Behavior of Different Fractions of Purified Hevea Rubber during Vulcanization

1949 ◽  
Vol 22 (4) ◽  
pp. 994-999
Author(s):  
G. T. Verghese
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
The Other ◽  
Stress Strain ◽  
Strain Behavior ◽  
Other Hand ◽  
The Difference

Abstract Considerable data on the vulcanization characteristics of molecular fractions of ordinary (unpurified) natural rubber are available. There is, on the other hand, little information of any systematic work on the vulcanization of purified rubber and of its fractions. Pummerer and Pahl vulcanized the sol and gel fractions obtained from purified Hevea rubber, and also the purified whole rubber. But apart from a statement that whole rubber vulcanized much faster than the two fractions obtained from it, no details have been published. Vulcanization of purified whole rubber and of its sol and gel fractions was studied also by Smith and Holt. They concluded that the difference which they observed in the stress-strain behavior of the fractions and whole rubber was due to differences in the rubber which persisted through vulcanization. The present paper deals with a study of the vulcanization characteristics of different fractions of purified rubber prepared by a method described in a previous paper. Also, for comparative purposes a similar study was made of the corresponding fractions of unpurified rubber. As the difference in molecular weight of some of the fractions obtained by the above method was rather small, a grouping of the fractions was made as follows :

Thermomechanical Effects Associated With Crystallization of Rubber Under Stretch and During Slow Extension

1997 ◽  
Vol 119 (3) ◽  
pp. 298-304 ◽  
Author(s):  
Mehrdad Negahban
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Thermodynamic Model ◽  
The Other ◽  
Equilibrium Stress ◽  
Rubber Sample ◽  
Other Hand ◽  
The Difference ◽  
Thermomechanical Effects

A natural rubber sample which crystallizes after stretching normally shows stress relaxation associated with this crystallization and normally ends up at a stress lower than that of the fully amorphous rubber before crystallization. On the other hand, a natural rubber sample which crystallizes during stretching becomes more rigid as a result of the crystallization and the stress required to extend it to a given stretch increases substantially above the stress needed to extend the fully amorphous rubber to the same elongation. Even though the former effect has been modeled and studied by the likes of Flory (1947), the latter effect has not yet been properly modeled or studied. The difference between crystallization during or after stretching will be studied in this article based on a thermodynamic model developed by the author to capture the thermomechanical effects of crystallization in natural rubber. The two limit cases of very rapid and very slow extension to a given stretch are singled out for comparison of the equilibrium stress.

Stress-Strain and Stress-Birefringence Studies on Natural Rubber, Isomerized Natural Rubber, and Synthetic Poly(Isoprene)

1974 ◽  
Vol 47 (5) ◽  
pp. 1234-1240 ◽  
Author(s):  
D. P. Mukherjee
Keyword(s):  
Natural Rubber ◽  
Rate Process ◽  
Stress Strain ◽  
Similar Reasoning ◽  
Strain Behavior ◽  
Three Samples ◽  
Strain Induced Crystallization ◽  
High Elongation ◽  
The Difference ◽  
Induced Crystallization

Abstract With respect to stress-birefringence, isomerized natural rubber behaves the same as natural rubber at low elongations, but at high elongation levels the natural rubber sample exhibits higher stress-hysteresis accompanied by higher mechanical loss energy. Therefore, it appears that at low elongation level the viscoelastic rate process governing the stress-strain hysteresis is not sensitive to structural imperfection (within the range of cis-1,4 content studied here), but the crystallization process at higher elongation is strongly dependent on the cis content. This is in agreement with the conclusion made by Scott and co-workers from their dynamic measurements on synthetic poly(isoprene)s. The difference in cis-content between Natsyn and natural rubber and the effect on crystallizability explains the lower hysteresis on the stress-birefringence plot for Natsyn. Similar reasoning explains the stress-birefringence difference between the A.C. rubber and Natsyn. The data, however, shows that Natsyn has the lowest amount of loss energy of the three samples (except at very high input energy >4.5). This difference might be due to effects of physical entanglements or gels which may differ. In addition, the difference in microstructure contributes to the difference in extent of strain-induced crystallization. Since the viscoelastic rate process governing the stress-strain behavior and the strain-induced crystallization are associated with molecular motion, they may not be independent.

