The Interaction between Rubber and Liquids. VII. The Heats and Entropies of Dilution of Natural Rubber by Various Liquids

1946 ◽  
Vol 19 (1) ◽  
pp. 1-13
Author(s):  
J. Ferry ◽  
Geoffrey Gee ◽  
L. R. G. Treloar
Keyword(s):  
Statistical Theory ◽  
Vapor Pressure ◽  
Natural Rubber ◽  
Methyl Alcohol ◽  
Research Association ◽  
Free Energies ◽  
Calorimetric Measurements ◽  
Heats Of Mixing ◽  
Heats Of Dilution ◽  
Fundamental Research

Abstract Calorimetric measurements of the heats of mixing of seven liquids with dihydromyrcene are used to estimate the heats of dilution of rubber by these liquids. Combining the results with free energies calculated from vapor pressure gives entropies of dilution which show significant deviations from the present statistical theory. A thermodynamic study of rubber + methyl alcohol shows similar but larger deviations. This work forms part of a program of fundamental research on rubber undertaken by the Board of the British Rubber Producers' Research Association.

The Interaction between Rubber and Liquids. VI. Swelling and Solubility in Mixed Liquids

1945 ◽  
Vol 18 (2) ◽  
pp. 241-255 ◽  
Author(s):  
Geoffrey Gee
Keyword(s):  
Binary Mixtures ◽  
Cohesive Energy ◽  
Ternary Mixture ◽  
Heat Of Mixing ◽  
Research Association ◽  
Linear Polymers ◽  
Heats Of Mixing ◽  
Fundamental Research ◽  
Solvent Properties ◽  
Solvent Power

Abstract The equations derived in the previous paper for the osmotic equilibrium between a ternary mixture of polymer + two liquids and a mixture of the two liquids are applied to the swelling of cross-linked polymers in mixed liquids and to the solubility of linear polymers in mixed liquids. A mixed liquid has solvent properties intermediate between those of its components only when these mix ideally. The larger the heat of mixing of the liquids, the greater is the solvent power of the mixture relative to those of the components. This conclusion forms the basis of an explanation of the enhanced swelling of rubbers in pairs of dissimilar liquids and of the fact that a mixture of two nonsolvents may be a solvent over a certain range of concentration. Experimental results are given for the swelling of vulcanized rubbers and the critical solubility limits of unvulcanized rubbers. It is shown that these can be explained qualitatively from the cohesive energy densities of the three components, and semiquantitatively from the measured heats of mixing of the three binary mixtures. The work described in these two papers forms a part of the program of fundamental research on rubber undertaken by the Board of the British Rubber Producers' Research Association.

The Interaction between Rubber and Liquids. 1. A Thermodynamical Study of the System Rubber-Benzene

1943 ◽  
Vol 16 (1) ◽  
pp. 89-110
Author(s):  
G. Gee ◽  
L. R. G. Treloar
Keyword(s):  
Vapor Pressure ◽  
Solution Temperature ◽  
Free Energies ◽  
Pressure Data ◽  
Heat Of Solution ◽  
Dilute Solutions ◽  
Heat Of Dilution ◽  
Vapor Pressure Data ◽  
Heats Of Dilution

Abstract Equations are developed relating the thermodynamic properties of a mixture of rubber + liquid with the vapor pressure of the liquid above the mixture. Experimental methods are described for the determination of vapor pressure over the whole range of composition of the mixture. By the use of four different methods, it was possible to measure relative vapor pressure lowerings Apo/po° from 2×10−6 to 0.997. Complete vapor pressure data are given for rubber-benzene mixtures at 25° C, together with the calculated Gibbs' free energies of dilution and solution. Temperature coefficient measurements at a number of concentrations are employed to calculate heats of dilution, and these are interpplated by a modified form of an equation due to Langmuir. In this way the heats of dilution and solution are also obtained over the whole range of composition. Combining the heat and free energy data gives the entropies of dilution and solution. The entropy of dilution is approximately twice the heat of dilution over a wide concentration range and, except in dilute solutions (< 5% rubber), both are independent of the molecular weight of the rubber. The entropy of dilution is very much larger than its ideal value, and can be approximately represented by an equation of Flory, though there are significant discrepancies in the region of dilute solutions. The molar heat of solution of rubber is so large that the miscibility of rubber and benzene can be explained only by the anomalously large entropy of solution.

