Oxidative Chain Reactions Research Articles

The characteristics and mechanism of NaHCO3 compound fly ash in suppressing gas explosions in pipeline networks

Gas has been widely concerned due to its importance in the industrial and energy fields. In order to improve the inhibition effect of gas explosion, under the self-constructed pipe network system, the inhibition of gas explosion by composite inhibitor of fly ash and NaHCO3 with different ratios was investigated, and the microscopic inhibition mechanism of the two kinds of powders on the explosion of gas was investigated based on the method of density functional theory and transition state theory from the perspective of molecular dynamics. The results show that: the composite powder explosion suppression is better than a single powder, explosion suppression effect with the increase in the proportion of the mass of NaHCO3 significantly improve the 5 groups of conditions NaHCO3 loading of 40% (by mass) is the best, this time, the explosion of the peak overpressure, the peak flame propagation velocity, the peak flame temperature compared to the maximum reduction in the percentage of the measures taken for the maximum of 74.42%, 81.93%, 68.71%. In addition, NaHCO3, fly ash effectively inhibit the key primitive reaction of gas explosion. When the temperature reaches a certain point, the two and O*, O2, OH* and H* reaction rate higher than the rate of CH4 oxidation chain reaction, the dominant reaction, the maximum difference in rate constants of 70.95, 58.81, 60.06, 44.94. The study of the transition from the macro-scale to the molecular level of the study, in-depth understanding of the mechanism of explosion suppression, to reduce the risk of explosion from the ground up, and enriches the Gas explosion prevention and control of the theoretical system, for the operators to provide a strong technical guarantee for safe production.

Research on the Potential of Persistent Free Radicals Triggering Open-Pit Coal Oxidation and Spontaneous Combustion

ABSTRACT This study attempts to reveal the triggering pathways of open-pit coal oxidation and spontaneous combustion from the perspective of persistent free radicals (PFRs). To this end, electron spin resonance technology, spin trap technology, and quantum chemical calculations were combined to study the occurrence characteristics of PFRs in coal and their photoreaction characteristics. Based on typical coal molecular fragments, the mechanism of PFRs triggering open-pit coal oxidation was further revealed. The results indicate that coal contains abundant PFRs, which produce reactive oxygen species (ROS) after exposure to sunlight, mainly including hydroxyl radicals (•OH) and superoxide anion radicals (O2 •−). Among them, the higher the initial content of PFRs or the longer the time of sunlight exposure, the more favorable it is for the production of •OH, the concentration of photoinduced •OH remains at the level of 1011 spin/mm3. Compared to O2 in the air, these photoinduced •OH have stronger oxidizing properties and can trigger free radical chain reactions of coal oxidation at room temperature (activation energies ＜ 40 kJ/mol), releasing reaction heat (average enthalpy change is −65.53 kJ/mol). As a common oxidant in coal spontaneous combustion (CSC) process, O2 does not possess these abilities (activation energies greater than 190 KJ/mol and enthalpy change greater than 160 KJ/mol). From the perspectives of thermodynamics and kinetics, PFRs in coal have the potential to indirectly trigger open-pit coal oxidation and spontaneous combustion. Therefore, the efficient quenching of PFRs or inhibiting the production of •OH will be beneficial for preventing the oxidation and spontaneous combustion of open-pit coal. This study provides a new perspective on revealing the mechanism of CSC and developing new inhibitors.

