Studies of conventional sulfur vulcanization of SBR rubber: Analysing the reaction products from thermal degradation of the accelerator by means of MCC-IMS technique

2020 ◽  
Vol 90 ◽  
pp. 106715 ◽  
Author(s):  
Dominik Pietrzak ◽  
Dariusz M. Bieliński ◽  
Daniela Henneicke
Keyword(s):  
Thermal Degradation ◽  
Reaction Products ◽  
Sulfur Vulcanization

Thermal degradation of EDTA chelates in aqueous solution

1982 ◽  
Vol 60 (10) ◽  
pp. 1207-1213 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
X. B. Cox III ◽  
Patrick Taylor ◽  
Arthur E. Martell ◽  
Brad Miles ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Thermal Degradation ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Iminodiacetic Acid ◽  
Reaction Products ◽  
Degradation Rates ◽  
Lower Temperature Range ◽  
Higher Temperature ◽  
Lower Temperature

The thermal degradation of Ca(II), Mg(II), Zn(II), Fe(II), and Ni(II) chelates of EDTA was investigated in alkaline aqueous solution at elevated temperatures (230–310 °C). The kinetics of decomposition were followed by nmr, titrimetry, and spectrophotometry. Reaction products were identified through nmr and by gas chromatography. The relative order of degradation rates, as measured by the loss of EDTA, was found to be Mg(II) > Ca(II) > Zn(II) > Fe(II) > Ni(II). The main degradation products formed in the lower temperature range (~250 °C) are iminodiacetic acid, hydroxyethyliminodiacetic acid, and ethylene glycol. Higher temperature products are primarily dimethylamine and carbon dioxide. The rates of degradation of Ca(II), Mg(II), and Zn(II) EDTA chelates are considerably enhanced when either phosphate is present or a glass-lined autoclave is employed.

scholarly journals “Thermal Peroxidation” of Dietary Pentapeptides Yields N-Terminal 1,2-Dicarbonyls

2021 ◽  
Vol 8 ◽  
Author(s):  
Maria Bikaki ◽  
Nikolai Kuhnert
Keyword(s):  
Lipid Peroxidation ◽  
Reaction Mechanism ◽  
Thermal Degradation ◽  
Primary Amine ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Degradation Mechanism ◽  
Reaction Products ◽  
Unsaturated Lipids

In this contribution we investigate the thermal degradation of dietary-relevant pentapeptides. Most unsaturated lipids degrade by the well-known peroxidation mechanism. Here we show a degradation mechanism of peptides analogous to lipid peroxidation, forming a series of novel degradation products with possible toxicological relevance. At elevated temperatures above 180°C, pentapeptides with an N-terminal phenylalanine moiety react via a debenzylation to form 1,2-dicabonyl compounds, replacing the N-terminal primary amine. We propose a radical-based reaction mechanism that leads via a common peroxoaminal intermediate to two distinct types of reaction products with a terminal α-1,2 diamide or an α-amide-aldehyde functionality.

Vulcanization. Part VII. Kinetics of Sulfur Vulcanization of Natural Rubber in Presence of Delayed-Action Accelerators

1965 ◽  
Vol 38 (1) ◽  
pp. 1-14 ◽  
Author(s):  
A. Y. Coran
Keyword(s):  
Positive Integer ◽  
Stearic Acid ◽  
Natural Rubber ◽  
Zinc Ion ◽  
Square Root ◽  
Reaction Products ◽  
Sulfur Concentration ◽  
Sulfur Vulcanization ◽  
Delayed Action ◽  
Kinetics Of

Abstract The scheme and treatment of the kinetics of scorch-delay vulcanization proposed in a previous paper were applied to natural rubber sulfur vulcanization accelerated by 2,2′-thiobisbenzothiazole (MBTS), 2-(N-cyclohexyl)benzothizaolesulfenamide (CBS), 2-(N-morpholinothio)benzothiazole (MOR), or 2-(N,N-diisopropyl)benzothiazolesulfenamide (DPBS). According to the scheme (see PDF for diagram) where the subscript x = a positive integer. The specific rates k1 and k2 and the ratiok4/k3′ were related to starting concentrations of accelerator, sulfur, and stearic acid. In general, an increase in stearic acid concentration or a decrease in accelerator concentration induces an increase in k1 or k4/k3′ but a decrease in k2. An exception to this is that, when the highly hindered sulfenamide DPBS is used as the accelerator, k1 does not change with changes in starting concentrations. It is interesting that k2 does not respond appreciably to changes in sulfur concentration when sulfenamides are used, unless the sulfur concentrations are extremely low. In contrast to this, k2 increases linearly with the square root of the sulfur concentration when MBTS is used. The changes in rates which occur with changes in the starting concentrations were attributed to the formation of chelates between zinc ion (brought into solution by stearic acid) and accelerator, intermediate reaction products, or crosslink precursors. The differences noted between the rates obtained with the three sulfenamides were attributed to differences in steric hindrance and stability.

