The Testing of Rubber at Low Temperatures

1939 ◽  
Vol 12 (2) ◽  
pp. 365-369 ◽  
Author(s):  
J. H. Carrington
Keyword(s):  
Low Temperatures ◽  
Point Of View ◽  
Published Data ◽  
Great Success ◽  
Suspension Systems ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Resistance To Oxidation ◽  
Extreme Cold ◽  
Available Information

Abstract Developments in modern compounding have in the last few years undoubtedly improved the general properties of vulcanized rubber. Ever-widening fields of application of rubber goods have extended the range of temperature over which rubber is expected to retain its properties. The search for rubber compounds that shall have greater resistance to oxidation, heat, oil and so forth has certainly been pushed forward with great success, but progress in the other direction, namely, towards rubber compounds resistant to extreme cold, does not appear to have been so rapid. In this country we do not experience the extreme cold which occurs in the upper atmosphere and in regions nearer the poles, but rubber suspension systems, etc., as used in ships in polar latitudes or vessels transporting foodstuffs, railway components of many kinds and the numerous rubber parts used in the construction of aircraft all suffer to some extent from loss of resilience when exposed to cold conditions. It therefore seems just as necessary to compound with a view to resisting changes induced by freezing as we normally do to resist heat. With this end in view it was decided to make a critical review of published data on the effect of low temperatures on rubber to serve as a guide to further practical work. As is to be expected, those countries experiencing great cold have already carried out considerable investigation, but the available information is fairly widely distributed, and no doubt there is much work of a private nature which has never been published. It will be convenient, in the summary which follows, to indicate the most important information under headings relating to the chief properties of rubber. As is so frequently the case, physical results have been obtained on mixings of unstated composition or state of vulcanization, or on mixings that are simple, no doubt, from the theoretical standpoint but almost unusual from the practical point of view.

Characteristic Properties of Rubber at Low Temperatures. A Discussion of the Stress-Strain Curves of Vulcanized Rubber at Low Temperatures

1934 ◽  
Vol 7 (4) ◽  
pp. 610-617 ◽  
Author(s):  
Takeo Fujiwara ◽  
Toramatsu Tanaka
Keyword(s):  
Physical Properties ◽  
Low Temperatures ◽  
External Heat ◽  
Point Of View ◽  
Special Importance ◽  
Stress Strain ◽  
Experimental Proof ◽  
Vulcanized Rubber ◽  
The Subject ◽  
Two Phases

Abstract The hardening of rubber at low temperatures is one of the well-known physical characteristics of rubber. The loss of elasticity of raw rubber by hardening at 0° to 10° C., its turning to the consistency of glass, and its fragility at −19° C. when cooled with liquid air, and its fibering when stretched to 60–70 per cent previous to breaking, give an experimental proof of the theory of the structure of rubber molecules. Vulcanization makes raw rubber physically less sensitive to heat and to low temperatures, and is of great significance, because it enables vulcanized rubber to be used around −30° C. without losing its elasticity. The effect of external heat on the physical properties, especially on the stress-strain relations, of vulcanized rubber has been discussed mainly for temperatures from −10° to +100° C., and only two papers deal with temperatures from −30° to −60° or −70° C. (cf. Le Blanc and Kröger, Kolloid Z., 37, 205 (1925); Tener, Kingsbury and Holt, Bureau of Standards Technologic Papers Vol. 22, No. 364). Of special importance are a means of recognizing changes m the physical properties (phenomenon of freezing-hard ness) of vulcanized rubber at −30° to −60° or −70° C., and the practical value of such information. Though there is a contradiction in the fundamental meaning of the “cold resistant theory” of rubber, investigations of the two phases of the subject may throw some light on practical problems and widen the scientific point of view.

