Effect of Oxygen Absorbers in Rubber

1936 ◽  
Vol 9 (2) ◽  
pp. 322-338
Author(s):  
A. A. Somerville
Keyword(s):  
Atmospheric Oxygen ◽  
Practical Experience ◽  
Working Hypothesis ◽  
Retarding Effect ◽  
Full Effect ◽  
Rubber Surface ◽  
Effect Of Oxygen ◽  
Cracking Tendency ◽  
Main Factor ◽  
Mechanism Of The Reaction

Abstract In this discussion of flex-cracking, its causes, and a means of controlling it, the theory that oxidation of the rubber is the main factor involved has been used as a foundation. No attempt has been made to prove chemically that oxidation of the rubber actually takes place. This would be difficult, since flex-cracked rubber does not necessarily show the ordinary signs of deterioration, but the work of Neal and Northam (4) has indicated that oxygen plays a part. The facts that oxygen absorbers definitely retard flex-cracking and also that the more strongly they are able to absorb oxygen, the greater is their retarding effect, would be difficult to explain on any other basis. The mechanism of the reaction, however, is obscure and is further complicated by the fact that the oxygen absorbers develop their full effect only in the presence of a catalytic antioxidant. As a working hypothesis it may be assumed that the oxygen absorber removes dissolved or absorbed oxygen within the rubber before and during vulcanization, while the antioxidant protects the rubber surface against atmospheric oxygen during service. It is realized that this hypothesis does not explain every fact connected with the use of oxygen absorbers to complete satisfaction and will doubtless be subject to change or modification as practical experience with these agents accumulates. In the meantime it is believed that a practical commercial means of greatly retarding the flex-cracking tendency of rubber goods has been developed.

Pupation and Emergence in Aëdes taeniorhynchus (Wied.)

1954 ◽  
Vol 45 (4) ◽  
pp. 757-768 ◽  
Author(s):  
E. T. Nielsen ◽  
J. S. Haeger
Keyword(s):  
Larval Stage ◽  
Sexual Difference ◽  
Pupal Stage ◽  
Time Of Day ◽  
Retarding Effect ◽  
Aedes Taeniorhynchus ◽  
Series Of Experiments ◽  
Males And Females ◽  
The Difference ◽  
Main Factor

A series of field observations and rearing experiments were carrried out in Florida to gain information on the duration of the larval stage and the time of day of pupation and emergence of the salt-marsh mosquito, Aëdes taeniorhynchus (Wied.).The technique adopted in a series of experiments is described.It was found that the duration of the larvel stage is dependent on several factors of which water temperature is probably the main factor. Hunger was also shown to be important either through lack of food or overcrowding. Larvae which later became male adults pupated before those which became female imagines.The period of maximum pupation is determined by the distribution of light and darkness, 83 per cent. of all pupation taking place during the evening periods, 15 to 24 hours after experimental midnight, and 48 per cent. in the period just after sunset, 18 to 21 after experimental midnight. The tendency to pupate around sunset is thought to have just as much accelerating as retarding effect on the larval development.Temperature is considered to be the only factor of importance in determining the duration of the pupal stage which varies from 61 hours at 20·8°C. to 45 hours at 25·5° and 37 hours at 29°.Both in nature as well as under controlled conditions in the laboratory it was found that, for a large number of larvae hatched simultaneously, the emergence of adults usually lasts three or fours days, with a maximum at the same hour on each of these days. The period of emergence is proportional to the duration of the post-embryonic development and may under unfavourable conditions last weeks.Maximum emergence of imagines has been found to occur at various times of the day. This is as should be expected since the hour of pupation is fixed to a certain period of the day, and the duration of the pupal stage is solely dependent on the temperature.The difference in the duration of pupation in males and females is very small but owing to the rather marked sexual difference in the duration of the larval stage, 129 hours for males against 145 for females at 29°, there is a preponderance of males during the first emergence maxima and of females in the last.It is concluded that if the temperature of the water in which the larvae are living in the field is known, it should be possible to predict at what hour of the day the emergence maxima will take place.

Isoprene and Rubber. Part 47. The Decomposition of Rubber by Acids

1937 ◽  
Vol 10 (3) ◽  
pp. 445-450
Author(s):  
H. P. Mojen
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Atmospheric Oxygen ◽  
Free Play ◽  
Destructive Effect ◽  
Organic Bases ◽  
Inorganic Acids ◽  
Close Relationship ◽  
Rubber Part ◽  
Long Time ◽  
Effect Of Oxygen