PHYTOCHEMICALS SCREENING, ANTIOXIDANT AND ANTIMICROBIAL ACTIVITY OF CARICA PAPAYA LEAF EXTRACTS

Objective: The objective of the present study aimed at investigating the phytochemical antioxidant and anti-microbial properties of Carica papaya leaf extracts. Methods: As phytochemicals are biologically active compounds and a powerful group of plant chemicals believed to stimulate the immune system along with antioxidants, the molecules which hinder oxidation of other molecules by the process of inhibiting or by generating the oxidizing chain reactions and preventing diseases. The anti-microbial activity on various gram-positive and gram-negative bacteria were determined using zone of inhibition and antioxidant by the 2,2,1-diphenyl-1-picrylhydrazyl method. Results: Phytochemical screening, antioxidant and antibacterial potential were determined using different aqueous and organic solvents in addition to the determination of trace element in leaves of C. papaya. Antioxidant activity using DPPH free radical scavenging assay indicated leaves extracts leaves showed inhibition of per oxidation. The result showed that the ethanolic extract of C. papaya possessed a significant antioxidant activity as compared to methanol and aqueous extract. The antibacterial study showed leaves extract is the best to cope infectious action of bacteria. Conclusion: This study was conducted to test the medicinal profile of C. papaya by extracting secondary metabolites with organic and aqueous solvents. Ethanol was found to be the best solvents of choice to extract natural products to get maximum medicinal benefits and could be used to medicinal formulation against different infectious diseases.

Determining the influence of synthesis gas additives on the environmental performance of internal combustion engine

The object of research is the environmental parameters of a reciprocating engine when using a synthesis gas additive to the main fuel. The research is aimed at solving the problem of reducing the concentration of harmful components in the exhaust gases of an internal combustion engine by adding synthesis gas to the main fuel. Experimentally, the dependences of the effect of the addition of synthesis gas to ethanol on the change in the environmental performance of a piston engine with spark ignition were obtained. The positive effect of the addition of synthesis gas obtained by thermochemical conversion to ethanol in an amount of up to 5 % by weight on the environmental performance of a spark-ignition piston engine was established. Provided that the engine achieves the same effective power, the use of a synthesis gas additive to the main fuel made it possible to reduce the concentration of CO by 61.5 % and CH by 51.3 % in the exhaust gases. no more than 25–30 words The addition of synthesis gas contributed to the formation of radicals that activate oxidation chain reactions, and also made it possible to increase the normal combustion rate of the fuel-air mixture by 6.25 %. This ensures normal engine operation on a leaner fuel-air mixture (α=1.21) without deterioration of environmental, energy and economic performance. no more than 25-30 words The simultaneous reduction of the concentration of harmful components in the exhaust gases and engine efficiency can be achieved by using fuels with a wide concentration limit of ignition and high combustion rate in a lean mixture. The experimental data obtained can be used in the design or modernization of transport and stationary power plants with internal combustion engines as an approach to meet ever-increasing environmental standards

System-wide coordination and communication of lipid metabolism atlas revealed cytotoxicity of epoxy triglyceride in deep-frying oil

The epoxy triglycerides generated by oxidation, cyclization, and free radical chain reaction of unsaturated dietary oils during deep-frying are demonstrated to have cytotoxicity and can induce lipid metabolism related diseases. Metabolic diseases are usually characterized by metabolic abnormalities in different tissues, however, the relationship between changes in intratissue coordination and communication induced by epoxy triglycerides and specific pathogenic mechanisms remains largely unknown. We conducted lipid metabolomics analysis across six different tissues in C57BL/6J mice, including the medial prefrontal cortex, interscapular brown adipose tissue, epididymal white adipose tissue, liver, intestine, and heart. Normal diet intake demonstrated a high degree of association between lipid metabolites, indicative of cross-communication and cooperation among various tissues and organs, while, a global correlation that was disrupted and restructured by epoxy triglycerides intake. Examination of blood samples revealed that epoxy triglycerides enhanced bacterial translocation from the gut to the systemic circulation, consequently stimulating the TLR4/CD36/NF-κB pathway. In summary, this study found that epoxy triglyceride upsets the comprehensive coordination and information exchange of lipid metabolism, providing a fresh perspective for future research on the systemic metabolic network and identifying metabolic disease markers and associated mechanisms induced by deep-frying oil.

