The Hysteresis of Vulcanized Rubber

1949 ◽  
Vol 22 (4) ◽  
pp. 1000-1008 ◽  
Author(s):  
Jacques Clouaire
Keyword(s):  
Internal Friction ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Experimental Work ◽  
Extensive Investigation ◽  
Recovery Curves ◽  
Vulcanized Rubber ◽  
Long Time ◽  
Underlying Causes ◽  
The Subject

Abstract The present paper is based on an extensive investigation of the tensile properties of vulcanized natural rubber, carried out at the French Rubber Institute from April 1944 to December 1946. The purpose of this paper is to show how, in problems such as hysteresis, the correlation of certain experimental facts which apparently bear no relation to one another may lead to an explanation of the phenomenon involved. The hysteresis effect shown by both natural rubber and synthetic rubbers after stretching has been recognized for a long time, and it can be defined as the nonsuperposition of the strain and recovery curves of one complete cycle of deformation. It should be noted that this definition makes no reference to the causes of the phenomenon nor to the idea of loss of energy, which is not so clearly defined as generally believed. As a matter of fact, although the literature on the elasticity of rubber is remarkably extensive, little information is to be found on the underlying causes of hysteresis. The only real experimental work on the subject was carried out by Bouasse, who succeeded in throwing light on some of the complexities of the phenomenon. However, it appears that since that time little attention has been paid to his work. This may account for the fact that the idea of hysteresis being due solely to internal friction is still so widely accepted, although actually so completely incorrect.

Flex Life and Crystallization of Synthetic Rubber

1944 ◽  
Vol 17 (2) ◽  
pp. 398-403 ◽  
Author(s):  
J. H. Fielding
Keyword(s):  
Natural Rubber ◽  
Experimental Work ◽  
Thermal Effects ◽  
X Ray ◽  
The Past ◽  
Synthetic Rubber ◽  
New Material ◽  
The Subject ◽  
And Performance ◽  
Ray Patterns

Abstract The crystalline structure of stretched natural rubber has been the subject of much experimental work in the past. A great deal of this has been devoted to the more theoretical aspects, such as x-ray patterns, thermal effects, and volume change. It is now known that neither Buna-N nor GR-S has a fiber diagram when stretched and that Butyl-B and Neoprene do have such patterns. Since the industry is now in the process of changing from natural rubber to GR-S, it is of interest to see just what this lack of crystallinity means from a compounding and performance standpoint. It is possible that many of our ideas based on rubber must change, that GR-S must be considered to be a new material, and that radical changes in formulation and construction must be made.

Crystallization in Natural Rubber. IV. Temperature Dependence

1956 ◽  
Vol 29 (3) ◽  
pp. 794-805
Author(s):  
A. N. Gent
Keyword(s):  
Stearic Acid ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Experimental Work ◽  
Crystallization Process ◽  
Vulcanized Rubber ◽  
Maximum Value ◽  
Similar Temperature Dependence ◽  
Similar Temperature

Abstract Considerable experimental work on the crystallization of unstrained natural rubber, both vulcanized and unvulcanized, has been described previously. The rate of crystallization of raw rubber increases as the temperature at which the crystallization occurs is reduced, until a maximum value is attained at about −26° C. On lowering the temperature further, the rate decreases continuously. A similar temperature dependence is found for vulcanized rubber, although the rate at any given temperature is lower. Small quantities of certain impurities, for example, stearic acid, greatly increase the rate of crystallization of raw rubber. Such impurities are normally present in plantation smoked-sheet rubber, on which many of the reported measurements of rates of crystallization have been made. The measurements now reported have, therefore, been made with a purified rubber (deproteinized pale crepe) containing negligible quantities of the relevant impurities. Peroxide vulcanizates prepared from such a rubber have also been examined. The crystallization process was followed dilatometrically.

