Starting Decomposition Temperature Research Articles

Study on Pyrolysis Characteristics of Phosphate Tailings under H2O Atmosphere.

The pyrolysis separation of calcium and magnesium from phosphate tailings is an important process due to its high-value resource utilization. In this paper, aiming to address the problems of high energy consumption, a slow decomposition rate and the low activity of decomposition products in the high-temperature pyrolysis of phosphate tailings, the medium-temperature pyrolysis of phosphate tailings under a H2O atmosphere was carried out, and the phase reconstruction and activation of pyrolysis process were discussed. The results showed that compared with N2, air and CO2 atmospheres, the pyrolysis process of phosphate tailings in a H2O atmosphere was changed from two stages to one stage, the starting decomposition temperature was reduced to 500 °C and the decomposition time was shortened to 30 min. The order of the influence of each factor on the pyrolysis of phosphate tailings was temperature > H2O pressure > holding time. Under the optimized pyrolysis conditions, the yield of CaMg(CO3)2 decomposition of phosphate tailings into MgO and CaO was 97.3% and 98.1%, respectively, and the reactivity of MgO was 31.6%. The distribution of Ca and Mg elements in the phosphate tailings after pyrolysis showed a negative correlation, and both of them no longer formed associated compounds; Ca mainly existed in the form of Ca(OH)2, Ca5(PO4)3F, CaSiO3 and CaF2, and Mg mainly existed in the form of MgO, MgF2 and Mg(OH)2.

Recycling of fiber reinforced composites: Online mass spectrometric tracing, offline physicochemical speciation and toxicological evaluation of a pilot plant pyrolytic conversion

The increasing demand for lightweight materials with exceptional stability and durability has resulted in a significant rise in fiber-reinforced plastic (FRP) production. These materials find applications in various fields. However, the exceptional properties and diverse compositional range of FRPs pose challenges to conventional recycling strategies. Pyrolysis has emerged as a highly promising approach for separating the fibers from the polymer matrix. In this study, we employed thermal analysis coupled with high-resolution mass spectrometry to investigate the pyrolysis process. Representative FRP showed a starting decomposition temperature of 300 °C and bisphenol A, styrene, alkenes, and phenols could be identified. The identified parameters were used to operate a pilot plant with a capacity of up to 50 kg/h FRP, and reactor products were directly analyzed with soft photoionization mass spectrometry. The findings demonstrated good agreement between the pilot plant results and laboratory experiments, particularly for smaller compounds (m/z<200). The non-condensable fraction showed a range of 17 to 22 MJ/m3 as lower heating value. Analysis of the recovered fibers (diameter between 6.20 and 8.05 μm) revealed residual coke, but no toxic fibers were detected, according to the World Health Organization's definition. Yet, the organic coating of the fibers contained small amounts of potentially harmful PAHs. A toxicological assessment using a multicellular in vitro model confirmed the low hazardous potential of the recovered fibers. The findings contribute to developing sustainable and environmentally friendly recycling strategies for FRP while addressing important aspects related to the safety and toxicological implications of the resulting chemicals and fibers.

Novel vanillin-based benzoxazine containing phthalonitrile thermosetting system: Simple synthesis, autocatalytic polymerization and high thermomechanical properties

Benzoxazine containing phthalonitrile, as one of the most advanced high performance thermosetting resin, has gained a lot of attention in the last decades. Indeed, the combination of the thermally activated ring-opening polymerization of the benzoxazine and the cyano addition reaction of the phthalonitrile allows the development of robust polymeric networks. Following this path, a renewable natural resource, vanillin, was used to develop a new benzoxazine containing phthalonitrile thermosetting system. The newly developed monomers present the advantage of a simple synthesis process along with an autocatalytic polymerization mechanism. The molecular structures of the synthesized monomers were characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy . Thermal properties were also characterized by differential scanning calorimetry and thermogravimetric analysis . Typically, the newly developed monomers showed excellent thermal stability with starting decomposition temperatures over 496.4°C with a char yield at 800°C of about 80.7%. The thermomechanical properties were investigated by dynamic mechanical analyzer and the fractured surfaces were studied by scanning electron microscopy Globally, the newly developed partially bio polymer showed outstanding thermal resistance along with excellent thermomechanical properties.

