Thermo-oxidative Decomposition Research Articles

Parameters of decomposition and combustion of reed vegetation: 1. Mechanism and kinetics of thermo-oxidative decomposition and pyrolysis

The parameters of decomposition and combustion of reed plants are formulated, which characterize combustible material and are necessary for physical and mathematical modeling of the occurrence and development of a fire, determining the risk of its consequences. According to the results of TGA, the content of the main components in the leaves and stem of the plant was estimated, the mechanism and parameters of the macrokinetics of their thermal-oxidative decomposition and pyrolysis were determined.

The effect of overload current on the thermo-oxidative decomposition behavior of polyvinyl chloride insulated wires investigated by TG-FTIR technique

The effect of overload current on the thermo-oxidative decomposition behavior of polyvinyl chloride insulated wires investigated by TG-FTIR technique

Parameters of Decomposition and Combustion of Reed Vegetation: 1. Mechanism and Kinetics of Thermooxidative Decomposition and Pyrolysis

Parameters of Decomposition and Combustion of Reed Vegetation: 1. Mechanism and Kinetics of Thermooxidative Decomposition and Pyrolysis

ТЕРМОСТОЙКОСТЬ ЗАЛИВОЧНЫХ ПЕНОПОЛИИЗОЦИАНУРАТОВ

In the modern construction industry for increasing the thermal resistance of structures and reducing heat losses, casting foams based on reactive oligomers with high performance characteristics are widely used. At the same time, special attention is paid to the use of polyisocyanurate foams (PIR). However, in the scientific and technical literature there are practically no data on the influence of the composition of polyisocyanurate foams on their thermal properties. The purpose of this work is to determine the influence of isocyanate/polyol ratio, modifier content (trichloropropyl phosphate) and apparent density of foams on thermal properties of casting PIRs. The thermal properties of PIRs, when heated in the temperature range of 30-800 ⁰C in nitrogen atmosphere and in air, were investigated using a multimodal thermal analytical complex DuPont-9900 (heating rate 20°C/min). It is revealed that thermo-oxidative decomposition of polyisocyanurate foams is a pronounced, two-stage process, and the destruction of PIR in inert medium (nitrogen) is a one-stage process, which indicates different mechanisms of decomposition of foams in air and nitrogen. As a result of experimental studies, it was revealed that the investigated PIRs are more resistant to thermo-oxidative degradation than to thermal degradation. The thermal properties of the above foams depend on the isocyanate/polyol ratio and TCPP content. The density of polyisocyanurate foams insignificantly affects their thermal stability. At the optimal content of initial components PIRs have higher thermal resistance compared to rigid polyurethane foams (FPU).

Potential of industrial symbiosis of petroleum residues and recycled polyethylene

In this work, a comparative study of the properties of polyethylene composites filled with the residue of solvent deasphalting of tar and asphaltenes isolated from it was carried out. Scanning electron microscopy analysis found that the compatibility of petroleum residue with the matrix was better than for asphaltenes. The observed effect was related to the present of petroleum resins, which have less polarity and long alkyl substituents that can improve molecular distribution asphaltenes in the nonpolar environment of polyethylene. Fourier transform infrared, thermo-gravimetric analysis, differential scanning calorimetry, and electron paramagnetic resonance methods have shown that asphaltenes play a key role in the thermal stabilization of composites. It is assumed that the radical traps in asphaltenes are free stable radicals, particles with unpaired electrons strongly delocalized on the π-system of polyaromatic molecules. Their antiradical action was associated to interactions with radicals formed during the thermal and thermo-oxidative decomposition of polyethylene result in the recombination and inhibition of further free-radical destruction. An analysis of the properties showed that the addition of a petroleum residue to the polyethylene makes it possible to maintain good mechanical properties after thermal-oxidative aging of composites. Thus, such asphaltene concentrates can be recommended as promising fillers for polyolefins in the polymer industry.