A study of the molecular interactions of hemoglobin with diverse classes of therapeutic agents

Investigation of the interaction of hemoglobin (Hb) with therapeutic agents may be useful from three perspectives. First, there are a few therapeutic agents targeting precisely Hb. Second, the high concentration in the blood makes it a likely target for (often unwanted) side reactions of drugs targeting other systems in the body. Third, with its complex and well-studied reactivity, Hb offers itself as a useful model protein for understanding the interactions of therapeutic molecules with proteins via various mechanisms that include allosteric effects, coordination chemistry, metal- or aminoacid-based redox processes, and solution-based oxidative and nitrosative stress chain reactions. Presented here is a review of the molecular interactions described for hemoglobin with various therapeutic agents of organic, coordinative, or organometallic types. These interactions are typically studied by spectroscopy (fluorescence, UV–vis, circular dichroism, infrared, NMR), X-rays diffraction and molecular modeling (especially docking). Classes of therapeutic agents whose molecular interactions with Hb have been described include antioxidants (e.g., ascorbate, tocopherol, glutathione, carotenoids), anti-sickling agents, various organic chemotherapeutics, and metallodrugs.

GCMS and HPLC profiling, antioxidant and anti-inflammatory activities of Crotalaria medicaginea Lamk

Inflammation is the underlying process to many degenerative diseases such as emphysema, cancer, Alzheimer's, arthritis, diabetes, and more recently COVID-19. The overproduction of free radicals in the cells is the major factor that leads to inflammation due to oxidative stress. These free radicals damage macromolecules in cells, including nucleic acids, proteins, lipids, and polyunsaturated fatty acids, through oxidation, thus affecting cell metabolism. Antioxidants can delay the oxidation of these molecules through inhibition of oxidizing chain reactions and can be helpful in treating inflammatory diseases. Crotalaria medicaginea Lamk (Fabaceae) is an important medicinal plant that is not extensively explored for its biological and pharmacological potential on scientific grounds. In this study, in vitro antioxidant and anti-inflammatory activities of the crude methanolic extract and different solvent fractions of the plant were determined. Phenolics, flavonoids, tannins, and saponins were quantified in each plant sample. The crude extract was characterized for its phytochemical constituents through GC–MS and HPLC analysis. Strong antioxidant and anti-inflammatory activities of plant extracts were recorded which can be attributed to the presence of phenolics, flavonoids, saponins, terpenes, and tannins in these extracts. GC–MS analysis confirmed the presence of Hexadecanoic acid, methyl ester, 9,12-Octadecadienoic acid (Z,Z)-, methyl ester, and 9-Octadecenoic acid, methyl ester, (E)- as major compounds while HPLC analysis confirmed the presence of gallic acid, taxifolin, quercetin and kaempferol in the plant.

Противодействие живых систем развитию возрастной катаракты. Физико-химическое объяснение

Simultaneous processes occur in living systems that lead to both an increase in entropy (chaos) and its decrease. A decrease in entropy is possible only in open systems, associated with a contin-uous flow of energy-intensive compounds into them, such as glucose, the oxidation of which is energetically associated with the synthesis of ATP, the universal carrier of chemical energy to en-sure functioning of living systems. When energy-intensive compounds are oxidized, entropy in-creases, and when ATP is synthesized, it decreases. In living systems, not only reactions associated with the synthesis of ATP and their functioning occur, but also aging does, namely, the oxidation of hydrophobic formations in cells, in particular, the membrane matrix, following the type of chain reactions with degenerate branching. The development of such chain reactions of oxidation in cells can be prevented by the penetration into them of various antioxidants, for example, resvera-trol, which is contained in grapes and other plants, and quenchers of molecular oxygen in the sin-glet state, for example, iodides, as well as by creating cyclic processes involving desaturases that prevent an increase in viscosity in the matrix of membranes up to certain limiting values, after which cell death becomes inevitable. In this regard, the processes leading to cataracts (clouding of the eye lenses) are indicative. In the absence of desaturases in the lens fibers of rats, exposure to UV light leads to cataracts in 2–4 months, while the presence of desaturases in human eye lens fi-bers makes it possible to avoid the occurrence of cataracts for many decades. The reaction of con-version of lipids with saturated fatty acids into unsaturated ones, catalyzed by desaturases, leads to counteracting the aging of the membrane matrix. The vital feature of this reaction is that it oc-curs only when the membrane matrix is cured. This reaction first leads to liquefaction of the ma-trix up to a certain state, after which it stops. The reasons leading either to revival of desaturase or to decrease in its activity are discussed in this article.

