Major Thermal Degradation Research Articles

A study on the thermal conductivity of proton irradiated CVD-SiC and sintered SiC, measured using a modified laser flash method with multi-step machining

CVD-SiC and sintered SiC (SPS-SiC) were proton irradiated at 340 ̊C receiving different levels of damage (0.05–0.25 dpa). A novel multi-step machining and measurement method using laser flash analysis (LFA) was developed to derive the thermal conductivity of the irradiated layer (∼46 µm). Before irradiation, the thermal conductivity of SPS-SiC was much lower than CVD-SiC, primarily due to its higher intrinsic defect concentration and smaller grain size which provide a greater density of barriers to phonon transmission. Following irradiation, major thermal conductivity degradation (∼90%) was found to occur to both types of SiC after only a low dose (∼0.1 dpa), with both saturating at a similarly low value (a few W/K⋅m), as the thermal resistivity due to the presence of high density of grain boundaries became less important. Thermal conductivity degradation after irradiation was primarily caused by point defects in both types of SiC, as reflected by Raman spectra.

Gas chromatography tandem mass spectrometric analysis of alkylphosphonofluoridic acids as verification targets of nerve agents

Alkylphosphonofluoridic Acids (APFA) are the major thermal degradation products of G- and A-series nerve agents and thus play a vital role in the verification analysis of Chemical Weapons Convention. Present study focuses on the development of sample clean-up, derivatization procedures and gas chromatography tandem mass spectrometric analysis of APFA in aqueous samples. APFA were found to be much more delicate than the corresponding alkylphosphonic acids and thus required subtle optimizations. Retention of analytes on silica and polymer-based anion exchangers followed by elution under alkaline conditions yielded best recoveries. Elution under acidic conditions led to partial or complete degradation of the analytes to alkylphosphonic acids. Silylation reactions, particularly with MTBSTFA were found the best in terms of chromatographic responses and resolution of the derivative peaks. Methylations with diazomethane, which requires acidic reaction media, failed to produce desired yields of the derivatives. Under optimized conditions, the analytes produced the recoveries ranging from 76.9 to 94.5% with RSD ≤9.2%. The best LOD's in the tandem mass spectrometric analysis ranged from 13 to 56 ng/ml. The applicability of the method was tested by spiking the analytes in the retained aqueous samples received for the 52nd proficiency test conducted by the Organization for the Prohibition of Chemical Weapons (OPCW).

Development and characterization of sustainable-active-edible-bio based films from orange and pomegranate peel waste for food packaging: Effects of particle size and acid/plasticizer concentrations

Sustainable packaging materials especially from food processing waste are of getting interest. The aim of the study was to develop edible bio based films from processing wastes of pomegranate and orange peels. For this purpose, pomegranate and orange peels were dried and processed into flour in different particle sizes. The effects of particle size, concentration of acid and plasticizer on physical and mechanical properties were investigated. Antimicrobial, antioxidant, morphological and thermal properties were further determined for the selected film formulations. Results showed that the particle size significantly affected mechanical properties of the films (p ≤ 0.05), with improvement of the mechanical properties for the reduced particle size. Pomegranate and orange peel based films showed very high antimicrobial activity against E. coli and S. aureus irrespective of particle sizes. The pomegranate and orange peel based films had homogeneous, smooth, and crack-free surfaces. Pomegranate and orange peel based films showed very similar thermal properties and major thermal degradation was observed between 160 and 300 °C for both type of films irrespective of particle sizes. Pomegranate and orange peels could be good potential as antioxidant and antimicrobial biopolymer sources for sustainable and active food coating/packaging.