Effects of the PMMA Molecular Weight on the Thermal and Thermo-Oxidative Decomposition as the First Chemical Stage of Flaming Ignition

The piloted and the spontaneous ignition of low and high molecular weight (LMW and HMW) polymethyl methacrylate are simulated using a one-dimensional condensed-gas phase model for constant heat fluxes in the range of 25–150 kW/m2. Purely thermal (nitrogen) and thermo-oxidative (air) decomposition is considered, described by a single and four-step kinetics for the low and high molecular weight polymer, respectively. Different optical properties are also examined. The same trends of the ignition time and other ignition parameters are always observed. Due to a more significant role of the chemical kinetics, the effects of the sample molecular weight and reaction atmosphere are higher at low heat fluxes. Times are shorter for the black HMW samples and thermo-oxidative kinetics. For piloted ignition, factors are around 2.8–1.6, whereas for thermal decomposition, they are 1.3–1.2. The corresponding figures are 1.8–1.3 and 1.3–1.1, in the same order, for the spontaneous ignition. Overall, the effects of the molecular weight are more important than those related to the reaction kinetics environment. These differences are confirmed by the comparison between predictions and measurements.

Composite Carbon Aerogels Containing Manganese Oxide: Synthesis via Thermo-Oxidative Decomposition of Mn2(CO)10 in Supercritical CO2

A new effective approach is suggested that allows for introducing nanosized highly dispersed particles of manganese oxide into carbon aerogels using the thermo-oxidative decomposition of Mn2(CO)10 dissolved in supercritical CO2. It is shown that the proposed procedure retains a branched porous structure of the material with a specific surface area of more than 600 m2/g. The resulting composite aerogels contain 4–16 wt % of manganese.

Non-Isocyanate Poly(Siloxane-Urethanes) Based on Oligodimethylsiloxanes Containing Aminopropyl and Ethoxy Substituents

Environmentally friendly method for the synthesis of crosslinked poly(siloxane-urethanes) avoiding the use of toxic isocyanates has been presented. The synthesis has been performed in two stages: at the first stage, non-isocyanate poly(siloxane-urethanes) have been synthesized via aminolysis of cyclocarbonates (differing in the structure and functionality) with oligomer dimethylsiloxanes bearing aminopropyl and ethoxy substituents, and crosslinked non-isocyanate poly(siloxane-urethanes) have been obtained via hydrolysis of the ethoxy groups with air moisture. According to the TGA data, processes of thermooxidative decomposition of the non-isocyanate poly(siloxane-urethanes) begin at 240‒260°C, depending on the structure of the organic block. Structural organization of the films has been investigated and glass transition temperature of two blocks (flexible siloxane and rigid urethane ones) has been determined by means of DSC and TMA. Surface of the film samples of non-isocyanate poly(siloxane-urethanes) has been assessed by means of scanning electron microscopy.

Influence of Coffee Variety and Processing on the Properties of Parchments as Functional Bioadditives for Biobased Poly(butylene succinate) Composites.

Fermented polymers like biobased poly(butylene succinate) (BioPBS) have become more relevant as technical substitutes for ductile petrochemical-based polymers but require biogenic functional additives to deaccelerate undesired thermo-oxidative degradation and keep a fully biobased character. In this paper, the influence of coffee parchment (PMT) from two different varieties and processings on the thermo-oxidative stabilization and mechanical properties of poly(butylene succinate) composites up to 20 wt.-% PMT were investigated. Micronized with a TurboRotor mill, both PMT powders differ in particle size and shape, moisture ab- and adsorption behavior and antioxidative properties. It could be shown that pulped-natural PMT consists partially of coffee cherry residues, which leads to a higher total polyphenol content and water activity. The homogeneous PMT from fully washed processing has a higher thermal degradation resistance but consists of fibers with larger diameters. Compounded with the BioPBS and subsequent injection molded, the fully washed PMT leads to higher stiffness and equal tensile strength but lower toughness compared to the pulped-natural PMT, especially at lower deformation speed. Surprisingly, the fully washed PMT showed a higher stability against thermo-oxidative decomposition despite the lower values in the total phenol content and antioxidative activity. The required antioxidative stabilizers might be extracted at higher temperatures from the PMT fibers, making it a suitable biogenic stabilizer for extrusion processes.

