Decomposition Temperature Range Research Articles

Effects of flame retardants on thermal decomposition of SARA fractions separated from asphalt binder

To better understand effects of flame retardants on thermal decomposition of saturates, aromatics, resins and asphaltenes (SARA) fractions in asphalt binder, different flame retardants were selected to match the thermal decomposition temperature range of each SARA fraction, respectively. Then inhibitory effects of matched flame retardants were discussed and microscopic morphology of combustion residues were observed. The results indicate that the decomposition process of each SARA fraction still includes two thermal mass loss stages after adding the matched flame retardants. However, the thermal decomposition rates are lowered, and the initial decomposition temperatures and maximum decomposition temperatures of each SARA fraction are elevated. Also, the matched flame retardants have few effects on the volatile constituents of four SARA fractions, but show an obvious influence on the release amount of gaseous products. CO2 and H2O are still the two main products of each SARA fraction after adding matched flame retardants. Few chemical reactions between SARA fractions and flame retardants are found during their decomposition. Additionally, the superposed and densified charring layers are formed due to the synergic effects of the composite flame retardants. The thick charring layer prevents the heat from transferring, and hinders the oxygen supply, and inhibits the release of flammable volatiles. Finally, the thermal stability of each SARA fraction is greatly improved by the matched flame retardants. The composite flame retardants show a synergistic flame retarding and smoke suppressing effects. This study is beneficial to develop new composite flame retardants for asphalt binder with a satisfactory flaming retarding and smoke suppressing effects.

A study of thermal decomposition of phases in cementitious systems using HT-XRD and TG

Significant variations have been reported on the temperature range of thermal decomposition of cementitious phases. Thus, this study identified temperature ranges on the phases in actual cementitious systems (portland cement (OPC) pastes, blended pastes of ground granulated blast furnace slag (GGBFS) with OPC, and Ca(OH)2-activated GGBFS) by simultaneously using thermogravimetry (TG) and high-temperature X-ray diffraction (HT-XRD) as follows: (1) 81°–91 °C for dehydration of ettringite, (2) ∼80°–240 °C for major dehydration of C-S-H, (3) ∼241°–244 °C for hydrogarnet, (4) ∼129°–138 °C for Al2O3-Fe2O3-mono phase (AFm), (5) ∼411°–427 °C for Ca(OH)2, and (6) ∼648°–691 °C for CaCO3. The CaO layers and SiO2 chains of C-S-H likely started to decompose from 615°–630 °C, and eventually transformed to new crystalline phases. This study also demonstrated that (a) the quantity of calcite could be overestimated due to additional carbonation when Ca(OH)2 is plentifully present in samples, and (b) the quantification of phases would be greatly affected by sample particle size when GGBFS is used in the system.

Influence of iron oxide on thermal decomposition behavior and burning characteristics of ammonium nitrate/ammonium perchlorate-based composite propellants

The thermal decomposition behavior and burning characteristics of ammonium nitrate(AN)/ammonium perchlorate(AP) propellants supplemented with Fe2O3 were investigated. Based on these data, the performance differences between the propellants with Fe2O3 and those without Fe2O3 were investigated to reveal the influence of Fe2O3 on the thermal decomposition behavior and burning characteristics of AN/AP-based composite propellants. TG-DTA showed the peak temperature and temperature range of thermal decomposition due to AN decomposition to be independent of the presence of Fe2O3. The peak and the offset temperature of thermal decomposition due to AP decomposition decreased owing to the addition of Fe2O3, while the onset temperature did not vary. The burning rate of the AN/AP propellant was increased by the addition of Fe2O3; the effect of Fe2O3 on increasing the burning rate was influenced by the type of oxidizer, AP content in the oxidizer (ξ), and AP size. Furthermore, Fe2O3 allowed the suppression of the remarkable heterogeneity of the combustion wave of the AN/AP propellant without Fe2O3. The ignitability of the AN/AP propellant was improved by the addition of Fe2O3, except for the propellant with a ξ of 0.4. The cause of depressed ignitability by the addition of Fe2O3 for the propellant with a ξ of 0.4 is discussed based on thermogravimetry-differential thermal analysis, the visual observations of the unignited propellant surfaces, and the decomposition phenomena of the propellants using a high-temperature observation equipment. A large quantity of AN remained on the surface of the unignited propellant at 0.5 MPa. The cause of the depressed ignitability is that AN, AP, and HTPB do not simultaneously decompose and as a result AN remains on the burning surface. Thus, the burning surface of AN did not regress simultaneously with the burning surface of the AP-filled region, the matrix of AP, and HTPB.