Synthesis, Crystal Structure, Optical Properties and Stability of New Bismuth‐Based Organic‐Inorganic Compounds (C6H9N2)aBibXc (X=Cl, Br, I)

AbstractWe report a series of high‐quality, low‐dimension, and bismuth‐based organic‐inorganic hybrid single crystals (C6H9N2)aBibXc (X=Cl, Br, I) fabricated via a simple hydrothermal method. The crystal structure, intermolecular interactions, morphology, chemical groups, bond characterization, and optical and thermal stability of the samples were detailed via X‐ray single crystal diffractomete, Hirshfeld surface analysis, field scanning electron microscopy (FSEM), fourier transform infrared spectrometer (FTIR), Raman, thermal gravimetric (TG), and Ultraviolet‐visible (UV‐vis) diffuse reflectance spectra. The results indicated that the (C6H9N2)2BiCl5 and (C6H9N2)2BiBr5 crystals displayed a monoclinic system with a P21/n space group at room temperature; the (C6H9N2)BiI4 crystal was P21/c. Meanwhile, the band gap could be continuously adjusted between 3.2 eV and 1.6 eV via the nature of halide ligands. The samples also have good thermal stability. The starting decomposition temperature of (C6H9N2)2BiCl5, (C6H9N2)2BiBr5, and (C6H9N2)BiI4 were 200 °C, 250 °C, and 300 °C, respectively. Therefore, this kind of organic‐inorganic hybrid compounds will be assumed to be a promising candidate for optical and electronic applications.

Pyrolysis and Carbon Dioxide Gasification Kinetics of Pine Cones and Lignite Blends

This study determines the kinetic parameters of blended Pinus kesiya, Pinus elliottii, and Indonesian lignite in co-pyrolysis and co-gasification. Nine binary blends and three ternary blends were tested using a thermogravimetric analyzer. Pyrolysis was carried out in an argon atmosphere and DTG plots showed that Pinus kesiya had the highest maximum pyrolysis rate while Pinus elliottii had the lowest starting decomposition temperature. Similarly, blends with Pinus elliottii had lower maximum pyrolysis rates and lower starting decomposition temperatures than those with Pinus kesiya. Ternary blends, however, have starting decomposition temperatures and maximum pyrolysis rates close to those of pure Pinus elliottii. The Kissinger-Akahira-Sunose (KAS) model was used to obtain the reaction rate constants and activation energies of the pyrolysis reactions of various blends. Co-gasification of the mixtures was also done in a CO2 environment at gasification temperatures of 700°C, 800°C, and 900°C. The conversion-time data obtained were fitted using five different gas-solid reaction models.

Influence of structural modification on the properties of poly(amide–imide)s

In this study, the influence of length of flexible groups on the properties of poly(amide–imide)s (PAIs), three-model polymers (poly(amide–imide)-4-aminobutyric acid, poly(amide–imide)-6-aminocaproic acid, and poly(amide–imide)-11-aminoundecanoic acid) possessing different flexible methylene units ((CH2)3, (CH2)5, and (CH2)10) in the main chain were designed. With increasing the number of methylene units, it is found that the tensile strength of PAIs decreased from 75 MPa to 55 MPa; meanwhile, the elongation at break increased from 6% to 15%. On the other hand, the glass transition temperature decreased from 207°C to 112°C; fortunately, the starting decomposition temperature kept almost same with a high point around 400°C. Furthermore, the PAI with (CH2)10 unit in the main chain is a semicrystalline polymer, while the one with (CH2)5 or (CH2)3 unit is an amorphous material. In other words, the length of the flexible chain in the polymer backbone not only plays an important role in mechanical and thermal performances but also affects their phase transition. These findings highlight the important role of structural modification in high-performance polymers and may help in the further development of novel PAIs for their potential applications in advanced technology.