3-(4-Pyridyl)-acetylacetone – a fully featured substituted pyridine and a flexible linker for complex materials

2014 ◽  
Vol 70 (4) ◽  
pp. 705-713 ◽  
Author(s):  
Carina Merkens ◽  
Khai-Nghi Truong ◽  
Ulli Englert
Keyword(s):  
Thermal Degradation ◽  
Molecular Complex ◽  
Mechanochemical Synthesis ◽  
Iron Complex ◽  
Reaction Products ◽  
Complex Materials ◽  
Ladder Structure ◽  
One Dimensional ◽  
Distorted Octahedral Coordination ◽  
Distorted Octahedral

3-(4-Pyridyl)-acetylacetone (HacacPy) acts as a pyridine-type ligand towards CdX2(X= Cl, Br, I). Chain polymers with six-coordinated metal cations are obtained from CdCl2and with alternating five- and six-coordinated Cd centers from CdBr2. In either case, the formation of these compounds does not depend on the precise stoichiometry. In contrast, two different reaction products form with the heavier congener CdI2, namely a ligand-rich molecular complex CdI2(HacacPy)2and a ligand-deficient one-dimensional polymer [CdI2(HacacPy)]1∞. Interconversion between these two iodo derivatives is possibleviathermal degradation and mechanochemical synthesis. The acetylacetone moiety in HacacPy may be deprotonated and chelated to FeIII, and the resulting complex Fe(acacPy)3reacts analogously to a bridging polypyridine ligand towards the same Cd halides as the molecule HacacPy itself. With CdCl2and CdBr2, isomorphous chain polymers are obtained in which the Cd cations adopt distorted octahedral coordination and one of the peripheric pyridyl groups remains uncoordinated. With CdI2, the iron complex acts as a \mu _{{3}}-Fe(acacPy)3bridge between tetrahedral Cd centers and gives rise to a ladder structure.

Chemistry of Various Accelerators in an E-SBR Model Compound

2006 ◽  
Vol 79 (1) ◽  
pp. 1-25 ◽  
Author(s):  
C. C. Pierre ◽  
S. Datta ◽  
R. N. Datta ◽  
A. G. Talma
Keyword(s):  
Reaction Kinetics ◽  
Model Compound ◽  
Reaction Products ◽  
Sulfur Vulcanization ◽  
Analytical Tools

Abstract Sulfur vulcanization was carried out with 5-phenyl hex-2-ene serving as a model of e-SBR. Various accelerators have been used to study and compare the reactivity in a system containing sulfur and activators. Both HPLC and GC-MS analytical tools were used to identify the reaction products. It has been observed that the vulcanization in the presence of N-cyclohexyl-2-benzothiazole sulfenamide (CBS) generates a large amount of 2-marcaptobenzothiazole (MBT), which continuously increases and finally decreases suggesting further participation in vulcanization generating new crosslinks. The sulfenamide, N-cyclohexyl-4,6 dimethyl-2-pyrimidine sulfenamide (CDMPS) behaves different. Although it generates considerable amount of corresponding thiol, (4,6-dimethyl pyrimidine-2-thiol, DMMP) at the beginning of the reaction, no decrease has been observed during the course of further reaction suggesting that the accelerator, DMMP, somehow remains deactivated and therefore no changes in network is feasible. Identical differences exist between bis(2,2′benzothiazyl) disulfide (MBTS) and corresponding bis (4-methyl-2,2′benzothiazyl)disulfide (M-MBTS) in the reaction kinetics.

Raman and ESR Spectroscopic Studies of Accelerator Systems. II. Thermal Degradation Vulcanizing Systems and Its Significance to Vulcanization Mechanisms

1973 ◽  
Vol 46 (4) ◽  
pp. 957-980 ◽  
Author(s):  
M. M. Coleman ◽  
J. R. Shelton ◽  
J. L. Koenig
Keyword(s):  
Thermal Decomposition ◽  
Thermal Degradation ◽  
Esr Spectroscopy ◽  
Spectroscopic Studies ◽  
Spectroscopic Techniques ◽  
Powerful Method ◽  
Sulfur Vulcanization ◽  
Derivatives Of

Abstract Raman and ESR spectroscopy has been used to study the thermal decomposition of accelerator systems based on derivatives of dimethyldithiocarbamic acid. The combination of these two spectroscopic techniques has proved to be a very powerful method for detecting intermediate compounds that are important for the elucidation of the mechanism of accelerated sulfur vulcanization.

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