Multifunctional foaming agent to prepare aluminum foam with enhanced mechanical properties

In this paper, CuSO4 was used as foaming agent to prepare close cell Aluminum foam(Al foam) at the temperature range of 680 °C ∼ 758 °C for the first time. The results show that CuSO4 has multifunctional such as, foaming, viscosity increasing, reinforcement in Al matrix, it has a wide decomposition temperature range of 641 °C ∼ 816 °C, its sustain-release time is 5.5 min at 758 °C. The compression stress and energy absorption of CuSO4-Al foam is 6.89 Mpa and 4.82 × 106 J m−3(compression strain 50%), which are 77.12% and 99.17% higher than that of TiH2-Al foam at the same porosity(76% in porosity) due to the reinforcement in Al matrix and uniform pore dispersion.

Thermogravimetric analysis of cork and cork components from Quercus variabilis

Cork and cork components (suberin, lignin, holocellulose, sclereids, and lenticels) were obtained by manual and chemical methods. Dynamic thermogravimetric analysis was used to investigate the thermal behavior of cork and its components. Thermal decomposition of cork was different from that of natural fibers. Characteristic temperatures of thermal decomposition for cork and impurities (sclereids and lenticels) were related to their chemical components. Cork lignin has the decomposition characteristics of G-type (guaiacyl units) lignin, typical of softwood with high residual solids. The pyrolysis characteristics of Quercus variabilis Blume (Q. variabilis) suberin was close to Quercus cerris L. (Q. cerris) suberin. The decomposition temperature range of cork, lignin, or suberin was wider than that of sclereids, lenticels, or holocellulose. Activation energy of cork was lower than that of natural fibers. The activation energy of cork and the extracted suberin was slightly increased when the conversion rate α was greater than 0.35. Activation energies of sclereids and lenticels were close to each other due to similar composition and proportion in them.

Pyrolysis and flame retardant behavior of a novel compound with multiple phosphaphenanthrene groups in epoxy thermosets

A novel flame retardant compound (TDBA) with multiple phosphaphenanthrene groups was synthesized and confirmed by chemical structural and elemental characterization. Contrastive analysis on thermal decomposition behavior showed that the two kinds of bridge bonds linking phosphaphenanthrene groups in TDBA caused a wider decomposition temperature range, contributing to inhibiting combustion in relatively longer time. The application of TDBA in epoxy thermosets suggested that, TDBA capacitated the limited oxygen index of thermosets to surpass 35% and 4wt.% or more loadings of TDBA made 4,4′-diamino-diphenyl methane curing thermosets pass UL94 V-0 rating especially. During combustion, the incorporated TDBA induced the matrix to decompose earlier, reduced the fuels production, reduced burning intensity and inhibited the combustion reaction of fuels in gaseous phase, and promoted the charring behavior of thermosets in condensed phase. The pyrolysis of TDBA proceeded along two main directions, namely substituted phosphaphenanthrene and bisphenol-A. Through releasing massive phenolic derivatives, PO free radicals and other certain phosphorus-containing substances, TDBA is capable to exert free radical quenching effect in gaseous phase, and to promote charring behavior to form compact residue with barrier effect on heat and fuels transportation in condensed phase. This bi-phase joint action mode from TDBA endowed epoxy thermosets with excellent flame retardancy.