Study on pyrolysis behavior of polymeric coated aluminium scrap using TGA and Py-GC/MS

Polymeric-coated aluminium scrap obtained from a local recycling plant in Thailand was used as raw material. The thermal decomposition behavior and evolved gas from the pyrolysis of the polymeric fraction coated on the aluminium surface were investigated using thermogravimetric analysis (TGA) and pyrolysis-GC/MS (Py-GC/MS). Initially, thermogravimetric analysis (TGA) was used to study the thermal decomposition of all the coated aluminium scraps (white, black, and brown color). From the TGA results, a major thermal degradation at 300–480 °C associated with the decomposition of the polymeric fraction was found in all the powder-coated samples. The weight loss was 4.57 wt %, 3.56 wt %, and 1.64 wt % in the white-, black-, and brown-coated scraps, respectively. Then, the pyrolysis of the polymeric layer coated on the surface was investigated using a Py-GC/MS. The effect of pyrolysis temperature (400–600 °C) and the type of coated aluminium scrap on product selectivity was studied. In terms of pyrolysis, the polymeric materials used in the coating would decompose via scission reaction generating volatile compounds. At a temperature of 600 °C, the carboxylic end groups (40.46–45.62 %) and aliphatic HCs (19.69–25.34 %) were the major pyrolytic products with a small number of aromatic HCs (2.76–7.76 %). In addition, low fractions of N-containing compounds (3.05–8.08 %) produced from the decomposition of cross-link agents were found. The maximum temperature (600°C) promoted high selectivity of hydrocarbons (aromatic and aliphatic) from β-H scission, cracking, and deoxygenation reactions. Aliphatic hydrocarbons consisted of alkenes, alkynes, and cycloalkenes with carbon in the range of C5–C24, while aromatic hydrocarbons with carbon in the range of C6–C20 were composed of mainly toluene, biphenyl, styrene, etc. These organic products can be utilized as chemical raw materials as well as alternative fuel. Additionally, to identify the remaining components after heat treatment at 600 °C, the chemical analysis was performed using the EDX technique. The residue compositions after heat treatment at 600 °C were C, Ti, Ba, Pb, Si, Ca, Fe, and S, chiefly corresponding to TiO2, SiO2, CaO, Fe2O3 as pigments and BaSO4 as a filler. Thus, the removal of these inorganic components remaining after thermal de-coating process should be considered to maintain melting cleanliness.

A Systematic Degradation Kinetics Study of Dalbavancin Hydrochloride Injection Solutions

The degradation kinetics of the glycopeptide antibiotic dalbavancin in solution are systematically evaluated over the pH range 1–12 at 70°C. The decomposition rate of dalbavancin was measured as a function of pH, buffer composition, temperature, ionic strength, and drug concentration. A pH-rate profile was constructed using pseudo first-order kinetics at 70°C after correcting for buffer effects; the observed pH-rate profile could be fitted with standard pseudo first order rate laws. The degradation reactions of dalbavancin were found to be strongly dependent on pH and were catalyzed by protons or hydroxyl groups at extreme pH values. Dalbavancin shows maximum stability in the pH region 4–5. Based on the Arrhenius equation, dalbavancin solution at pH 4.5 is predicted to have a maximum stability of thirteen years under refrigerated conditions, eight months at room temperature and one month at 40°C. Mannosyl Aglycone (MAG), the major thermal and acid degradation product, and DB-R6, an additional acid degradation product, were formed in dalbavancin solutions at 70°C due to hydrolytic cleavage at the anomeric carbons of the sugars. Through deamination and hydrolytic cleavage of dalbavancin, a small amount of DB-Iso-DP2 (RRT-1.22) degradation product was also formed under thermal stress at 70°C. A greater amount of the base degradation product DB-R2 forms under basic conditions at 70°C due to epimerization of the alpha carbon of phenylglycine residue 3.

Synthesis, Characterization, Isoconversional Analysis and Degradation Kinetics of Novel Acetate Coated Hydroxyethyl Starch: A New Candidate as a Drug Carrier

The hydroxethyl starch (HES) is very trending biopolymer in biomedical field. In recent research we have successfully synthesized a novel ester of HES, i.e., HES-acetate by acetylation of HES followed by investigation of its thermal behavior. The successful acetylation of HES was confirmed by Fourier Transform Infrared (FTIR) and Proton-Nuclear Magnetic Resonance (1H NMR) spectroscopic techniques. Thermal stability and thermal degradation kinetics of HES-acetate were investigated by thermo-gravimetric analysis. Flynn–Waal–Ozawa model was fitted to the thermal data to find the values of thermodynamic triplet (ΔS, ΔG and ΔE). Energy of activation (Ea) values of the major thermal degradation steps were found to be 242.85 and 287.17 kJ mol–1 for HES and HES-acetate, respectively. The order of degradation, integral procedural decomposition temperature (IPDT) and index of intrinsic thermal stability (ITS) were also taken into account. The results of the thermal analysis reveal that the HES-acetate gained significant thermal stability as compared to that of HES. This benign polysaccharide-based material was investigated for its potential in drug release studies by taking caffeine as a model drug. HES-acetate-based matrix tablets showed sustained release behavior of the drug indicating its potential for the development of oral delivery systems for sustained drug release.

