Thermal Destruction Processes Research Articles

THE INFLUENCE OF ELECTRONIC EXPOSURE AND HEAT TREATMENT ON THE ELECTROCONDUCTIVITY OF EPOXYPOLYMER MATERIALS

The influence of electron irradiation fluxes with energy of 12 MeV and heat treatment on the electrical properties of epoxypolymers with PEPA content of 11, 12 and 13 wt.h. per 100 wt. including epoxy resin. It is show that the electrical conductivity of epoxypolymer increases with electron irradiation fluxes greater than 10 kGy. It found that extra heat treatment of irradiated samples with a hardener content of 12 wt. h. hours leads to an increase in their electrical conductivity. The nature of the obtained dependences of electrical conductivity is determine by the processes of cross-linking, radiation, thermal destruction and mass fraction of the hardener. Radiation-stimulated increase in the conductivity of epoxypolymers can be use to create conductive protective coatings and sensor electronics elements

The Metod of Control of Influence of Temperature on Processes of Oxidation and Thermal Destruction of Full Synthetic Motor Oil ALPHA’S 5W-40 SN

The results of the study of influence of the processes of oxidation and thermal destruction on the optical properties, the kinematic viscosity, volatility and anti-wear properties of full synthetic motor oil are presented. It was found, that the processes of thermal destruction have reduced the rate of change of optical density, volatility, kinematic viscosity and anti-wear properties, however the processes of thermal destruction have dominated at the processes of oxidation, when optical density is more 0,4

Tri- and tetranuclear heteropivalate complexes with core {Fe2NixO} (x = 1, 2): Synthesis, structure, magnetic and thermal properties

The reactions of complex [Fe2Ni(O)(Piv)6(Et2O)(H2O)2] (1) with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) gave the following new coordination compounds: the trinuclear complex [Fe2Ni(O)(Piv)6(phen)H2O]·(C2H5)2O (2), the tetranuclear ones [Fe2Ni2(OH)2(Piv)8(phen)2] (3) and [Fe2Ni2(OH)2(Piv)8(bpy)2] (4), depending on the crystallization conditions. According to single crystal X-ray diffraction data, all the compounds have molecular structures. The Mössbauer spectra of 1–3 correspond to high-spin Fe3+ ions in an octahedral environment consisting of oxygen atoms. The DC magnetic susceptibility studies and quantum-chemical analysis of intra- and intermolecular J pathways using broken-symmetry density functional theory (DFT) showed that all exchange interactions in tri- (1, 2) and tetranuclear (3) complexes are antiferromagnetic. The exchange coupling is weaker in 3 due to the lower ability of the bridging OH-groups to mediate superexchange. Thermal destruction processes have been studied for 2 and 3. The final products of thermolysis are the mixed oxide NiFe2O4.

Coupled problems of high-speed aerodynamics and thermomechanics of heat-shielding structures

An algorithm for the numerical solution of the coupled problem of high-speed aerodynamics of aircraft and thermomechanics of heat-shielding structures from thermally decomposing polymer composite materials is proposed. The algorithm is step-by-step and at each time step includes the steps of solving the Navier-Stokes equations with chemical reactions, calculating the heat fluxes to the structure, calculating the internal heat transfer in the material of the structure, calculating the structural ablation, calculating the temperature field in the structure, calculating the stress-strain state of the composite structure materials taking into account phase transformations and temperature degradation of the materials characteristics. In the calculations, the temporary effects of elastic characteristics changing and shrinkage caused by the processes of thermal destruction of the composite are also taken into account. The results of simulation for a model aircraft design illustrating the application of the proposed algorithm are presented.

Physicomathematical Modeling of Ignition of a Heterogeneous Mixture of Methane, Hydrogen, and Coal Microparticles

A physicomathematical model is developed for ignition and combustion of a methane–air mixture containing coal microparticles. The model takes into account the detailed kinetics of oxidation of the gaseous methane–hydrogen–air mixture and the processes of thermal destruction of coal particles with release of volatiles (methane and hydrogen) to the gas phase, ignition and combustion of these volatiles in the gas phase, and heterogeneous reaction of carbon oxidation. It is demonstrated that addition of coal particles to the methane–air mixture in the temperature interval from 900 to 1450 K reduces the ignition delay time. Moreover, addition of coal particles to the methane–air mixture leads to shifting of the ignition limit of the gas mixture toward lower temperatures. The calculated delay time of coal ignition in the air–coal mixture and the predicted delay times of methane and coal ignition in the methane–air–coal mixture are found to be in reasonable agreement with experimental data obtained in a rapid compression machine.

