Volatile Thermal Decomposition Products Research Articles

Liquid crystalline polyurethane/POSS hybrid nanocomposites pyrolysis studies by Py-GC/MS and TG/FTIR techniques

The process of pyrolysis of liquid crystalline polyurethane (LCPU) composites with polyhedral oligomeric silsesquioxanes (POSS) has been studied using pyrolysis - gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/Fourier transform infrared spectroscopy (TG/FTIR) coupled thermoanalytical techniques. LCPU elastomers modified with POSS molecules with different architectures, bearing aromatic, isobutyl and cycloaliphatic moieties, yield various volatile products of pyrolysis that were collected and characterized. The TG study showed significant differences in the thermal behavior of composites studied, evidencing the influence of the silsesquioxane type on the polyurethane pyrolysis paths. FTIR study of volatile products of thermal decomposition showed the presence of characteristic bands originated from carbonyl, amine, ether, methylene, and unsaturated hydrocarbon linkages. GC/MS investigation confirmed the existence of compounds identified by the IR method. The application of both thermoanalytical methods made it possible to postulate the thermal decomposition routes of PU/POSS hybrids and to point out the main factors responsible for changes in the thermal stability.

Characterization of Metal-Bound Benzimidazole Derivatives, Effects on Tumor Cells of Lung Cancer.

Four new ligands and four new copper (II) coordination compounds were prepared and characterized by chemical, elemental analysis, cytotoxicity, and FTIR spectroscopy (Fourier transform infrared spectroscopy). The nature of metal–ligand coordination was investigated. The thermal properties of complexes in the solid state were studied using TG-MS techniques (thermogravimetric analysis coupled with mass spectrometry) under dynamic flowing air atmosphere to analyze the principal volatile thermal decomposition and fragmentation products that evolved during thermolysis. The intermediate and final solid thermolysis products were also determined. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assay was used to evaluate active metabolic cells as an IC50 (half maximal inhibitory concentration). The relationship between antitumor activity and the position of nitrogen atoms in the organic ligand has been shown.

Synthesis, Spectroscopic, Thermal and Catalytic Properties of Four New Metal (II) Complexes with Selected N- and O-Donor Ligands.

Four solid compounds with formulae: Co(OAc)2(Im)·H2O (I), Ni(OAc)2(Im)1.5·2H2O (II), Cu2(OAc)4(Im) (III) and Zn(OAc)2(Im)·H2O (IV) (where: Im = 1H-Imidazole) were prepared and characterized by chemical and elemental analysis, powder X-ray diffraction patterns and FTIR spectroscopy. Catalytic properties of each complex for styrene oxidation reaction were investigated. Furthermore, thermal properties of compounds were studied using the TG-DTG and DSC techniques under dry air atmosphere. Additionally, volatile thermal decomposition and fragmentation products were also investigated using the TG-FTIR spectra in air.

On determining coal classification indicators for establishing dangerous properties of mines

Currently, more than 20 qualification indicators are known by which degree of metamorphic coal transformations are established. Most of these indicators are designed for determining technological properties with industrial use of coal in mind. Due to sufficient knowledge of the indicators used, industrial classifications are constantly being improved. The modern classification by genetic and technological parameters groups the coals by the grades based on ten indicators. Of these, only one - the mass yield of volatile substances during the thermal decomposition of coal - is used as the main indicator of the manifestation of dangerous properties of coal seams without due scientific justification. Dangerous properties of coal seams during mining include: gas content of coal, a tendency to gas-dynamic phenomena and spontaneous combustion, dust forming ability and explosiveness of coal dust. In industrial classifications, the main indicator is determined for the dry ash-free state of organic matter. Manifestation of dangerous properties of coal seams occurs in the presence of both moisture and mineral impurities. This fact is not taken into account by other auxiliary indicators used to predict the hazardous properties of coal seams. Moisture in coal seams is in at least four states, and it is completely removed while analyzing the samples and is not taken into account in volatile products of thermal decomposition of coal. Thus, when using the indicator of mass output of volatile substances, influence of moisture in any form of its presence in coal on the occurrence of emergency situations is automatically ignored. The probability of emergencies during mining is largely determined by the ratio between components of organic mass (C, O, H, S, N) and mineral impurities. It is also not taken into account in normative documents which regulate safety of coal seam mining. The classification indicators defined in different ways characterize different aspects of coal conversion in metamorphic processes. Volatiles yield and average vitrine reflectance, well studied in industrial applications, correspond to different aspects of degree of conversion of starting organic matter. In order to establish dangerous properties of coal seams, their mutual substitution is unacceptable, which is confirmed by nonlinear connection between them. The existence of a genetic relationship between the outburst and fire hazard of coal seams has been established. This indicates the need to develop a unified classification of the hazardous properties of coal seams by genetic, mining engineering and geological parameters. The scientifically substantiated use in regulatory documents of a set of classification indicators that directly characterize the manifestations of the hazardous properties of coal seams will help to reduce number of accidents and injuries in coal mines.