Prediction of Aging Performance of Particle-Filled Polymer Composites Based on RVE Model.

In this study, the aging performance of particle-filled polymer composites (PFPCs) under thermo-oxidative conditions was investigated on multiple scales. High-temperature-accelerated tests were conducted to analyze the effects of aging time and temperature. A representative volume element (RVE) model was established for the PFPCs using a random particle-filling algorithm. A predictive model for the crosslink density was conducted based on the closed-loop chain reaction of polymer oxidation. According to the theory of polymer physics, the relation between the crosslink density and matrix modulus was determined. The particle/matrix interface in the RVE model was represented by the cohesive zone model (CZM). The parameters of the CZM were determined by the inversion techniques. Then, a comprehensive multiscale RVE model was constructed, which was applied to predict the modulus and dewetting strain of the aged PFPCs. The predicted results show good agreement with the test results, which verifies the reliability of our model.

Evaluation of the photosensitizer activity of hydrophobic phosphorus(V)porphyrins using the absorption spectral change of 1-benzyl-1,4-dihydronicotinamide

Under visible light irradiation, water-insoluble P(V)porphyrins oxidized 1-benzyl-1,4-dihydronicotinamide (BNADH), a model compound for nicotinamide adenine dinucleotide, and diminished the typical absorption of BNADH at around 340 nm. A singlet oxygen quencher, sodium azide, partially inhibited photosensitized BNADH oxidation. This BNADH oxidation photosensitized by P(V)porphyrins in the presence of sodium azide can be explained by electron transfer oxidation from BNADH to the photoexcited P(V)porphyrins. The quantum yields of BNADH oxidation via electron transfer by these P(V)porphyrins were larger than those of a singlet oxygen mechanism. Redox potential measurements supported the electron transfer mechanism from a thermodynamic point of view, and fluorescence lifetime measurement also suggests this mechanism. The process of this electron transfer oxidation involves the radical formation of BNADH and the further reaction of this radical to the oxidized form (cationic form of BNADH). Analysis of the quantum yields of BNADH photooxidation by P(V)porphyrins suggests that the photoinduced electron transfer from BNADH to photoexcited P(V)porphyrins triggers the radical chain reaction of BNADH oxidation. The electron transfer rate coefficient and this efficiency were increased with an increase in the Gibbs energy of electron transfer from tryptophan to photoexcited P(V)porphyrins (−ΔG). However, the BNADH oxidation quantum yield via electron transfer decreased with an increase in the -ΔG of electron transfer. These results suggest that reverse electron transfer inhibits the decomposition of BNAD radicals. This assay using BNADH can be used to evaluate the photosensitizer activity of water-insoluble compounds. These P(V)porphyrins may be used as photosensitizers for photodynamic therapy in a relatively hydrophobic environment in cancer tissues.

Realizing brain therapy with "smart medicine": mechanism and case report of molecular hydrogen inhalation for Parkinson's disease.

The Michael J. Fox Foundation has been funding research on Parkinson's disease for 35 years, but has yet to find a cure. This is due to a problem with the philosophy behind the development of modern medical treatments. In this paper, we will introduce "smart medicine" with a substance that can solve all the problems of central nervous system drugs. The substance is the smallest diatomic molecule, the hydrogen molecule. Due to their size, hydrogen molecules can easily penetrate the cell membrane and enter the brain. In the midbrain of Parkinson's disease patients, hydroxyl radicals generated by the Fenton reaction cause a chain reaction of oxidation of dopamine, but hydrogen entering the midbrain can convert the hydroxyl radicals into water molecules and inhibit the oxidation of dopamine. In this paper, we focus on the etiology of neurological diseases, especially Parkinson's disease, and present a case in which hydrogen inhalation improves the symptoms of Parkinson's disease, such as body bending and hand tremor. And we confidently state that if Michael J. Fox encountered "smart medicine" that could be realized with molecular hydrogen, he would not be a "lucky man" but a "super-lucky man."