Thermal Decomposition Enhancement of HMX by Bonding with TiO2 Nanoparticles

AbstractThe appropriate structure and properties of a composite material, including the morphology, particle size, and bond strength, are very important for its performance and practical applications. The energetic material HMX (C4H8N8O8, cyclotetramethylenetetranitramine) is typically mixed with nanocatalysts to improve its thermal decomposition, which is advantageous for its detonation performance in practical applications. Inspired by the bioadhesion of mussels, a HMX@PDA@TiO2 (HMX first coated with PDA film and second coated with TiO2 nanoparticles) composite was developed in this study to greatly advance the thermal decomposition temperatures. A simple stirring process was used to prepare the composite from HMX and TiO2 nanoparticles under dopamine solutions with different pH values. Nanocatalyst TiO2 nanoparticles were anchored on the surface of HMX by reacting with the dopamine and polydopamine coatings. Compared with other reference samples, the thermal behavior of the obtained composite showed that the starting decomposition temperature was lower, at approximately 60 °C, and that the decomposition peak decreased by 35 °C, indicating that the composite properties should have great effects on the thermal performance of the materials. The findings offer a valuable composite preparation method to enhance the thermal behavior and the effect of the catalyst on the composite via bonding effects.

On the preparation and properties investigations of highly performant MXene (Ti3C2(OH)2) nanosheets-reinforced phthalonitrile nanocomposites

Taking into consideration the latest advances in both ceramic and polymer fields, a new generation of high-performance polymer composites based on the state-of-the-art MXene (Ti3C2(OH)2) ceramics and one of the leading high-performance thermosets, namely the phthalonitrile resins, is presented. The synergistic combination between the two phases led to nanocomposites exhibiting an outstanding thermal stability with starting decomposition temperatures not less than 484°C for 3 wt% of nanoloading. The tensile properties were as high as those obtained with fiber-reinforced polymer composites. For instance, the tensile strength reached its highest value of 276 MPa for the maximum loading of 3 wt%. The morphological studies carried out by scanning and transmission electron microscopies corroborated the improvements of the thermal and mechanical properties. Undoubtfully, such materials expected to be used in extreme conditions can be seen as the next generation of ceramics-reinforced polymer composites.

Reduction of brominated flame retardants (BFRs) in plastics from waste electrical and electronic equipment (WEEE) by solvent extraction and the influence on their thermal decomposition

Consumption of electronics increases due to modern society’s growing needs, which leads to increasing generation of waste electrical and electronic equipment (WEEE). Recycling of WEEE has been a global concern during the last few decades because of the toxic compounds that are produced during recycling. Different recycling techniques have been adapted on a commercial scale in order to overcome this issue, but the recycling of WEEE still lacks the technology to treat different kinds of feedstocks and to maximise the recycling rates. Pyrolysis is an alternative that has not been commercialised yet. One of the challenges for the implementation of this technology is the toxic brominated organic compounds that can be found in the pyrolysis oils.In this study, tetrabromobisphenol A (TBBPA), one of the major flame retardants, is reduced in three different WEEE fractions through solvent extraction as a treatment prior to pyrolysis. Two solvents have been experimentally investigated: isopropanol and toluene, the latter of which can be derived from pyrolysis oil. The results indicate that TBBPA was extracted during pre-treatment. Moreover, the total bromine content of WEEE material was reduced after the treatment with a maximum reduction of 36.5%. The pyrolysis experiments indicate that reduction of several brominated organic compounds was achieved in almost all the tested cases, and two brominated compounds (2,4,6-tribromophenol and 2,5-Dibromobenzo(b)thiophene) reached complete removal. Also, the thermal decomposition behaviour of the raw samples and the treated was investigated, showing that the reduction of TBBPA influences the decomposition by shifting the starting decomposition temperature.