Thermal degradation behaviour of resins in aluminium composite under isothermal condition

As a member of the aluminium composite, GLARE (GLAss fibre/epoxy REinforced aluminium laminates) was used in the upper fuselage of Airbus A380 because of its superior mechanical properties over monolithic aluminium alloys. Thermal processing is a potential method for materials recycling and reuse from GLARE scrap with the aim of environmental protection and economic benefits. Thermal delamination is a crucial pre-treatment step for GLARE recycling. Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA) tests have been used to identify the decomposition temperature range of epoxy resins under non-isothermal condition in our previous work [1]. To obtain an appropriate solution for GLARE thermal delamination, the thermal degradation behaviour of epoxy resins in GLARE under isothermal conditions were investigated and isothermal decomposition kinetic models were built up based on DSC and thermogravimetric analysis TGA. The thermal delamination process of GLARE is determined based on thermal analysis results and experimental optimization.

Transient materials from thermally-sensitive polycarbonates and polycarbonate nanocomposites

Transient materials, or materials with designed short lifetimes, are of great interest in many fields of research. This work describes the development of polycarbonates as a thermally-triggered vaporizable substrate platform. Good mechanical properties over operational temperature ranges in combination with fast and clean decomposition at slightly higher temperatures create an effective transient substrate. Therefore, characterization of the thermal and mechanical properties of vaporizable polycarbonates (VPC) and their composites are indispensable for creating such materials systems. A tailor-made VPC and its blends with a commercially available poly(propylene carbonate) were investigated. Both polycarbonates have acid sensitive backbones; therefore, when combined with an acid source, catalyzed decomposition was observed within minutes, achieving a range of decomposition temperatures between 160 °C and 250 °C. Polymer with organo-modified montmorillonite nanocomposites were investigated to provide structural support. These nanocomposites resulted in Young's moduli ranging from 4 MPa to ∼2 GPa. Their tunable nature allows for designer control over the substrate's properties based on application needs.

Research on Plasticizing Properties and Mechanism of PVA

Taking glycerol as the plasticizer, through its effect on melting and crystallization of PVA, this paper researches on the plasticizing properties and mechanism of PVA, and provides experimental and theoretical basis for the realization of PVA’s melt processing. Research Methods: Matching samples respectively, mix each sample in an electric high-speed mixer with a mixing temperature of 80 °C. And then, put each sample in a Banbury mixer, mixing for 10 minutes with a rotational speed of 45rm/min. Take out each sample to analyze its characterization and do some tests, including infrared analysis, DSC test, X-ray diffraction test, and rheological curve measurement. Experimental Results: After adding glycerol, there exist two more absorption peaks near the point of 1621cm-1 in the PVA infrared spectrum, and the crystallization peak at 1267cm-1 is decreased gradually. In the DSC chart, when the amount of glycerol increasing to 16.67%, the melting point of PVA is decreased to 212 °C, and its melting range is 191 °C-223 °C. Under this condition, the melting range has been completely separated from the decomposition temperature range. X-ray diffraction shows that glycerol is added no significant effect on the diffraction angle of the PVA, the diffraction peak intensity decreased significantly increases the degree of dispersion. Under the same temperature, with the shear rate increasing, the shear viscosity has a downward trend; as the temperature increases, the shear viscosity and shear stress of the system are gradually decreasing. Conclusion: Glycerol may lower the melting temperature because it can improve the segmental mobility of PVA and reduce the crystalline regions. However, the amount of glycerol should not be too much, or the plasticizing effects will be drastically reduced because of the separation. The research also find that a certain amount of glycerol used alone cannot reduce the decomposition temperature but decrease the melting temperature, which still cannot meet the melt processing conditions. The excessive glycerol can easily be precipitated from PVA, resulting in the product surface being oily and crisp.

A novel alkaline hemicellulosic heteroxylan isolated from alfalfa (Medicago sativa L.) stem and its thermal and anti-inflammatory properties.