The Behavior of Rubber at Low Temperatures

1939 ◽  
Vol 12 (2) ◽  
pp. 344-364 ◽  
Author(s):  
M. Sagajłło ◽  
J. BobiŃska ◽  
H. Saganowski
Keyword(s):  
Elastic Properties ◽  
Low Temperatures ◽  
Small Degree ◽  
Freezing Resistance ◽  
Shock Absorbers ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
The Difference ◽  
Winter Time ◽  
High Degree

Abstract (1) Raw rubber, smoked sheet as well as crepe, freezes to a high degree at low temperatures. The difference between the freezing at −10° and −60° C. is comparatively small at initial elongations of 300 and 400%. With smaller initial elongations there is a greater difference in degree of freezing at temperatures of − 10° and −60° C. A complete loss of the elastic properties of the rubber takes place at −70° C. (2) Previous heating of raw rubber, even at a temperature of 140° C, has no effect on its freezing-resistance. (3) The susceptibility of rubber to freezing increases with increase of the elongation, this effect being strongly marked above an elongation of 200%. (4) An increase in the vulcanization temperature, and therefore a shortening of the vulcanizing time, has only an insignificant effect on the freezing-resistance of rubber compounds. (5) The freezing effect increases as the temperature is lowered. (6) An entire loss of the elastic properties of vulcanized rubber takes place for the lower initial elongations at a temperature of —70° C; for higher elongations; however, they are still retanied at this temperature in a very small degree. (7) “Pure” rubber compounds have a much greater resistance to freezing than loaded ones. (8) The minimum susceptibility to freezing for loaded compounds is obtained with those that are slightly overvulcanized. At the higher elongations this minimum is distinctly shifted into the region of overvulcanization. (9) Softeners have in general no effect in reducing susceptibility to freezing. (10) The use of phenyl-β-naphthylamine has no effect on the susceptibility to freezing. (11) The aging of rubber, even when producing 40% of loss of tensile product, has no effect in lowering its resistance to freezing either at −10° or −60° C. and at initial elongations of from 100 to 400%. On the other hand, the resistance to freezing of aged samples is less at temperatures of −40° and −50° C. with initial elongations of 100 to 200% ; at an initial elongation of 300% they show almost no change in relation to unaged samples, while at an elongation of 400% they show a distinct increase in resistance to freezing. (12) Airplane and balloon shock-absorbers of “pure” rubber compounds possess, within the limits of their elongation during use, even at a temperature of — 40° C, quite insignificant susceptibility to freezing. An entire loss of their elastic properties occurs at −70° C. (13) Keeping airplanes in improvised sheds in winter time even at −20° C. has practically no effect on the usefulness of rubber shock-absorbers.

Geometric Factor in Skeletal Reactions of 2-Methylpentane on Stepped Surfaces of Platinum Catalyst

1992 ◽  
Vol 57 (10) ◽  
pp. 2012-2020
Author(s):  
Vladimír Hejtmánek
Keyword(s):  
Active Sites ◽  
Platinum Catalyst ◽  
Point Of View ◽  
Geometric Factor ◽  
Published Data ◽  
Stepped Surfaces ◽  
Geometric Conditions ◽  
Surface Intermediates ◽  
Isomerization Mechanism

The role of geometric factor in the course of skeletal reactions (isomerization, hydrogenolysis) of 2-methylpentane on stepped (119), (557) and reconstructed R(557) surfaces of single crystals of platinum was evaluated with computer designed models. These calculations were compared with reported experimental data. It was found by analysis of geometric conditions that there are accessible active ensembles on double step of the reconstructed R(557) surface. In addition, these active sites are unsaturated in their coordination sphere and thus catalytically effective. This finding is consistent with published data, confirming higher catalytic activity of this surface. The various pathways of Bond Shift isomerization mechanism of 2-methylpentane from the point of view of steric demands of surface intermediates on differently located ensembles are discussed, too.

scholarly journals Parasites of the head of Scomber colias (Osteichthyes: Scombridae) from the western Mediterranean Sea

2014 ◽  
Vol 59 (1) ◽  
Author(s):  
Salvatore Mele ◽  
Maria Pennino ◽  
Maria Piras ◽  
José Bellido ◽  
Giovanni Garippa ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
Parasite Fauna ◽  
Point Of View ◽  
Published Data ◽  
Multivariate Techniques ◽  
Western Mediterranean Sea ◽  
Scomber Colias ◽  
Non Parametric