Hysteresis and Reinforcement

1932 ◽  
Vol 5 (3) ◽  
pp. 336-350
Author(s):  
H. Barron ◽  
F. H. Cotton
Keyword(s):  
Internal Friction ◽  
Potential Energy ◽  
Tensile Properties ◽  
Hysteresis Loss ◽  
Breaking Point ◽  
Vulcanized Rubber ◽  
Extension Work ◽  
Rubber Filler

Abstract 1. The relationships between work of extension, work of retraction, and hysteresis loss in vulcanized rubbers loaded with fillers have been examined. 2. The hysteresis loss in vulcanized rubber during a cycle of extension and retraction increases with amplitude to an extent comparable with the increase in work of extension. 3. If the work required to extend a vulcanized rubber to a given elongation be increased by compounding with fillers, the energy lost through hysteresis on slow retraction increases to a comparable extent. Hence reinforcement does not appreciably increase the ability of rubber to store energy. 4. With any rubber vulcanized to optimum tensile properties, hysteresis loss and work of retraction from any elongation are proportional to the work required to extend to that elongation. Therefore if the hysteresis loss during a given cycle be known, the work of retraction from the breaking point can be calculated. 5. The work of retraction from the ultimate breaking point of a vulcanized rubber increases slightly with reinforcement, and becomes greatest when reinforcement is at a maximum. This is thought to be a function of the rubber-filler interface. 6. No filler was found to lessen the work of retraction from the breaking point until the rubber was highly compounded. 7. It is suggested that the increased work required to rupture rubber that has been reinforced with fillers is mainly dissipated in overcoming consequent increased internal friction; a small quantity being converted to potential energy through strain of the filler-rubber interface.

The Influence of the Test-Specimen on the Results Obtained In Tensile Tests of Soft Vulcanized Rubber Mixtures

1953 ◽  
Vol 26 (2) ◽  
pp. 465-480
Author(s):  
R. Herzog ◽  
R. H. Burton
Keyword(s):  
Natural Rubber ◽  
Tensile Properties ◽  
Test Specimen ◽  
Tensile Tests ◽  
Stress Strain ◽  
Vulcanized Rubber ◽  
Different Types ◽  
Small Test ◽  
Soft Rubber

Abstract The small test-specimen of the VSM-1 type should not be used for measuring the tensile properties of pure-gum vulcanizates; instead, the VSM-1a type of test-specimen should be used for such vulcanizates. Results obtained with the different types of test-specimen differ greatly; hence, in reporting the results of any tests of this kind, the type of test-specimen used should be stated, and only results obtained with one particular type of test-specimen should be compared. For example, substitution of the VSM-2 type of test-specimen by the KTA-II type of test-specimen, which is of approxmately the same size, unfortunately does not result in any better agreement. Based on these differences, which in the case of natural rubber have been found to vary from one type of vulcanizate to another, it is natural to expect corresponding unpredictable differences with various synthetic elastomers. The determination of stress-strain properties of soft rubber vulcanizates is, therefore, fundamentally a problem of agreement on methods of testing, i.e., of standardization.

An Adaptive and Learning System for Feedback-Controlled Evoked Response Studies

1981 ◽  
Vol 20 (03) ◽  
pp. 169-173
Author(s):  
J. Wagner ◽  
G. Pfurtscheixer
Keyword(s):  
Brain Activity ◽  
Evoked Response ◽  
Learning System ◽  
Time Interval ◽  
Electrical Brain Activity ◽  
Long Time ◽  
The Subject ◽  
Eeg Power ◽  
Stimulation System ◽  
Background Eeg

The shape, latency and amplitude of changes in electrical brain activity related to a stimulus (Evoked Potential) depend both on the stimulus parameters and on the background EEG at the time of stimulation. An adaptive, learnable stimulation system is introduced, whereby the subject is stimulated (e.g. with light), whenever the EEG power is subthreshold and minimal. Additionally, the system is conceived in such a way that a certain number of stimuli could be given within a particular time interval. Related to this time criterion, the threshold specific for each subject is calculated at the beginning of the experiment (preprocessing) and adapted to the EEG power during the processing mode because of long-time fluctuations and trends in the EEG. The process of adaptation is directed by a table which contains the necessary correction numbers for the threshold. Experiences of the stimulation system are reflected in an automatic correction of this table. Because the corrected and improved table is stored after each experiment and is used as the starting table for the next experiment, the system >learns<. The system introduced here can be used both for evoked response studies and for alpha-feedback experiments.

