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 Raw Rubber When Stretched Isothermally

1938 ◽  
Vol 11 (4) ◽  
pp. 647-652 ◽  
Author(s):  
H. Hintenberger ◽  
W. Neumann
Keyword(s):  
Room Temperature ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Steep Ascent ◽  
Flow Effect ◽  
Vulcanized Rubber ◽  
Flow Phenomena ◽  
Entropy Effect ◽  
The Subject

Abstract The S-shaped form of the stress-strain curve of rubber is today explained in a quite satisfactory way. In the first part of the curve, i. e., the gradual ascent, work must be expended because of the van der Waals forces of attraction of the molecules; in the second part, i. e., the steep ascent, the elasticity is chiefly an entropy effect, which is finally exceeded by crystallization phenomena. The phenomenon of crystallization itself has been the subject of extensive investigations, but in most cases vulcanized rubber has been employed, and because of the various accelerators and fillers which the rubber has contained, the products have been rather ill-defined. It is evident that the phenomena involved in crystallization would be much more clearly defined if the substance under investigation were to be in a higher state of purity. If experiments are carried out with raw rubber, a flow effect is added to the various other phenomena. As a result of this flow effect, Rosbaud and Schmidt, and Hauser and Rosbaud as well, found that the stress-strain curve depends on the rate of elongation at very low extensions, with a greater stiffness at high rates of elongation. As found recently by Kirsch, there is no evidence of any flow phenomena in vulcanized rubber at room temperature. Most investigations have been so carried out that the stress has been measured at a definite elongation. It was therefore of interest to determine the elongation at constant stress, and the changes in this relation with time and with temperature, of various types of raw rubber.

Isothermal and Adiabatic Stress-Strain Curves of Vulcanized Rubber

1939 ◽  
Vol 12 (1) ◽  
pp. 64-70 ◽  
Author(s):  
V. Hauk ◽  
W. Neumann
Keyword(s):  
Chemical Nature ◽  
Absolute Temperature ◽  
Strain Diagram ◽  
Stress Strain ◽  
Isothermal Conditions ◽  
Adiabatic Conditions ◽  
Vulcanized Rubber ◽  
The Subject ◽  
The Difference ◽  
Thermodynamic Interpretation

Abstract The stress-strain diagram of rubber has been the subject of a large number of investigations, including those of Röntgen, Gough, and Joule in the nineteenth century, those on isothermal phenomena by Meyer and Ferri, and Wiegand and Snyder, and most recently those on adiabatic phenomena of Ornstein, Eymers, and Wouda. The investigations of Meyer and Ferri are concerned chiefly with the dependence of the stress-strain phenomena on the temperature, and they confirm experimentally the hypothesis that within a certain range of temperature and with highly vulcanized samples, the stress is proportional to the absolute temperature, i. e., S=aT+b. At lower states of vulcanization this proportionality does not hold true. The work of Ornstein and his collaborators, which is frequently cited in the literature, is concerned with the phenomena which take place when raw rubber and weakly vulcanized rubber are stretched adiabatically; that of Wiegand and Snyder is concerned chiefly with a thermodynamic interpretation of stress-strain curves obtained experimentally. Now in spite of the fact that stress-strain curves of rubber have been determined so frequently, particularly under isothermal conditions, these measurements are for the most part of limited value, since the chemical nature of the types of rubber employed is not described definitely. Then again in most cases little attention was paid to the difference between isothermal and adiabatic stretching. In view of these facts, it seemed desirable to throw further light on the problem by obtaining stress-strain curves of one particular well-defined material. The object of the present work was then: 1. To obtain true isothermal stress-strain curves as a function of the degree of vulcanization and as a function of the temperature, and thus to study stresses as a function of temperature. 2. To obtain data on the same vulcanizates under adiabatic conditions. 3. To compare the stress-strain results under isothermal conditions with those under adiabatic conditions.

