STUDIES OF THE MICROHETEROGENEITY OF POLYBUTADIENE AND GR-S: I. THE PROPAGATION MECHANISM IN THE POLYMERIZATION OF BUTADIENE

1950 ◽  
Vol 28b (7) ◽  
pp. 373-382 ◽  
Author(s):  
J. Longfield ◽  
R. Jones ◽  
C. Sivertz
Keyword(s):  
Free Radical ◽  
Physical Properties ◽  
Propagation Mechanism ◽  
Emulsion System ◽  
Initiation Step ◽  
One To One

When n-butyl mercaptan is reacted in a one to one ratio with butadiene in an emulsion system containing persulphate, crotyl n-butyl thioether is exclusively formed as the product of the initiation step. That is, no 1, 2 or 3, 4 addition was found for this step but only the 1, 4. Crotyl n-butyl thioether and methylvinylcarbinyl n-butyl thioether have both been synthesized and certain physical properties determined. It is concluded that in all free radical attacks upon butadiene, the terminal carbon is attacked. The resulting radical may or may not resonate between structures which yield 1, 4 addition and 1, 2 addition; for example, when a mercaptan radical attacks, the resonance is suppressed, but, when styryl or butadienyl radical attacks, the resonance results in the observed ratios of 1, 2, 1, 4 addition in polybutadiene and copolymers of butadiene and styrene. The nature of the products and the yield indicates that the overwhelming number of initiations are made by butyl mercaptan radicals and termination is almost exclusively made by mercaptan.

scholarly journals Preparation and Thermal and Anti-UV Properties of Chitosan/Mica Copolymer

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Yih-Sheng Huang ◽  
Sheng-Haur Yu ◽  
Yea-Ru Sheu ◽  
Kuo-Shien Huang
Keyword(s):  
Experimental Data ◽  
Thermal Stability ◽  
Free Radical ◽  
Physical Properties ◽  
Ammonium Persulfate ◽  
Sodium Bisulfite ◽  
The Other ◽  
Other Hand

This experiment aims to produce a free radical while annoying the oxidizing-reducing reagent of the ammonium persulfate and the sodium bisulfite under nitrogen, then trigger copolymerization between modified-mica and chitosan to prepare a variety of copolymers. This experiment also aims to study the related properties of these copolymer materials. The experimental data shows that the copolymer has more thermal stability and better absorption of UV than chitosan. But the above physical properties will be less if the mica ratio in copolymer is more than 8%. On the other hand, the SEM photo of the microstructure also shows that the modified mica distributes homogeneously on the surface of the film of the copolymer.

Chemical and Physical Properties and Potential Mechanisms: Melatonin as a Broad Spectrum Antioxidant and Free Radical Scavenger

2002 ◽  
Vol 2 (2) ◽  
pp. 181-197 ◽  
Author(s):  
Dun-xian Tan ◽  
Russel Reiter ◽  
Lucien Manchester ◽  
Mei-ting Yan ◽  
Mamdouh El-Sawi ◽  
...  
Keyword(s):  
Free Radical ◽  
Physical Properties ◽  
Broad Spectrum ◽  
Free Radical Scavenger ◽  
Radical Scavenger

Changes in Elastomers Due to Radiation from Cobalt

1955 ◽  
Vol 28 (1) ◽  
pp. 12-18 ◽  
Author(s):  
S. D. Gehman ◽  
L. M. Hobbs
Keyword(s):  
Free Radical ◽  
Service Life ◽  
Gamma Radiation ◽  
Physical Properties ◽  
Radiation Resistance ◽  
Exposure Dose ◽  
Radical Reactions ◽  
Free Radical Reactions ◽  
Chemical Agents ◽  
Intense Radiation

Abstract A survey has been made of the effects of intense gamma radiation on the physical properties of elastomers and plastics. Such information is required to determine the types of elastomers which are most resistant to radiation, to estimate the service life of elastomers exposed to radiation, and to show favorable trends in compounding for radiation resistance. Intense radiation may affect the physical properties of elastomers benficially or adversely, depending on the type of elastomer and the exposure dose, although hardening and embrittlement are most commonly observed. The possibility is apparent of developing elastomer compounds with improved radiation resistance, especially by the use of chemical agents which affect free-radical reactions. The nature of the elastomer, however, will probably severely limit what can be accomplished by compounding.

Wear of Metal by Rubber

1980 ◽  
Vol 53 (1) ◽  
pp. 176-185
Author(s):  
A. N. Gent ◽  
C. T. R. Pulford
Keyword(s):  
Free Radical ◽  
Physical Properties ◽  
Butyl Rubber ◽  
The Other ◽  
Radical Species ◽  
Wear Rates ◽  
Metal Wear ◽  
The Stability ◽  
Direct Attack ◽  
Mechanical Rupture

Abstract Rates of wear have been determined for steel and bronze scrapers sliding over rubber surfaces. The wear rates were found to depend strongly upon the particular elastomer used, varying by orders of magnitude even though the other ingredients in the compound and the physical properties of the rubber were largely unchanged. In the absence of oxygen the metal scrapers were found to wear away much faster in general; by a factor of 5 to 50 times, depending upon the elastomer. Butyl rubber was anomalous in this respect, however, causing three times greater wear in air than in nitrogen. These diverse observations are attributed to the direct attack upon metals of free radical species generated by mechanical rupture of elastomer molecules during abrasion. The rate of metal wear is closely correlated with the stability of polymeric radicals formed in this way. When the radical is highly reactive it is thought to take part primarily in internal reactions and thus cause little wear of the scraper. On the other hand, relatively stable polymer radicals appear to attack metals vigorously.