Investigation of Thermal Destruction Processes of Waste Insulation of Main Gas Pipelines

The possibility of applying the thermal method for neutralizing waste re-insulation during the major overhaul of main gas pipelines is considered. The initial composition of the organic part of the waste is shown. The thermal effects observed during the decomposition of waste in a controlled atmosphere, the composition of waste gases and the results of thermal analysis of waste samples resulting from the replacement of insulation of gas pipelines selected for maintenance and repair of linear sections of main gas pipelines are examined. Ways of solving the problem of elimination of waste generated during the gas pipeline overhaul are suggested.

Встановлення ефективності вогнезахисту деревини органо-неорганічною композицією

Опис поведінки вогнезахисних засобів у момент формування теплоізоляційної структури є окремим і складним завданням, а просочення характеризується розкладом антипіренів під дією температури з поглинанням тепла та виділенням негорючих газів, гальмування окислення в газовій і конденсованій фазі та утворенням на поверхні деревини теплозахисного шару коксу. Наведено результати дослідження процесу термодеструкції деревини сосни і визначено термограми її розкладу та встановлено, що кінетика процесу розкладу деревини вогнезахисної композицією "Skela-i" зміщується у напрямку високих температур, із коксовим залишком у 4 рази більшого ніж для необробленої деревини. Експериментально встановлено, що під дією теплового потоку на вогнезахищені зразки відбувається інтенсивне виділення інертних газів та зменшення горючих, що доводить про ефективність вогнезахисту. Після випробувань виявлено, що інтенсивність утворення негорючих газів переміщується у сторону підвищеної температури з утворенням пінококсу. Газохроматографічними дослідженнями аналізу летких продуктів піролізу вогнезахищених зразків виявлено збільшення негорючих газів у 8 разів та зменшення вмісту горючих – понад 50 %. Здійснено дослідження з визначення групи горючості деревини та встановлено зменшення у 3 рази втрати маси зразків захищеної деревини, порівняно з необробленими, а температура димових газів становила менше 165°С.

Recent developments in fire-retardant thermoset resins using inorganic-organic hybrid flame retardants

Abstract Inorganic-organic hybrid modifiers have attracted attention of scholars worldwide because they combine the advantages of both different components and provide a way for modifying the structure and properties of polymeric materials. The article describes and investigates a positive effect of reduced flammability of thermoset resins resulting from the use of nanocomposites containing new inorganic-organic hybrid flame retardants (FRs) that combine conventional phosphorous/nitrogen modifiers interacting with nanofillers. The impact of these inhibitors on the level of flammability of thermoset resin compositions was defined by determining the value of limiting oxygen index, thermogravimetric and cone calorimeter analysis of thermal destruction processes. Morphology of composites was assessed using a scanning microscope and an analysis of actual scanning electron micrographic images. The analysis of thermal decomposition of the materials under examination confirmed flammability reducing properties of the inorganic-organic hybrid FR used, and a synergist to generate integrated flame retarding effect was observed between conventional modifiers and nanofillers, in particular carbon nanofillers: expandable graphite, graphene and graphene oxide. The inorganic-organic hybrid FR will provide a new solution to efficient FR polymeric materials.

New heterometallic pivalates with FeIII and ZnII ions: Synthesis, structures, magnetic, thermal properties

Techniques for synthesizing Zn(II)-Fe(III) heterometallic molecular complexes [Fe2Zn4O2(Piv)10] (1), [Fe4Zn3O3(Piv)12(H2O)]·1.5Et2O (2) and [Fe3Zn2O2(Piv)9(1,10-phen)] (3) (where HPiv is pivalic acid, 1,10-phen – C12H8N2) have been developed. It has been found that recrystallization of the solid product formed from reaction mixture of Fe(NO3)3, Zn(NO3)2, KOH and HPiv (in the 3:2:13:34 ratio) in water («Reagent A») from acetone results in hexanuclear complex 1, whereas thermolysis of «Reagent A» at 130°C in air followed by crystallization of the thermolysis products from ether makes it possible to isolate complex 2. It has been found that dissolution of thermolyzed «Reagent A» in MeCN in the presence of 1,10-phenanthroline leads to formation of complex 3. The structures of complexes 1–3 were determined by single crystal X-ray diffraction analysis. The doublet Mössbauer spectra of complexes 1 and 2 correspond to high-spin Fe3+ ions in an octahedral environment of oxygen atoms, while the non-equivalence of the environment of iron ions in compound 3 (FeO6 and FeO4N2) is reflected by two observed doublets with different intensities. Based on the results of magnetic data simulation and quantum-chemical calculations, it has been shown that antiferromagnetic exchange coupling exists in complexes 1 and 2 (J12=−3.05cm−1 for 1 and J12=−0.4, J13=−13.5, J23=−3.6, J24=−27.2 and J34=−30.1cm−1 for 2). The value of the exchange integral between pairs of metal ions correlates with the Fe-O distances and the Fe-O-Fe angles in the bridging oxo ligands. Processes of thermal destruction have been studied for complexes 1 and 2 in argon atmosphere in the temperature range of 25–500°C.

