A Study of the Mechanism of the Deactivation Effect

1954 ◽  
Vol 27 (1) ◽  
pp. 157-164 ◽  
Author(s):  
Jacques Le Foll
Keyword(s):  
Chemical Structure ◽  
A Priori ◽  
Natural Aging ◽  
Chain Scission ◽  
Nitro Compounds ◽  
Active Part ◽  
Relaxation Phenomena ◽  
Chain Molecules ◽  
Vulcanized Rubber ◽  
The Subject

Abstract The only method by which significant differences between the effects of antioxygenic agents and deactivating agents can be detected has been found to be a study of relaxation phenomena. An investigation by this method has also furnished further support to the theories of Tobolsky and his coworkers. The changes which take place during aging in the physical properties of vulcanized rubber are the result of two independent phenomena which occur simultaneously: (1) chain scission, and (2) formation of intermolecular bonds. As far as the aging of vulcanizates of natural rubber under normal conditions, e.g., socalled natural aging, is concerned, the chief phenomenon involved is scission of the chain molecules. In principle, therefore, there are two methods for combatting the deterioration of rubber on aging: (1) to impede chain scission by obstructing the fixation of oxygen, and (2) to promote the progressive formation of intermolecular bonds which compensate for the effects of the scission process. The first of these processes is that in which antioxygenic agents play the active part; in the second process, deactivating agents play the active part. From this viewpoint, deactivating agents play a part analogous to that of accelerators, and they may be regarded as representing a special type of acceleration. This theory makes possible a better understanding of a number of facts which, a priori, seem surprising: (1) the relationships of both chemical structure and mode of action of accelerators and deactivating agents, and (2) the protective effect of litharge, peroxides, and nitro compounds, all of which are vulcanizing agents. With respect to the intimate mechanism of the deactivating effect, one question remains unanswered, viz., how are intermolecular bonds formed under the influence of deactivating agents? This question recalls the question of the function of vulcanization accelerators, which has been the subject of many investigations, but which still remains a mystery.

scholarly journals Overdurability and Technical Wear of Materials Used in the Construction of Old Buildings

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 378
Author(s):  
Jarosław Konior
Keyword(s):  
Inverse Relationship ◽  
Residential Buildings ◽  
A Priori ◽  
Natural Aging ◽  
Distribution Functions ◽  
A Posteriori ◽  
Technical Maintenance ◽  
The Subject ◽  
Materials Used ◽  
The Many

The technical maintenance of old tenement houses traditionally constructed is an ongoing problem, and will continue to be so in the coming years. The subject of the article includes old residential buildings from the turn of the XIX and XX centuries, which are a part of Wroclaw’s downtown district. They can be understood as an essential link in the process of shaping the cultural and social microenvironment of man. The ability of them to meet the multiple expectations of residents depends on the natural aging of tenement houses’ materials, the methods of their maintenance and use, and the influence of the many factors that cause their accelerated wear. The assumed durability is the main reference parameter of the changing age of the inspected tenement houses. The course of the theoretical and observed degree of the technical wear of these buildings was compared with their durability. For the age of these buildings, the technical wear should reach 100%. It was observed that in the first period of use of tenement houses, the phenomenon of “infradurability” occurs, and after exceeding a certain age—depending on the maintenance conditions of the building—the phenomenon of “overdurability” of the building occurs. It was shown that the durability of important elements of old buildings, as a parameter that was defined “a posteriori”, ranges from 153 to 177 years, and is greater than the corresponding literature values indicated “a priori”. The probability of reaching such an age of an element, in which the observed values of technical wear exceed the theoretical values, is much higher than the probability of an opposite event. A comparative analysis of the distribution functions of these probabilities indicates that the probabilities of theoretical wear values are higher than those observed in the case of the assumed literature durability of elements. There is also an inverse relationship for durability that corresponds to the age of the oldest examined elements of tenement houses.