Analytical and thermal investigations of new solid Y(III) and La(III) complexes

New compounds with formulae Y(2,4′-bpy)1.5Cl3·8H2O (I), Y(2,4′-bpy)0.5Br3·8H2O (II), La(2,4′-bpy)Cl3·5H2O (III) and La(2,4′-bpy)1.5Br3·5H2O (IV) were prepared and characterized by chemical and elemental analysis, IR spectroscopy and powder X-ray diffraction. The thermal properties of compounds in the solid state were studied using TG-DTA techniques under dry air atmosphere. The thermal behavior of investigated compounds was studied in the temperature range 298–1273 K. They are stable up to 323 K. The complexes decompose in several stages, accompanied by endo- and exothermic effects. In all cases, the first step of pyrolysis is partial or total dehydration. When the temperature rises, deamination takes place. The solid final products of decomposition are Y2O3 and La2O3, respectively. Additionally, for all complexes mass spectrometry was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis under dry air atmosphere.

3-D lanthanide coordination polymers with the flexible 1,3-phenylenediacetate linker: Spectroscopic, structural and thermal investigations

Four isostructural lanthanide coordination polymers of the formula [Ln2(1,3-pda)3(H2O)]·H2O where Ln = Gd(1), Dy(2), Er(3), Lu(4) and 1,3-pda = 1,3-phenylenediacetate were hydrothermally synthesized and characterized by vibrational spectroscopy, thermal analysis, powder and single-crystal X-ray diffraction methods. All 1,3-phenylenediacetates act as μ4-linkers and connect the eight-coordinate lanthanide ions into the 3-D coordination networks. Carboxylate groups in the ligands molecules exhibit diverse conformations: both trans or trans and cis. Changes of Ln–O bond lengths among the investigated compounds point out to the lanthanide contraction. Infrared and Raman spectra confirmed that both carboxylic groups of ligand were deprotonated. The presence of the band of non-hydrogen bonded hydroxyl group from water molecule in the infrared spectra was discussed. Thermal behaviour of the complexes was investigated by the TG-DSC and TG-FTIR methods. The investigated complexes are thermally stable in air and nitrogen atmosphere up to 106–135 °C. Further heating of the complexes leads to dehydration and decomposition. Water, carbon oxides, m-xylene and methane are main volatile products of complexes thermal decomposition in nitrogen.

Thermal-Decomposition Products of Hexane-Insoluble Asphaltenes from Coal Pitch

The thermal-destruction products of hexane-insoluble asphaltenes from coal pitch and petroleum asphaltenes are compared. The volatile thermal-decomposition products of the asphaltenes are studied by thermal analysis and gas–liquid chromatography and mass spectroscopy. The morphology and structure of the solid residue is investigated by scanning electron microscopy and X-ray phase analysis. By that means, the analysis of the thermal-decomposition products permits assignment of the asphaltenes to known structural types and prediction of the coke residue’s morphology. The volatile thermal-decomposition products from coal pitch are aromatic polycondensed compounds with 3–7 aromatic nuclei, including N- and S-bearing compounds. The thermal decomposition of petroleum asphaltenes is accompanied by the liberation of alkanes, alkenes, and O-bearing compounds, with chain length from C11 to C30. The content of arenes and polyaromatic hydrocarbons in the volatile thermal-decomposition products from petroleum asphaltenes is considerably less than the content of aliphatic hydrocarbons. Morphological data indicate that the solid thermolytic residues of the asphaltenes differ in structure. For petroleum asphaltenes, the structure is porous and, according to X-ray phase analysis, shows no signs of graphite-like structure. For the asphaltenes from coal pitch, the residue contains graphite-like structure and has a distinctive luster.