Changing the Structure of Resin-Asphaltenes Molecules in Cracking

In the paper, structural changing of resin-asphaltene molecules in cracking process of oil sand bitumen are investigated. Cracking process to natural bitumen carried out in an open-to-air reactor, which extracted from oil sand by organic solvent. Reaction temperature was 450 °С and process duration was 60 min. The reactor was heated at a rate of 10 °C/min up to the desired temperature. Di-tert-butyl peroxide was used as radical formation additive. When limiting oxygen, it can be used catalyst molecule supplies as the oxidizer. The thermal destruction processes of heavy hydrocarbons with the catalyst make it possible to increase the yield of low boiling liquid products with the formation of coke and gas as by-products. High temperature leads to increase the oil content, and decrease the total resinasphaltene components in bitumen. Monte Carlo method used for construction the molecular structure of resin-asphaltene components. The calculations data determined the most stable conformation of resins and asphaltenes molecules, that the stability of the molecules affect structural characteristics such as the number of structural blocks, their size and spatial arrangement of atoms with respect to each other. Microscopic images showed that the asphaltenes have around 40‒50 nm of particle size, which large monolithic switching, weakly focused on a major surface, provided with amorphous carbon.

New method of investigation of polysulfone thermal destruction

The regularities of branching and thermal destruction processes of polysulfones of different chemical structure at 150–500°С are studied depending on the nature of the reactive medium and blocking method of the terminal groups with the use of a special device for a gas chromatograph allowing one to investigate the branching and thermal destruction of polymers. It is found that the nature of the solvent and deactivator of the terminal hydroxyl groups substantially affects the crosslinking and destruction processes of polysulfones.

Thermal Properties of Anionic Polyurethane Composition for Leather Finishing

Thermal properties of anionic polyurethane composition mixed with collagen product and hydrophilic sodium form of montmorillonite for use in the finishing of leather were studied by thermogravimetric method. The thermal indices of processes of thermal and thermo-oxidative destruction depending on the polyurethane composition were determined. The influence of anionic polyurethane composition on thermal behavior of chromium tanned gelatin films that imitate the leather were studied. APU composition with natural compounds increases their thermal stability both in air and in nitrogen atmosphere due to the formation of additional bonds between active groups of APU, protein and chrome tanning agent as the result of chemical reactions between organic and inorganic parts with the new structure formation.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.10043

Disordering effect on electronic mechanism of thermal destruction of GeE'-centers in glassy GeO2

Thermal destruction processes of paramagnetic GeE'-centers in two different types of GeO2 glass have been studied. By investigating the temperature dependence of the electron emission typical of these processes, we found that the electron energy is sensitive to the structural disorder. The obtained results obtained were interpreted within the framework of modified Perel-Karpus model for the ionization of local centers in electric field. It was found that the electron-phonon coupling for GeE'-centers is a parameter that depends on the structure. We have shown that relatively weak electron-phonon coupling and low values of internal electric field are characteristic features of glassy GeO2 with high degree of continual disorder. Thus, the structural disorder, that at least depends on the synthesis conditions, can be considered as an effective tool governing the fundamental and functional properties of the glass.

The Influence of the Content of Furfuryl Alcohol Monomer on the Process of Moulding Sand's Thermal Destruction

Abstract The article discusses the issue of the influence of furfuryl alcohol content in resin binders on properties of moulding sand at elevated temperature. Reducing the share of this component - due to the requirements of the European Union regarding its toxicity - may cause a decrease in temperature of moulding sands’ destruction and, consequently, the thermal deformation of moulds and the creation of many casting defects. The study examined the impact of the furfuryl alcohol content of the thermal destruction processes and on the strength of the moulding sand at an ambient temperature and the tendency to thermal deformation.

Structurization and destruction of compounds from shale phenols

The specific features of the thermal and radiation-induced structurization and simultaneous destruction processes of compounds from shale phenols containing water-saturated fillers (radiation-active ion exchangers) were studied. The empirical time dependence of the strength of hardened blocks was found, which made it possible to recommend operating conditions without significant changes in the physicomechanical properties.

