Calculation of the entropy of formation of free radicals and the dissociation energy of chemical bonds by the method of group contributions

1984 ◽  
Vol 33 (6) ◽  
pp. 1227-1230 ◽  
Author(s):  
Yu. D. Orlov ◽  
Yu. A. Lebedev
Keyword(s):  
Free Radicals ◽  
Dissociation Energy ◽  
Chemical Bonds ◽  
Group Contributions ◽  
Entropy Of Formation ◽  
Energy Of Chemical Bonds

Mechanochemical Phenomena in Polymers. II. The Effects of Initiators and Inhibitors of Chain Processes

1963 ◽  
Vol 36 (2) ◽  
pp. 480-487
Author(s):  
E. V. Reztsova ◽  
B. T. Kipkina ◽  
G. L. Slonimskii
Keyword(s):  
Free Radicals ◽  
Fatigue Resistance ◽  
Substantial Effect ◽  
Chemical Bonds ◽  
Chain Processes ◽  
Radical Processes ◽  
Effect Of Inhibitors ◽  
Dynamic Fatigue

Abstract 1. The substantial effect of inhibitors and initiators of chain radical processes on the change in the properties of rubbers in milling, as well as on the resistance of vulcanizates to fatigue, has been shown. This indicates a mechanochemical mechanism for processing of polymers and in the fatigue of elastomers. The act of mechanical scission of chemical bonds, with the formation of free radicals which initiate the secondary chain processes, rests on these processes. 2. The possibility has been shown of regulating the properties of polymers during processing, and also of increasing the dynamic fatigue resistance of vulcanizates by incorporating small quantities of additives active in regard to free radicals.

Oxygen free radicals and disorders of pregnancy

2001 ◽  
Vol 12 (4) ◽  
pp. 273-298 ◽  
Author(s):  
Irina A Buhimschi ◽  
Carl P Weiner
Keyword(s):  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Free Radical ◽  
Oxygen Radicals ◽  
Oxygen Free Radicals ◽  
Energy State ◽  
Oxygen Species ◽  
Chemical Bonds ◽  
Physiological Processes ◽  
Living Organisms

Oxygen radicals and reactive oxygen species are normal attributes of aerobic life. In most molecules, the electrons are paired and, with the exception of hydrogen, the four outer most pairs of each atom form chemical bonds. Electrons are in a relatively stable energy state when paired. A free radical is a molecule with an unpaired electron. Free radicals of oxygen are of particular importance to living organisms in which they are involved in the genesis of a wide array of diseases and physiological processes (e.g. life span and ageing).

Mechanochemical Phenomena in Polymers. III. Strength of the Bond between Elements of Multiply Polymer Articles

1960 ◽  
Vol 33 (4) ◽  
pp. 953-958
Author(s):  
G. L. Slonimskiĭ ◽  
G. P. Drugova
Keyword(s):  
Free Radicals ◽  
Chemical Processes ◽  
Chemical Bonds ◽  
Mechanochemical Process ◽  
Vulcanized Rubber ◽  
Radical Processes

Abstract 1. The basis of the process of ply separation of multiply rubber articles under repeated deformations is fatigue of the material in the region of the joint of the plies, which is a mechanochemical process, as previously studied, consisting of the development of chain chemical processes initiated by free radicals which are formed in the mechanical scission of chemical bonds in the molecules. 2. By the addition of substances inhibiting chain radical processes to the polymer it is possible to raise considerably the strength of the bond between elements of multiply vulcanized rubber articles.

Combination of Rubber and Carbon Black on Cold Milling

1955 ◽  
Vol 28 (4) ◽  
pp. 1032-1043 ◽  
Author(s):  
W. F. Watson
Keyword(s):  
Free Radicals ◽  
Carbon Black ◽  
Chemical Bond ◽  
Strong Evidence ◽  
Carbon Black Particle ◽  
Systematic Investigation ◽  
Chemical Bonds ◽  
X Ray ◽  
Radical Acceptor ◽  
Black Particle

Abstract Although the structure of carbon black is imperfectly known, x-ray analysis has shown it to consist of layers of condensed rings of carbon atoms. Unsaturation and discontinuities in the layers are likely to provide sites for attack of free radicals, and thus make carbon black a radical acceptor of a special polyfunctional type. Assuming combination of rubber radicals and carbon black, a particle could terminate more than one sheared rubber chain. Furthermore, rubber chains attached to a carbon black particle could also undergo scission by shear and be terminated by combination with other particles. The result anticipated from this picture is a network of rubber and carbon black held together by chemical bonds. In rubber solvents, such a network would be insoluble and merely become swollen gel. Insolubilization of rubber on milling with carbon black has been reported on occasion, but the evidence is not sufficiently extensive to draw reliable conclusions as to its cause. This paper reports a systematic investigation of the occurrence of rubber-carbon black gel on cold milling. This gel has been shown to form, and the conditions for its formation and its properties have been interpreted as strong evidence for the above hypothesis of chemical-bond attachment of rubber and carbon black.

Polymerization Phenomena in the Vulcanization Process

1954 ◽  
Vol 27 (4) ◽  
pp. 920-924 ◽  
Author(s):  
B. Dogadkin ◽  
M. Feldstein ◽  
A. Dobromyslova ◽  
V. Shkurina ◽  
M. Kalpunov
Keyword(s):  
Spectral Analysis ◽  
Free Radicals ◽  
Hydrogen Bonds ◽  
Functional Groups ◽  
Chemical Reaction ◽  
Van Der Waals ◽  
Chemical Bonds ◽  
Polarization Orientation ◽  
Vulcanization Process

Abstract According to theories developed by the authors, vulcanization consists essentially in the formation of local chemical van der Waals bonds (polarization, orientation bonds) and hydrogen bonds between the molecular chains of rubber. These bonds are formed as a result of the chemical reaction of the rubber with the vulcanizing agent, oxygen, and accelerators, and with other components of the vulcanizing system which contain functional groups. The essential type of chemical bonds consists of atomic groups of the vulcanizing agent (in the case of sulfur vulcanizates, “bridge” sulfur). Hypotheses were advanced concerning the course during vulcanization of the polymerization processes, initiated by the free radicals which are formed by the vulcanizing agent, and leading to the formation of —C — C—bonds between the molecular chains of the rubber. However, no proof of the existence of such processes has been obtained ; furthermore, certain data, for example, data obtained by spectral analysis, contradict such an assumption. The present paper is devoted to a description of experiments which show the existence of polymerization processes involving free radicals in vulcanized systems which contain accelerators of the disulfide and sulfenamide type.

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