The Mechanism of the Deactivating Effect

1957 ◽  
Vol 30 (4) ◽  
pp. 1166-1167
Author(s):  
Jeanle Bras ◽  
Jean Claude Danjard
Keyword(s):  
Test Piece ◽  
Chemical Structure ◽  
Relaxation Method ◽  
Chain Scission ◽  
Initial Structure ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Relaxation Measurements ◽  
Aging Properties ◽  
Continuous Relaxation

Abstract It was shown by one of us that certain substances, called deactivates, can protect vulcanized rubber against aging by a process which is different from that of antioxidants. The proposed mechanism involved a deactivation of the primary peroxides by transforming them into oxides of rubber without causing any chain scission. This hypothesis, however, did not appear to be completely satisfactory. In fact, deactivators do not protect raw rubber against oxidation, but actually accelerate its degradation in solution, especially in the presence of a peroxide which enhances this deterioration. Moreover, if was shown that the deactivators possess a chemical structure which is very similar to that of certain vulcanization accelerators, and also that they have an effect on the vulcanization. This had led to the suggestion that their effect could be attributed to the initial structure of the vulcanized rubber. We have considered the possibility of obtaining some useful information on this subject by means of stress relaxation measurements which involve the decrease in tensile strength with time of a stretched test piece. The measurements were carried out either by maintaining the test piece at constant elongation (continuous relaxation), or by stretching the relaxed sample to a constant elongation from time to time (discontinuous relaxation). It has been established that the continuous relaxation method accounts solely for the chain scissions which are produced in the vulcanized rubber network, whereas the intermolecular linkages formed during the tests contribute to the discontinuous relaxation picture. The results of some preliminary experiments we have carried out are given in Figure 1. Two rubber compounds, accelerated with diphenylguanidine and mercaptobenzothiazole, respectively, and known to have quite different aging properties, were employed. Vulcanizates containing either an antioxidant A (phenyl-2-naphthylamine) or a deactivator D (zinc mercaptobenzimidazolate) were compared with the control vulcanizates T.

Chemical Structure Changes and Correlation Analysis of High Density Polyethylene after Natural and Xenon Aging

2014 ◽  
Vol 809-810 ◽  
pp. 323-329
Author(s):  
Jun Jun Guo ◽  
Hua Yan ◽  
Zhi De Hu ◽  
Jian Jian Yang
Keyword(s):  
High Density Polyethylene ◽  
Chemical Structure ◽  
Natural Aging ◽  
Chain Scission ◽  
Attenuated Total Reflection ◽  
High Density ◽  
Polymeric Chain ◽  
Unsaturated Compounds ◽  
Leading Role ◽  
Structure Changes

Elucidation of the chemical structure changes that take place of high density polyethylene (HDPE) used as rotational packaging case by attenuated total reflection infrared spectroscopy (ATR-FTIR), when natural aging of Lasa Tibet and xenon aging. The variations of carbonyl index (CI), hydroxyl index (HI), branching degree (N) and crystallinity (Xc) have been studied from qualitative and quantitative. Finally, the correlations between natural and xenon aging have been closely followed. It found that the oxidation and growth of unsaturated compounds play a leading role in the natural aging progress, but the polymeric chain scission is weak effect. However, the samples show a slower growth of unsaturated compounds and a sharp increase in polymeric chain scission after xenon aging. The CI, HI and N increased generally in a line fashion after natural and xenon aging while the Xc changes little.

Educación y valores

2014 ◽  
pp. 83
Author(s):  
Sabino de Juan López
Keyword(s):  
Key Words ◽  
A Priori ◽  
Palabras Clave ◽  
The Subject ◽  
The Relationship ◽  
Problem Of The Criterion