Substituent Effects on Thermal and Mechanical Properties of Resorcinol‐Based Semiaromatic Polyesters

AbstractRecently biobased plastics draw attention as eco‐friendly materials, and it is important to study the effects of substituents, which are popularly found in natural products, on the characteristics of the resulted polymers. In this study, twelve resorcinol‐based semiaromatic polyesters are successfully synthesized using four types of resorcinol derivatives (resorcinol, 2‐methylresorcinol, 5‐methylresorcinol, and 2,5‐dimethylresorcinol) and three types of dicarboxylic acids (glutaric acid, adipic acid, and pimelic acid) to investigate the effect of methylation at the 2‐ and 5‐positions in resorcinol. Glass‐transition temperature of the polyesters is located from ‐3.1 to 37.9 °C, and rises with increasing the number of methyl groups in a resorcinol unit. Crystallinity of the polyesters decreases by methylation to a resorcinol unit, except the polyester from 2‐methylresorcinol and pimelic acid. The mechanical properties of the solvent‐cast films for the polyesters are tunable by the site and number of methyl groups in a resorcinol unit. The major thermal degradation of the polyesters is observed above 300 °C, and the minor thermal decomposition appears between 100 and 200 °C for the polyesters without the resorcinol methylated at the 2‐position and pimelic acid unit.

The influence of terpenes on the release of volatile organic compounds and active ingredients to cannabis vaping aerosols.

Dabbing and vaping cannabis extracts have gained large popularity in the United States as alternatives to cannabis smoking, but diversity in both available products and consumption habits make it difficult to assess consumer exposure to psychoactive ingredients and potentially harmful components. This work studies the how relative ratios of the two primary components of cannabis extracts, Δ9-tetrahydrocannabinol (THC) and terpenes, affect dosage of these and exposure to harmful or potentially harmful components (HPHCs). THC contains a monoterpene moiety and has been previously shown to emit similar volatile degradation products to terpenes when vaporized. Herein, the major thermal degradation mechanisms for THC and β-myrcene are elucidated via analysis of their aerosol gas phase products using automated thermal desorption-gas chromatography-mass spectrometry with the aid of isotopic labelling and chemical mechanism modelling. Four abundant products – isoprene, 2-methyl-2-butene, 3-methylcrotonaldehyde, and 3-methyl-1-butene – are shown to derive from a common radical intermediate for both THC and β-myrcene and these products comprise 18–30% of the aerosol gas phase. The relative levels of these four products are highly correlated with applied power to the e-cigarette, which indicates formation of these products is temperature dependent. Vaping THC–β-myrcene mixtures with increasing % mass of β-myrcene is correlated with less degradation of the starting material and a product distribution suggestive of a lower aerosolization temperature. By contrast, dabbing THC–β-myrcene mixtures with increasing % mass of β-myrcene is associated with higher levels of HPHCs, and isotopic labelling showed this is due to increased reactivity of β-myrcene relative to THC.

Comparative isoconversional thermal analysis of Artemisia vulgaris hydrogel and its acetates; a potential matrix for sustained drug delivery

Artemisia vulgaris hydrogel (AVH) was acetylated (AAVH) and characterized by FTIR, CP/MAS 13C-NMR spectroscopic techniques and thermogravimetric analysis. Flynn–Waal–Ozawa model was used to investigate thermal degradation kinetics. Energy of activation (Ea) values of first and major thermal degradation steps were found to be 128.14 and 116.85 kJmol−1 for AVH and AAVH, respectively. Thermodynamic triplet, order of degradation reaction, integral procedural decomposition temperature (IPDT) and comprehensive index of intrinsic thermal stability (ITS) were also taken into account. In vitro caffeine release from AVH-based matrix tablets indicates potential of AVH for the development of oral delivery systems for sustained drug release.