A novel hemicellulosic polysaccharide (ACAP) was purified from the cold alkali extraction of alfalfa stems and characterized as a heteroxylan with a weight-average molecular weight of 7.94 × 10(3) kDa and a radius of 58 nm. Structural analysis indicated that ACAP consisted of a 1,4-linked β-D-Xylp backbone with 4-O-MeGlcpA and T-L-Araf substitutions at O-2 and O-3 positions, respectively. Transmission electron microscopy (TEM) examination revealed the entangled chain morphology of ACAP molecules. The evaluation of thermal degradation property revealed a primary decomposition temperature range of 238.8-314.0 °C with an apparent activation energy (Ea) and a pre-exponential factor (A) of 220.0 kJ/mol and 2.81 × 10(24)/s, respectively. ACAP also showed significant inhibitory activities on IL-1β, IL-6, and COX-2 gene expressions in cultured RAW 264.7 mouse macrophage cells. These results suggested the potential utilization of ACAP in functional foods and dietary supplement products.

Mechanical performance of structurally optimized AlSi7 aluminum foams – an experimental study

AlSi7 aluminum foams produced via the powder compact melting process suffer from deficiencies in the pore structure that are linked to the mismatch between the decomposition temperature range of the common blowing agent TiH2 and the solidus and liquidus temperature of the matrix alloy. To alleviate these deficiencies, two main paths have been discussed in the past: One is the adaptation of the matrix alloy towards lower melting temperatures, the other the modification by heat treatment of the foaming agent itself, which leads to higher decomposition temperatures. The present paper compares the mechanical response of foams produced according to the second approach to that of the reference material, AlSi7 foamed using untreated TiH2 as blowing agent. Mechanical performance is evaluated based on uniaxial, quasi‐static compression tests over a wide range of densities. In parallel, the pore and microstructure of the respective materials is characterized using metallographic sections and computed tomography for image acquisition, as well as image analysis to derive quantitative parameters. Foams based on thermally treated blowing agents show increased compressive strength at technically relevant density levels. The advantage is lost at very high porosities in excess of 85–90% only.

A molecular based kinetic study on the thermal decomposition of poly-α-methyl styrene

Solid polymer thermal decomposition involves complex physical and chemical processes that are closely related to the microscopic molecular information (chemical structure, physical configuration, etc.). However, some important molecular information such as molecular weight is seldom involved in previous solid thermal decomposition studies due to the complexity of solid polymer itself. This work proposes a kinetic equation to study solid polymer thermal decomposition in which the influence of molecular weight to the decomposition is included based on an independent identical particle (IIP) model. Applications of this equation to the thermal decomposition of solid poly-α-methyl styrene (PαMS) show that: 1) there is good agreement between experimental and theoretical thermal decomposition rates; 2) molecular weight can affect not only the activation energy but also the pre-exponential factor of the thermal decomposition kinetic equation; 3) the higher the molecular weight is, the faster the PαMS decomposes in the main decomposition temperature range.

Synthesis of graphene-polystyrene nanocomposites via RAFT polymerization

Synthesis of graphene-polymer nanocomposites is of current interest due to their exceptionally physical and chemical properties. However, the ability to produce conductive inks/coatings retaining the properties of the graphene is still a major challenge. In this study, functionalized polydopamine-coated reduced graphene oxide (PDA/RGO) was reacted with a RAFT agent, 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT), to form macro-RAFT agents via an esterification reaction. The chemistry and kinetics of RAFT living/controlled polymerization of styrene was examined from the surface of these macro-RAFT agents to form polystyrene-grafted PDA/RGO (PS-g-PDA/RGO). By examination of the kinetics and GPC traces of the free and grafted polymer, living/controlled polymerization was confirmed. To examine the utility of this approach, the synthesized PS-g-PDA/RGO samples containing different amounts of grafted PS were employed in the preparation of graphene-PS nanocomposites by mixing them with commercial PS. Graphene was found to be well distributed in the PS matrix by this approach, increasing the decomposition temperature range. This research provides an efficient route towards the design and development of value-added functional graphene-PS composites.