Failure Properties of Natural Rubber Double Networks

1995 ◽  
Vol 68 (1) ◽  
pp. 124-131 ◽  
Author(s):  
P. G. Santangelo ◽  
C. M. Roland
Keyword(s):  
Tensile Strength ◽  
Natural Rubber ◽  
Crosslink Density ◽  
The Other ◽  
Direction Transverse ◽  
Mechanical Fatigue ◽  
Other Hand ◽  
Failure Properties ◽  
The Difference ◽  
Double Networks

Abstract When measured parallel to the curing deformation, double networks of natural rubber have a higher modulus than single networks of equal crosslink density. The difference is greater at higher strains. Despite the higher modulus, the mechanical fatigue lifetimes of double networks were found to be as much as a factor of ten higher than for conventionally crosslinked NR. The double network's tensile strength, on the other hand, was slightly lower. In contrast to these results, the modulus and tensile strength in the direction transverse to the curing strain are minimally affected by the presence of a composite network.

Determination of Degree of Crosslinking in Natural Rubber Vulcanizates. Part III

1961 ◽  
Vol 34 (1) ◽  
pp. 279-289 ◽  
Author(s):  
L. Mullins
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
Intrinsic Viscosity ◽  
Stress Strain ◽  
Strain Behavior ◽  
Equilibrium Volume ◽  
Volume Swelling ◽  
Natural Rubber Vulcanizates

Abstract The two previous parts of this series described an attempt to relate the physical properties of natural rubber vulcanizates to their network structure. The first established an empirical relationship between the stress-strain behavior of highly swollen natural rubbers in simple extension, and their equilibrium volume swelling in n-decane. It also examined the effect of changes in initial molecular weight of the unvulcanized masticated rubber on these properties, and an empirical correction making allowance for network flaws due to chain-segments terminated by a crosslink at only one end was obtained. The second part gave measurements of the equilibrium volume swelling and the intrinsic viscosity before vulcanization for each of a range of natural rubber vulcanizates which had been prepared by a method which enabled the number of crosslinks to be determined by chemical analysis. These measurements permitted a comparison to be made between (i) the chemical estimate of the actual number of crosslinks introduced and (ii) the number derived from the data on equilibrium volume swelling, by means of the empirical relations derived in Part I. For this purpose, an assumption was made that the stress-strain behavior of highly swollen rubbers was in accord with the predictions of the statistical theory. Recent studies of both the stress-strain properties of highly swollen rubbers and the method of determining number-averaged molecular weight from intrinsic viscosity measurements have provided an improved basis for the quantitative determination of the degree of crosslinking from measurements of physical properties. The results described in Parts I and II of this series are reinterpreted here to take account of both of these developments ; in addition, the effect of the introduction of a correction for a network defect equivalent to chain entanglements is examined.

scholarly journals Another Name for Liberty: Revelation, ‘Objectivity,’ and Intellectual Freedom in Barth and Marion

Open Theology ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 430-450
Author(s):  
Kristóf Oltvai
Keyword(s):  
A Priori ◽  
The Other ◽  
Christian Theology ◽  
Intellectual Freedom ◽  
Specific Kind ◽  
Absolute Truth ◽  
Saturated Phenomenon ◽  
Other Hand ◽  
The Difference ◽  
The Relationship