The Phantom Defense: America's Pursuit of the Star Wars Illusion. By Craig Eisendrath, Melvin A. Goodman, and Gerald E. Marsh. Westport, CT: Praeger, 2001. 216p. $24.95. Ballistic Missile Defense and the Future of American Security: Agendas, Perceptions, Technology, and Policy. By Roger Handberg. Praeger, 2001. 264p. $62.00. Rockets' Red Glare: Missile Defenses and the Future of World Politics. Edited by James J. Wirtz and Jeffrey A. Larsen. Boulder, CO: Westview, 2001. 368p. $28.50.

2002 ◽  
Vol 96 (4) ◽  
pp. 879-880
Author(s):  
David Goldfischer
Keyword(s):  
World Politics ◽  
Ballistic Missile ◽  
Missile Defense ◽  
Star Wars ◽  
Technological Context ◽  
The Future ◽  
Ballistic Missile Defense ◽  
Long Time ◽  
Strategic Defense ◽  
The Subject

As Michael O'Hanlon concludes in his excellent contribution to Rockets' Red Glare: “We should…get used to the debate over ballistic missile defenses. It has been around a long time, and no final resolution is imminent” (p. 132). In one sense, a review of these three recent books makes clear that many analysts had grown a bit too used to positioning themselves in terms of the 1972 ABM Treaty. Preoccupied with arguments over whether the treaty should be preserved, modified, or rewritten in light of a changing strategic and technological context, no one seemed to have anticipated that President George W. Bush would simply withdraw from it, invoking Article XV's provision that either party could withdraw if “extraordinary events related to the subject matter of this Treaty have jeopardized its supreme interests.” Even many strategic defense supporters who deemed the treaty obsolete (as Robert Joseph persuasively maintains in his contribution to Rockets' Red Glare) generally believed that it should only—and would only—be scrapped if negotiations over U.S.-proposed changes broke down. (“The Bush Administration,” surmises O'Hanlon, “will surely try very hard to amend it before going to such an extreme”) (p. 112). In the event, the president's team disavowed even the word “negotiation,” saying they were willing only to “consult” the Russians regarding the treaty's impending demise.

scholarly journals Rheometer Evidences for the Co-Curing Effect of a Bismaleimide in Conjunction with the Accelerated Sulfur on Natural Rubber/Chloroprene Rubber Blends

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1510
Author(s):  
Marek Pöschl ◽  
Shibulal Gopi Sathi ◽  
Radek Stoček ◽  
Ondřej Kratina
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Crosslinking Agent ◽  
Alder Reaction ◽  
Diels Alder ◽  
Ene Reactions ◽  
Rubber Blends ◽  
Diels Alder Reaction ◽  
Chloroprene Rubber

The rheometer curing curves of neat natural rubber (NR) and neat chloroprene rubber (CR) with maleide F (MF) exhibit considerable crosslinking torque at 180 °C. This indicates that MF can crosslink both these rubbers via Alder-ene reactions. Based on this knowledge, MF has been introduced as a co-crosslinking agent for a 50/50 blend of NR and CR in conjunction with accelerated sulfur. The delta (Δ) torque obtained from the curing curves of a blend with the addition of 1 phr MF was around 62% higher than those without MF. As the content of MF increased to 3 phr, the Δ torque was further raised to 236%. Moreover, the mechanical properties, particularly the tensile strength of the blend with the addition of 1 phr MF in conjunction with the accelerated sulfur, was around 201% higher than the blend without MF. The overall tensile properties of the blends cured with MF were almost retained even after ageing the samples at 70 °C for 72 h. This significant improvement in the curing torque and the tensile properties of the blends indicates that MF can co-crosslink between NR and CR via the Diels–Alder reaction.