Volatilization behaviors of molybdenum and sulfur in vacuum decomposition of molybdenite concentrate

Thermodynamic calculation, ab initio molecular dynamics (AIMD) and vacuum decomposition experiments were performed to study the volatilization behaviors of Mo and S from molybdenite concentrate by vacuum decomposition. In thermodynamic calculation, starting decomposition temperatures of reactions were calculated, and saturated vapor pressures of Mo, S and MoS2 were also analyzed. In AIMD, geometries of the S n (n≤8), Mo m (m≤8) and Mo m S n (m+n≤8) clusters have been optimized using density functional theory (DFT) with generalized gradient approximation (GGA). And these clusters were simulated in DFT with Cambridge Sequential Total Energy Package (CASTEP) code of Material Studio software. Structures and stabilities of these clusters before and after molecular dynamics simulations were discussed, and diffusion coefficients were also calculated. In vacuum decomposition experiments, relationship between heat preservation time and volatilization rate of Mo and S was obtained, while the constant temperature and chamber pressure were 1823 K and 5–35 Pa, respectively. Above all, both the theoretical and experimental results showed that volatilization behaviors of Mo and S during vacuum decomposition process of molybdenite concentrate were as follows: Mo could partly evaporate into the condensate in the form of clusters, and S could easily evaporate into the condensate.

Hydrogen storage properties of Nb-compounds-catalyzed LiBH4–MgH2

In order to improve the hydrogen storage properties of LiBH4–MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4–MgH2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH4–MgH2 system was investigated. The experimental results show that LiBH4–MgH2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320 °C, and there is a long period of incubation time (around 220 min) for the occurrence of the second decomposition step even at high temperature of 450 °C. It needs more than 10 h to complete the decomposition process and release around 9 wt% H2. After addition of 5 mol% NbF5, the starting decomposition temperature for the first dehydrogenation step is around 150 °C, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.

Heat resistance and surface properties of polyester resin modified with fluorosilicone

Abstract In this work, fluorosilicone modified polyester resin (FSP) prepared from polyester (PET) and fluorosilicone resin (FS) with excellent heat resistance and surface wettability was reported. FS was synthesized by hydrolysis and condensation reaction of 1H,1H,2H,2H-perfluoroalkyltriethoxysilane (FTEOS), methyltriethoxysilane (MTEOS), phenyltriethoxysilane (PTEOS), dimethyldimethoxysilane (DMDMOS), and diphenyldimethoxysilane (DPDMOS). The surface chemical composition and morphology of the resins were determined by Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The surface wettability and thermal property of the FPS films were studied via contact angle measurements and thermogravimetric analysis (TGA), respectively. The modified resin displayed excellent heat resistance, water and organics repellence due to the native high bond energy and low surface free energy of fluorosilicone. For the FSP resin containing 50 wt% of fluorosilicone resin (F5SP50), the starting decomposition temperature Td10 (10% weight loss) reached 360 °C, which was 40 °C higher than that of neat PET. The residual weight at 700 °C was also remarkably increased. Moreover, hydrophobicity, oleophobicity and hardness of FSP films were enhanced by optimizing the addition of fluorosilicone in polyester resin. The prepared fluorosilicone modified polyester resin has a great potential in the application of high-temperature coating.

Effect of silane surface modified titania nanoparticles on the thermal, mechanical, and corrosion protective properties of a bisphenol-A based phthalonitrile resin

Abstract A new type of nanocomposites was prepared by reinforcing a high performance bisphenol-A phthalonitrile resin with different amounts of silane surface modified titania nanoparticles. The effect of the nanofillers amount on the thermal, mechanical, and corrosion protective properties was investigated. Thermogravimetric analysis shows that the starting decomposition temperatures and the residual weight at 800 °C were highly improved upon adding the nanofillers. At 6% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced reaching 364.4 °C and 3.2 GPa, respectively. The tensile strength and modulus as well as the microhardness values increased with the increasing of the nanoparticles amount. The tensile modulus calculations were investigated using Series, Halpin–Tsai, and Kerner models. Haplin–Tsai model was found to reproduce the experimental data with the best accuracy. Finally, results from electrochemical impedance spectroscopy revealed that the neat resin and its related nanocomposites offer excellent corrosion protective properties.

