Study on the effects of flame retardants on the thermal decomposition of wood by TG–MS

The effect of three flame retardants, K₂CO₃, Na₂SiO₃·9H₂O, and Na₂B₄O₇·10H₂O on the process and composition of volatile products of the thermal degradation of wood has been investigated by the thermogravimetric (TG), differential thermogravimetry (DTG), differential thermal analysis (DTA), and the synchronous thermogravimetry–mass spectrometry (TG–MS) analysis methods. The results showed that the ion current intensity and ion peak area of m/z = 18 and 44 MS signals were increased by the flame retardants but the ion peak area of m/z = 28 MS signal was decreased (except K₂CO₃) at the meantime. What’s more, the ion current intensity and ion peak area of m/z = 60 and 68 MS signals were also decreased (except K₂CO₃), which mean that Na₂B₄O₇ can significantly enhances the dehydration and inhibits the depolymerization of wood. Although K₂CO₃ accelerates the dehydration reaction, it cannot inhibit the depolymerization reaction effectively, so the flame retardant efficiency of K₂CO₃ is decreased with the higher concentration. The catalysis of dehydration reaction of Na₂SiO₃ is the worst one.     

Using TG–FTIR and TG–MS to study thermal degradation of metal hypophosphites

Three typical metal hypophosphite flame retardants La(H₂PO₂)₃·H₂O (LHP), Ce(H₂PO₂)₃·H₂O (CHP), and Al(H₂PO₂)₃ (AHP) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis (TG), derivative thermogravimetric analysis, and differential thermal analysis. The thermal degradation products from the synthesized metal hypophosphites were also investigated using thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR) and thermogravimetry coupled with mass spectrometry (TG–MS). The synthesized metal hypophosphites were also used as flame retardants for poly (1,4-butylene terephthalate) (PBT), and the combustion properties of flame-retarded PBT were evaluated using the limiting oxygen index and UL-94 tests. The results showed that the metal hypophosphites LHP, CHP, and AHP can be used as effective flame retardants for PBT, and these compounds can be obtained through a simple precipitation method. TG–FTIR and TG–MS results showed that the degradation process of AHP involves two steps, corresponding to the removal PH₃ reaction and the further dehydration reaction of the hydrogen phosphate aluminum. While LHP and CHP have three degradation steps, the additional step is due to that LHP and CHP which will loss the crystal water at lower temperature.     

TG–DSC–FTIR–MS study of gaseous compounds evolved during thermal decomposition of styrene-butadiene rubber

The thermal decomposition behavior of styrene-butadiene rubber was studied using a system equipped with thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, and mass spectroscopy. Two different experiments were conducted. From these experiments, thermogravimetric analysis results indicated a mass loss of 58 % in the temperature range of ~290–480 °C and a mass loss of 39 % in the temperature range beyond 600 °C. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy confirmed the presence of oxides, even at 1,000 °C, accounting for the Zn, Mg, Al, Si, and Ca in the original sample.     

DSC-TG studies on kinetics of curing and thermal decomposition of epoxy–ether amine systems

The cure behavior of diglycidyl ether of bisphenol A with a simple ether amine (4,7,10, trioxa -1,13, tridecane diamine), system I and a polyether amine (polypropylene glycol block polyethylene glycol block polypropylene glycol bis 2 amino propyl ether), system II was compared by Differential Scanning Calorimetry. The exothermicity of the curing reaction of system I is higher than that of system II (316 ± 15 J g^?1 for System I and 230 ± 15 J g^?1 for system II). Kinetic parameters viz., activation energy, pre-exponential factor, and rate constant for curing were evaluated by Kissinger method and Kissinger–Akahira–Sunose isoconversion method. Both systems showed low glass transition temperatures and System II shows a much lower T _g (?38 °C) than system I (26 °C). The thermogravimetric analysis of the two cured epoxy amine systems showed comparable thermal stability.     

Activation energy in the thermal decomposition of MgH2 powders by coupled TG–MS measurements

The thermal desorption of hydrogen from commercial MgH₂ powders was investigated by coupled thermogravimetry and mass spectroscopy (TG–MS). The analysis of the evolved gas species gives a detailed picture of the composition of the initial specimen and of its thermal decomposition: just before the H₂ release from MgH₂, additional H₂O and CO₂ are detected, sensing the presence of MgCO₃ and Mg(OH)₂ in the initial specimen. Measurements done at different heating rates allowed the determination of apparent activation energies for the whole thermal process. Moreover, by considering appropriate ion current signals of the MS data, the activation energies of the single chemical reactions, leading to the formation of H₂O, CO₂, and H₂, were obtained. Differences coming from the choice of the (model-free isoconversion) method of analysis (Kissinger–Akahira–Sunose; Flynn–Wall–Ozawa; Starink; Friedman equations) are evidenced and discussed.     