The Formation and Structure of Vulcanizates

1949 ◽  
Vol 22 (1) ◽  
pp. 96-104
Author(s):  
J. Bardwell ◽  
C. A. Winkler
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Physical Properties ◽  
Network Structure ◽  
Weight Distribution ◽  
Elastic Behavior ◽  
Cross Linking ◽  
Structural Factors ◽  
Experimental Proof ◽  
Vulcanized Rubber

Abstract The characteristic mechanical properties of vulcanized rubber are believed to result from a network structure made up of chainlike molecules bonded together by occasional cross-linkages. In relating the physical properties of the vulcanizate to the structure of the network, it is therefore necessary to consider the concentration of cross-linkages and the molecular-weight distribution of the rubber molecules before cross-linking. Various theories have been proposed for the dependence of elastic properties on these structural factors, but experimental proof of the suggested relations has been meager, largely because of the complexities met with in, vulcanization reactions. In the present investigation some of these difficulties have been overcome, and the quantitative relations between the elastic behavior of GR-S and its network structure have thereby been revealed.

An Exploration of the Role of Description in Psychology as a Descriptive Science

1989 ◽  
Vol 19 (2) ◽  
pp. 65-74 ◽  
Author(s):  
Rex J. van Vuuren
Keyword(s):  
Qualitative Research ◽  
Human Science ◽  
Point Of View ◽  
Theoretical Justification ◽  
Life World ◽  
The Subject ◽  
Two Phases ◽  
Phenomenological Point

From a phenomenological point of view psychology as a human science is a descriptive science. Psychology as a descriptive science and psychology as an explanatory science are two distinct types of science and should not be viewed as two phases of science. The major arguments of Amedeo Giorgi's theoretical justification of descriptive science are presented. His arguments are the grounds on which two leading questions are explicated: What is description and what is the role of description in qualitative research? In reflecting on the context of gathering, creating and analysing descriptions, a distinction between description1 (concrete life-world descriptions) and description2 (psychological description of a phenomenon) is made. Descriptions are placed in the context of the researcher's interest; the researcher's request for a description by a subject; the subject as a narrator; the meaning of a description as a text; the researcher as a reader of descriptions and the researcher as author of description2. The conclusion consists of what might be ‘good’ descriptions.

X-Ray Investigation of the Crystallization of Vulcanized Rubber on Stretching

1948 ◽  
Vol 21 (3) ◽  
pp. 621-626 ◽  
Author(s):  
B. V. Lukin ◽  
V. I. Kasatochkin
Keyword(s):  
Tensile Strength ◽  
Crystalline Phase ◽  
Oxidative Degradation ◽  
Point Of View ◽  
Crystal Formation ◽  
Stress Strain ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Cross Links ◽  
Ray Methods

Abstract 1. x-Ray methods have been used to investigate the amount of crystalline phase in stretched samples as a function of the vulcanization time. 2. Curves relating the percentage of crystalline phase to the vulcanization time have sharply defined maxima. 3. A comparison of the curves relating tensile strength to vulcanization time with the curves of crystal formation shows their analogous character, the position of the maxima approximately corresponding to one and the same vulcanization time. 4. The position of the maxima on the curves of crystal formation is not related to the degree of stretching. 5. The effect of accelerators is to shift the maximum on the curve of crystal formation to the region of short vulcanization times and to increase the percentage of crystalline phase. 6. The curves of crystal formation and of tensile strength, and thus the behavior of the stress-strain curves for various vulcanization times, is interpreted from the point of view of the existence of two processes—the process of forming a network of cross-links by the interaction of rubber with sulfur, and the process of oxidative degradation of the rubber.

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.

scholarly journals On the effect of the temperature of liquid hydrogen (-252.8° C.) On the tensile properties of forty-one specimens of metals comprising (a) pure iron 99.85%; (b) four carbon steels; (c) thirty alloy steels; (d) copper and nickel; (e) four non-ferrous alloy

1933 ◽  
Vol 232 (707-720) ◽  
pp. 297-332 ◽  
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Practical Importance ◽  
Carbon Steels ◽  
Point Of View ◽  
Ferrous Alloy ◽  
Iron And Steel ◽  
Active Attention ◽  
Alloy Steels ◽  
The Subject