Kinetics of the thermal reactions of ethylene. Part II. Ethylene–ethane mixtures

1968 ◽  
Vol 46 (14) ◽  
pp. 2427-2433 ◽  
Author(s):  
M. L. Boyd ◽  
M. H. Back
Keyword(s):  
Free Radical ◽  
Product Formation ◽  
Radical Chain ◽  
Thermal Reactions ◽  
Temperature Range ◽  
Initiation Step ◽  
Chain Polymerization ◽  
Main Effects ◽  
Kinetics Of ◽  
Simplified Mechanism

Mixtures of ethane and ethylene have been pyrolyzed in the temperature range 563–600 °C and at pressures from 30–60 cm. The products were similar to those obtained from the pyrolysis of ethylene by itself, described m Part I, with a marked increase in the yields of the saturated products. The initial rates of product formation and the dependence of these rates on the concentration of ethane suggest that the initiation step is the same as that proposed in the pyrolysis of ethylene alone, viz.[Formula: see text]and that the reaction[Formula: see text]is not an important source of radicals. A simplified mechanism is outlined to account for the main effects of ethane on the free radical chain polymerization.

scholarly journals Situated Counting

2020 ◽  
Author(s):  
Peter Gärdenfors ◽  
Paula Quinon
Keyword(s):  
Working Memory ◽  
Physical Properties ◽  
Conceptual Knowledge ◽  
Counting Process ◽  
Central Feature ◽  
Internal Representations ◽  
Memory And Attention ◽  
External Organization ◽  
One To One ◽  
Special Arrangement

Abstract We present a model of how counting is learned based on the ability to perform a series of specific steps. The steps require conceptual knowledge of three components: numerosity as a property of collections; numerals; and one-to-one mappings between numerals and collections. We argue that establishing one-to-one mappings is the central feature of counting. In the literature, the so-called cardinality principle has been in focus when studying the development of counting. We submit that identifying the procedural ability to count with the cardinality principle is not sufficient, but only one of the several steps in the counting process. Moreover, we suggest that some of these steps may be facilitated by the external organization of the counting situation. Using the methods of situated cognition, we analyze how the balance between external and internal representations will imply different loads on the working memory and attention of the counting individual. This analysis will show that even if the counter can competently use the cardinality principle, counting will vary in difficulty depending on the physical properties of the elements of collection and on their special arrangement. The upshot is that situated factors will influence counting performance.

scholarly journals Influence of emotional-painful stress on affinity of blood to oxygen, the state antioxidant system and physical properties hepatocyte microsomal membrane

2010 ◽  
Vol 56 (3) ◽  
pp. 359-371
Author(s):  
A.N. Maltsev ◽  
A.A. Grekova ◽  
E.A. Kits
Keyword(s):  
Lipid Peroxidation ◽  
Free Radical ◽  
Physical Properties ◽  
Liver Microsomes ◽  
Antioxidant Defence ◽  
Stress Treatment ◽  
Mixed Blood ◽  
Microsomal Membranes ◽  
Treatment Changes ◽  
Radical Processes

The emotional-painful stress causes a more pronounced decrease in affinity of hemoglobin to oxygen in portal blood compared with mixed blood. This contributes to increased oxygen pressure in hepatocytes and activates free radical processes in liver microsomes. Activation of lipid peroxidation is accompanied by changes in physical properties (microviscosity, polarity) of microsomal membranes. However, the increase in duration of stress treatment changes in the studied parameters become adaptive; this is accompanied by gradual normalization in blood affinity to oxygen, physical properties of membranes and the increase in antioxidant defence. Possible mechanisms of interaction of these systems during adaptation and regulation of free radical oxydation are discussed.

Effect of Amphoteric Acrylic Retanning Agent on the Physical Properties of the Resultant Leather

2011 ◽  
Vol 284-286 ◽  
pp. 1925-1928 ◽  
Author(s):  
Li Qiang Jin ◽  
Yu Lu Wang ◽  
De Yi Zhu ◽  
Qing Hua Xu
Keyword(s):  
Free Radical ◽  
Physical Properties ◽  
Radical Copolymerization ◽  
Free Radical Copolymerization ◽  
Acrylic Copolymer ◽  
Acrylic Polymer ◽  
Function Mechanism ◽  
Mechanical And Physical Properties

The unique physical properties of leather make it ideally suited for the manufacture of a variety of products. Retanning has important effects on the mechanical and physical properties of the resultant leather. In this paper, a novel amphoteric acrylic copolymer as retanning material was prepared by free radical copolymerization. The effects of this copolymer on the physical properties of the resultant leather have been investigated by measuring physical and mechanical indexes of the retanned leather. The function mechanism of this copolymer was also researched. Results showed that this copolymer could improve the properties of the resultant leather including softness and strength, and increase leather’s dyeability in contrast to anionic acrylic polymer.

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