Hybrid materials based on PEGDMA matrix and europium(III) carboxylates -thermal and luminescent investigations

The synthesis and characterization of luminescent hybrid materials containing three different europium(III) complexes incorporated into the polymeric host during the copolymerization process with the commercially available monomer: ethylene glycol dimethacrylate (EGDMA) is reported. A new method of synthesis of organic–inorganic materials in the form of microspheres was proposed. The chemical structure of these materials was confirmed by the ATR–FTIR analysis. Thermal stability and pathways of thermal decomposition of the luminescent europium(III) complexes as well as obtained materials were investigated by means of the thermal analysis methods (TG–DTG–DSC) in air and inert atmosphere. Volatile products of thermal decomposition of polymeric matrix and hybrid materials were analyzed by the TG–QMS method. Luminescence properties of the complexes as dopants in the obtained materials were investigated in detail.

Design and commissioning of a thermal stability test-rig for mixtures as working fluids for ORC applications

A novel test-rig for studying the thermal stability of mixtures as working fluids for ORC applications was designed and commissioned at the Laboratory of Compressible-fluid dynamics for Renewable Energy Applications (CREA) of Politecnico di Milano, in collaboration with the University of Brescia. The set-up is a standard one, in which a vessel containing the fluid under scrutiny is placed in a vertical oven for ~ 100 hours at a constant temperature T = Tstress. During the test, the pressure P is monitored to detect thermal decomposition of the fluid. After the test, the vessel is placed in a controlled thermal bath, where the pressure is measured at different value of the temperature T, with T < Tstress and T < Tc (Tc critical temperature). The resulting isochoric pressure-temperature dependence is compared to that obtained before the fluid underwent thermal stress. If departure from the initial fluid behavior is observed, significant thermal decomposition occurred and a chemical analysis of the decomposition products is carried out using gas chromatography and mass spectroscopy. The novelty of the set-up is the possibility of taking samples of both liquid and vapor phases of the fluid, a capability that was introduced to study thermal decomposition of mixtures, whose composition depends on the pressure and temperature, as well as to capture the more volatile products of thermal decomposition of pure fluids and mixtures. Preliminary experimental results are reported for the pure siloxane fluid MDM (Octamethyltrisiloxane, C8H24O2Si3).

Synthesis, thermal study and some properties of Zn(II), Cd(II) and Pb(II) compounds with mono-, di- and trichloroacetates

New complexes with formulae: Zn(CClH2COO)2·2H2O, Zn(CCl2HCOO)2·2H2O, Zn(CCl3COO)2·2H2O, Cd(CCl2HCOO)2·H2O, Cd(CCl3COO)2·2H2O and Pb(CCl3COO)2·2H2O, were prepared and characterized by chemical, elemental analysis and IR spectroscopy. The nature of metal–ligand coordination was studied. They are small crystalline. The thermal properties of compounds in the solid state were studied using TG–DTG techniques under dynamic flowing air atmosphere. Mass spectrometer was used to analyze principal volatile thermal decomposition and fragmentation products of Zn(CCl3COO)2·2H2O evolved during pyrolysis in dynamic flowing air and in argon atmosphere.

Synthesis, thermal study and some properties of Gd(III), Tb(III), Dy(III) and Er(III) complexes with 4,4′-bipyridine and dibromoacetates

New complexes with formulae: Ln(4-bpy)(CBr2HCOO)3·3H2O (where Ln(III) = Gd, Tb, Dy) and Er(4-bpy)1.5(CBr2HCOO)3·3H2O, were prepared and characterized by chemical, elemental analysis and IR spectroscopy. The nature of metal–ligand coordination was studied. All of them are crystalline. Gd(III), Tb(III) and Dy(III) complexes are isostructural in one group. Conductivity studies (in methanol, dimethyloformamide and dimethylsulfoxide) were also discussed. The thermal properties of complexes in the solid state were studied using TG–DTG techniques under dynamic flowing air atmosphere. TG–MS system was used for Tb(III) (as an example of isostructural compound) and Er(III) complexes to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis in dynamic flowing air atmosphere.