How Far Scientific is Snakebite Prevention and First Aid Treatment in School Textbook?

2019 ◽  
Vol 31 (1) ◽  
pp. 39-40
Author(s):  
Faiha Fairouz ◽  
Rumana Rashid ◽  
Abdullah Abu Sayeed
Keyword(s):  
Health Problem ◽  
Rural Areas ◽  
Elementary Science ◽  
First Aid ◽  
Primary Treatment ◽  
National Guidelines ◽  
Long Time ◽  
Class Viii ◽  
The Subject ◽  
School Books

Background: Snakebite is an old health problem in rural areas. In Bangladesh, the snakebite issue is included in school syllabus, in curriculum since long time, so that people can take/get immediate first aid treatment and can prevent snakebite. The success of snakebite treatment depends more on providing first aid treatment immediately after snakebite by learning and by sending the patients quickly to hospital. Snakebite is a preventable health problem indeed. If it can be prevented the rate of snakebite will also decrease. In the recently published snake bite management Guideline by WHO it has been targeted to reduce 50% of mortality & disability due to snakebite by 2030.1 Methods: a. The snakebite topic or issue has been thoroughly reviewed in the secondary and higher secondary school books. b. National Guidelines on snakebite in providing/ giving first aid treatment has been reviewed.2 c. The correlation between the topic to learn the subject and the national guidelines have been reviewed and given taken into account. d. The similarity or correlation between the national guidelines and the topic in the prevention of snakebite in the book have been observed & reviewed. It was a descriptive/narrative research study. Results: In the book of class IV in Primary and Secondary level students, ‘Elementary Science, (‘Prathomiik Bigghan’) page no. 86 and in book of class VIII Home Science (‘Gharjhastha Biggan’) page no. 16 the Snakebite issue/topic is mentioned.2,3 There are 22 information on the first aid/primary treatment of Snakebite among which 5 (five) are nonscientific rather harmful. (Table & Picture) Bangladesh J Medicine Jan 2020; 31(1) : 39-40

scholarly journals Dynamics of life expectancy and life span equality

2020 ◽  
Vol 117 (10) ◽  
pp. 5250-5259 ◽  
Author(s):  
José Manuel Aburto ◽  
Francisco Villavicencio ◽  
Ugofilippo Basellini ◽  
Søren Kjærgaard ◽  
James W. Vaupel
Keyword(s):  
Life Expectancy ◽  
Life Span ◽  
Health Policies ◽  
Public Health Policies ◽  
Dynamic Relationship ◽  
Mortality Increase ◽  
Long Time ◽  
Underlying Causes ◽  
The Relationship ◽  
Over Time

As people live longer, ages at death are becoming more similar. This dual advance over the last two centuries, a central aim of public health policies, is a major achievement of modern civilization. Some recent exceptions to the joint rise of life expectancy and life span equality, however, make it difficult to determine the underlying causes of this relationship. Here, we develop a unifying framework to study life expectancy and life span equality over time, relying on concepts about the pace and shape of aging. We study the dynamic relationship between life expectancy and life span equality with reliable data from the Human Mortality Database for 49 countries and regions with emphasis on the long time series from Sweden. Our results demonstrate that both changes in life expectancy and life span equality are weighted totals of rates of progress in reducing mortality. This finding holds for three different measures of the variability of life spans. The weights evolve over time and indicate the ages at which reductions in mortality increase life expectancy and life span equality: the more progress at the youngest ages, the tighter the relationship. The link between life expectancy and life span equality is especially strong when life expectancy is less than 70 y. In recent decades, life expectancy and life span equality have occasionally moved in opposite directions due to larger improvements in mortality at older ages or a slowdown in declines in midlife mortality. Saving lives at ages below life expectancy is the key to increasing both life expectancy and life span equality.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

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