Abstract The phenomena observed in the experiments which have been described can be explained in the following way. As already mentioned, raw rubber contains certain antioxygens which protect the rubber molecules from attack by oxygen. Very little is known about the nature of these antioxygens, but it is probably correct to assume that these substances are of a basic nature, like commercial antioxygens, which for the most part are complex organic bases. The activity of these anti-catalysts is stopped by the addition of organic or inorganic acids. As a result there is no longer any obstacle to an attack by oxygen, and decomposition can proceed under these conditions much more rapidly and much more extensively. The antioxygens are destroyed by the acids, even when oxygen is excluded during the experiments, but demolition of the fiber molecules does not then take place. The intense destructive effect of oxygen on rubber does not therefore depend on the action of acids on the fiber molecules of rubber, but is to be attributed solely to the fact that antioxygens which inhibit decomposition by oxygen are destroyed; destruction of the rubber itself is caused only by oxygen. It is not impossible that these phenomena bear a close relationship to the stickiness acquired by rubber. Rubber which has become sticky is composed of extensively decomposed rubber molecules. This phenomenon is noticeable at times in rubber goods which have been stored for a long time, and may be explained by the fact that atmospheric carbon dioxide destroys the natural antioxygens in the rubber. With their destruction, atmospheric oxygen then has free play to attack the rubber molecules. The acidic substances which are formed in this oxidation then destroy any remaining antioxygens, so that oxygen can destroy all of the rubber. Grateful acknowledgment is due Professor Staudinger, at whose instigation this work was carried out, who offered advice in various ways, and who took an active part in the investigation.

CVII.—The retarding effect of oxygen on the rate of interaction of chlorine and hydrogen

1909 ◽  
Vol 95 (0) ◽  
pp. 959-964 ◽  
Author(s):  
David Leonard Chapman ◽  
Patrick Sarsfield MacMahon
Keyword(s):  
Retarding Effect ◽  
Effect Of Oxygen

The decomposition of nitrous oxide catalysed by palladium-gold alloy wires

1966 ◽  
Vol 294 (1436) ◽  
pp. 1-19 ◽  
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Fermi Level ◽  
Apparent Activation Energy ◽  
Frequency Factor ◽  
Kcal Mole ◽  
Dissociative Chemisorption ◽  
Retarding Effect ◽  
Effect Of Oxygen ◽  
Decomposition Of Nitrous Oxide

The rate of decomposition of nitrous oxide has been examined by pressure measurements, at temperatures between 500 and 900 °C and pressures between 10 -2 and 1 torr. The reaction is first order, but shows retardation by oxygen, but not nitrogen. Over the range of alloys, from Pd to nearly 40 at. % Pd, the velocity at 650 °C falls by a factor of 104, the apparent activation energy falls from 30 to 13 kcal/mole, and the retarding effect of oxygen falls to zero. Over this range of alloys the Fermi level which lies in the d band hardly changes but the concentration of the d band vacancies falls to zero. Over the range of alloys from 40 at. % Pd to Au the velocity at 650 °C remains constant but the apparent activation energy and frequency factor, which show an abrupt increase at 40 at. % Pd, show a continuous fall. The retarding effect of oxygen remains zero. In this range the Fermi level has entered the s band and increases to Au. A steady state treatment of an irreversible dissociative chemisorption of nitrous oxide, together with an oxygen chemisorption equilibrium, yields an equation for the velocity in quantitative agreement with the results found. It is also possible to account for the increase in apparent activation energy with oxygen coverage of the surface. The heat of adsorption of oxygen is derived as 32-2±2 kcal/mole, and the activation energy for chemisorption of nitrous oxide as 12-7 ±0-5 kcal/mole.

scholarly journals THEORETICAL AND METHODOLOGICAL FUNDAMENTALS OF THE STAFF COMPETITIVENESS MANAGEMENT IN PERSONNEL SECURITY ASPECT

2018 ◽  
Vol 1 (2(14)) ◽  
pp. 173-179
Author(s):  
Inna Volodymyrivna Korol ◽  
Maksym Anatoliiovych Slatvinskyi ◽  
Hanna Mykolaivna Chyrva
Keyword(s):  
Staff Development ◽  
Scientific Work ◽  
Practical Experience ◽  
Enterprise Development ◽  
Practical Application ◽  
Target Setting ◽  
Existing Problems ◽  
Management Concepts ◽  
Methodological Problems ◽  
Main Factor

Urgency of the research. The importance of analyzing and solving the existing problems of the staff competitiveness is a matter of current interest as it is the main factor of enterprise development. Target setting. It is reasonable to study the tools of the staff competitiveness management for revealing opportunities of its application at domestic enterprises. Actual scientific researches and issues analysis. In the scientific work such of scholars as Sotnikova, S. I., Krotova, N. V., Molodchik, A. V. and others; the theoretical and practical aspects of the staff competitiveness management are investigated. Uninvestigated parts of general matters defining. Scholars have not worked out the methodological problems of staff competitiveness management in personnel security aspect, which complicates the practical application of appropriate management mechanisms. The research objective. The article aims to develop main directions of staff competitiveness management based on theoretical generalizations and practical experience of enterprises. The statement of basic materials. The authors classified and systematized the basic tools of personnel management at various stages of staff development. The main positions of staff competitiveness management concepts are analyzed, domestic and foreign experience of their implementation are investigated. The method of staff competitiveness management in personnel security aspect is developed.. Conclusions. Approaches to increasing the loyalty of domestic enterprises staff, its motivation for education and professional development should be conceptually reconstructed on the basis of various incentive systems for certain categories of staff to motivate its advances.