Understanding of surface fouling of brackish water reverse osmosis spiral wound membrane using an integrated analysis of seawater quality and membrane autopsy

To understand the cause of the scale, an integrated analysis of the saline water quality and discarded reverse osmosis membranes was developed. Damaged areas on the membrane were excised and characterized by the Fujiwara test, infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. A spatula and sonication were used to remove scale. Thermodynamic modeling (PHREEQC) was used to predict scale formation at 75 bar, resulting in saturation index values for both mixed and pure compounds. Fujiwara's test revealed damage to the polyamide and organic fouling by polysaccharides, silica, and aromatics. Thermo-oxidative decomposition and residual masses of metal oxides and salts were observed. The microscopy detected incrustations in the membrane by analyzing compounds with silicon, oxygen, calcium, magnesium, aluminum, etc. The modeling indicated the low-solubility compounds of scale are aluminum silicates, clays, quartz, etc., identified experimentally. PHREEQC can model desalination to predict scale problems, allowing for early decision-making.

Strategies towards thermochemical valorisation of spent coffee grounds (SCG): Kinetic analysis of the thermal and thermo-oxidative decomposition

The thermochemical conversion of spent coffee grounds (SCG) under inert and oxidative conditions was comprehensively evaluated as a feasible valorisation route for this biomass. Dynamic thermogravimetric assays were carried out at different heating rates, where the individual contribution of the pseudo-components (hemicellulose, cellulose, lignin) was assessed by a deconvolution approach with Lorentz curves. The kinetic triplet, constituted by the apparent activation energy (Ea), the pre-exponential factor (A) and the model of reaction (g(a)), was defined for each pseudo-component through the application of iso-conversional methods, Master-Curves and Perez-Maqueda criterion. Under an inert atmosphere, the devolatilization of humidity, decomposition of hemicellulose, cellulose and part of lignin, and finally the completion of lignin were identified, resulting in a remaining percentage of 20% of biochar. For hemicellulose, Ea was 217 kJ mol−1, for cellulose 214 kJ mol−1, and lignin 151 kJ mol−1. Under oxidative conditions, analogous mass-loss stages were found, with the only difference being that biochar was decomposed until only ash (∼2%) was obtained as residue. The advantage of using SCG as biofuels, with a high LHV and HHV (∼20 MJ kg−1), was thus demonstrated. The Ea for the hemicellulose was 194 kJ mol−1, for cellulose 147 kJ mol−1, and for lignin was 173 kJ mol−1. Similar decomposition paths were found regardless of the atmosphere for hemicellulose (F4), hemicellulose (D3), and lignin (F2/4), which suggests that the temperature, the reactant concentration, the particle shape and the diffusion of products control the decomposition of SCG during non-isothermal pyrolytic or combustive thermochemical processes.

Comparison of the effects of antimony trioxide and zinc, calcium and copper stannates on the thermal degradation of polyamide-6,6

Thermal and thermo-oxidative decompositions of polyamide 6.6 (PA66) in the presence and absence of zinc (ZnSt), calcium (CaSt) and copper stannates (CuSt), and in the presence of antimony trioxide (ATO), have been studied by TGA-FTIR and pyrolysis GC/MS. It is shown that whilst ATO has a negligible effect on the rate of decomposition and products of pyrolysis under both slow heating on a TGA and rapid heating on a pyrolysis/GC/MS apparatus, the stannates have a catalytic effect in the order ZnSt ≈ CaSt > CuSt, evident through release of volatiles at a lower temperature and in a different product distribution following rapid high temperature pyrolysis. In particular, rapid pyrolysis at high temperature in the presence of the stannates promotes formation amongst the pyrolysis products of, for example, 6-aminohexanenitrile. 1,6-hexanediamine, 1-methyl-3-formylindole and 1,2,3,7-tetramethylindole, whilst yields of others are reduced, e.g., hexanedinitrile, caprolactam, diaminomethylidene(2-hydroxypropyl)azanium, prop‑2-enenitrile (acrylonitrile) and azacyclodecan-5-ol. We suggest that these effects arise from complexation of the electropositive metal in the stannate (Zn, Ca or Cu) with the C=O groups of PA66, thus weakening the C(O)-C and C-N bonds adjacent to the C=O groups. The fact that ZnSt has the most pronounced effect on the pyrolysis product distribution and CuSt the least, we explain in terms of the order of electropositivity of the metal (Zn>Ca>Cu).

