Suppression of hydrocarbon flames by organophosphorus compounds and their based mixtures

The minimum extinguishing concentrations of mixtures consisting of organophosphorus and iodine-containing compounds and inert diluents were measured with the cup-burner and cylinder techniques. The results obtained were used to develop and test new effective fire-suppressing compositions whose components exhibit a synergetic effect. For these mixtures, the lower temperature limit of application was estimated. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 22–29, May–June, 2008.     

Production of nanoparticles of MgO, BAO, and A12O3 in a premixed flame and its relation to the flame structure

Formation of nanoparticles of magnesium, barium, and aluminum oxides in a fuel-lean oxy-acetylene flame is studied by means of flame sampling. The size distributions and concentrations of particles are measured in various areas of the flame. Possible reaction paths are considered. MgO and BaO nanoparticles are demonstrated to form in the reaction zone where there is a high concentration of radicals. Formation of Al₂O₃ particles is hindered by the reaction AlO + AlO₂ → Al₂O₃ being termolecular. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 25–32, November–December, 2006.     

Studies of fundamental physical–chemical mechanisms and processes of flame extinguishing by powder aerosols

Theoretical and experimental studies on mechanisms of interaction of the fire‐extinguishing aerosol with flame are carried out. The factors of heterogeneous inhibition of flame free radicals (O, OH, H, CH_x) on a crystal surface of inorganic salts being the basic components of fire‐extinguishing powders and aerosols are measured using laboratory equipment. The semi‐empirical calculations by methods of quantum chemistry for heterogeneous and homogeneous inhibition reactions of burning are executed. The thermal mechanism for fire extinguishing is evaluated. The universal mechanism of influence on flame of a crystal surface of a fire‐extinguishing powder particle is offered. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of the addition of triphenylphosphine oxide,hexabromocyclododecane, and ethyl bromide on a CH<Subscript>4</Subscript>/O<Subscript>2</Subscript>/N<Subscript>2</Subscript> flame at atmospheric pressure

The chemical and thermal structure of a Mache-Hebra burner stabilized premixed rich CH₄/O₂/N₂ flame with additives of vapors of triphenylphosphine oxide [(C₆H₅)₃PO], hexabromocyclododecane (C₁₂H₁₈Br₆), and ethyl bromide (C₂H₅Br) was studied experimentally using molecular beam mass spectrometry (MBMS) and a microthermocouple method. The concentration profiles of stable and active species, including atoms and free radicals, and flame temperature pro.les were determined at a pressure of 1 atm. A comparison of the experimental and modeling results on the flame structure shows that MBMS is a suitable method for studying the structure of flames stabilized on a Mache-Hebra burner under near-adiabatic conditions. The relative flame inhibition effectiveness of the added compounds is estimated from changes in the peak concentrations of H and OH radicals in the flame and from changes in the flame propagation velocity. The results of the investigation suggest that place of action of the examined flame retardants is the gas phase. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 12–20, September–October, 2007.     

Inhibition effectiveness of dry chemical in methane/air flames

Inhibition effectiveness of dry chemical powders has been examined by detecting the temperature changes in the quenched flat-flame burner. A special particle delivery system was constructed to supply reliable particle concentration to a quenched flat flame. Particle evaporation phenomena in the flat flame environment was investigated by utilizing laser attenuation method which could determine the fraction of particle disappearance in the flame. The result from the flat flame inhibition experiments have clearly demonstrated that the ranking of effectiveness among KHCO₃, NaHCO₃, and NaCl reverses over the 1200–2000 K temperature range as flame suppressants. The results also showed that dry chemicals are effective inhibitor in the high temperature condition such as in the gaseous flame but not effective one in the coal flame of low temperature. It is concluded that, of all the experiment-specific flame properties, the maximum flame temperature at which the inhibitor evaluation is conducted, was a major parameter to determine the flame inhibition effectiveness in this work.     