RESUMEN En el artículo se ofrece una reflexión en torno a la educación y valores. Tras una referencia a los diferentes sentidos en que se puede plantear el problema en función de la forma como se puede entender la relación entre los dos sustantivos “educación” y “valores”, la reflexión se centra en algunos problemas relacionados con los valores en cuanto contenidos de la educación. Primeramente se refiere al problema del criterio en función del cual determinar los valores de la educación, concluyendo en que el criterio no podía ser ni de carácter a priori, ni empírico, sino “sintético”. A continuación, se afronta el problema del principio, de la fuente de los valores, o la concreción del criterio de los valores de la educación, entendiendo que éstos deberían ser determinados a partir del sujeto de la educación. Se concluye con la referencia a una exigencia de los valores de la educación, la configuración de una totalidad unitaria e interactiva. Palabras clave: educación, valores, fuente de valores, integración, cultura EDUCATION AND VALUES ABSTRACT The article offers a reflection on education and values. After a reference to the different senses in which one can pose the problem in terms of how you can understand the relationship between the two nouns “education” and “values”, reflection focuses on some problems related to the values in the contents of education. First, it concerns the problem of the criterion against which to determine the values of education, concluding that the criterion could be neither a priori in nature, not empirical, but “synthetic”. Herein, the problem of principle is faced, the source of values, or the realization of the criterion of the values of education, understanding that these should be determined from the subject of education. It concludes with the reference of a requirement of the values in education, setting up a unitary and interactive whole. Key Words: education, values , power values , integration, culture

Self and Selves

2017 ◽  
Author(s):  
Ralph C.S. Walker
Keyword(s):  
Personal Identity ◽  
Moral Philosophy ◽  
A Priori ◽  
The Status ◽  
The Subject ◽  
Synthetic A Priori

Kant is committed to the reality of a subject self, outside time but active in forming experience. Timeless activity is problematic, but that can be dealt with. But he holds that the subject of experience is not an object of experience, so nothing can be known about it; this raises a problem about the status of his own theory. But he ought to allow that we can know of its existence and activity, as preconditions of experience: the Critique allows that synthetic a priori truths can be known in this way. However, its identity conditions remain unknowable. Kant’s unity of apperception shares much with Locke’s continuity of consciousness, but does not determine the identity of a thing. Personal identity is bodily identity. Only Kant’s moral philosophy justifies recognizing other selves; it could warrant ascribing a similar status to animals.

scholarly journals Discovery of a natural cyan blue: A unique food-sourced anthocyanin could replace synthetic brilliant blue

2021 ◽  
Vol 7 (15) ◽  
pp. eabe7871
Author(s):  
Pamela R. Denish ◽  
Julie-Anne Fenger ◽  
Randall Powers ◽  
Gregory T. Sigurdson ◽  
Luca Grisanti ◽  
...  
Keyword(s):  
Protein Design ◽  
Food Industry ◽  
Chemical Structure ◽  
Nutritional Value ◽  
Blue Dye ◽  
Spectroscopic Techniques ◽  
Design Tools ◽  
Enzymatic Transformation ◽  
Food And Beverage ◽  
The Subject

The color of food is critical to the food and beverage industries, as it influences many properties beyond eye-pleasing visuals including flavor, safety, and nutritional value. Blue is one of the rarest colors in nature’s food palette—especially a cyan blue—giving scientists few sources for natural blue food colorants. Finding a natural cyan blue dye equivalent to FD&C Blue No. 1 remains an industry-wide challenge and the subject of several research programs worldwide. Computational simulations and large-array spectroscopic techniques were used to determine the 3D chemical structure, color expression, and stability of this previously uncharacterized cyan blue anthocyanin-based colorant. Synthetic biology and computational protein design tools were leveraged to develop an enzymatic transformation of red cabbage anthocyanins into the desired anthocyanin. More broadly, this research demonstrates the power of a multidisciplinary strategy to solve a long-standing challenge in the food industry.

The Chemical Structure Responsible for the Deactivating Effect of Compounds Which Protect Rubber from Deterioration by Oxygen

1951 ◽  
Vol 24 (3) ◽  
pp. 638-639
Author(s):  
Jean Le Bras ◽  
Jacques Le Foll
Keyword(s):  
Nitrogen Atom ◽  
Systematic Study ◽  
Chemical Structure ◽  
Thiol Group ◽  
Vulcanized Rubber ◽  
Thiol Form

Abstract One of the present authors has already offered evidence which indicates the existence of a deactivating effect, whereby vulcanized rubber is protected against deterioration by oxygen. This effect is evident with such compounds as mercaptobenzimidazole (I), mercaptobenzoxazole, and ethylene-bis (N,N′-phenylthiourea) (II), and the phenomenon seems to be connected in some way with the presence in the molecule of a thiol group united to a nitrogen atom under such conditions that the possible tautomerism between the thion and thiol forms (III) is probably displaced toward the thiol form. We have completed these earlier experiments by a more systematic study, which has included an examination of the influence of cyclization, the nature of the ring, and hetero atoms.