Controlling the Physical Properties of Magnesium Oxide Using a Calcination Method in Aerogel Synthesis: Its Application to Enhanced Sorption of a Sulfur Compound

To synthesize mesoporous magnesium oxide (MgO) with a high surface area and pore volume, a calcination procedure was developed for hydrated MgO prepared by the same aerogel method. The sorption capacities of as-prepared MgO compounds were evaluated by breakthrough experiments to remove methylmercaptan (291 μmol/mol) from methane. The surface area of nanosized MgO varied from 296.6 to 503.5 m2/g, depending on the calcination procedure. The physical properties and sorption capacity of MgO were affected by the final temperature, step, and heating rate during calcination, but the sorption capacity could not be evaluated only by the surface area and pore volume. MgO prepared by the four-step calcination method, which had two additional steps in the significant decomposition temperature range, had 2–11 times higher sorption capacity than MgO by other calcination methods. This suggests that optimizing the calcination method is as important as searching for a new synthesis route.

The mechanism and kinetics of the thermal decomposition of telbivudine

The thermal decomposition of Telbivudine (LdT) was measured with thermogravimetry (TG), differential scanning calorimetry (DSC), and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA–FTIR). The infrared spectra of LdT, its gaseous products, and the remainders of thermal decomposition at various temperatures were determined. The molecular bond orders were calculated by GAMESS program of quantum chemistry, and the mechanism of thermal decomposition of LdT is discussed. The kinetic parameters of thermal decomposition such as activation energy Ea and the pre-exponential factor A were obtained with the Ozawa method. The prospective lifetime of LdT was estimated with the Dakin equation. The results indicated that the thermal decomposition of LdT is a two-step process. Fracture of the peptide bond connecting the thymine and furan rings occurs in the initial step. Under nitrogen atmosphere, the temperature range of decomposition is from 198°C to 314°C, the Ea and A of the thermal decomposition process at the initial stage are 120.9kJmol−1 and 1.66×1011min−1, respectively. In air, the temperature range of decomposition is from 199°C to 309°C, and the corresponding Ea and A are 133.0kJmol−1 and 3.89×1012min−1, respectively. The thermal stability of LdT is very good under routine temperatures.

Color- and Morphology-Controlled Self-Assembly of New Electron-Donor-Substituted Aggregation-Induced Emission Compounds

Four electron-donor-substituted aggregation-induced emission (AIE) compounds, N,N'-bis(4-methoxylsalicylidene)-p-phenylenediamine (BSPD-OMe), N,N'-bis(4-methylsalicylidene)-p-phenylenediamine (BSPD-Me), N,N'-bis(salicylidene)-p-phenylenediamine (BSPD), and N,N'-bis(4-hydroxylsalicylidene)-p-phenylenediamine (BSPD-OH), are designed and synthesized. They are all found to exhibit controlled self-assembly behaviors and good thermal properties. By changing the terminal electron-donor groups, they are controlled to self-assemble into three emission colors (green, yellow, and orange) and four morphologies (microblocks, microparticles, microrods, and nanowires) in THF/water mixtures. Their self-assembled structures were investigated with scanning electron microscopy (SEM), fluorescent microscopy images, transmission electron microscopy (TEM), and powder X-ray diffraction (PXRD) techniques. In addition, the emission colors of BSPD-OH can be successfully controlled to three colors (green → yellow → orange) through simply changing the water fraction (fw). Their thermal gravimetric analysis (TGA) results indicate that their thermal decomposition temperatures (Td, corresponding to 5% weight loss) range from 282 to 319 °C. Their differential scanning calorimetry (DSC) data show that BSPD-OH bears a glass-transition temperature (Tg) of 118 °C. The good Td and Tg values will ensure them to be luminogens for organic light-emitting diodes (OLEDs). The theoretical calculations and single-crystal X-ray diffraction (XRD) analysis of BSPD-OMe and BSPD suggest that the stronger electron donor substituent can twist the molecular conformation, decrease the degree of π conjugation, increase the energy gap, and then induce the emission colors' blue shift and morphology variation. The results are meaningful in controlling the emission colors and self-assembly shapes of these derivatives, and they also provide a novel but facile way to get color-tunable AIE luminogens for OLEDs.