Evaluation of in vitro antioxidant activity of edible Basidiomycetes mushroom fungi

Introduction: Basidiomycetes mushroom fungi have been known for their nutritional values they can be considered as functional foods which can provide health benefits beyond the traditional nutrients. They are the excellent source of natural antioxidants because some synthetic antioxidants are now suspected to be potentially harmful to human health. As free radicals can cause inflammatory diseases, cancer, atherosclerosis, and aging, Consuming dietary antioxidant supplements can inhibit oxidative chain reactions. Materials and Methods: The antioxidant potential of the basidiomycetes mushroom fungal strains was established by total flavonoid content, FRAP assay, ABTS assay, Metal chelating activity, Phosphomolybdenum assay, Assay of superoxide radical scavenging activity, Free radical scavenging activity on DPPH along with the determination of total phenolic and tannin contents in the mushroom mycelial extracts. Results: Different Basidiomycetes mushroom fungi extracts (Hot water, Acetone and Hexane) were tested for antioxidant activities. Among these different extracts of Basidiomycetes mushroom fungi the hexane extract of Pleurotus pulmonarius showed potential antioxidant activity. Discusion and Conclusion: The results of this study suggest the possibility of using Basidiomycetes mushroom fungi as a natural antioxidant source for the pharmaceutical industry and could act as safe and cost-effective with potential antioxidant activities. These findings encourage studying these fungal strains further for their potential biological applications.
 Keywords: Flavonoid, Tannin, FRAP, ABTS, DPPH and Free Radical

Isolation and Characterization of Curcumenotone, a Sesquiterpene from Curcuma aeruginosa Roxb as Antioxidant

Antioxidant compounds are necessary to block the initiation of oxidation chain reactions and inhibit the formation of ROS which are the cause of various diseases. Natural antioxidants can be isolated from various sources, one of them from Curcuma aeruginosa Roxb Rhizome. This study was aimed to isolate and identify antioxidant compounds from Curcuma aeruginosa Roxb rhizome. To isolate the active compound, the 2,2-diphenyl-1-picrylhidrazyl (DPPH) free radical scavenging activity guide was used. Initially the Curcuma aeruginosa Roxb rhizome powdered material macerated with ethanol 70% to give ethanol extract (EE). The EE was then fractionated gradually with increasing polarity solvents to give n-hexane (HF), ethyl acetate (EAF), ethanol (EF) and insoluble (IF) fractions. The EF was the active fraction, was fractionated into 6 fractions (EE.a-f) based on their TLC picture. Two compounds (EF.a1 and EF.a2) were isolated from active fraction (EF.a) by preparative TLC. The EF.a2 appeared as white crystals demonstrates better activity as anti radical DPPH, having 96.24% purity (HPLC). EF.a2 appeared as a single peak in GC (Rt 12,78), and having molecular weight at m/z 234. There were 2 absorbtion peaks at 226 nm and 260 nm in Uv-Vis spectrophotometer and absorption bands at 3364, 3314, 2905 and 1653 cm-1 on the FT-IR spectrum. Based on spectroscopic data (1H-,13C-NMR) and comparison with reported data, the EF.a2 was identified as sesquiterpene, curcumenotone (C15H22O2). The curcumenotone was shown potent antioxidant in DPPH radical scavenging assay had an IC50 53.24±1.51 µg/mL, ABTS radical scavenging assay had an IC50 41.33±3.15 µg/mL, and FRAP assay had an IC50 37,82±2.02 µg/mL.

Temperature Dependence of the Oxidation of Hydrogen with Sulfur Dioxide

An experimental study is performed of the mechanism of sulfur dioxide–hydrogen interaction (4Н2 + 2SО2 → S2 + 4H2О) at temperatures of 623, 673, 723, and 773 K and a pressure of 198 Torr. The mechanism is analyzed via mathematical modeling. It is found to be a chain reaction of hydrogen oxidation with sulfur dioxide, which results in the formation of molecular sulfur (S2). The process is characterized by negative Gibbs free energy ΔG723 = −49.950 kcal/mol. The potential energy surface of the (HOSO + HOSO) system is studied by various means of quantum chemistry, and the thermodynamic parameters of the НОSO + НОSO → SO + SO2 + Н2О reaction are determined. A new mechanism of the reaction, supplemented by elementary acts, is discussed. Good agreement is found between energies of activation determined experimentally and calculated using data from our numerical kinetic analysis.