Surface Treatment of Cu:NiOx Hole-Transporting Layer Using β-Alanine for Hysteresis-Free and Thermally Stable Inverted Perovskite Solar Cells.

Inverted perovskite solar cells (PSCs) using a Cu:NiOx hole transporting layer (HTL) often exhibit stability issues and in some cases J/V hysteresis. In this work, we developed a β-alanine surface treatment process on Cu:NiOx HTL that provides J/V hysteresis-free, highly efficient, and thermally stable inverted PSCs. The improved device performance due to β-alanine-treated Cu:NiOx HTL is attributed to the formation of an intimate Cu:NiOx/perovskite interface and reduced charge trap density in the bulk perovskite active layer. The β-alanine surface treatment process on Cu:NiOx HTL eliminates major thermal degradation mechanisms, providing 40 times increased lifetime performance under accelerated heat lifetime conditions. By using the proposed surface treatment, we report optimized devices with high power conversion efficiency (PCE) (up to 15.51%) and up to 1000 h lifetime under accelerated heat lifetime conditions (60 °C, N2).

The effect of torrefaction and ZSM-5 catalyst for hydrocarbon rich bio-oil production from co-pyrolysis of cellulose and low density polyethylene via microwave-assisted heating

This study aims to investigate the effect of microwave torrefaction and ZSM-5 catalyst for hydrocarbon rich bio-oil production from microwave co-pyrolysis of cellulose and low density polyethylene (LDPE). FTIR analysis displayed remarkable reductions of active hydroxyl and ether groups in microwave torrefied cellulose (MTC), demonstrating that cellulose was less stable than MTC. GC/MS analysis indicated that the hydrocarbons content was ranged from 18.36% to 54.94% in the obtained bio-oils under different conditions, and the maximum hydrocarbons content (54.94%) which also contained the highest aromatic hydrocarbons (19.49%) was obtained from MTC catalytic co-pyrolysis. Microwave-assisted Thermogravimetric analyzer (MW-TGA) analysis showed that MTC catalytic co-pyrolysis apparently shifted the major thermal degradation to a lower temperature area, an evident synergistic effect was observed during MTC catalytic co-pyrolysis. Kinetics study revealed that the activation energy was significantly reduced from 97.87 kJ/mol to 63.86 kJ/mol for co-pyrolysis and MTC catalytic co-pyrolysis, respectively.

Enhancing the thermal stability of silica-mineralized wood via layer-by-layer self-assembly

Employing a combination of a layer-by-layer self-assembly and sol gel methods, a negatively charged silica sol was successfully deposited into the cell wall and cell cavity of wood by the electrostatic attraction of cationic polyelectrolytes. The physical and mechanical properties, microscopic morphology and the chemical structure of the silica-mineralized wood were characterized using mechanical testing, scanning electron microscopy (SEM–EDS), Fourier-transform infrared spectroscopy and X-ray diffraction (XRD). The thermal performance of the treated wood was investigated using a cone calorimeter, thermogravimetry analysis (TG). SEM images and XRD results showed that the mineralization layer of the treated wood had various forms of amorphous nano-SiO2 particles, which could be attributed to multi-layers of polyelectrolytes. The mechanical strength of the mineralized wood was greatly improved. Based on the TG results, the major thermal degradation (mass loss at about 50%) began at higher temperatures for the silica-mineralized wood. Fire resistance testing demonstrated that the maximum heat release rate of the modified wood was less than that of the untreated wood, indicating that the silica mineralized layer had effectively altered the combustion mechanism. In addition, this work also considered the hydrophobic properties of silica-mineralized wood. In conclusion, the thermal stability and dimensional stability of silica-modified wood was insignificantly improved.

