation of thermal decomposition of polymer nanocomposites with different char residues

The pyrolysis process of polypropylene (PP), PP‐based nanoclay composites, acrylonitrile‐butadiene‐styrene (ABS), and ABS/metal hydroxide nanorods (MHR)/grapheme nanosheets (GNS) composites in a cone calorimeter test was simulated with a recently developed numerical codes, the Federal Aviation Administration ThermaKin. First, the heat release rate (HRR) and the surface temperature as a function of time were compared with experiment data. With reasonable input parameters, the pyrolysis behaviors were predicted reasonably. Subsequently, the influence of the properties of char residue on the HRR was discussed. The char residue of PP/nanoclay acted as a heat transfer barrier, while the char layer of ABS/MHR/GNS acted as a mass transfer barrier. Finally, the sensitivity of the residue characteristic parameters to the model output was discussed. Copyright © 2015 John Wiley & Sons, Ltd.