scholarly journals On the Origin of Alkali-Catalyzed Aromatization of Phenols

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1119 ◽  
Author(s):  
Yu Ji ◽  
Qiang Yao ◽  
Yueying Zhao ◽  
Weihong Cao
Keyword(s):  
Radical Anion ◽  
Homolytic Cleavage ◽  
Oxygen Anion ◽  
Strong Electron ◽  
Free Radical Reactions ◽  
Aromatic Carbon ◽  
Degradation Pattern ◽  
Degradation Step ◽  
Bond Strengths ◽  
Thermal Stability Of

To gain an insight of the chemistry in the alkali-promoted aromatization of oxygen-containing heavily aromatic polymers or biomass; thermal degradations of sodium phenolates with different substituents have been investigated. The -ONa group strongly destabilizes the phenolates. The thermal stability of phenolates is largely in parallel with bond strengths of Ar substituents. De-substituents and the removal of aromatic hydrogens are dominant reactions in the main degradation step. CO is formed only at a very late stage. This degradation pattern is completely different from that of phenol. To account for this distinctive decomposition; a mechanism involving an unprecedented formation of an aromatic carbon radical anion generated from the homolytic cleavage of Ar substituent (or Ar–H) in keto forms has been proposed. The homolytic cleavage of Ar substituent (or Ar–H) is facilitated by the strong electron-donating ability of the oxygen anion. A set of free-radical reactions involved in the alkali-catalyzed aromatization have been established.

scholarly journals Preparation, Characterization, and Thermal Degradation Studies ofp-Nitrophenol-Based Copolymer

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Pawan P. Kalbende ◽  
Mangesh V. Tarase ◽  
Anil B. Zade
Keyword(s):  
Thermal Degradation ◽  
Thermal Activation ◽  
Frequency Factor ◽  
Spectral Studies ◽  
H Nmr ◽  
Degradation Pattern ◽  
Degradation Step ◽  
Ft Ir ◽  
Uv Visible ◽  
Most Probable Structure

Polycondensation reaction was employed to synthesize a new copolymer resin (p-NP-4,4′-MDA-F) from p-nitrophenol (p-NP) and 4,4′-methylene dianiline (4,4′-MDA) with formaldehyde (F) in presence of 2 M hydrochloric acid as a catalyst at130±1°C. The resin was characterized by elemental analysis and spectral studies such as UV-visible, FT-IR, and1H-NMR spectra which were used to confine the most probable structure of synthesized copolymer. Thermal degradation pattern and kinetics have been investigated by thermogravimetric analysis. Thermal degradation curve have been studied with minute detail for each degradation step. Friedman, Chang, Sharp-Wentworth, Freeman-Carroll, and Coat-Redfern methods have been implemented in order to compute the kinetic parameters, that is, thermal activation energy (Ea), order of reaction (n), and frequency factor (z).

Thermal Stability of Nacre Proteins of the Polynesian Pearl Oyster: A Proteomic Study

2016 ◽  
Vol 672 ◽  
pp. 222-231 ◽  
Author(s):  
Alexandre Parker ◽  
Françoise Immel ◽  
Nathalie Guichard ◽  
Cédric Broussard ◽  
Frédéric Marin
Keyword(s):  
Pearl Oyster ◽  
Insoluble Fraction ◽  
Inorganic Composites ◽  
Shell Matrix ◽  
Degradation Pattern ◽  
The Matrix ◽  
Shell Proteins ◽  
Proteomic Study ◽  
Powder Samples ◽  
Thermal Stability Of

Mollusc shells are organic-inorganic composites that are often preserved in the fossil record. However, the way the organic fraction, also called shell matrix, gets fossilized remains an unsolved question, in spite of several old and more recent studies. In the present paper, we have tried to mimic a diagenetic process by constantly heating for ten days at 100°C fresh nacre powder samples of the Polynesian pearl oyster Pinctadamargaritifera. Each day, aliquots of nacre powder were sampled and the matrix was subsequently extracted. It was further analysed by direct weigh quantification, by immunological techniques and by proteomics. Our preliminary data suggest that nacre proteins, when heated at 100°C in dry condition, degrade rather slowly. We evidenced a differential degradation pattern of the soluble and insoluble fractions, and showed that some nacre proteins of the insoluble fraction are stable after ten days of heating. Factors that influence the diagenetic stability of some shell proteins are discussed.