The effect of low temperatures on the mechanical properties of metals, and specially of iron and steel, first received active attention many years ago. The earliest investigations were stimulated by the practical importance of this effect, which, it was known or suspected, was to embrittle ordinary iron and steel. The first reports of any magnitude on the subject were those by the Canadian Dominion Board of Trade and the German Railways. Both of these reports appeared in 1871, and were mostly concerned with the possible dangers through iron and steel becoming brittle owing to the specially low natural temperatures, occurring over large districts in those countries. The practical importance of the behaviour of iron and steel at low temperatures has since increased with the development of refrigeration and the liquefaction of gases on a practical scale, also through the use of aircraft, which in the higher altitudes experience temperatures as low as — 50° C. or even still lower. The subject is also of considerable interest from the purely scientific point of view. Much information has been accumulated regarding the effect on the mechanical and other properties of iron and steel at above room temperatures, the acquirement of which knowledge has in recent years been much stimulated by the increasing use of what are known as heat-resisting steels. Such knowledge cannot be regarded as complete without exploring the whole possible range of temperature.

On the colouring and extractive matters of urine.-Part I

1867 ◽  
Vol 15 ◽  
pp. 1-4
Keyword(s):  
Physical Properties ◽  
Chemical Nature ◽  
Point Of View ◽  
Abnormal State ◽  
Imperfect Knowledge ◽  
The Subject ◽  
Normal Urine

Notwithstanding the labour bestowed by many eminent men On the chemistry of urine during the last sixty years, there are portions of the subject of which we have but a very imperfect knowledge. Of all the properties of urine, none is more obvious, even to the ordinary observer, than its colour; and yet very little is known concerning the chemical nature of the substances to which its colour is due. Our ignorance in this respect may be ascribed to various causes, among which may be mentioned the extremely minute quantities of these substances occurring in the secretion, the facility with which some of them are decomposed, their chemical and physical properties (which present to our notice very little that is characteristic), and, lastly, the little interest which they possess for the chemist, notwithstanding their importance from a physiological and pathological point of view. According to the author, the colouring-matters . peculiar to urine may be divided into three classes, viz.— 1st. Those which are only found occasionally in it, in consequence either of disease or of some abnormal state of the system. 2ndly. Those which are produced by spontaneous decomposition, or by the action of reagents on substances, either coloured or colourless, preexisting in the urine. 3rdly. The colouring-matter or matters occurring in normal urine, and to which its usual colour is due.

Point and planar defects in the iron sulfide compounds Fe1-xS

1984 ◽  
Vol 42 ◽  
pp. 434-435
Author(s):  
Thao A. Nguyen
Keyword(s):  
Low Temperatures ◽  
Direct Evidence ◽  
Iron Sulfide ◽  
Planar Defects ◽  
Selective Area ◽  
Vacancy Ordering ◽  
Different Types ◽  
Lattice Images ◽  
The Subject ◽  
Beam Lattice

It is well known that the large deviations from stoichiometry in iron sulfide compounds, Fe1-xS (0≤x≤0.125), are accommodated by iron vacancies which order and form superstructures at low temperatures. Although the ordering of the iron vacancies has been well established, the modes of vacancy ordering, hence superstructures, as a function of composition and temperature are still the subject of much controversy. This investigation gives direct evidence from many-beam lattice images of Fe1-xS that the 4C superstructure transforms into the 3C superstructure (Fig. 1) rather than the MC phase as previously suggested. Also observed are an intrinsic stacking fault in the sulfur sublattice and two different types of vacancy-ordering antiphase boundaries. Evidence from selective area optical diffractograms suggests that these planar defects complicate the diffraction pattern greatly.

A Modified Chair Geometry for Whole Body Counting

1976 ◽  
Vol 15 (05) ◽  
pp. 246-247
Author(s):  
S. C. Jain ◽  
G. C. Bhola ◽  
A. Nagaratnam ◽  
M. M. Gupta
Keyword(s):  
Marked Improvement ◽  
Point Of View ◽  
Whole Body ◽  
Spatial Response ◽  
Body Counting ◽  
The Subject ◽  
Whole Body Counting ◽  
The Buddha

SummaryIn the Marinelli chair, a geometry widely used in whole body counting, the lower part of the leg is seen quite inefficiently by the detector. The present paper describes an attempt to modify the standard chair geometry to minimise this limitation. The subject sits crossed-legged in the “Buddha Posture” in the standard chair. Studies with humanoid phantoms and a volunteer sitting in the Buddha posture show that this modification brings marked improvement over the Marinelli chair both from the point of view of sensitivity and uniformity of spatial response.

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