Preparation of copper ferrite by sol–gel method and the synergistic catalytic for the thermal decomposition of ammonium perchlorate

Journal of Sol-Gel Science and Technology - In the present work, copper ferrite was prepared by a simple and mild sol–gel method followed by low-temperature calcination, and characterized by...     

Theoretical study of mechanism and kinetics for the reaction of hydroxyl radical with 2′-deoxycytidine

The reaction mechanism and kinetics for the abstraction of hydrogen and addition of hydroxyl radical (OH) to 2′-deoxycytidine have been studied using density functional theory at MX06-2X/6-311+G(d,p) level in aqueous solution. The optimized geometries, energies, and thermodynamic properties of all stationary points along the hydrogen abstraction reaction and the addition reaction pathways are calculated. The single-point energy calculations of the main pathways at CCSD(T)/6-31+G(d,p)//MX06-2X/6-311+G(d,p) level are performed. The rate constants and the branching ratios of different channels are evaluated using the canonical variational transition (CVT) state theory with small-curvature tunneling (SCT) correction in aqueous solution to simulate the biological system. The branching ratios of hydrogen abstraction from the C1′ site and the C5′ site and OH radical addition to the C5 site and the C6 site are 57.27% and 12.26% and 23.85% and 5.69%, respectively. The overall calculated rate constant is 4.47?×?10⁹ dm³ mol^?1 s^?1 at 298 K which is in good agreement with experiments. The study could help better understand reactive oxygen species causing DNA oxidative damage.     

Study on thermal degradation of cattlehide collagen fibers by simultaneous TG–MS–FTIR

Leather was useful materials since dawn of human history for excellent properties, but thermal degradation mechanism was not very clear yet. In this paper, much progress has been made in elucidating the thermal stability and thermal degradation mechanism by thermoanalytical study in argon. Thermogravimetric analysis simultaneously coupled with mass spectrometry and Fourier transform infrared spectrometry was employed to study the thermal degradation of cattlehide collagen fibers through in-depth analysis of the evolved gas. Thermogravimetry analyses carried out on sample, deprived from any residual catalyst and highlighted a two-step thermal degradation. New evidence demonstrates that the process during temperature range from 373 to 513 K was phase transformation. Photographs of polarizing microscope confirmed the conclusion. The decomposition of cattlehide collagen fibers starts at about 523 K. The cattlehide collagen fibers may undergo the process of melting, oxidation and decomposition. In decomposition, more than three steps take place. The mass spectra and Fourier transform infrared spectrometry stated clearly that double bond of carbon to oxygen, carbon to sulfur and carbon to nitrogen were destroyed firstly because the carbon dioxide, carbon monoxide and ammonia evolved simultaneously. The second peak of carbon monoxide in mass spectra indicated that some organic fragments were decomposed above 1073 K which confirmed that thermal degradation of leather is more than three steps.     

Theoretical studies on the mechanism of the thermal decarboxylation and decarbonylation of a number of α-keto-acids

Both processes of decarboxylation and decarbonylation of a number of acids including RCOCO2H,R=H,CH3,CH2F,CF3,CH=CH2,Ph,OH have been studied by semi-empirical MO theory AMI method to verify the reaction mechanism of each process and the effect of different substituents on them.The calculated results are consistent with the experimental reports and can be summed up as follows:(1) The decarboxylation of these acids to form aldehydes and carbon dioxide is concerted and takes place through a 4-membered ring transition state in which a partial negative charge develops on the carbon of the α-carbonyl group,so that the inductive effect of some substituents is favourable for this process.(2) Their decarbonylation into carboxylic acids and carbon monoxide however is the attack of the OH on the carbon of the alkyl portion of the acid,forming a 3-membered ring transition state.(3) The activation energy of decarbonylation is lower than that of decarboxylation,since oxygen is more nucleophilic than hydrogen and als     

Facile synthesis of TiO2–PC composites for enhanced photocatalytic abatement of multiple pollutant dye mixtures: a comprehensive study on the kinetics,mechanism, and effects of environmental factors

Research on Chemical Intermediates - In the recent era, the inevitable emergence of versatile micropollutants in ground and surface water has become a serious concern for the long-term...     