INVESTIGATION INTO THE INFLUENCE OF FLAME RETARDANT ADDITIVES ON SOME FIRE PROPERTIES OF POLYESTER MATERIALS APPLYING SMALL-SCALE TESTING TECHNIQUES

In order to investigate the impact of some inorganic additive flame retardants on the selected fire properties of the materials based on polyester resin Polimal 1033 APy, small-scale fire testing techniques have been used. Seven samples have been studied: unmodified PES, PES modified with MoO3 (7, 14 and 21 wt%) and PES modified with Sb2O3 (7, 14 and 21 wt%). The following flammable properties of materials have been determined: the heat of combustion (HOC), the ignition temperature of volatile thermal decomposition products (Tig), self-ignition temperature and oxygen index. A cone calorimeter method has been used for determining heat release rate (HRR), mass loss, specific extinction area (SEA) and other combustion parameters. The toxicological analysis of combustion products has been conducted. Based on the obtained results, the following conclusions have been made: (1) MoO3 and Sb2O3 added to the studied material change its flammable properties and fire parameters. It can be indicated by higher HOC, higher Tig and self-ignition temperature, as well as by lower HRR and SEA. Modified materials become safer in terms of fire hazard. (2) A significant reduction in HRRmax of approx. 40% in the content of 7 wt% has been observed. The lowest HRRmaxof approximately 300 kW/m2 and 450 kW/m2 have been obtained for 21 wt% in a range of 200–600 s at 30 kW/m2 and 100–400 s at 50 kW/m2 respectively. Except for a sample containing 7 wt% of Sb2O3, a clear local reduction in HRR (from 50 to 150 kW/m2), in case of all modified samples has been noticed. (3) Sb2O3 has a greater impact on the thermostability of the studied materials compared to MoO3 in all cases of heat flux density and additive concentrations. The effectiveness of Sb2O3, as a flame retardant is the most evident at 21 wt%.

Synthesis and some properties of light lanthanide complexes with 4,4′-bipyridine and dibromoacetates

In this study, new complexes with formulae: Ce(4-bpy)(CHBr2COO)3·H2O, Ln(4-bpy)0.5(CHBr2COO)3·2H2O (where Ln(III) = Pr, Nd, Sm; 4-bpy = 4,4′-bipyridine) and Eu(4-bpy)(CHBr2COO)3·2H2O were prepared, and characterized by chemical and elemental analyses, and IR spectroscopy. The way of metal–ligand coordination was discussed. They are small crystalline. The complexes of Pr(III), Nd(III), and Sm(III) are isostructural in group. Conductivity studies (in methanol, dimethylformamide, and dimethylsulfoxide) were also performed and described. The thermal properties of complexes in the solid state were studied using TG–DTG techniques under dynamic flow of air atmosphere. TG–MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolyses of Ce(III) and Sm(III) complexes in dynamic flow of air atmosphere.

ТЕРМОДЕСТРУКЦИЯ В АТМОСФЕРЕ АЗОТА ДРЕВЕСИНЫ СОСНЫ, МОДИФИЦИРОВАННОЙ БОРАЗОТНЫМИ СОЕДИНЕНИЯМИ

Studied the thermal destruction of pine wood in a nitrogen atmosphere. As modifiers used in aqueous solutions boron- nitrogen compounds. Found that the modification of pine boron- nitrogen compounds leads to partial cross-linking (enlargement) of the fragments of carbohydrates and lignin, which will reduce the output of low-molecular compounds forming fraction of combustible volatile thermal decomposition products in a nitrogen atmosphere. Moreover, as a consequence, decreases the value of the mass loss of modified pine wood samples compared to non-modified samples. Changes in the chemical composition of the surface of the wood as a result of the modifications amine borates facilitates the process of carbonization.

Synthesis, thermal behavior, and other properties of Y(III) and La(III) complexes with 4,4′-bipyridine and trichloro- or dibromoacetates

New Y(III) and La(III) complexes with 4-bpy (4,4′-bipyridine) and trichloro- or dibromoacetates with the formulae: Y(4-bpy)2(CCl3COO)3·H2O I, La(4-bpy)1.5(CCl3COO)3·2H2O II, Y(4-bpy)1.5(CHBr2COO)3·3H2O III, and La(4-bpy)(CHBr2COO)3·H2O IV were prepared and characterized by chemical, elemental analysis, and IR spectroscopy. Conductivity studies (in methanol, dimethyloformamide, and dimethylsulfoxide) were also described. They are small, crystalline substances. The way of metal–ligand coordination was discussed. The thermal properties of complexes in the solid state were studied by TG-DTG techniques under dynamic flowing air atmosphere. TG-FTIR system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis in dynamic flowing argon atmosphere for La(III) compounds.