Multi-Scale Model for the Aging Performance of Particle-Filled Polymer Composites.

In this study, we developed a novel multi-scale model to predict the aging performance of particle-filled polymer composites (PFPCs) under thermo-oxidative aging conditions. To investigate the aging behavior, high-temperature accelerated aging tests were conducted in combination with macroscopic and microscopic characterization. At the microscopic level, the crosslinking density of the polymer matrix is calculated using the closed-loop chain reaction of polymer oxidation. In addition, the theory of polymer physics was used to determine the relationship between crosslinking density and elastic modulus. Relationships between elastic modulus and dewetting strain were analyzed at the macroscopic level. Based on the observations and analyses, a multi-scale model was developed to predict the aging performance of PFPCs. The predicted results show good agreement with the test results, which verifies the reliability of the model.

The Potential of Underutilized Plant Resources and Agricultural Wastes for Enhancing Biodiesel Stability: The Role of Phenolic-Rich Natural Antioxidants

Growing concerns about energy security and environmental sustainability have fueled demand for sustainable and renewable energy sources in recent years. Biodiesel, a renewable alternative to conventional fuels, has gained significant attention as a potential source of energy. However, the stability of biodiesel during storage and its susceptibility to oxidation remain major challenges. To address these issues, researchers have turned their focus to the utilization of natural antioxidants. Studies on sources of natural antioxidants, particularly those made from waste, such as food, have been extensively conducted. However, there are still some restrictions, such as inconsistency in quality, the development of microbes, and difficulties with regulations, all of which have an impact on sustainability and the phenolic contents. Phenolic compounds are known for their excellent antioxidant properties and ability to inhibit the oxidation process. The review provides an overview of various underutilized plant resources and agricultural wastes that are rich in phenolic contents and demonstrate higher antioxidant activities, such as Vitex doniana, Uapaca kirkiana, Parinari curatellifolia, Tamarindus indica L, fruit peels, and crop residues. It discusses the extraction methods employed to obtain phenolic antioxidants from these sources and highlights their antioxidant activities. Additionally, the review examines the effects of phenolic antioxidants on key parameters, including induction period, peroxide value, acid value, and viscosity. The review concluded by highlighting the potential of underutilized plant resources and agricultural wastes as sustainable sources of phenolic-rich natural antioxidants for enhancing biodiesel stability. According to the literatures, phenolic antioxidants present in underutilized plant resources and agricultural wastes can chelate metal ions, scavenge free radicals, and break oxidation chain reactions, thereby preventing the degradation of biodiesel. Moreover, the limitation of the use of natural antioxidants in the stabilization of biodiesel like instability at high temperatures has been highlighted.

Migraine and plant antioxidant: Review article

Even though the pathophysiology of migraine has been the subject of many works, the precise molecular mechanism regarding the disturbances that underlie migraine remains unknown. Additionally, it is thought that oxidative stress contributes significantly to migraine development. For many years, the idea that migraine sufferers experience oxidative stress was addressed. The so-called nutraceutics, which include antioxidants, have received a lot of attention in the last few years among the substances which may be utilized to cure migraines. Antioxidants that are supplied with the food prevent the oxidative stress through suppressing the propagation, initiation, and actual oxidative chain reaction. The agents now being utilized to prevent migraines do in fact have certain antioxidative activity. Antioxidants that have been addressed in this research are growing more regularly utilized through the migraine sufferers not just because of low or even lack of side effects, yet as well due to their efficiency (shortening of an episode duration or reduced frequency of migraine episodes).