Monitoring of methylglyoxal/indole interaction by ATR-FTIR spectroscopy and qTOF/MS/MS analysis

Sugar derived reactive 1,2-dicarbonyl intermediates are considered important precursors for the formation of Maillard reaction products. Efficient strategies are needed to modulate their formation in food. Indole a major thermal degradation product of tryptophan, has been shown to scavenge such 1,2-dicarbonyls at high temperatures. In this study, the trapping of methylglyoxal by indole was monitored at various temperatures either by (a) ATR-FTIR spectroscopy or (b) in-solution using qTOF/MS/MS analysis. Information obtained through these studies have indicated that even at room temperature indole can quickly react with methylglyoxal forming an adduct as confirmed by the emergence of a new peak at 1729 cm−1 and by qTOF/MS/MS analysis. On the open surface of the ATR crystal this adduct underwent a fast oxidization into carboxylic acid as evidenced by the disappearance of the band at 1729 cm−1 and the formation of a new band at 1712 cm−1 and its subsequent conversion into a carboxylate band under basic conditions.

Thermal degradation mechanism of a cured acetylene/aldehyde functional benzoxazine with high thermal stability

A cured mono-benzoxazine (PHB-apa) with both acetylene and aldehyde functional groups exhibits excellent heat resistance. The thermal degradation process of this polybenzoxazine was studied in this work. The pyrolysis temperature range and major thermal degradation products were determined by TGA-FTIR analysis. The stepwise-temperature Py-GC/MS was employed to identify the structures and the contents of the pyrolysis products at different temperature stages. Transformation of chemical structures of the polymer bulk during the pyrolysis process was speculated. The results suggest that the concerted reaction of the aldehyde groups and the polymerization of the acetylene groups form special crosslinking structures that can effectively prevent the release of the amines and the phenols.

Identification of a thermal degradation product of CUMYL-PEGACLONE and its detection in biological samples.

The structural diversity of synthetic cannabinoids makes it a challenging task to have a comprehensive screening method for this class of drugs. The difficulty is increased by the fact that some synthetic cannabinoids undergo thermal decomposition during common routes of administration, such as smoking or vaping. CUMYL-PEGACLONE is a relatively new synthetic cannabinoid which has a structural variant from most other synthetic cannabinoids: a γ-carbolinone core. To investigate its thermal stability, CUMYL-PEGACLONE was heated in an oven at temperatures ranging from 200 to 350o C, and a major thermal degradation product, N-pentyl-γ-carbolinone, was subsequently identified. Unlike some other synthetic cannabinoids, the thermal degradation product of CUMYL-PEGACLONE is not one of its known metabolites, nor were any known metabolites detected during the thermal stability experiments. The degradation product was formed in significant amounts at temperatures above 250°C, and has been detected (along with CUMYL-PEGACLONE) in case samples, including post-mortem blood and urine, and residue found at a scene.

Thermo-kinetics and product analysis of the catalytic pyrolysis of Pongamia residual cake

Catalytic fast pyrolysis of Pongamia residual cake (PRC) and the kinetics of this were evaluated using thermogravimetry and pyrolysis-gas chromatography/mass spectrometry analyses. The influence of the heating rate on the devolatilization process was studied to obtain corresponding kinetic information. Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) model-free isoconversion methods were used to predict the kinetic parameters. The major thermal degradation of PRC occurred around 150–550 °C with an activation energy of 97.2–394.3 kJ/mol or 114.5–412.2 kJ/mol as determined by the KAS and FWO methods, respectively. Micro-scale pyrolysis trials were performed to determine the effects of the PRC particle size, reaction temperature and PRC: catalyst weight ratio on the pyrolytic product distribution and upgraded pyrolytic vapor properties for the 5 wt% Ni impregnated on activated carbon (AC), aluminium(III) oxide (Al2O3), kaolin and zeolite NaA supports. The results indicated that using a 1:5 PRC: Ni/AC catalyst weight ratio with medium-sized PRC particles (125–425 μm) was the most effective condition for the conversion of oxygenated (O)-compounds to hydrocarbons (HCs) through decarbonylation, decarboxylation and dehydration reactions, giving the highest decrease (99%) in O-compounds. Increased HC yields, to more than 58%, were also obtained with this catalyst. Similarly, using the other synthesized Ni catalysts resulted in a reduction in the O-compounds and production of favorable HC species, albeit to a lesser extent. Therefore, the catalytic pyrolysis process of this residue, especially with a Ni/AC catalyst, has the potential to be a viable option for producing upgraded pyrolysis oil, which may be applied as a quality alternative biofuel.