Fire retardancy of ethylene vinyl acetate/ultrafine kaolinite composites

The flame retardant effect of ultrafine kaolinite in Ethylene Vinyl Acetate copolymer (EVA) was studied and compared to that conferred by aluminum trihydrate (ATH). The thermal degradation and flammability of EVA composites were evaluated up to 60 wt% filler loading. Thermogravimetric (TG) and cone calorimeter analyses showed a higher decomposition temperature range and an improved FR performance for EVA/kaolinite composites in comparison to EVA/ATH composites. For a loading of 35 wt%, the peak of heat release rate (pHRR) of EVA/kaolinite was reduced by 55% compared to EVA/ATH. Moreover, we observed that kaolinite leads to a significant intumescent behavior during cone calorimeter tests. Finally, the rheology in the molten state of the different samples was studied and viscosity seems to play an important role on the fire retardancy of EVA/kaolinite composites.

Low Temperature Synthesis of a Stable Compound of Magnesium Aluminum Titanate Using Microwave Heating

The major problem associated with application of aluminum titanate is decomposition to Al2O3 and TiO2 oxides during heat treatment (in the range of 900-1280 °C ). In the present study, a stable compound of magnesium aluminum titanate ceramics (Mg0.6Al0.8Ti1.6O5) has been successfully synthesized with a straightforward non hydrolytic sol-gel process using inorganic metal compound. The raw materials were MgCl2.2H2O, AlCl3, TiCl4, and citric acid that were dissolved in ethanol. Prepared gel was dried at 120 °C and calcined at various temperatures using microwave heating. The results of X-ray Diffraction (XRD) and Simultaneous Thermal Analysis (STA) demonstrate that the direct crystallization of mono-phase magnesium aluminum titanate from fluffy precursor at a temperature below aluminum titanate decomposition temperature range is feasible. The formation of crystalline Mg0.6Al0.8Ti1.6O5 phase starts at about 400 °C. Also, Field Emission Scanning Electron Microscopy (FESEM) study and BrunauerEmmettTeller (BET) analysis represent the nanometric size of the mesoporous particles. The average particle size and specific surface area of powders were lower than 20 nm and more than 98 m2g-1, respectively, at low temperatures.

Thermal characterization and kinetic analysis of nesquehonite, hydromagnesite, and brucite, using TG–DTG and DSC techniques

Nesquehonite, hydromagnesite, and brucite are important precursors for the preparation of high-purity magnesia (MgO) using magnesium resources from salt lake as raw materials. In this paper, TG–DTG and DSC were used to investigate the thermal decomposition behaviors of the three precursors. Decomposition kinetic parameters at each stage were evaluated based on the TG data using the iso-conversional method. Decomposition mechanisms were determined using the master-plots method. The decomposition temperature range, heat absorption, and kinetic parameters of the three phases were then compared. The most probable mechanism of each stage from the perspective of crystal structure was found to be consistent with the calculation results from the master-plots method. Results led to the conclusion that nesquehonite is the most appropriate precursor for the preparation of high-purity MgO. Further studies on precursor selection and calcining condition selection for the preparation of MgO using bischofite will benefit from this research.

Preparation of nano-sized Mg 0.6 Al 0.8 Ti 1.6 O 5 powders using the inorganic salts route

Abstract Stable magnesium aluminum titanate ceramics (Mg0.6Al0.8Ti1.6O5) compound has been successfully synthesized with a straightforward non-hydrolytic sol–gel process using an inorganic metal compound as cation source supplier at about 600 °C. The raw materials MgCl2·2H2O, AlCl3, TiCl4, and citric acid were dissolved in ethanol. Prepared gel was dried at 120 °C and calcined at various temperatures in an electric furnace. The results of X-ray diffraction (XRD) and simultaneous thermal analysis (STA) demonstrate that the direct crystallization of mono-phase magnesium aluminum titanate from fluffy precursor at a temperature below aluminum titanate decomposition temperature range is feasible. Field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET) analysis show the nano-metric size of particles. The particle size and specific surface area of the powders varied from 16.5 to 27.6 nm and from 98.2 to 58.7 m2 g−1 according to calcination temperatures (600 and 700 °C), respectively. The nano-particles had a strong tendency to agglomerate and were partially sintered at 1100 °C.