Abstract Karl Barth’s and Jean-Luc Marion’s theories of revelation, though prominent and popular, are often criticized by both theologians and philosophers for effacing the human subject’s epistemic integrity. I argue here that, in fact, both Barth and Marion appeal to revelation in an attempt to respond to a tendency within philosophy to coerce thought. Philosophy, when it claims to be able to access a universal, absolute truth within history, degenerates into ideology. By making conceptually possible some ‚evental’ phenomena that always evade a priori epistemic conditions, Barth’s and Marion’s theories of revelation relativize all philosophical knowledge, rendering any ideological claim to absolute truth impossible. The difference between their two theories, then, lies in how they understand the relationship between philosophy and theology. For Barth, philosophy’s attempts to make itself absolute is a produce of sinful human vanity; its corrective is thus an authentic revealed theology, which Barth articulates in Christian, dogmatic terms. Marion, on the other hand, equipped with Heidegger’s critique of ontotheology, highlights one specific kind of philosophizing—metaphysics—as generative of ideology. To counter metaphysics, Marion draws heavily on Barth’s account of revelation but secularizes it, reinterpreting the ‚event’ as the saturated phenomenon. Revelation’s unpredictability is thus preserved within Marion’s philosophy, but is no longer restricted to the appearing of God. Both understandings of revelation achieve the same epistemological result, however. Reality can never be rendered transparent to thought; within history, all truth is provisional. A concept of revelation drawn originally from Christian theology thus, counterintuitively, is what secures philosophy’s right to challenge and critique the pre-given, a hermeneutic freedom I suggest is the meaning of sola scriptura.

Markedness and Perspective in the Interpretation of the Active and Passive Voice

1974 ◽  
Vol 26 (2) ◽  
pp. 189-195 ◽  
Author(s):  
Irene Klenbort ◽  
Moshe Anisfeld
Keyword(s):  
Information Content ◽  
Focal Point ◽  
The Other ◽  
Clear Pattern ◽  
Passive Voice ◽  
Other Hand ◽  
Logical Subject ◽  
The Difference

The subjects were presented with active and passive sentences. For each sentence, they had to choose between two alternative implications. The pattern of choices indicates that in the passive the logical subject was interpreted by the subjects as the focal point of the information asserted by the sentence and as the carrier of overall responsibility for the sentential proposition. In contrast to the passive, there was no clear pattern of preferences for the active. The difference between the two voices was attributed to their markedness asymmetry, the passive being marked and the active unmarked. It is concluded that the active offers a neutral structure for conveying information; a structure available for use when one does not want to superimpose on the information content any stylistic or connotational implications. The passive, on the other hand, suggests special connotations in addition to the basic message.

Effect on Polymer Chain Structure Caused by the Molar Fraction of 4-Hydroxybutyrate in Poly(3-hydroxybutyrate- co -4-hydroxybutyrate)

2012 ◽  
Vol 602-604 ◽  
pp. 776-780
Author(s):  
Zhi Qiang Li ◽  
Mei Li ◽  
Wei Jia Fan
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Polymer Chain ◽  
Molar Fraction ◽  
Chain Structure ◽  
The Other ◽  
Mean Square ◽  
Polarizing Microscope ◽  
Other Hand ◽  
The Mean

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)copolymer [P(3HB-co-4HB)] is a kind of biodegradable high molecular polymer produced by bioaccumulation. Because of the good biodegradability and biocompatibility, P(3HB-co-4HB)s have attracted wide attention . At first, the intrinsic viscosity[η] in good solvent of P(3HB-co-4HB) s with varying contents of 4HB was investigated in different temperature. Second, observed the changes of crystallization gathered state caused by the varying contents of 4HB by polarizing microscope. The results show that to the P(3HB-co-4HB)s in same molecular weight, the intrinsic viscosity[η] in good solvent barely changes when the mole fractions of 4HB increase. On the other hand, the mean square end to end distances[0] of macromolecular flexible chains increase with the mole fractions of 4HB. At the same time, the states of aggregation change from spherulites to dendrites. In this investigation, we discuss the reasons of the differences in depth.

Scenarios as Tools of the Scientific Imagination: The Case of Climate Projections

2021 ◽  
Vol 29 (1) ◽  
pp. 36-61
Author(s):  
Michael Poznic ◽  
Rafaela Hillerbrand
Keyword(s):  
Scientific Community ◽  
Climate Science ◽  
The Other ◽  
Climate Projections ◽  
Public Realm ◽  
The Public ◽  
Other Hand ◽  
The Difference ◽  
The One ◽  
Scientific Imagination

Climatologists have recently introduced a distinction between projections as scenario-based model results on the one hand and predictions on the other hand. The interpretation and usage of both terms is, however, not univocal. It is stated that the ambiguities of the interpretations may cause problems in the communication of climate science within the scientific community and to the public realm. This paper suggests an account of scenarios as props in games of make-belive. With this account, we explain the difference between projections that should be make-believed and other model results that should be believed.

