High temperature stability of larger aromatic compounds

Lefort, Benoîte; Tsang, Wing

doi:10.1016/j.combustflame.2010.12.020

Cited by 10 publications

(4 citation statements)

References 17 publications

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“…107 In terms of which hydroxyl groups are lost, we infer from bond energies that aliphatic alcohols are the most thermally labile as the phenolic OH bond energy is 430 kJ mol À1 . 104 On the other hand, ATR-IR shows that the HTC carbonyl peak increases with milling, which we interpret as reaction of carbon species (presumably aliphatic side chains since aromatic carbons themselves should be more thermodynamically stable to oxidation [108][109][110][111] ) with oxygen contained in the milling vessel.…”

Section: Carbon Disorder (Raman Microspectroscopy)mentioning

confidence: 89%

Spectroscopic tracking of mechanochemical reactivity and modification of a hydrothermal char

et al. 2016

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Section: Carbon Disorder (Raman Microspectroscopy)mentioning

confidence: 89%

Spectroscopic tracking of mechanochemical reactivity and modification of a hydrothermal char

et al. 2016

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“…As examples of chemical activation effects in combustion systems, Lefort and Tsang presented an empirically based approach to deriving the pressure-dependent rate constants of chemically activated reactions of adducts formed by association of methyl radicals with aromatic radicals. They used a hindered rotor model but noted that they “...do not attach any particular physical significance to the hindrance...”, rather it is used to “...calibrate an empirical methodology...” with a special emphasis on applicability of their approach to large molecules.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Hydrogen Radical Reactions with Toluene Including Chemical Activation Theory Employing System-Specific Quantum RRK Theory Calibrated by Variational Transition State Theory

2016

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Pressure-dependent reactions are ubiquitous in combustion and atmospheric chemistry. We employ a new calibration procedure for quantum Rice-Ramsperger-Kassel (QRRK) unimolecular rate theory within a chemical activation mechanism to calculate the pressure-falloff effect of a radical association with an aromatic ring. The new theoretical framework is applied to the reaction of H with toluene, which is a prototypical reaction in the combustion chemistry of aromatic hydrocarbons present in most fuels. Both the hydrogen abstraction reactions and the hydrogen addition reactions are calculated. Our system-specific (SS) QRRK approach is adjusted with SS parameters to agree with multistructural canonical variational transition state theory with multidimensional tunneling (MS-CVT/SCT) at the high-pressure limit. The new method avoids the need for the usual empirical estimations of the QRRK parameters, and it eliminates the need for variational transition state theory calculations as a function of energy, although in this first application we do validate the falloff curves by comparing SS-QRRK results without tunneling to multistructural microcanonical variational transition state theory (MS-μVT) rate constants without tunneling. At low temperatures, the two approaches agree well with each other, but at high temperatures, SS-QRRK tends to overestimate falloff slightly. We also show that the variational effect is important in computing the energy-resolved rate constants. Multiple-structure anharmonicity, torsional-potential anharmonicity, and high-frequency-mode vibrational anharmonicity are all included in the rate computations, and torsional anharmonicity effects on the density of states are investigated. Branching fractions, which are both temperature- and pressure-dependent (and for which only limited data is available from experiment), are predicted as a function of pressure.

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“…Furthermore, the rigidity of the benzene ring enables the HB‐Ts to effectively resist stress and deformation in the resin, resulting in higher rigidity and improved energy storage modulus. However, HB‐TBdfda is inferior to HB‐TPPA and HB‐TDDM in the magnitude of enhancement of T g and cross‐linking density of BA‐a since it contains a higher number of furanic rings that are less stable than benzene rings 60 …”

Section: Resultsmentioning

confidence: 97%

“…However, HB-TBdfda is inferior to HB-TPPA and HB-TDDM in the magnitude of enhancement of T g and crosslinking density of BA-a since it contains a higher number of furanic rings that are less stable than benzene rings. 60 Poly(BA-a/HB-TD230) decreased the cross-linking density by 37.8% when compared with poly(BA-a) due to the introduction of numerous flexible chains, which increased the spatial separation between resin molecules, made it difficult for the active centers of the cross-linking reaction to be in close proximity, which finally reduces the crosslink density. 61,62 In addition, the decomposition of flexible chain segments at high temperatures resulted in a mere 21.4 C increase in T g for HB-TD230 in comparison with BA-a.…”

Section: Dma Analysis Of Copolymersmentioning

confidence: 99%

Synthesis of triphenol‐diamine‐type hyperbranched benzoxazine and improvement of thermal properties and toughness of typical benzoxazines

Hu,

Wang,

Guo

et al. 2024

J of Applied Polymer Sci

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A series of triphenol‐diamine‐type hyperbranched benzoxazines are synthesized by using polyformaldehyde, 1,1,1‐tri(4‐hydroxyphenyl) ethane, and primary amines such as p‐phenylenediamine, 4,4′‐diaminodiphenylmethane, polyetheramine, and bifuranocyclic diamine via Mannich condensation. Then, copolymers with bifunctional benzoxazine (BA‐a) are prepared to obtain superior properties. The polymerization behavior of the copolymers examined using a differential scanning calorimeter and a Fourier transform infrared indicates that the introduction of hyperbranched benzoxazines facilitates the benzoxazine curing reaction, decreasing the onset and peak temperatures of the curing process. Thermogravimetric analysis results suggest the cured hyperbranched benzoxazine demonstrates good thermal stability and can improve the heat resistance of benzoxazine. In addition, dynamic mechanical analysis suggests the glass transition temperature of the copolymers with BA‐a was increased after copolymerization, thus making all the copolymers obtain higher service temperatures. The test results from the universal testing machine and the fracture morphologies of copolymers indicate the hyperbranched benzoxazines with branched structures cause dendritic folds to appear on the surface of copolymers upon polymerization, preventing rapid cracking and spreading of the thermoset resin by dissipating more impact energy through this irregular dendritic appearance, thus obtaining strength and toughness superior to that of BA‐a resins.

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High temperature stability of larger aromatic compounds

Cited by 10 publications

References 17 publications

Spectroscopic tracking of mechanochemical reactivity and modification of a hydrothermal char

Spectroscopic tracking of mechanochemical reactivity and modification of a hydrothermal char

Kinetics of Hydrogen Radical Reactions with Toluene Including Chemical Activation Theory Employing System-Specific Quantum RRK Theory Calibrated by Variational Transition State Theory

Synthesis of triphenol‐diamine‐type hyperbranched benzoxazine and improvement of thermal properties and toughness of typical benzoxazines

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