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.

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

1960 ◽  
Vol 33 (4) ◽  
pp. 946-952
Author(s):  
E. V. Reztsova ◽  
B. G. Lipkina ◽  
G. L. Slonimskiĭ
Keyword(s):  
Free Radicals ◽  
Fatigue Resistance ◽  
Substantial Effect ◽  
Chemical Bonds ◽  
Elastic Materials ◽  
Industrial Processing ◽  
Chain Processes ◽  
Radical Processes ◽  
Effect Of Inhibitors ◽  
Highly Elastic Materials

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 of the processes occurring in processing polymers and of the fatigue of highly elastic materials (e.g., rubber vulcanizates). 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 in the course of their industrial processing, and also of increasing the dynamic fatigue resistance of vulcanizates by incorporating small quantities of additives active in regard to free radicals.

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.

Oxidation-Reduction Systems for Initiation of Radical Processes. VI. Systems Involving Oxygen for Initiation of Oxidative Degradation of Polymers

1959 ◽  
Vol 32 (1) ◽  
pp. 231-243 ◽  
Author(s):  
E. I. Tinyakova ◽  
B. A. Dolgoplosk ◽  
V. N. Reĭkh
Keyword(s):  
Free Radicals ◽  
Low Temperatures ◽  
Oxidative Degradation ◽  
Chain Process ◽  
Iron Salts ◽  
Oxidation Reduction ◽  
A Chain ◽  
Radical Processes ◽  
Effective Source ◽  
Hydrocarbon Media

Abstract 1. The mechanism of action of various oxidation-reduction systems containing organic reducing agents, iron salts, and oxygen, is investigated, and it is shown that in hydrocarbon media these systems are an effective source of free radicals at low temperatures. 2. The possibility of utilization of these systems for initiation of a chain process of oxidative degradation of unsaturated and some saturated polymers, at low temperatures, is shown.

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).

The influence of Intermolecular Action on the Dynamic Fatigue of Rubbers

1959 ◽  
Vol 32 (2) ◽  
pp. 454-462
Author(s):  
V. E. Gul ◽  
D. L. Fedyukin ◽  
B. A. Dogadkin
Keyword(s):  
Functional Groups ◽  
Fatigue Resistance ◽  
Convenient Method ◽  
Physical Effect ◽  
Optimum Composition ◽  
Mechanical Loss ◽  
Freeze Resistance ◽  
Dynamic Fatigue

Abstract The determination of the physical effect of softeners by an investigation of their influence on the swelling of vulcanizates is a convenient method for investigating the optimum composition of a compound which will produce given properties in the cured stock. This makes possible the improvement of such important properties of vulcanizates as fatigue resistance, mechanical loss, freeze resistance and others by using softeners with the appropriate functional groups.

Advances in C(sp3)–H Bond Functionalization via Radical Processes

Synthesis ◽  
2019 ◽  
Vol 51 (24) ◽  
pp. 4531-4548 ◽  
Author(s):  
Tong Zhang ◽  
Yue-Hua Wu ◽  
Nai-Xing Wang ◽  
Yalan Xing
Keyword(s):  
Free Radicals ◽  
Hydrogen Atom ◽  
Functional Groups ◽  
Organic Molecules ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Significant Progress ◽  
Bond Functionalization ◽  
Direct Functionalization ◽  
Radical Processes

C(sp3)–H Bonds are the most common structures in organic molecules. In recent years, the direct functionalization of C(sp3)–H bonds has attracted wide attention and made significant progress. This review mainly focuses on C(sp3)–H bond functionalization of alkanes with or without functional groups via radical processes reported since 2017. In particular, three methods of generating free radicals are discussed: the use of a radical initiator such as TBHP or DTBP; photocatalysis, and via 1,5-hydrogen atom transfer (1,5-HAT).1 Introduction2 C(sp3)–H Bond Functionalization of Alkanes3 C(sp3)–H Bond Functionalization of Alkanes with a Functional Group4 Conclusions

Redox Systems in the Initiation of Radical Processes. Mechanism of Action

1959 ◽  
Vol 32 (1) ◽  
pp. 244-256
Author(s):  
B. A. Dolgoplosk ◽  
E. I. Tinyakova
Keyword(s):  
Free Radicals ◽  
Mechanism Of Action ◽  
Low Temperatures ◽  
Oxidation States ◽  
Reversible Systems ◽  
Redox Systems ◽  
The Third ◽  
Destructive Processes ◽  
Radical Processes ◽  
Variable Valency

Abstract The following redox systems capable of initiating radical polymerizations are discussed: (1) Systems of the first type, where the reaction leads to the formation of a single radical: (a) Mechanism of action of reversible systems involving dienols and salts of metals of variable valency. (b) Mechanism of the decomposition of hydroperoxides by the action of salts of metals of variable valency in their higher oxidation states. (2) Systems of the second type, where the reaction leads to the formation of two radicals. Mechanism of action and effectiveness of systems involving hydroperoxides, quinol, and sulfite. (3) Systems of the third type, in which the formation of free radicals is not directly linked to the redox process. Mechanism of action of systems involving diazoamino compounds and “polyamine” systems. (4) Crosslinking of unsaturated polymers at low temperatures by the action of redox systems. Transition from crosslinking to destructive processes in presence of oxygen.

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.

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