Thermal and mechanical properties enhancements obtained by reinforcing a bisphenol-a based phthalonitrile resin with silane surface-modified alumina nanoparticles

A new type of nanocomposites based on a high performance bisphenol-A phthalonitrile resin and surface-modified alumina nanoparticles was prepared by a hot compression molding technique. The effect of adding different amounts of the reinforcing phase on the thermal and mechanical properties of the resulting nanocomposites was investigated. Thermogravimetric analysis showed that the starting decomposition temperatures and the residual weight at 800°C were highly improved upon adding the nanofillers. At 15 wt% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced, reaching 346°C and 3.4 GPa, respectively. The tensile strength and modulus as well as the microhardness values increased with the increasing amount of the nanoparticles. The tensile modulus calculations were investigated using Series, Halpin-Tsai, and Kerner models. Haplin-Tsai model was found to reproduce the experimental data with the best accuracy. Estimation of the nanofillers shape factors for both Haplin-Tsai and Kerner models significantly improved the precision of the cited predictive models. The fractured surface of the nanocomposites analyzed by SEM exhibited homogeneous and rougher surfaces compared to that of the pristine resin. Finally, this new kind of nanocomposites is a highly attractive candidate for use in advanced technological applications such as the aerospace and military fields.POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Characterization and phthalate esters sorption of organic matter fractions isolated from soils and sediments

The sorption of two phthalate esters (PAEs) and phenanthrene (PHE) by different natural organic matter fractions (NOMs) was examined. The surface area of the NOMs correlated positively with the starting decomposition temperature (SDT), implying increased number of micropores with the rise of condensation. Sorption of PHE on nonhydrolyzable carbons (NHCs) and other NOMs was respectively dependent on aromatic and aliphatic C contents. Likely physical blocking of the aliphatic moieties and input of black carbon materials led to elevated sorption capacity for PHE of aromatic domains in the NHCs. Sorption of PAEs by NOMs excluding NHCs was jointly regulated by hydrophobic partitioning and H-bonding interactions. The SDT of the NOMs correlated negatively with the Koc when SDT ≥304 °C, likely because the highly condensed domains may impair the availability of amorphous moieties for sorption. This study highlights the influence of domain accessibility of NOMs on sorption of hydrophobic organic contaminants.

High thermal and thermomechanical properties obtained by reinforcing a bisphenol-A based phthalonitrile resin with silicon nitride nanoparticles

A new kind of nanocomposites based on phthalonitrile resin reinforced with silicon nitride (SiN) nanoparticles was prepared by a hot compression molding technique. For different weight ratios ranging between 0% and 15%, the effect of nano-SiN particles on the thermal and thermomechanical properties has been studied. Results from thermal analysis revealed that the starting decomposition temperature and the residual weight at 800°C were highly improved upon adding the reinforcing phase. At the maximum nano-SiN loading, dynamic mechanical analysis showed an enhancement in both storage modulus and glass transition temperature, reaching 4GPa and 360°C respectively. Scanning electron microscope analysis confirmed that these improvements are essentially attributed to the good dispersion and adhesion between the particles and the resin thanks to the particles treatment with silane coupling agent.

Effect of Fe additive on the hydrogenation-dehydrogenation properties of 2LiH + MgB2/2LiBH4 + MgH2 system

Lithium reactive hydride composite 2LiBH4 + MgH2 (Li-RHC) has been lately investigated owing to its potential as hydrogen storage medium for mobile applications. However, the main problem associated with this material is its sluggish kinetic behavior. Thus, aiming to improve the kinetic properties, in the present work the effect of the addition of Fe to Li-RHC is investigated. The addition of Fe lowers the starting decomposition temperature of Li-RHC about 30 °C and leads to a considerably faster isothermal dehydrogenation rate during the first hydrogen sorption cycle. Upon hydrogenation, MgH2 and LiBH4 are formed whereas Fe appears not to take part in any reaction. Upon the first dehydrogenation, the formation of nanocrystalline, well distributed FeB reduces the overall hydrogen storage capacity of the system. Throughout cycling, the agglomeration of FeB particles causes a kinetic deterioration. An analysis of the hydrogen kinetic mechanism during cycling shows that the hydrogenation and dehydrogenation behavior is influenced by the activity of FeB as heterogeneous nucleation center for MgB2 and its non-homogenous distribution in the Li-RHC matrix.