THE DECOMPOSITION OF NITROUS OXIDE ON THE SURFACE OF PLATINUM: II. THE EFFECT OF FOREIGN GASES

1936 ◽  
Vol 14b (3) ◽  
pp. 84-89 ◽  
Author(s):  
E. W. R. Steacie ◽  
J. W. McCubbin
Keyword(s):  
Nitrous Oxide ◽  
Inert Gases ◽  
Previous Conclusion ◽  
Retarding Effect ◽  
Kinetics Of ◽  
Decomposition Of Nitrous Oxide ◽  
Mechanism Of The Reaction

Further experiments have been made on the kinetics of the decomposition of nitrous oxide on the surface of platinum. Observations on the effect of foreign gases confirm the previous conclusion that inert gases may exert a surprisingly large retarding effect by hindering the diffusion of the reactant to the more remote parts of a porous catalyst.Adsorption measurements have also been made, and their bearing on the mechanism of the reaction is discussed.

scholarly journals EFFECT OF OXYGEN ON SIZE-CONTROLLED SYNTHESIS OF CdSe QDs

2014 ◽  
Vol 9 (2) ◽  
Author(s):  
Charles Ahamefula Ubani ◽  
Mohamad Yusof Sulaiman ◽  
Ibarahim Zahari ◽  
Kamarruzaman Sopian ◽  
Noor bayaa Ibrahim ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Atmospheric Oxygen ◽  
Synthesis Method ◽  
Optical Absorption Spectroscopy ◽  
X Ray Diffraction ◽  
Cdse Qds ◽  
One Pot ◽  
Withdrawal Time ◽  
X Ray ◽  
Effect Of Oxygen

Unique properties of quantum dots (QDs) are controlled by their customizable particle sizes which can be engineered to suit local need. One-pot organometallic injection synthesis of cadmium selenide (CdSe) QDs is reported. The operation started with the injection of a week old selenium (Se) precursor into a boiling non-coordinating octadecene (ODE) at 195oC resulting in the formation of monodispersed size tunable CdSe QDs with discrete homogeneous nucleation. Differences in the injection and withdrawal time of the sample resulted to the dissimilarity in the shape, size and the opto-electronic properties of the QDs. The effect of oxygen on the synthesized CdSe QDs was studied by exposing freshly prepared sample to atmospheric oxygen for 206 days. The samples were characterized using optical absorption spectroscopy (UV-vis), optical photoluminescence (PL), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM), electron dispersive X-ray (EDX) X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS). Noticeable deformation on the size, shape and the crystalline orientation of the CdSe QDs were observed on the oxygen-interacted sample.Although the synthesis method is safe and produced good quality CdSe QDs, the interaction of the sample with oxygen degrades their opto-electronic quality.

A TEM study of the effect of oxygen on nanocavity formation and precipitation in rapid - solidified Fe-16Ni-9Cr stainless steels

1994 ◽  
Vol 52 ◽  
pp. 700-701
Author(s):  
S. Wisutmethangoon ◽  
T. F. Kelly ◽  
J.E. Flinn
Keyword(s):  
Stainless Steels ◽  
High Mobility ◽  
Hot Extrusion ◽  
Extrusion Ratio ◽  
Gas Atomization ◽  
Cavity Formation ◽  
Nucleation Sites ◽  
Heat Treated ◽  
Different Types ◽  
Effect Of Oxygen

Vacancies are introduced into the crystal phase during quenching of rapid solidified materials. Cavity formation occurs because of the coalescence of the vacancies into a cluster. However, because of the high mobility of vacancies at high temperature, most of them will diffuse back into the liquid phase, and some will be lost to defects such as dislocations. Oxygen is known to stabilize cavities by decreasing the surface energy through a chemisorption process. These stabilized cavities, furthermore, act as effective nucleation sites for precipitates to form during aging. Four different types of powders with different oxygen contents were prepared by gas atomization processing. The atomized powders were then consolidated by hot extrusion at 900 °C with an extrusion ratio 10,5:1. After consolidation, specimens were heat treated at 1000 °C for 1 hr followed by water quenching. Finally, the specimens were aged at 600 °C for about 800 hrs. TEM samples were prepared from the gripends of tensile specimens of both unaged and aged alloys.

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