Combustion properties of paper treated with chicken egg shell: A potential solid waste

A sustainable flame-resistant paper was prepared by using chicken egg shell, a solid waste material. Chicken Egg shell powder was dissolved in water (pH 4.5) and the mixture (ESS) has been applied on the paper by padding technique at different concentrations (200 and 300 g/L), followed by drying. Treated papers have shown LOI of 23%–27% and the applied organic coating also assisted to arrest flame spread time, smoke density and afterglow time in flammability test. Char morphology of the treated paper revealed that bio calcium carbonate present in the ESS act as an volume expansion agent, reduced the heat flow rate through-out the paper. Thermo-oxidative decomposition of the dried ESS has shown 100% mass retention up to 500 °C and the treated paper shows earlier decomposition (catalytic pyrolysis) and 25% more char mass retention at higher temperature as compared to the control paper material. Forced combustion results at 35kw/m2 revealed that ESS treated paper has shown almost 50% less heat release as compared to the control paper. Besides, mechanism lies behind the flame retardancy has been established. Tensile strength properties of the control and the treated paper also has been examined and registered in the context. Finally, dye ability of the ESS treated paper also has been examined with both anionic and cationic dyes.

Synthesis and characterization of medium- and long-chain structural lipid rich in α-linolenic acid and lauric acid

Medium- and long-chain triglycerides (MLCT) have been widely concerned. In this study, lauric acid (La) was incorporated into flaxseed (Linum usitatissimum L.) oil (FO, aLna-riched) by lipase-catalyzed acidolysis. The synthesis efficiency of four immobilized lipases (Lipozyme RM IM, TL IM, AOAB8 and Novozym 435) was compared, while Lipozyme AOAB8 reaction for 2 h was the best scheme. Further, the optimal conditions for synthesizing structural lipids (aLSLs, rich in aLna and La) were obtained by response surface methodology: the reaction temperature was 44.6 °C, substrate molar ratio was 12 (La/FO), and enzyme loading was 9.11%. After purification by molecular distillation, the triglycerides (TAGs) of aLSLs contained 75.35% of TAGs with α-linolenic acid (aLna), 40.82% of MLCTs with La, and 26.75% (65.53% of the total MLCTs) of TAGs with both aLna and La (ɑ-MLCT). Meanwhile, the content of La and aLna in aLSLs were 22.38% and 39.78%, respectively. The chemical structure and microstructure of aLSLs were similar to FO. In addition, the thermo-oxidative decomposition behavior of aLSLs was significantly improved compared with physical mixture oil. This improvement might be related to the insertion of La and the structure of TAG. In all, this study firstly developed a novel thermo-oxidatively stable MLCT with high levels of aLna and La.

Hybrid Polyurethane–Inorganic Thermal Insulation: Fire Hazard and Thermo-Oxidative Decomposition

Hybrid Polyurethane–Inorganic Thermal Insulation: Fire Hazard and Thermo-Oxidative Decomposition