AbstractThe metazoan parasite assemblage of the head of 30 specimens of the Atlantic chub mackerel (Scomber colias) from the western Mediterranean Sea was analysed. Eight species of parasites were found, four mazocraeid monogeneans: Grubea cochlear (prevalence = 10%), Kuhnia scombercolias (59%), K. scombri (52%), Pseudokuhnia minor (86%); three didymozoid trematodes: Nematobothrium cf. faciale (21%), N. filiforme (41%), N. scombri (7%); and one laerneopodid copepod: Clavelissa scombri (7%). Results were compared with previously published data from 14 localities of the eastern Mediterranean Sea and the Atlantic Ocean, using non-parametric univariate and multivariate analyses, and the whole parasite fauna of S. colias was compared with that of the congeners (S. australasicus, S. japonicus and S. scombrus). Parasites showed to reflect the biogeographical and phylogenetic history of host. From a methodological point of view, the use of both non-parametric univariate and multivariate techniques proved to be effective tools to detect dissimilarities between parasite assemblages.

Effect on Vulcanized Rubber Compounds of Immersion in Boiling Water

1931 ◽  
Vol 4 (3) ◽  
pp. 426-436
Author(s):  
K. J. Soule
Keyword(s):  
Water Absorption ◽  
Room Temperature ◽  
Anomalous Behavior ◽  
Boiling Water ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Different Temperatures ◽  
Actual Change

Abstract Further work is very desirable on the effect of different accelerators, antioxidants, and fluxes. It is possible that their study will throw more light on the mechanism of the swelling phenomena, and also help to explain the anomalous behavior of some of the fillers tested. It would also seem to be worth while to study the action of a few selected stocks in water, at several temperatures between room temperature and 100° C., to determine if the water absorption and swelling merely increase with rising temperatures, or whether there might be an actual change in behavior at different temperatures.

Optical Transitions in Chalcogenide Glasses From the Point of View of a Barrier-Cluster Model

2008 ◽  
Vol 39-40 ◽  
pp. 253-256
Author(s):  
Ivan Baník
Keyword(s):  
Optical Absorption ◽  
Low Temperatures ◽  
Cluster Model ◽  
Chalcogenide Glasses ◽  
Temperature Shift ◽  
Point Of View ◽  
Optical Transitions ◽  
Influence Of Temperature ◽  
Exponential Tails ◽  
Influence Of Temperature On

A barrier-cluster model of chalcogenide glasses is employed to analyze optical transitions near the absorption edge. The influence of temperature on the optical absorption is studied. The model is used to explain the temperature shift of exponential tails of the optical absorption and the temperature dependence of the optical forbidden-band width at low temperatures.

scholarly journals Cell Bioprinting: The 3D-Bioplotter™ Case

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4005 ◽  
Author(s):  
Angelats Lobo ◽  
Ginestra
Keyword(s):  
3D Structure ◽  
Three Dimensional ◽  
Petri Dish ◽  
Two Dimensions ◽  
Point Of View ◽  
Lack Of Information ◽  
Synthetic Materials ◽  
Different Types ◽  
Available Information ◽  
User Friendly

The classic cell culture involves the use of support in two dimensions, such as a well plate or a Petri dish, that allows the culture of different types of cells. However, this technique does not mimic the natural microenvironment where the cells are exposed to. To solve that, three-dimensional bioprinting techniques were implemented, which involves the use of biopolymers and/or synthetic materials and cells. Because of a lack of information between data sources, the objective of this review paper is, to sum up, all the available information on the topic of bioprinting and to help researchers with the problematics with 3D bioprinters, such as the 3D-Bioplotter™. The 3D-Bioplotter™ has been used in the pre-clinical field since 2000 and could allow the printing of more than one material at the same time, and therefore to increase the complexity of the 3D structure manufactured. It is also very precise with maximum flexibility and a user-friendly and stable software that allows the optimization of the bioprinting process on the technological point of view. Different applications have resulted from the research on this field, mainly focused on regenerative medicine, but the lack of information and/or the possible misunderstandings between papers makes the reproducibility of the tests difficult. Nowadays, the 3D Bioprinting is evolving into another technology called 4D Bioprinting, which promises to be the next step in the bioprinting field and might promote great applications in the future.