Thermoanalytical, spectral and biological study of 4-bromobenzoatozinc(II) complexes containing bioactive organic ligands

New zinc(II) 4-bromobenzoate complex compounds with general formula [Zn(4-BrC6H4COO)2L2]·xH2O (where L = urea, nicotinamide, phenazone or thiourea, x = 0–2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition, the neutral organic ligand, bis(4-bromophenyl)methanone and carbon dioxide were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 800 °C was zinc oxide, which was confirmed by X-ray powder diffractometry. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternata and M. gypseum). It was found that bacterium S. aureus and fungi A. alternata are the most sensitive to the studied compounds.

Pyrolysis study of hydrophobic tholins By TG-MS, TG, DTA and DSC methods

This study presents the thermogravimetry (TG) of hydrophobic tholins, obtained from different simulation experiments of prebiotic synthesis carried out in a CH4/N2/H2 atmosphere with spark discharge activation of aqueous aerosols and liquid water. Differential thermal analysis and differential scanning calorimetry were also used to evaluate the thermal behaviour of these complex organic compounds that could play an important role in prebiotic chemistry. A coupled thermogravimetry-mass spectrometry system allowed us to analyse the principal volatile thermal decomposition and fragmentation products of the hydrophobic tholins under dynamic conditions and an inert atmosphere. During their thermal degradation, which occurs in two stages, a wide variety of hydrocarbon products including methane, vinyl monomers (such as ethylene and propylene), acetylene, oligomers, and some other unknown compounds are found. Besides, a thermally stable structure is present (graphitic structure) in these particular organic substances. Finally, data collected from TG experiments in an oxidative atmosphere showed significant differences at temperatures above 240 °C. According to these results, the different techniques of thermal analysis here applied have proved to be an adequate methodology for the study and characterization of these complex systems, structures of which remain controversial even in these days.

Thermal behavior and other properties of Pr(III), Sm(III), Eu(III), Gd(III), Tb(III) complexes with 4,4′-bipyridine and trichloroacetates

A novel mixed-ligand complexes with empirical formulae: Ln(4-bpy)1.5(CCl3COO)3·nH2O (where Ln(III) = Pr, Sm, Eu, Gd, Tb; n = 1 for Pr, Sm, Eu and n = 3 for Gd, Tb; 4-bpy = 4,4′-bipyridine) were prepared and characterized by chemical, elemental analysis and IR spectroscopy. Conductivity studies (in methanol, dimethylformamide and dimethylsulfoxide) were also described. All complexes are crystalline. The way of metal–ligand coordination was discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Pr6O11, Ln2O3 (for Sm, Eu, Gd) and Tb4O7. TG-MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Pr(III) and Sm(III) compounds in air.

Thermal characterization of HCN polymers by TG–MS, TG, DTA and DSC methods

This paper presents a thermogravimetry (TG) study of hydrogen cyanide polymers, synthesized from the reaction of equimolar aqueous solutions of sodium cyanide and ammonium chloride. Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were also used to evaluate the thermal behaviour of these black polymers, which play an important role in prebiotic chemistry. A coupled TG–mass spectrometer (MS) system allowed us to analyze the principal volatile thermal decomposition and fragmentation products of the isolated HCN polymers under dynamic conditions and an inert atmosphere. After dehydration, a multi-step decomposition occurred in this particular polymeric system, due to the release of ammonia, hydrogen cyanide (depolymerization reaction), isocyanic acid (or cyanic acid) and formamide; these two latter species allow us identify bond connectivities. Finally, data collected from TG experiments in an oxidative atmosphere showed significant differences at higher temperatures, above 400 °C. According to these results, the different techniques of thermal analysis here applied have demonstrated to be an adequate methodology for the study and characterization of this complex macromolecular system, whose structure remains controversial even today.

Thermal decomposition and antimicrobial activity of zinc(II) 2-bromobenzoates with organic ligands

New zinc(II) 2-bromobenzoate complex compounds with general formula Zn(2-BrC6H4COO)2·nL·xH2O (where L = urea, nicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, isonicotinamide, phenazone n = 0–2, x = 0–2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition organic ligand, carbon dioxide and bis(2-bromophenyl)ketone were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 1073 K was zinc oxide. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternate and M. gypseum). It was found that the selected bacteria were more sensitive to the studied zinc(II) complex compounds than the yeast and the filamentous fungi.