Thermal Behavior of Estonian Graptolite–Argillite from Different Deposits

Graptolite–argillites (black shales) are studied as potential source of different metals. In the processing technologies of graptolite–argillites, a preceding thermal treatment is often applied. In this study, the thermal behavior of Estonian graptolite–argillite (GA) samples from Toolse, Sillamäe and Pakri areas were studied using a Setaram Labsys Evo 1600 thermoanalyzer coupled with the Pfeiffer OmniStar Mass Spectrometer. The products of thermal treatment were studied by XRD, FTIR, and SEM analytical methods. The experiments were carried out under non-isothermal conditions of up to 1200 °C at different heating rates in the atmosphere containing 79% Ar and 21% O2. The differential isoconversional Friedman method was applied for calculating the kinetic parameters. All studied GA samples are characterized with high content of orthoclase (between 38.0 and 57.3%) and quartz (between 23.8 and 35.5%), and with lower content of muscovite, jarosite, pyrite, etc. The content of organic carbon in GA samples studied varied between 7.3 and 14.2%. The results indicated that, up to 200 °C, the emission of hygroscopic and physically bound water takes place. Between 200 °C and 500–550 °C, this is followed by thermo-oxidative decomposition of organic matter. The first step of thermo-oxidation of pyrite with the emission of water, carbon and sulphur dioxide, nitrogen oxides, and different hydrocarbon fragments indicated the complicated composition of organic matter. At higher temperatures, between 550 °C and 900 °C, the transformations continued by dehydroxylation processes in clay minerals, and the decomposition of jarosite and carbonates took place. At temperatures above 1000–1050 °C, a slow increase in the emission of sulphur dioxide followed, indicating the beginning of the second step of thermo-oxidative decomposition of pyrite, which was not completed for temperatures of up to 1000 °C. Kinetic calculations prove the complicated mechanism of thermal decomposition of GA samples: for Pakri GA samples, it occurs in two steps, and for Silllamäe and Toolse GA samples, it occurs in three steps. Preliminary tests for the estimation of the influence of pre-roasting of GA samples on the solubility of different elements contained in GA at the following leaching in sulphuric acid is based on Toolse GA sample.

A novel DOPO derivative containing multifunctional groups aiming to improve fire safety, thermal stability and curing state towards epoxy resin

A novel reactive flame retardant (PABO) was synthesized via a one-pot reaction from para-aminobenzonitrile, p-hydroxy benzaldehyde and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and applied on epoxy resin (EP). The curing state of the EP mixture with the addition of PABO was excellent as detected by the cure index (CI). Thermogravimetric analysis showed that compared with DOPO, PABO possessed a higher degradation temperature, a lower thermal decomposition rate and the Char800 (char residues at 800°C) increased from 1.5 to 26.5 wt%. The EP/PABO-5 with only 5 wt% PABO content attained a limiting oxygen index of 32.7% and possessed the UL-94 V-0 level. The calculated flame retardant index (FIGRA) showed that the fire safety of EP/PABO-5 was superior to that of EP/DOPO-5. For flame retardant mechanism, in the gas phase, PABO possessed the function of retarding the thermo-oxidative decomposition of EP, the quenching effect of phosphorus radicals and the diluting effect of non-combustible nitrogen-containing gas. In the condensed phase, the trimerization reaction of nitrile groups happened and the existence of the phosphaphenanthrene group together promoted the formation of a stable char layer, which could obstruct the transfer of heat and oxygen.

Supercritical CO2 with co-solvent extraction of blackberry (Rubus spp. Xavante cultivar) seeds

Blackberry seed extracts (BSEs) were obtained by extraction using supercritical CO2 and ethanol as co-solvent. Conditions of 70 °C and 25 MPa provided the best results: 24.05 wt% of yield, total phenolic content of 3856 mg GAE 100 g−1, and 12,948, 12,996 and 14,243 µmol TE 100 g−1 for the assays ABTS, DPPH and FRAP, respectively. The nutritional lipid indices were PUFA/SFA ratio of 9.60, hypocholesterolemic/hypercholesterolemic ratio of 16.23, atherogenicity 0.06 and thrombogenicity 0.17. The main phenolic compounds were rutin and protocatechuic acid. The thermo-oxidative decomposition of the extract started at 196.25 °C and storage at − 29.52 °C. Rancimat analysis showed that the extract has a protective effect against the oxidation of soybean oil. These results indicate good potential for the application of this extract as an antioxidant.