Guideline for screening antioxidant against lipid‐peroxidation by spectrophotometer

AbstractLipid peroxidation (LPO), an oxidative chain reaction often occurring in the human body and food, is harmful to human health. Due to its convenience and low cost, this guideline highlights the benefits and drawbacks of LPO models by spectrophotometer in vitro and in vivo. The preparation process and reaction mechanism of lipid substrates, oxidation triggers and detection methods are discussed in this paper to better screen antioxidants. The lipid substrates mostly consist of rat liver/brain homogenate, microsomal, low‐density lipoprotein (LDL), and linoleic acid (LA), are appropriate for modeling oxidative damage in a variety of situations. Transition metals, ascorbic acid, 2,2′‐azobis (2‐amidinopropane) hydrochloride (AAPH), sodium Nitroprusside (SNP), 3‐morpholinosydnonimine (SIN‐1) and nicotinamide adenine dinucleotide phosphate (NADPH) make up the majority of the oxidizing triggers. The following LPO quantification techniques have been reviewed: (a) thiobarbituric acid reactive substances (TBARS) assay, (b) measurement of conjugated‐diene (CV), (c) β‐carrot bleaching assay, (d) thiocyanate method, (e) ferrous oxidation‐xylenol orange (FOX‐2) assay. It can be concluded that more than one test system should be applied to obtain comprehensive results. In a word, this guideline provides a scientific basis for future research on antioxidants screening in food and body systems.

Phenylenediamine‐phenyl phosphonic acid salts toward good flame retardancy and smoke suppression epoxy resin

AbstractAn environmentally friendly flame retardant named PO‐PA was designed to enhance the flame retardancy of epoxy resin (EP). Following the principles of efficiency and simplicity, PO‐PA was synthesized through a one‐pot reaction between phenyl phosphonic acid and p‐phenylenediamine. The chemical structure of PO‐PA was characterized by Fourier‐transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), elemental analysis (EA) and thermogravimetric analysis (TGA). EP containing 10 wt% PO‐PA (EP/10%PO‐PA) passed the UL94 V‐0 rating without dripping. In the cone calorimeter test, the total heat release and total smoke production of EP/10%PO‐PA decreased by 44% and 65%, respectively. TG‐FTIR and Py‐GC/MS were used to investigate the pyrolysis gases of the EP composites and PO‐PA, respectively. Scanning electron microscopy (SEM), FTIR, EA and XPS were utilized to study the char residues. It was proved that PO‐PA notably promoted the formation of smooth protective char layer in the condensed phase and effectively inhibited the oxidation chain reactions through releasing the phosphorus‐containing radicals in gas phase, which was not mentioned in the similar research based on phenyl phosphonic acid.

Study on the mechanism of free radical scavenger TEMPO blocking in coal oxidation chain reaction

The inhibitory effect of free radical scavenger 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) on the spontaneous combustion process of coal has been experimentally confirmed. However, the mechanism of free radical trapping in coal by TEMPO is not clear. This paper revealed the mechanism of free radical capture in coal by TEMPO from three perspectives by quantum chemistry method, including capture radicals directly, regenerative cycle chain and hydrogen transfer. It was regarded as a beginning that the formation of free radicals (R-CH2∙, CH3∙) by breaking alkane groups in the side chain of the coal molecule. The oxidation process of these free radicals was analyzed and the capturing models of radicals were described. The thermodynamic data for reactions (R2 ∼ R5) are calculated to reveal the initial reaction process of coal. The adsorption energy and thermodynamic data for reactions (Process1 ∼ 4, R6 ∼ R10, R12 ∼ R13) are computed to illustrate spontaneity and difficulty of traps free radicals by TEMPO. The results indicate that the initial reaction (R2, R4) of free radicals with oxygen in coal is exothermic and some other reactions (R3, R5) need to overcome large reaction energy barriers. TEMPO can capture free radicals in coal directly, reducing the concentration of free radicals, and is most effective in capturing ∙OH and alkyl radicals. At the same time, TEMPO can capture peroxide radicals and alkyl radicals in coal through regenerative cycle chains and keep reborn to maintain the efficiency of its capture. For coals under acidic conditions, TEMPO can bind to H+ first, then transfers hydrogen with oxygen-containing radicals in the coal. This process is prone to occur due to the presence of hydrogen bonds. In future applications, the pH value of TEMPO can be appropriately reduced to enhance the effect of capturing free radicals in coal.