Chemical Structure of Vulcanized Rubber

1939 ◽  
Vol 12 (1) ◽  
pp. 43-55
Author(s):  
J. R. Brown ◽  
E. A. Hauser
Keyword(s):  
Chemical Structure ◽  
Empirical Knowledge ◽  
Extensive Investigation ◽  
Practical Application ◽  
True Nature ◽  
Rubber Industry ◽  
Vulcanized Rubber ◽  
Metallic Salts ◽  
Other Substances

Abstract A CENTURY ago, Charles Goodyear in America and Th. Hancock in England found that the properties of crude rubber could be greatly improved by heating it with sulfur. The product resulting was more elastic, more resistant to tear and abrasion, less affected by solvents, and decidedly less thermoplastic. The treatment of rubber to give these desired properties is known generally as vulcanization and must be considered as the basis for the enormous growth of the rubber industry and the extensive use of rubber products in our everyday life. Broadly speaking, vulcanization involves the reaction, in some fashion, of sulfur with rubber. Extensive investigation has revealed other substances, such as benzoyl peroxide or polynitrobenzenes, which can transform rubber into a “vulcanized” condition. Experience has also shown that metallic salts of zinc or lead and especially certain organic compounds called “accelerators” greatly affect the rate of vulcanization, and these are favorably employed in practice. A vast amount of empirical knowledge has been gained which has greatly improved the practical application of vulcanization and the quality of rubber products, but which has failed as yet to reveal a complete picture of the true nature of the process.

scholarly journals An application of the theory of probabilities to the study of a priori pathometry.—Part II

1917 ◽  
Vol 93 (650) ◽  
pp. 212-225 ◽  
Keyword(s):  
Royal Society ◽  
A Priori ◽  
Active Service ◽  
The Subject ◽  
Government Grant

Part I of this paper was published in the ‘Proceedings', A, vol. 92 (1916), having been read on November 11, 1915. In June last, the Royal Society was kind enough to give a Government Grant for providing me with assistance in order to complete the paper, and for carrying on further studies upon the subject; and Miss Hilda P. Hudson, M. A., Sc. D., was appointed for the work from May 1, 1916. The continuation of the paper has accordingly been written in conjunction with her; and I should like to take the opportunity to express my obligations to her for her valuable assistance, especially in regard to Part III—which is to appear shortly. I must apologise for the rather numerous small errors in Part I—due to the fact that the proofs were received by me when I was abroad on active service.

scholarly journals Empirical evidence reveals the phase diagram of patch patterns in Mediterranean drylands

2017 ◽  
Author(s):  
Fernando Meloni ◽  
Cristiano R. F. Granzotti ◽  
Alexandre S. Martinez
Keyword(s):  
Phase Diagram ◽  
Phase Transitions ◽  
Satellite Images ◽  
A Priori ◽  
Continuous Phase ◽  
Adequate Description ◽  
Scaling Exponents ◽  
Open Issue ◽  
The Subject ◽  
Ecological Functioning

AbstractDrylands are ecosystems with limited water resources, often subjected to desertification. Conservation and restoration efforts towards these ecosystems depend on the interplay between ecological functioning and spatial patterns formed by local vegetation. Despite recent advances on the subject, an adequate description of phase transitions between the various vegetated phases remains an open issue. Here, we gather vegetation data of drylands from Southern Spain using satellite images. Our findings support three vegetated phases, separated by two distinct phase transitions, including a continuous phase transition, with new relations between scaling exponents of ecological variables. The phase diagram is obtained without a priori assumption about underlying ecological dynamics. We apply our analysis to a different dryland system in the Western United States and verify a compatible critical behavior, in agreement with the universality hypothesis.

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