On the nature of the burning rate-controlling reaction of energetic materials for the gas-phase model

For model systems with known kinetics of elementary reactions (CH₃NO₂ and HN₃), temperature ranges are established in which the rate-controlling reactions are the initial endothermic decomposition of the starting material or the subsequent secondary reactions. Heat release in reactions of NO₂, NO, and N₂O with various fuels, such as CH₂O, CO, H₂, and HCN, is modeled to establish the kinetic parameters and nature of the rate-controlling reactions in gas flames of nitro compounds. It is shown that the activation energy of the heat-release reaction due to the interaction of NO₂ with a hydrocarbon fuel (which is characteristic of the first flame of nitro compounds) is in the range of 29–33 kcal/mole, depending on the type of fuel. According to the calculations performed, the activation energy of the rate-controlling heat-releasing process due to the deoxidation of NO and N₂O (which is typical of the second flame of nitro compounds) is 43–58 kcal/mole. In the range of high pressures, where the flames merge, the kinetic parameters of heat release are determined by the reactions of the most reactive nitrogen oxide NO₂. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 3, pp. 59–71, May–June, 2007.     

Synthesis of series of pure polyethylene glycol ethers based onn-tridecanol,7-tridecanol,and oxo-process tridecyl alcohol

Puren-tridecyl, 7-tridecyl andoxo-tridecyl polyethylene glycol monoethers, C₁₃H₂₇O (C₂H₄O)_nH, were made by the Williamson reaction with n=4,6,8,10 and 12. Related crystalline diethers derived fromn-tridecanol were made in the range of 4–16 oxyethylene units. The compounds were extensively purified by crystallization (where applicable) or by chromatography and distillation. The final products are new compounds important for comparative studies of surface properties. Characterizing constants and physical properties including those of a large number of pure intermediates are reported. All but the lowest member of then-tridecyl monoether series are crystalline, melting between 26 and 40C. The related diethers melting between 37 and 50C have a minimum melting point when they contain between 6 and 8 oxyethylene units. Theoxo-tridecyl and 7-tridecyl monoethers are liquids.     

Flame propagation in mixtures of monogermane and oxygen. I. Limits, flame propagation characteristics, and gas-phase products

The concentration limits for flame propagation in GeH₄−O₂ (air) mixtures are determined over a wide range of initial pressures (0.7–100 kPa) at room temperature. Flame propagation is found to be of a chain-thermal character and excited intermediate particles are involved in the reactions which limit the branching rate. The gas-phase reaction products (H₂O₂, H₂O, and H₂) are determined and its is shown that the relative yields of these components and the stoichiometry, as a whole, vary with the composition of the initial gas mixture. Chemically induced decomposition of GeH₄ by a branching-chain oxidation process for oxidation of the hydride by oxygen is observed. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 72–76, January–February 1999.     

Glass transition temperatures of copolymers from methyl methacrylate,styrene, and acrylonitrile: binary copolymers

By using a new theoretical glass transition temperature (T _g)–composition equation, T _g’s of statistic binary copolymers obtained from MMA, St and AN were investigated in this article. The copolymers were prepared by bulk copolymerization using azo-bis-isobutyronitrile (AIBN) as initiator. The compositions and T _g’s were determined by NMR and DSC, respectively. The monomer reactivity ratios were obtained by nonlinear fitting with Mayo–Lewis equation. Excellent fitting results were obtained when relations of T _g’s of MMA–St, MMA–AN, and St–AN copolymers with their compositions were investigated by using a new equation which assumed additivity of bond stiff energy (Liu et al. J Phys Chem B 112:93–99, 2008). This equation contains mole fractions of triads and T _g’s of corresponding periodic copolymers. Compared with the widely used Johnston equation and Barton equation, the new equation showed its superiority. Meanwhile, T _g’s of the assumed periodic copolymers that have not been acquired were tentatively predicted which may provide useful information.     