Study of effect of phosphate and uranium ions on the thermal properties of surfactant-modified natural red clay using TG–FTIR–MS techniques

Products of sorption of uranyl ions on HDTMA-red clay in the presence of phosphates were characterized by thermal analysis. It was established on the basis of DTG curves of the sorption products and FTIR spectra of the gaseous phase of sorption products decomposition that the thermal stability of the mineral increased when P(V) ions were sorbed along with U(VI) ions, i.e., the temperature of defragmentation/oxidation of surfactant increased when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay to P(V)–HDTMA-clay. The DSC curves of the sorption products showed that defragmentation/oxidation was an exothermic process and dehydration and dehydroxylation had an endothermic character. The investigated sorption system has practical importance, since an evident increase in U(VI) sorption over the entire pH range is observed when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay.

     

Effect of different nanoparticles on thermal decomposition of poly(propylene sebacate)/nanocomposites: Evaluation of mechanisms using TGA and TG–FTIR–GC/MS

In the present study poly(propylene sebacate) (PPSeb) nanocomposites containing 2 wt% of fumed silica nanoparticles (SiO₂) or multiwalled carbon nanotubes (MWCNTs), or montmorillonite (MMT) were prepared by in situ polymerization. The thermal degradation of nanocomposites was studied using thermogravimetric analysis (TGA). It was found that the addition of MWCNTs and MMT enhances the thermal stability of the polymer, while SiO₂ nanoparticles do not affect it. From the variation of the activation energy (E) with increasing degree of conversion it was found that the decomposition of nanocomposites proceeded with a complex reaction mechanism with the participation of at least two different steps. To evaluate the thermal decomposition mechanisms and mainly the effect of nanoparticles on the thermal decomposition of PPSeb, TGA/FTIR and a combination of TG-gas chromatography–mass spectrometry (TG/GC–MS) were used. From mass ions detection of the formed decomposition compounds it was found that the decomposition of PPSeb and its nanocomposites, takes place mainly through β-hydrogen bond scission and, secondarily, through α-hydrogen bond scission. The main decomposition products were aldehydes, alcohols, allyl, diallyl, and carboxylic acids.     

Crystal structure and thermal decomposition mechanism of the supramolecular complex of barium chloride with inositol

The single crystal of [Ba(H2O)2(C6H12O6)2Cl2] was obtained based on the phase equilibrium results. Its structure was determined by X-ray crystallographic analysis. The crystals are monoclinic and in space group C2/c with a=1.901 7(2) nm, b = 0.682 13(8) nm, c = 0.162 60(2) nm,β=96.593(2)°and V= 2.095 3(4) nm3, Z= 4, DC=1.917 g·cm-3. In its solid state, this supramolecular complex is a three-dimensional network with double layers connected by hydrogen bondings. The molecule structure of [Ba(H2O)2(C6H12O6)2Cl2] has a central barium ion that is coordinated to two water molecules, two chlorides, and four hydroxyls from the two inosi-tols. Losing the coordinating water is controlled by random nucleation and growth mechanism (n = 2/3) and 3-dimensional diffusion mechanism (n=2).     

TG/MS study of the thermal devolatization of Copoazú peels (Theobroma grandiflorum)

The Amazonian rain forest is the source of several numbers of species in the world, some of those vegetal species have been carried to different places due to their utility. One of those species is the Thehobroma grandiflorum, pulp and seeds of which have several usages in the food industry, but the shell has no extensive use. One of the possibilities due to the nature of the material is the pyrolysis process for obtaining valuable products. Thermal analysis was studied for the biomass thermochemical conversion process under TG/MS techniques. Three different heating rates were used for the thermochemical process. A variety of hydrocarbon and oxygenated products with industrial importance were obtained. The kinetics of the evolved species was studied under three different models. DAEM model fit the thermogravimetric data with good agreement. The parameters obtained for the model agreed with the studied intensities of the MS data. Those ones that did not fit were due to possible gas-phase reactions between the compounds obtained.     

Effect of the annealing temperature on crystalline phase of copper oxide nanoparticle by copper acetate precursor and sol–gel method

A sol–gel route to synthesize copper oxide nanoparticles with an average size of ca. 63 nm from copper acetate precursor and monoethanolamine as the capping agent is reported. Structural characterization showed the formation of a cubic phase for CuO. The effect of annealing temperature on formation of crystalline phases was investigated. Characterization of the products was performed using thermo-gravimetric analysis, X-ray diffraction, field emission scanning electron microscopy, and diffuse reflectance. The results showed that there are significant differences in the morphological, crystallographic, structural, and optical properties of the nanostructures prepared at different annealing temperatures. The optical properties and band gap of CuO nanoparticles were studied by UV–Vis spectroscopy. According to the results of the optical measurements, the band gap is estimated to be 1.41 eV. These results showed that the band gap energy changed with increase of annealing temperature, which can be attributed to the change in grain size of the samples.