Estimation, from Swelling, of the Structural Contribution of Chemical Reactions to the Vulcanization of Natural Rubber. Part III. Restricted Method

1964 ◽  
Vol 37 (2) ◽  
pp. 576-582 ◽  
Author(s):  
R. M. Russell ◽  
D. A. Smith ◽  
G. N. Welding
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Volume Fraction ◽  
Direct Method ◽  
Previous Method ◽  
Equilibrium Volume ◽  
Rubber Part ◽  
Structural Contribution ◽  
Large Correction ◽  
Equilibrium Volume Fraction

Abstract A method is described whereby the structural contribution of vulcanizing reactions may be estimated graphically from measurements of the equilibrium volume fraction of rubber in a vulcanizate swollen in n-decanc at 25.0°. Use is made of the data of Moore and Watson represented in the form of a relation between (ρMc−1)vulc and υτ. The method is applicable with technically important vulcanizing systems for which no direct method of estimation is available, and is simpler than the previous method (Part I). The method is limited to natural rubber of fixed primary molecular weight, but the limitation avoids a large correction for free ends of chains. Suitable experimental techniques are described.

Estimation, from Swelling, of the Structural Contribution of Chemical Reactions to the Vulcanization of Natural Rubber. Part I. General Method

1964 ◽  
Vol 37 (2) ◽  
pp. 563-570 ◽  
Author(s):  
Bryan Ellis ◽  
G. N. Welding
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Chemical Reactions ◽  
Network Structure ◽  
Reference Data ◽  
Direct Method ◽  
High Elasticity ◽  
Rubber Part ◽  
Structural Contribution ◽  
General Method

Abstract A procedure is described for estimating indirectly the contribution of vulcanization reactions to the build-up of network structure. This method is useful with technically important vulcanizing systems for which no direct method of estimation has been found. Errors of the theory of high elasticity are avoided by using published results, such as those of Moore and Watson of direct chemical estimates obtained with a special vulcanizing system that is chemically well understood. Reliance on the theories of end correction and swelling is also avoided by using published experimental relations. The method is applicable to any linear primary polymer of arbitrary molecular weight and any suitable swelling liquid, for which the required reference data have been obtained.

Estimation, from Swelling, of the Structural Contribution of Chemical Reactions to the Vulcanization of Natural Rubber. Part II. Estimation of Equilibrium Degree of Swelling

1964 ◽  
Vol 37 (2) ◽  
pp. 571-575 ◽  
Author(s):  
Bryan Ellis ◽  
G. N. Welding
Keyword(s):  
Natural Rubber ◽  
Chemical Reactions ◽  
Volume Fraction ◽  
Equilibrium Degree ◽  
Degree Of Swelling ◽  
Rubber Part ◽  
Structural Contribution

Abstract An investigation has been made of the measurement of degree of swelling of vulcanizates and the estimation of υτ, the volume fraction of polymer in a vulcanizate swollen to equilibrium. Methods have been established for dealing with a volatile swelling liquid, allowing for small percentages of nonpolymer in the vulcanizates, testing for diffusion equilibrium and correcting for swelling increment. The resulting values of υτ are suitable for use as described in the preceding Part I.

Elastic Heterophase Domains in Ferroelectric Epitaxial Films

2011 ◽  
Vol 1369 ◽  
Author(s):  
A. L. Roytburd ◽  
J. Ouyang ◽  
B. M. Boyerinas ◽  
H. A. Bruck ◽  
J. Slutsker ◽  
...  
Keyword(s):  
Experimental Data ◽  
Piezoelectric Properties ◽  
Volume Fraction ◽  
Epitaxial Films ◽  
Ferroelectric Films ◽  
Equilibrium Volume ◽  
Electromechanical Responses ◽  
Film Substrate ◽  
Equilibrium Volume Fraction ◽  
Good Agreement

ABSTRACTA heterophase polydomain structure has been recently discovered in BiFeO3 epitaxial ferroelectric films, which provides large electromechanical responses. In this work, the formation of such a microstructure is explained by theory of elastic domains. The thermodynamics of the heterophase polydomain microstructure is analyzed to predict the equilibrium volume fraction of domains at different film-substrate lattice misfits. Extrinsic mechanical and piezoelectric properties are discussed for the heterophase polydomains. It is shown that an applied electric field, which increases electrostatic interaction between domains, may lead to dramatic increase of piezo response. The results of this work are in good agreement with experimental data for BiFeO3.