Thermal and Electrical Conductivities of Sodium from 40 to 360 K

1972 ◽  
Vol 50 (12) ◽  
pp. 1386-1401 ◽  
Author(s):  
J. G. Cook ◽  
M. P. Van der Meer ◽  
M. J. Laubitz
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Low Temperatures ◽  
Characteristic Temperature ◽  
Published Data ◽  
Inelastic Electron ◽  
Conductivity Data ◽  
Electron Collisions ◽  
Electrical Conductivities ◽  
Flow Apparatus

We present data on the electrical and thermal resistivities and the thermopower of three pure Na specimens from 40 to 360 K. The measurements were made using a guarded longitudinal heat flow apparatus that had previously been calibrated with Au and Al. The specimens were placed in a vacuum environment using no solid inert liner.The electrical resistivity data indicate ΘR = 194 K. The thermal conductivity data show a 4% minimum near 70 K and an ice point value of 1.420 W/cm K. The reduced Lorenz function L/L0 agrees with published data at low temperatures but above 300 K levels off at approximately 0.91. On the basis of published data for liquid Na, L/L0 does not change by more than 3% at the melting point.The minimum in the thermal conductivity and a part of the high temperature deviations of L from L0 are tentatively ascribed to inelastic electron–phonon collisions having a characteristic temperature near that of longitudinal phonons. The possibility that electron–electron collisions further depress L at high temperatures is critically examined.

scholarly journals Гермотим из Клазомен и начало афинской философии

2020 ◽  
Vol 53 (3) ◽  
pp. 141-148
Author(s):  
О.А. Матвейчев
Keyword(s):  
Ancient Greece ◽  
Fundamental Principle ◽  
History Of Philosophy ◽  
Point Of View ◽  
Greek Philosophy ◽  
History Of ◽  
The Difference ◽  
Classical Greek Philosophy ◽  
Available Information ◽  
Greek World

Гермотим из Клазомен – фигура в истории греческой философии, можно сказать, маргинальная. В современной литературе он появляется разве что в ряду других колдунов и мистиков VII–VI вв. до н.э. В таком статусе он включается и в собрание Дильса. Анализируя сведения о Гермотиме, автор ставит перед собой цель найти ему место среди малоазийских философов первой величины, которых считают основателями греческой философии. Различение духа (души) и материи (тела) станет основополагающим принципом греческой философии, понятие Ума (нуса) выступит фундаментом для системы Анаксагора, первого афинского философа, с которого, собственно, и начнется история классической греческой философии. Автор разделяет точку зрения Э. Доддса и др., что появление нового для Греции представления о различии души и тела коренится в северной (гиперборейской?) ментальности, привнесенной в греческий мир во времена колонизации VII–VI вв. до н.э., а возможно – и в более ранние. Ключевые слова: история философии, Древняя Греция, Гиперборея, Гермотим из Клазомен, Анаксагор, шаманизм, нус, душа, тело Hermotimus of Clazomenae can be called a marginal figure in the history of Greek philosophy. In modern literature he is mentioned only among other sorcerers and mystics of the VIIth–VIth centuries BC. The collection of Hermann Diels describes him in the same manner. Analyzing available information about Hermotimus, the author makes an attempt to place him among the primary Anatolian philosophers who are considered the founders of Greek philosophy. The distinction between spirit (soul) and matter (body) will become the fundamental principle of Greek philosophy; the concept of Nous (cosmic Mind) will be the foundation for the system of Anaxagoras, the first Athenian philosopher, from which, in fact, the history of classical Greek philosophy begins. The author shares the point of view of E. Dodds and others that the emergence of a new concept about the difference between soul and body in Greece is rooted in the northern (Hyperborean?) mentality introduced into the Greek world during the colonization of the VIIth–VIth centuries BC or possibly in earlier times. Keywords: history of philosophy, Ancient Greece, Hyperborea, Hermotimus of Clazomenae, Anaxagoras, shamanism, nous, soul, body

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