Flame-Retardancy Improvement of Novel Styrene–Maleic Anhydride Based Copolymers

Brominated flame-retardants are one of the common and efficient compounds in producing flame retardant plastics and antimony trioxide is often used as a synergistic agent for halogenated flame-retardants. In this research, a new reactive flame retardant, maleated tetrabromobiphenol-A (MTBBA) crystals, has been introduced for the first time and its structure was fully characterized by high-field ¹H NMR and ¹³C NMR spectroscopy. The improvement in flame-retardancy effect of styrene–maleic anhydride copolymer by MTBBA and also their compounded samples with Sb₂O₃ was investigated as the main purpose in this work. Limiting oxygen indexes (LOI) for the neat terpolymers and the compounded samples were measured by flammability tests. Also thermal gravimetry analysis (TGA) and differential scanning calorimetry (DSC) were applied in order to study thermal behavior of the samples. The results of thermal analysis were used to observe the effect of insertion of this novel monomer into the copolymer chain in comparison with styrene–maleic anhydride copolymer.     

Experimental study of the structure of a rich premixed 1,3-butadiene/CH4/O2/Ar flame

The structure of a laminar rich premixed 1,3-butadiene/CH₄/O₂/Ar flame has been investigated, 1,3-butadiene, methane, oxygen, and argon mole fractions being 0.033, 0.2073, 0.3315, and 0.4280, respectively, for an equivalence ratio of 1.80. The flame has been stabilized on a burner at a pressure of 6.7 kPa. The concentration profiles of stable species have been measured by gas chromatography after sampling with a quartz probe. The quantified species include carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, cyclopropane, 1,3-butadiene, butenes, 1-butyne, vinylacetylene, diacetylene, C₅ compounds, benzene, and toluene. The temperature distribution in the flame has also been measured. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 6, pp. 89–95, November–December, 2006.     

Thermal Decomposition and Combustion of Ammonium Dinitramide (Review)

A comprehensive review of thermal decomposition and combustion of ammonium dinitramide (ADN) has been conducted. The basic thermal properties, chemical pathways, and reaction products in both the condensed and gas phases are analyzed over a broad range of ambient conditions. Detailed combustion-wave structures and burning-rate characteristics are discussed. Prominent features of ADN combustion are identified and compared with other types of energetic materials. In particular, the influence of various condensed- and gas-phase processes in dictating the pressure and temperature sensitivities of the burning rate is examined. In the condensed phase, decomposition proceeds through the mechanisms ADN → NH₄NO₃ + N₂O and ADN → NH₃ + HNO₃ + N₂O, the former mechanism being the basic one. In the gas phase, the mechanisms ADN → NH₃ + HDN and ADN → NH₃ + HNO₃ + N₂O are prevalent. The gas-phase combustion-wave structure in the range of 5–20 atm consists of a near-surface primary flame followed by a dark-zone temperature plateau at 600–1000°C and a secondary flame followed by another dark-zone temperature plateau at 1000–1400°C. At higher pressures (60 atm and above), a final flame is observed at about 1800°C without the existence of any dark-zone temperature plateau. ADN combustion is stable in the range of 5–20 atm and the pressure sensitivity of the burning rate has the form r _b = 20.72p ^0.604 [mm/sec] (p = 0.5–2.0 MPa). The burning characteristics are controlled by exothermic decomposition in the condensed phase. Above 100 atm, the burning rate is well correlated with pressure as r _b = 8.50p ^0.608 [mm/sec] (p = 10–36 MPa). Combustion is stable, and intensive heat feedback from the gas phase dictates the burning rate. The pressure dependence of the burning rate, however, becomes irregular in the range of 20–100 atm. This phenomenon may be attributed to the competing influence of the condensed-phase and gas-phase exothermic reactions in determining the propellant surface conditions and the associated burning rate. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 6, pp. 54–79, November–December, 2005.     

Preparation of ferric phosphonate/phosphinate and their special action on flame retardancy of epoxy resin

Fe‐ and P‐based compounds have demonstrated promising performance in enhancing flame retardancy of epoxy resins. In this context, this work focuses on the preparation of new Fe/P hybridized nanomaterials and their effect on flame retardancy of epoxy resins. The Fe/P hybrids were facilely prepared via forming ferric phosphinates and phosphonates using hydrothermal reaction. Attractively, ferric phosphinates and phosphonates exhibit the morphology of 1D nanorod and 2D nanosheet, respectively. When incorporating these two fillers in epoxy resin, the limiting oxygen index values of composites were enhanced to above 28 and the composites exhibited self‐extinguishing behavior, thus indicating greatly improved fire resistance. Further investigation revealed that the flame retarding behavior, in particular for ferric phosphonate nanosheets, took place mainly in gas phases via delaying the release of flammable gas. Attractively, it was found that the Fe/P hybrids took part into the pyrolysis reaction of epoxy resins through forming Fe? O and P? O bonds. This finding may provide a new insight to design a series of high performance flame retardants for epoxy resins. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46206.     