Prevalence and Causal Factors of Playing-Related Musculoskeletal Disorders of the Upper Extremity and Trunk among Japanese Pianists and Piano Students

2006 ◽  
Vol 21 (3) ◽  
pp. 112-117
Author(s):  
Shinichi Furuya ◽  
Hidehiro Nakahara ◽  
Tomoko Aoki ◽  
Hiroshi Kinoshita
Keyword(s):  
Musculoskeletal Disorders ◽  
Age Groups ◽  
Significant Risk ◽  
Significant Risk Factor ◽  
Daily Practice ◽  
The Other ◽  
Causal Factors ◽  
Western Countries ◽  
Other Hand ◽  
The Difference

The purpose of this study was to investigate the prevalence of playing-related musculoskeletal disorders (PRMDs) among Japanese female classical pianists of different age groups. The causal factors for PRMDs also were examined. A group of 203 senior pianists, including piano teachers and students with piano majors at high schools and colleges, were surveyed using questionnaires. Results showed that 77% of these pianists suffered from PRMDs in at least one of their body portions. This value was larger than those reported in Western countries. Forty-four percent of these were serious enough to warrant medical treatment, which was a lower rate than reported in Western countries. The difference in these numbers may reflect the current state of understanding of PRMDs among Japanese pianists and their educators. The prevalence of PRMDs was found to be age-dependent. In the student groups, the finger/hand had the highest rate of PRMDs, followed by the forearm and shoulder. The senior group, on the other hand, had the highest PRMD incidence at the neck/trunk, followed by the forearm and hand/finger. Care may need to be exercised for these differences. The results also indicated that prolonged daily practice (>4 hours), playing chords forcefully, eagerness about practice, and nervous traits were found to contribute to the development of PRMDs in these pianists. Hand size was, on the other hand, not a significant risk factor of PRMDs.

Distinction between Dolus and Culpa with reference to Arson in Zakon Sudnyj LJudem, the Vinodol Law and the Statute of Senj

De Jure ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Daniel Haman ◽  
◽  
◽  
Keyword(s):  
Criminal Law ◽  
The Other ◽  
Legal Documents ◽  
The Third ◽  
Other Hand ◽  
Criminal Offenses ◽  
The World ◽  
The Difference ◽  
Different Levels ◽  
Better Than

The difference between intent (dolus) and negligence (culpa) was rarely emphasized in codified medieval laws and regulations. When compared to the legal statements related to intent, negligence was mentioned even more rarely. However, there are some laws that distinguished between the two concepts in terms of some specific crimes, such as arson. This paper draws attention to three medieval Slavic legal documents – the Zakon Sudnyj LJudem (ZSLJ), the Vinodol Law and the Statute of Senj. They are compared with reference to regulations regarding arson, with the focus being on arson as a crime committed intentionally or out of negligence. The ZSLJ as the oldest known Slavic law in the world shows some similarities with other medieval Slavic legal codes, especially in the field of criminal law, since most of the ZSLJ’s articles are related to criminal law. On the other hand, the Vinodol Law is the oldest preserved Croatian law and it is among the oldest Slavic codes in the world. It was written in 1288 in the Croatian Glagolitic script and in the Croatian Chakavian dialect. The third document – the Statute of Senj – regulated legal matters in the Croatian littoral town of Senj. It was written in 1388 – exactly a century after the Vinodol Law was proclaimed. When comparing the Vinodol Law and the Statute of Senj with the Zakon Sudnyj LJudem, there are clear differences and similarities, particularly in the field of criminal law. Within the framework of criminal offenses, the act of arson is important for making a distinction between intent and negligence. While the ZSLJ regulates different levels of guilt, the Vinodol Law makes no difference between dolus and culpa. On the other hand, the Statute of Senj strictly refers to negligence as a punishable crime. Even though the ZSLJ is almost half a millennium older than the Statute of Senj and around 400 years older than the Vinodol Law, this paper proves that the ZSLJ defines the guilt and the punishment for arson much better than the other two laws.

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