scholarly journals Base Promoted Intumescence of Phenols

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 261 ◽  
Author(s):  
Yu Ji ◽  
Qiang Yao ◽  
Weihong Cao ◽  
Yueying Zhao
Keyword(s):  
Great Influence ◽  
Steric Effects ◽  
Homolytic Cleavage ◽  
Strong Electron ◽  
Elimination Reactions ◽  
Electron Withdrawing Group ◽  
Hydrogen Radical ◽  
Weak Electron ◽  
Electronic And Steric Effects

The intumescent process of sodium (substituted) phenolates has been studied. The generation of hydrogen radical via a homolytic cleavage of the Ar–H bond and the subsequent hydroarylation of phenolates to cyclohexadienes along with cyclization and elimination reactions of cyclohexadienes are critical steps in the base promoted intumescence of phenols. The substituents show great influence on the intumescence of phenolates. Phenolates substituted with a weak electron donating group enable intumescence while those with an electron withdrawing group or strong electron donating group suppresses intumescence. This distinction can be justified by both electronic and steric effects of substituents on the generation of hydrogen radical and the degree of hydroarylation.

scholarly journals Poultry Feather Waste as Bio-Based Cross-Linking Additive for Ethylene Propylene Diene Rubber

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3908
Author(s):  
Markus Brenner ◽  
Oliver Weichold
Keyword(s):  
Carbon Black ◽  
High Volume ◽  
Cross Linking ◽  
Epdm Rubber ◽  
Feather Waste ◽  
Degradation Step ◽  
Ethylene Propylene Diene Rubber ◽  
Poultry Feather ◽  
Diene Rubber ◽  
Thermal Stability Of

Most rubbers used today rely on sulphur as a cross-linking agent and carbon black from fossil resources to modify the mechanical properties. A very promising substitute can be found in natural keratins such as feathers. These are not only tough, but also contain a relevant amount of sulphur in the form of disulphide bridges. The present study shows that these can be activated under vulcanisation conditions and then bind covalently to EPDM rubber to form a cross-linked network. Feathers were cut into lengths of 0.08, 0.2, and 1 mm and incorporated at 38, 69, or 100 phr into EPDM mixtures containing either no carbon black or no carbon black nor sulphur. The presence of feather cuttings increases the tensile and compressive strength as well as the hardness, and reduces the rebound resilience. Due to their high (approximately 17%) nitrogen content, the feathers also improve the thermal stability of the composite, as the main degradation step is shifted from 400 °C to 470 °C and the decomposition is significantly slowed down. Since elastomers are a large market and feathers in particular are a high-volume waste, the combination of these two offers enormous ecological and economic prospects.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

Physical, Chemical, and Crystallographic Characterization of Anodic Coatings on High Strength Aluminum Base Alloys

1976 ◽  
Vol 34 ◽  
pp. 636-637
Author(s):  
R. E. Herfert ◽  
N. T. McDevitt
Keyword(s):  
Sulfuric Acid ◽  
Salt Spray ◽  
High Strength ◽  
Environmental Stability ◽  
Anodic Films ◽  
Sodium Dichromate ◽  
Corrosion Resistant ◽  
Aerospace Applications ◽  
Bond Strengths ◽  
Adhesive Bonded Joints

Durability of adhesive bonded joints in moisture and salt spray environments is essential to USAF aircraft. Structural bonding technology for aerospace applications has depended for many years on the preparation of aluminum surfaces by a sulfuric acid/sodium dichromate (FPL etch) treatment. Recently, specific thin film anodizing techniques, phosphoric acid, and chromic acid anodizing have been developed which not only provide good initial bond strengths but vastly improved environmental durability. These thin anodic films are in contrast to the commonly used thick anodic films such as the sulfuric acid or "hard" sulfuric acid anodic films which are highly corrosion resistant in themselves, but which do not provide good initial bond strengths, particularly in low temperature peel.The objective of this study was to determine the characteristics of anodic films on aluminum alloys that make them corrosion resistant. The chemical composition, physical morphology and structure, and mechanical properties of the thin oxide films were to be defined and correlated with the environmental stability of these surfaces in humidity and salt spray. It is anticipated that anodic film characteristics and corrosion resistance will vary with the anodizing processing conditions.

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