Study on the relationship between the particle size distribution and the effectiveness of the K‐powder fire extinguishing agent

The relationship between the particle size distribution and the extinguishing effectiveness of the new K‐powder fire extinguishing agent has been studied experimentally, to explore the reason of the great extinguishing efficiency exhibited by the new K‐powder fire extinguishing agent on Class B fire (liquid fuel fire). The results of the experiment showed that the extinguishing effectiveness increased along with the decrease of the particle size distribution. In addition, a sharp discontinuity appeared around the limiting size, about 40 μm. The powder with the particle size below 40 μm exhibited highly effective extinguishing with the minimum effective extinguishing concentration C_xr = 23 g·m^?3, while the powder with the particle size above 40 μm exhibited little fire extinguishing efficiency. Compared with other fire extinguishing agents produced by different substances, the new K‐powder fire extinguishing has the bigger limiting size. That means, in the same particle size distribution, the new K‐powder fire extinguishing agent contains more highly effective powder than others contain, and is more effective.     

Reduced kinetic mechanism for combustion of synthesis gas at elevated temperatures and pressures

The key combustion reactions of synthesis gas at elevated initial temperatures (T ₀ = 500–700 K) and pressures (p = 10–30 atm) are identified by analyzing the kinetic mechanism. A reduced mechanism of the oxidation reactions of synthesis gas consisting of 14 elementary reactions involving 13 species is proposed which adequately describes the results of experimental data on the burning velocities of mixtures of synthesis gas with oxygen and inert diluents at T ₀ = 300–700 K, p = 10–30 atm, and ratios CO/H₂ = 0.05–0.95, and satisfactorily predicts the flame structure and the dependence of the flammability limits on the initial temperature at atmospheric pressure.     

Synthesis,Characterization and Optoelectronic Properties of Dimeric and Polymeric Metallaynes Derived from 3,6-Bis(buta-1,3-diynyl)-9-butylcarbazole

A thermally stable platinum(II) polyyne polymer incorporating carbazole-based linking units, trans-[–Pt(PBu₃)₂C≡CC≡CRC≡CC≡C–] _n (R = 9-butylcarbazole-3,6-diyl), was prepared by polycondensation polymerization of trans-[PtCl₂(PBu₃)₂] with H–C≡CC≡CRC≡CC≡C–H. We report the optical absorption and photoluminescence spectra of this carbon-rich metallopolymer and compare its photophysics with its molecular dinuclear model complex trans-[Pt(Ph)(PEt₃)₂C≡CC≡CRC≡CC≡CPt(Ph)(PEt₃)₂] as well as the group 11 gold(I) congener, [(PPh₃)AuC≡CC≡CRC≡CC≡CAu(PPh₃)]. Characterization of the polymer and metal complexes was accomplished by FT-IR and NMR spectroscopies and FAB mass spectrometry. Our investigations showed that harvesting of the organic triplet emissions can be achieved by the heavy-atom effect of Pt and Au centers, which enables a very high efficiency of intersystem crossing from the S₁ singlet excited state to the T₁ triplet excited state. The influence of the metal and the C≡C chain length on the intersystem crossing rate and the spatial extent of singlet and triplet excitons is characterized. The present work indicates that high-energy triplet states intrinsically give more efficient phosphorescence in metal-containing diethynylcarbazole systems than in the corresponding bis(butadiynyl) congeners and can thus enhance the radiative decay pathway.Dedicated to Professor Richard J. Puddephatt in recognition of his outstanding contribution to inorganic and organometallic chemistry.     

