The localization model of rubber elasticity and the deformation of a network formed by cross-linking a strained melt

1988 ◽  
Vol 20 (3) ◽  
Author(s):  
RichardJ. Gaylord ◽  
ThomasE. Twardowski ◽  
JackF. Douglas
Keyword(s):  
Rubber Elasticity ◽  
Cross Linking ◽  
Localization Model

Entropically Influenced Reconstruction at the PBD-ox/Water Interface:  The Role of Physical Cross-Linking and Rubber Elasticity

2000 ◽  
Vol 33 (23) ◽  
pp. 8802-8812 ◽  
Author(s):  
Deborah H. Carey ◽  
Stephen J. Grunzinger ◽  
Gregory S. Ferguson
Keyword(s):  
Rubber Elasticity ◽  
Cross Linking ◽  
Water Interface

The Localization Model of Rubber Elasticity

2010 ◽  
Vol 291-292 (1) ◽  
pp. 230-238 ◽  
Author(s):  
Jack F. Douglas
Keyword(s):  
Rubber Elasticity ◽  
Localization Model

The ‘localization model’ of rubber elasticity: comparison with torsional data for natural rubber networks in the dry state

Polymer ◽  
1991 ◽  
Vol 32 (12) ◽  
pp. 2128-2134 ◽  
Author(s):  
Gregory B. McKenna ◽  
Jack F. Douglas ◽  
Kathleen M. Flynn ◽  
Yihong Chen
Keyword(s):  
Natural Rubber ◽  
Rubber Elasticity ◽  
Localization Model

THE FORMATION AND PROPERTIES OF THREE-DIMENSIONAL POLYMERS: III. THE EFFECT OF NETWORK STRUCTURE ON ELASTIC PROPERTIES

1949 ◽  
Vol 27b (2) ◽  
pp. 139-150 ◽  
Author(s):  
J. Bardwell ◽  
C. A. Winkler
Keyword(s):  
Molecular Weight ◽  
Statistical Mechanics ◽  
Elastic Properties ◽  
Network Structure ◽  
Three Dimensional ◽  
Butyl Rubber ◽  
Rubber Elasticity ◽  
Cross Linking

The tension exerted by stretched rubber at a given temperature and elongation is determined by the initial molecular weight and the concentration of cross-linkages. With the copolymer of butadiene and styrene (GR-S) the effect of molecular weight on elastic properties is identical with that found by Flory for butyl rubber and arises from the inactivity of terminal chains. When the molecular weight is fixed, the retractive force is approximately linear with the degree of cross-linking, in agreement with the statistical mechanics of rubber elasticity.

Dependence of Elastic Properties of Vulcanized Rubber on the Degree of Cross-Linking

1950 ◽  
Vol 23 (1) ◽  
pp. 9-26
Author(s):  
Paul J. Flory ◽  
Norman Rabjohn ◽  
Marcia C. Shaffer
Keyword(s):  
Statistical Theory ◽  
Network Structure ◽  
Short Circuit ◽  
Elastic Equilibrium ◽  
Butyl Rubber ◽  
Rubber Elasticity ◽  
Cross Linking ◽  
Substantial Part ◽  
Vulcanized Rubber ◽  
Low Degrees

Abstract The results reported above demonstrate a progressive increase in the force of retraction τ at fixed elongation with increase in the fraction p of the structural units which are cross-linked from ρ=0.10×10−2 to 3.0×10−2. Over this range, τ at 100 per cent elongation increases about thirteenfold. Swelling measurements indicate that the increase in τ with ρ continues over an additional tenfold range in ρ. Previous assertions that the modulus of elasticity of soft gum rubber vulcanizates depends largely on chain interaction and entanglements other than those imposed by the cross-linkages, and that the modulus is, therefore, not directly related to the degree of cross-linking, are without foundation. The statistical theory of rubber elasticity expresses the force of retraction as a function of the temperature, vulcanizate structure and elongation; no arbitrary constants are involved. The magnitudes of τ for α=2 are in remarkably close agreement with the predictions of the theory over most of the range in ρ. This fact is of the utmost significance in confirmation of the statistical theory of rubber elasticity and of the analysis of the network structure of vulcanized rubber. On the other hand, τ increases less rapidly with ρ than the direct proportionality prescribed by theory. Forces of retraction are higher than the theory predicts at low degrees of cross-linking, and an opposite deviation is observed for values of ρ greater than about 1×10−2. Previous observations on Butyl rubber, vulcanized to p values from about 0.16×10−2 to 0.28×10−2 indicated forces of retraction (for infinite molecular weight M) which exceed by about threefold those predicted from the theory. This deviation is decidedly larger than has been observed here in the same range for ρ. A substantial part of the discrepancy observed for Butyl rubber may have arisen from failure to secure elastic equilibrium, however. Deviations in the values of τ from theory probably originate largely from oversimplifications in the treatment of the network structure. Entanglements of the sort previously discussed tend to enhance the restraints imposed on the chains when the rubber is elongated. Their percentage effect should be greatest for low degrees of cross-linking, hence the observed τ values are higher than theory at low degrees of cross-linking. “Intramolecular” cross-linkages, yielding short-circuit structures contributing nothing to the elastic reaction of the network, should become increasingly important at higher degrees of cross linking. Such wastage of cross-linkages may account for the low values of τ obtained for higher ρ values.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Embedding Procedure for Water Swollen Samples

1970 ◽  
Vol 28 ◽  
pp. 504-505
Author(s):  
Ann M. Thomas ◽  
Virginia Shemeley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Exchange ◽  
Structural Changes ◽  
Cross Linking ◽  
Ion Exchange Resins ◽  
Transmission Electron ◽  
First Pass ◽  
Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

The Current Situation in Chemical Stabilization of Biological Materials

1972 ◽  
Vol 30 ◽  
pp. 132-133
Author(s):  
John H. Luft
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Molecular Level ◽  
Cross Linking ◽  
Chemical Stabilization ◽  
Specimen Preparation ◽  
Sufficient Condition ◽  
Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

Parathyroid gland before and after cisplatin treatment

1987 ◽  
Vol 45 ◽  
pp. 860-861
Author(s):  
S.K. Aggarwal ◽  
J.M. Fadool
Keyword(s):  
Parathyroid Gland ◽  
Wistar Rats ◽  
Antitumor Agent ◽  
The Body ◽  
Cross Linking ◽  
Limiting Factor ◽  
Hormonal Changes ◽  
Primary Mechanism ◽  
Before And After ◽  
Dna Strands

Cisplatin (CDDP) a potent antitumor agent suffers from severe toxic side effects with nephrotoxicity being the major dose-limiting factor, The primary mechanism of its action has been proposed to be through its cross-linking DNA strands. It has also been shown to inactivate various transport enzymes and induce hypocalcemia and hypomagnesemia that may be the underlying cause for some of its toxicities. The present is an effort to study its influence on the parathyroid gland for any hormonal changes that control calcium levels in the body.Male Swiss Wistar rats (Crl: (WI) BR) weighing 200-300 g and of 60 days in age were injected (ip) with cisplatin (7mg/kg in normal saline). The controls received saline injections only. The animals were injected (iv) with calcium (0.5 ml of 10% calcium gluconate/day) and were killed by decapitation on day 1 through 5. Trunk blood was collected in heparinized tubes.

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