Long Thermal Stability of Inverted Perovskite Photovoltaics Incorporating Fullerene‐Based Diffusion Blocking Layer

AbstractIn this article, the stability of inverted (p‐i‐n) perovskite solar cells is studied under accelerated heat lifetime conditions (60 °C, 85 °C, and N2 atmosphere). By using a combination of buffer layer engineering, impedance spectroscopy, and other characterization techniques, the interaction of the perovskite active layer with the top Al metal electrode through diffusion mechanisms is proposed as the major thermal degradation pathway for planar inverted perovskite photovoltaics (PVs) under 85 °C heat conditions. It is shown that by using thick solution processed fullerene buffer layer the perovskite active layer can be isolated from the top metal electrode and improve the lifetime performance of the inverted perovskite photovoltaics at 85 °C. Finally, an optimized reliable solution processed inverted perovskite PV device using thick fullerene diffusion blocking layer with over 1000 h accelerated heat lifetime performance at 60 °C is presented.

The Influences of Zirconium Dioxide on ENR-25/ZrO2 Composites: FTIR and TGA Analysis

The characterization and thermal stability of purified epoxidized natural rubber with 25 mol% epoxidation (ENR-25) and treated epoxidized natural rubber with 25 mol% epoxidation / Zirconium dioxide (ENR-25/ZrO2) Composites were studied using Fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analysis (TGA). The ENR-25/ZrO2 composites were treated with acetic acid and two different loading (50 and 100 mg) of ZrO2 were used to form the composites. FTIR results show the ester (C-O) peaks at 1000-1300 cm-1 due to the presence of acetic acid in the composites. The disappearance of epoxide peak at range 880-875 cm-1 indicated that ZrO2 have formed hybrid bonds with opened epoxide rings. The both ENR/ZrO2 composites showed 2 major thermal degradation steps (304 - 489°C and 493 – 551°C) for 50 mg ZrO2 loading and (306 - 497°C 512 – 581°C) for 100 mg ZrO2 loading indicating that the thermal stability of the composites have improved.

Thermal analysis of heat-treated silver fir wood and larval frass

Among the widespread pests belongs Hylotrupes bajulus, which attacks mostly wooden beams in the roof of the houses. Heat sterilisation of wood is used to kill all forms of pests (eggs, larvae, adults) in solid wood materials. We compared thermal stability of heat sterilised silver fir wood to larval frass in regard to fire safety. The samples were treated at 60 and 120 °C for 10 h. Methods of chemical analysis, thermal analysis and statistical analysis were used. During the heat sterilisation of silver fir wood, only the amount of hemicelluloses decreased significantly. In larval frass samples, the holocellulose fraction decreased during the heat treatment. The hemicellulose yields in the larval frass samples were about 12% lower in average than in the wood samples. The major thermal degradation started at lower temperatures for untreated samples than for the heat-treated samples for both, silver fir wood and larval frass. Therefore, heat sterilisation does not deteriorate fire safety of wooden parts of buildings and can be used without significant alteration of the wood composition and properties.

Temperature influence on product distribution and characteristics of derived residue and oil in wet sludge pyrolysis using microwave heating.

Sludge taken from a wastewater treatment plant of the petrochemical industry was dewatered and pyrolyzed to produce liquid oil as an alternative fuel via microwave heating. Element contents of dried sludge were 45.9±3.85wt.% carbon, 7.70±1.43wt.% hydrogen, 4.30±0.77wt.% nitrogen and 3.89±0.52wt.% sulfur. Two major thermal degradation peaks of sludge were determined during the microwave pyrolysis process, one at 325-498K (most of the water was vaporized, and the weight loss was over 85wt.%) and the other at 548-898K for sludge constituent decomposition. Zn content was high in the dried raw material and residues. Other toxic elements such as Ni, Cr, Pb, As and Cd contents were 0.61-0.99, 0.18-0.46, 0.15-0.25, 0.018-0.034, and 0.006-0.017mg/g, respectively. About 14-20wt.% of oil was produced based on the dried sludge cake, and the oil major elements were C (69-72wt.%), H (5.7-6.7wt.%), N (1.9-2.2wt.%), and S (0.58-0.82wt.%). The heat values of liquid oils were 8700-9200kcal/kg at 400-800°C.