The Role of Ozone-reactive Compounds, Terpenes, and Green Leaf Volatiles (GLVs), in the Orientation of Cotesia plutellae

The emission of inducible volatile organic compounds (VOCs), i.e., inducible terpenes, and green leaf volatiles (GLVs), is a common response of plants to herbivore attack. These VOCs are involved in the orientation of natural enemies, i.e., predators and parasitoids, toward their herbivore prey or hosts (indirect defense of plants). Terpenes and some GLVs are readily oxidized by ozone (O₃), an important oxidant of the low atmosphere and predicted to increase as a result of anthropogenic activity. It has been recently reported that O₃ degradation of terpenes and GLVs does not affect signaling in two selected tritrophic systems. Natural enemies may have learned to use oxidation products that are more stable in nature to locate their prey. To understand the role of these compounds on the tritrophic system Brassica oleracea–Plutella xylostella–Cotesia plutellae, we assessed the preference of wasps to different combinations of cabbage VOCs (intact vs. herbivore-induced and herbivore-induced vs. herbivore-induced VOCs) in the presence or absence of O₃. We found that C. plutellae preferred P. xylostella-damaged plants at 0 and 120 nl l⁻¹ O₃ to intact plants at 0 nl l⁻¹ O₃. However, wasps preferred P. xylostella-damaged plants at 0 nl l⁻¹ to P. xylostella-damaged plants at 120 nl l⁻¹ O₃. The results suggest that compounds other than terpenes and GLVs are crucial for the orientation of the wasps, but terpenes and GLVs contribute to the behaviorally active VOC blend of herbivore-damaged cabbages by increasing their attraction to them. The products resulting from oxidation of terpenes and GLVs do not seem to play a role in the host location process as speculated previously.     

Laminar flame structure in a low-pressure premixed H2/O2/Ar mixture

The chemical structure of a stoichiometric hydrogen-oxygen flame stabilized on a flat burner at a pressure of 47 torr is studied by molecular-beam mass spectrometry and computer simulation. Concentration profiles are measured for the stable flame components H₂, O₂, and H₂O, as well as for the atoms and radicals H, O, and OH. The concentration profiles calculated using two different kinetic mechanisms are in acceptable agreement with experimental data. It is also shown that for sampling probes with thin walls (<-0.1 mm) at their tips, there is no need to perform the calculations using a specified temperature profile measured by thermocouples located near the aperture of the sampler, as recommended by a number of authors. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 29–34, May–June 1999.     

Platinum Cyclooctadiene Complexes with Activity against Gram-positive Bacteria

Antimicrobial resistance is a looming health crisis, and it is becoming increasingly clear that organic chemistry alone is not sufficient to continue to provide the world with novel and effective antibiotics. Recently there has been an increased number of reports describing promising antimicrobial properties of metal-containing compounds. Platinum complexes are well known in the field of inorganic medicinal chemistry for their tremendous success as anticancer agents. Here we report on the promising antibacterial properties of platinum cyclooctadiene (COD) complexes. Amongst the 15 compounds studied, the simplest compounds Pt(COD)X₂ (X=Cl, I, Pt1 and Pt2 ) showed excellent activity against a panel of Gram-positive bacteria including vancomycin and methicillin resistant Staphylococcus aureus. Additionally, the lead compounds show no toxicity against mammalian cells or haemolytic properties at the highest tested concentrations, indicating that the observed activity is specific against bacteria. Finally, these compounds showed no toxicity against Galleria mellonella at the highest measured concentrations. However, preliminary efficacy studies in the same animal model found no decrease in bacterial load upon treatment with Pt1 and Pt2 . Serum exchange studies suggest that these compounds exhibit high serum binding which reduces their bioavailability in vivo, mandating alternative administration routes such as e. g. topical application.     

Effect of trimethylphosphate additives on the flammability concentration limits of premixed methane-air mixtures

The effect of small additives of trimethylphosphate (TMP) on the lean and rich flammability concentration limits of CH₄/air gas mixtures were studied using an opposed-flow burner and numerical modeling based on detailed kinetic mechanisms. TMP was found to narrow the flammability concentration limits of premixed CH₄/air mixtures. Modeling using a previously developed model for flame inhibition by phosphorus compounds showed that the model provides a satisfactory fit to experimental results on the effect of TMP additives on the lean concentration limit. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 12–21, January–February, 2008.