The Dispersion of Carbon Black in Rubber Part IV. The Kinetics of Carbon Black Dispersion in Various Polymers

1994 ◽  
Vol 67 (2) ◽  
pp. 237-251 ◽  
Author(s):  
A. Y. Coran ◽  
F. Ignatz-Hoover ◽  
P. C. Smakula
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Natural Rubber ◽  
Kinetic Parameters ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Rapid Technique ◽  
Rubber Part ◽  
Kinetics Of ◽  
Carbon Black Dispersion

Abstract A rapid technique for evaluating the rate and state of dispersion of carbon black in natural rubber has been extended to study the dispersion of carbon black in various polymers. The technique measures the extent and rate of dispersion of the black in the rubber. The kinetics of dispersion was characterized for a variety of polymers (e.g. SBR, EPDM, IR, IIR, BR and NR). Kinetic parameters were correlated with molecular weight and molecular weight distribution.

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.

Effect and Detection of Loose Chain Ends in Crosslinked Polyurethane Elastomers

1971 ◽  
Vol 44 (1) ◽  
pp. 152-165 ◽  
Author(s):  
A. E. Oberth
Keyword(s):  
Crosslink Density ◽  
Volume Fraction ◽  
Present Theory ◽  
Swelling Ratio ◽  
Polyurethane Elastomers ◽  
Equilibrium Volume ◽  
Equilibrium Swelling ◽  
Volume Swelling

Abstract The effect of loose chain ends on tensile properties and equilibrium swelling of crosslinked polyurethane rubbers is studied. As in plasticized elastomers, tensile strength and elastic modulus are reduced approximately by a factor (1−νE,P)2, where νE,P is the volume fraction of loose chain ends, plasticizer, or both. This effect is much larger than predicted by present theory. Also the equilibrium volume swelling ratio, V0/V, of rubbers having terminal chains or an equal volume of plasticizer is the same, provided they do not differ in crosslink density. However, the volume fraction of “network rubber” in the equilibrium swollen specimen, ν2, differs owing to the non-extractability of terminal chains. On this basis a method is proposed which allows experimental determination of the volume fraction of loose ends. Elastomers abounding in loose chain ends show markedly less long term stress relaxation. This effect is not clearly understood but is useful to detect the presence of non load-bearing network.

Relation between Molecular Weights and Physical Properties of Rubber Fractions

1941 ◽  
Vol 14 (3) ◽  
pp. 580-589 ◽  
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Physical Properties ◽  
High Molecular Weight ◽  
Elastic Properties ◽  
Elastic Material ◽  
Experimental Results ◽  
Molecular Weights ◽  
High Elasticity ◽  
Latex Rubber

Abstract As high elasticity is a property possessed only by substances of high molecular weight, it is of interest to enquire into the relation between the elastic properties of a highly elastic material such as rubber and its molecular weight. An investigation on these lines has been made possible through the work of Bloomfield and Farmer, who have succeeded in separating natural rubber into fractions having different average molecular weights. The more important physical properties of these fractions have been examined with the object of determining which of the properties are dependent on molecular weight and which are not. Fairly extensive observations were made on the fractions from latex rubber referred to as Nos. 2, 3 and 4 by Bloomfield and Farmer, and some less extensive observations were carried out on the less oxygenated portion of fraction No. 1 obtained from crepe rubber (called hereafter 1b) . Before considering these experimental results, and their relation to the molecular weights of the fractions, it will be necessary to refer briefly to the methods used for the molecular-weight determinations, and to discuss the significance of the figures obtained.

Chemical Depolymerisation of Natural Rubber in Biphasic Medium

2014 ◽  
Vol 1024 ◽  
pp. 193-196
Author(s):  
Ibrahim Suhawati ◽  
Asrul Mustafa
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Chemical Structure ◽  
Inner Core ◽  
Particle Surface ◽  
Natural Rubber Latex ◽  
Carbonyl Groups ◽  
Latex Particles ◽  
Liquid Natural Rubber ◽  
Biphasic Medium

The molecular weight of natural rubber (NR) can be reduced via depolymerization reaction to produce liquid natural rubber (LNR) with a molecular weight less than 50 000 g/mol. In the reaction, hydrogen peroxide and sodium nitrite were added to natural rubber latex to initiate a redox type reaction which then breaks the NR chain. Low permeation of reagents into latex particles allows the degradation to occur greater at the latex particle surface relative to the inner core contributes to high molecular weight distribution (MWD) or polydispersity of the LNR obtained. In this recent works, the reaction was carried out in a biphasic medium consisting of water and toluene phases. Toluene swells latex particles as indicated by the SEM micrographs showing changes in the size of latex particles. This occurrence is suggested to increase the influx of reagents into the latex particles. Consequently, with higher permeation of reagents into the latex particles resulted in the decrease of molecular weight and lower polydispersity of the LNR obtained. Chemical structure analysize showed that the LNRs obtained were attached with hydroxyl and carbonyl groups.

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