Self-heating evaluation on thermal analysis of polymethyl methacrylate (PMMA) and linear low-density polyethylene (LLDPE)

Thermal analysis has been proven to be an efficiently technique to analyse thermal decomposition reactions of different type of materials. This technique is widely used in different fields. Among them, fire science, where polymeric materials are very common, has a particular issue, being the combustion reactions recurrent on these analyses. Thermal analysis has different particularities depending on the studied material. For instance, polymeric materials could undergo different decomposition reactions that are highly dependent on definition of the thermal analysis boundary conditions. The International Confederation for Thermal Analysis and Calorimetry (ICTAC) (Vyazovkin et al. in Thermochim Acta 590:1–23, 2014) and standards (ISO 11358-1. Plastics—Thermogravimetry (TG) of polymers—Part 1: General principles. ISO. 2014; https://www.iso.org/standard/59710.html. Accessed 31 Jan 2022), (ISO 11357-1. Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles. ISO. 2016; https://www.iso.org/standard/70024.html. Accessed 31 Jan 2022) stablish how to set-up these boundary conditions in the thermogravimetric (TG) and differential scanning calorimetry (DSC) standards. As far as initial amount of sample mass is concern, some discrepancies can be found between the standards. For instance, the standards suggest a sample mass between 10 and 100 mg for TG and between 2 and 40 mg for DSC, whereas the ICTAC recommendations suggests that the sample mass times the heating rate should not exceed 100 mg K·min−1 in thermo-oxidative decomposition analysis, which is equivalent to samples masses lower than 10 mg for heating rates of 10 K·min−1, or lower than 5 mg for heating rates of 20 K·min−1. This discrepancy may lead to obtain different results from the tests. Additionally, according to the thermal and thermo-oxidative decomposition of polymers, the ICTAC remarks the influence on the results of the sample thicknesses, carrier gas and heating rates, but it does not analyse the influence of self-heating as it does for the hazardous materials. This work presents a study of the self-heating influence in the thermal decomposition processes of two widely used polymers as poly methyl methacrylate (PMMA) and linear low-density polyethylene (LLDPE). TG/DSC tests are used to evaluate the thermal decomposition processes. Boundary conditions of the tests definition as sample mass, atmospheres, and heating rate are considered to evaluate its influence on the polymers self-heating effect on the thermal decomposition. It also includes how to check if TG/DSC tests follows the theoretical principles of the thermal analysis, or if the results are affected by the self-heating. In the present study, a series of 32 experimental tests has been performed, analysing 16 boundary conditions. These experimental tests allow evaluating the influence of selected boundary conditions on the mass loss, the heat flux, and the materials decomposition reactions. Additionally, we analyse the effect of the boundary conditions on the temperature of the sample. Results show the impact of each different boundary conditions of the self-heating effect, and its influence in the final thermal decomposition measured and they represent an aid to define the suitable conditions to perform TG/DSC test on PMMA and LLDPE, or similar polymer materials. This is done by the evaluation of the influence of the self-heating in parameters as the sample temperature lags defined in [1], the reactions heat fluxes, and the difference between the sample and the programmed temperature. It is also analysed the influence of the auto-ignition temperature in the thermal analysis. It is remarkable the PMMA auto-ignition temperature effect on the TG/DSC results. Finally, some useful recommendations have been defined.

The catalytic thermo-oxidative decomposition of glimepiride using the isoconversional method

Applying the isoconversional method to data obtained from thermogravimetric analysis (TGA) can provide vital kinetic information. In this work, the thermal decomposition and oxidation of the antidiabetic drug glimepiride is analyzed in the presence of N2 and O2. The study was done with and without metal oxide catalysts to explore their potential application in solid wastewater upgrading. The analysis was conducted using thermogravimetric analysis. The isoconversional methods of Kissinger–Akahira–Sunose and Friedman were used to estimate the effective activation energies as a function of the extent of conversion (α). Density functional calculations were used to estimate the bond dissociation energies in glimepiride. The Ea values obtained from the Friedman method and the DFT calculations indicate an initial S–N bond breaking in glimepiride. The pre-exponential factor (A) and the kinetic triplet (ΔH‡, ΔS‡, and ΔG‡) are also discussed. When glimepiride oxidation was studied in the presence of the metal oxides, the catalyst activity was found to follow the order {text{VO}}_{{2}} > {text{ CuO }} > {text{ MnO}}_{{2}} > {text{ Al}}_{{2}} {text{O}}_{{3}} > {text{ TiO}}_{{2}}.