Mechanical and thermal properties of phthalonitrile resin reinforced with silicon carbide particles

Abstract A new type of composite based on phthalonitrile resin reinforced with silicon carbide (SiC) microparticles was prepared. For various weight ratios ranging between 0% and 20%, the effect of the micro-SiC particles on the mechanical and thermal properties has been studied. Results from thermal analysis revealed that the starting decomposition temperature and the residual weight were significantly improved upon adding the reinforcing phase. At the maximum micro-SiC loading, dynamic mechanical analysis (DMA) showed an important enhancement in both the storage modulus and glass transition temperature ( T g ), reaching 3.1 GPa and 338 °C, respectively. The flexural strength and modulus as well as the microhardness were significantly enhanced by adding the microfillers. Tensile test revealed enhancements in the composites toughness upon adding the microparticles. Polarization optical microscope (POM) and scanning electron microscope (SEM) analysis confirmed that mechanical and thermal properties improvements are essentially attributed to the good dispersion and adhesion between the particles and the resin.

Inclusion Mechanism and Heat Stability of the Complex of 4'-Hydroxychalcone and Hydroxypropyl-&amp;#946;-Cyclodextrin

Purpose: To study the inclusion mechanism and heat stability of the complex formed between 4'hydroxychalcone and hydroxypropyl-β-cyclodextrin (HP-β-CD) Methods: The inclusion mechanism of the complex of 4'-hydroxychalcone and HP-β-CD was investigated by phase solubility method. The physicochemical properties of the complex were evaluated by Fourier transform infrared spectroscopy (FT-IR) and x-ray diffractometry (XRD) while the heat stability of the complex was measured by thermogravimetric/differential scanning calorimetry (TG/DSC). Results: The stability constants of the complexes were higher than those of β-CD at all temperatures. For the formation of the complex, Gibbs energy (-16.87 KJ/mol at 20 °C) was negative, and positive entropy (31.15 KJ/mol) along with a slightly positive enthalpic change (163.89 J/mol) was also found. IR and XRD analysis showed that the physical phase of 4-hydroxylchalcone was changed and completely dispersed in HP-β-CD while TG/DSC data indicate that the starting decomposition temperature of 4'hydroxychalcone (200 °C) was significantly enhanced to 397 °C due to the formation of inclusion complex with HP-β-CD in the solid state. Conclusion: The stability constant of HP-β-CD for 4'-hydroxychalcone is higher than that of β-CD. The inclusion is a spontaneous process, driven by hydrophobic forces. The heat stability of 4’hydroxychalcone is significantly enhanced by complexing with HP-β-CD.

Morphology and Properties of Injection Molded Microcellular Poly(ether imide) (PEI)/Polypropylene (PP) Foams

A series of PEI/PP blends were injection molded by conventional and microcellular methods. Polypropylene (PP) was selected as the disperse phase in order to improve the cell nucleation of poly(ether imide) (PEI)/PP blends. The effect of the PP content on the morphology of the PEI/PP blends or foams, the mechanical, thermal and dielectric properties was investigated. In the immiscible PEI/PP blends, the cell density of microcellular PEI/PP foams increased greatly with the increasing of the content of PP because the surface tension effect and interface effect significantly promoted the cell nucleation in the PEI/PP blends. Meanwhile, a large amount of gaps appeared in the interface because the processing temperature of the blends was close to the starting decomposition temperature of PP, which significantly improved the PEI/PP blends toughness because of tiny spherical cells that acted as crack arrestors by blunting the crack tip.