Computer Simulation of Decomposition Mechanisms for CL‐20, Hydrazine, and Their Binary System

AbstractAn approach to simulate thermal destruction processes of energetic materials has been developed. It is based on the classification of structural features for nitro compounds and the experimental data regarding their decomposition mechanisms. This approach consists of the mathematical simulation of thermal decomposition mechanisms to predict the likely reactions that may occur during the destruction of organic compounds. On the basis of contemporary experimental data on the decomposition of energetic materials from various chemical classes, a set of semi‐empirical rules for modeling possible reaction pathways has been formulated. These rules allow the generation of a whole set of possible decomposition mechanisms for substances at different steps of their destruction. In this study, the suggested methodology is applied to 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) and hydrazine and to their binary energetic mixture. It has been shown that thermal decomposition of the binary system consists in decompositions of the separate compounds at the initial stage with subsequent collisions and interactions of the resultant intermediates and decomposition products at different stages. In addition to some experimentally found decomposition products, our simulation showed some other possible compounds among the final products.

Microencapsulated fire-extinguishing fluids and reactive fire-extinguishing composites formed on their basis

The application of microencapsulated liquid gasifiable fire-extinguishing agents as reactive filling compounds for fire-extinguishing composites is considered. A new process for microencapsulation of environmentally friendly fire-extinguishing agents possessing enhanced stability is designed. Novel composite materials are produced with these agents. The thermal-destruction processes of microcapsules containing liquid gasifiable fire-extinguishing agents of different compositions are considered. Laboratory and bench-mark firing tests of the materials are performed.

Physicochemical characterization and decomposition kinetics of trandolapril

The purpose of this work was to study the physicochemical properties of trandolapril, to perform a detailed kinetic study of its decomposition and also to evaluate its thermal stability in order to provide the essential tools to design a thermal destruction method for expired trandolapril-based drugs. Trandolapril was characterized with FTIR, XRPD and SEM and its thermal behaviour was studied with DSC and TGA in dry air and nitrogen flows. The decomposition process was also followed by Py-GC–MS, the activation energy was calculated with isoconversional methods and the reaction model was determined with model-fitting method. Trandolapril is stable until the onset of its melting (110°C) in both nitrogen and dry air environments. Thermal degradation of trandolapril can be described by two consecutive mechanisms of n-th order with activation energies 97.4 and 180.0kJ/mol respectively. Trandolapril reaches zero residual at 510 and 560°C in nitrogen and dry air flow respectively. The detailed analysis of decomposition mechanism allows the industry to design integrated thermal destruction processes for expired trandolapril-based drugs. The results of Py-GC–MS agree with the theoretical calculations of thermal analysis techniques, which highlights that the different techniques used in this work are complementary and equally important.

Investigation of the thermal stability of nucleic acids and their structural components

The thermal stability of homopolynucleotides (poly(A), poly(G), poly(C), poly(U)) and natural DNA, as well as their structural components: nucleoside (uridine), nucleotides (uridine-5'-monaphosphate, uridine-5'-diphosphate, and uridine-5'-triphosphate) and sugar (D-ribose) have been studied by the method of differential scanning microcalorimetry. The dependences of the heat flow on temperature have been obtained for the compounds having individual features in the temperature range from 20 to 400 degrees C. All samples showed exothermic peaks at temperatures higher than 200 degrees C (for DNA, this peak was found at a temperature of approximately 160 degrees C), which are related to processes of irreversible thermal destruction. The temperatures of thermal destruction and the effective energy of activation of this process for all compounds studied have been determined. The values of the effective heat of exothermal processes have been calculated for the polynucleotides. The experimental results indicate that there is a significant difference in the thermal stability between these homopolynucleotides and DNA, poly(G) being the most stable and DNA, the least stable. Based on the analysis of D-ribose, nucleoside, and nucleotides, it was concluded that the sugar ring is the most probable region of the destruction.

Thermal destruction of asphaltites in supercritical fluids

The processes of thermal destruction of asphaltites recovered from the Rafaelita and Toribia deposits in the presence of water, benzene, tetralin, and ethanol in the supercritical state are studied. The solvent nature plays an important role in the thermal destruction, with the maximum conversion (99 wt %) of both asphaltites into liquid products being achieved in a tetralin medium. Not more than 70 wt % of asphaltites is converted into synthetic oil in an aqueous medium. High-molecular compounds, resins, and asphaltenes, the total content of which amounts to more than 60 wt %, are the main components of the liquid products. No more than 40 wt % asphaltene structures, 33 wt % resins, and 40 wt % oils are formed in tetralin and ethanol media. In all the experiments, saturated hydrocarbons and polyaromatic structures are the main components of oil. A high content of saturated and polyaromatic hydrocarbons found in the products of asphaltite cracking is probably due to the destructive hydrogenation and dissolution of asphaltite organic matter.