Stress Optical Behavior of Rubber Networks at Large Deformations

1966 ◽  
Vol 39 (5) ◽  
pp. 1436-1450
Author(s):  
K. J. Smith ◽  
D. Puett
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Statistical Theory ◽  
Natural Rubber ◽  
Large Deformations ◽  
Strong Support ◽  
Theoretical Development ◽  
Statistical Parameters ◽  
Strain Behavior ◽  
Optical Behavior

Abstract The birefringence of natural rubber networks at large deformations has been investigated experimentally and compared with the simultaneously determined stress—strain behavior. Our data is analyzed using a statistical theory of flexibly jointed chains, derived herein, which is believed to be more significant for the particular range of deformation used than the theories of Treloar and of Kuhn and Grün. In addition, the experimental data of Saunders is commented on in light of our theoretical development. We find that for network extensions exceeding those of the Gaussian region there is little correlation between the observed and theoretical behavior of the stress and birefringence (based upon the theory of flexibly jointed chains) and this lack of agreement is attributed to the fact that the statistical parameters needed for the description of the optical chain properties differ in magnitude from those required for the mechanical properties. Furthermore, by considering the points of incipient crystallization the strain behavior of the stress-optical coefficient is highly indicative of nonGaussian behavior rather than crystallization, and therefore yields strong support for the position that nonGaussian behavior does exist in rubber networks.

scholarly journals Notizen:Mischungsenthalpien beim flüssigen System Wasser + Essigsäure / Heats of Mixing for the Liquid System Water + Acetic Acid

1972 ◽  
Vol 27 (10) ◽  
pp. 1527-1529 ◽  
Author(s):  
R. Haase ◽  
P. Steinmetz ◽  
K.-H. Dücker
Keyword(s):  
Acetic Acid ◽  
Power Series ◽  
Liquid System ◽  
Heat Of Mixing ◽  
Pure Liquid ◽  
Calorimetric Measurements ◽  
Heats Of Mixing ◽  
Free Parameters ◽  
C 30 ◽  
System Water

Calorimetric measurements of the heats of mixing for the liquid system water+acetic acid at 17 °C, 20 °C, 25 °C, 30 °C, 40 °C, and 50 °C show that there is a change of sign in the function H̅E(x), where H̅E denotes the molar heat of mixing and x the mole fraction of acetic acid. The process of mixing the pure liquid components is weakly exothermic for low acid concentrations, but strongly endothermic for high acid concentrations. The function H̅E can be approximately represented by the usual power series with respect to x, five free parameters at each temperature being necessary.

The Statistical Length of Long-Chain Molecules

1946 ◽  
Vol 19 (4) ◽  
pp. 1002-1008 ◽  
Author(s):  
L. R. G. Treloar
Keyword(s):  
Independent Method ◽  
Distribution Functions ◽  
Research Association ◽  
Chain Molecules ◽  
Isoprene Unit ◽  
Fundamental Research ◽  
A Chain ◽  
Long Chain

Abstract A formula is derived for the complete function representing the probability of a given distance between the ends of a chain of universally jointed equal links. The formula is computed for chains of 25 and 100 links. The distribution functions derived from this formula are compared with those previously worked out by an independent method for polyisoprene and paraffin chains. It is shown that the polyisoprene chain is statistically equivalent to a randomly-jointed chain of length corresponding to 1.42 links per isoprene unit. This work forms part of a program of fundamental research on rubber undertaken by the Board of the British Rubber Producers' Research Association.

Mastication and Compounding of Natural Rubber in an Oxygen-Free Atmosphere

1950 ◽  
Vol 23 (3) ◽  
pp. 537-552 ◽  
Author(s):  
C. M. Blow ◽  
R. I. Wood
Keyword(s):  
Natural Rubber ◽  
Physical Properties ◽  
Research Association ◽  
High Modulus ◽  
Free Atmosphere ◽  
Wide Range ◽  
Viscosity Changes

Abstract Confirmation has been obtained that raw rubber when masticated in the absence of oxygen undergoes only a limited amount of breakdown; and it has been shown that two of the better known socalled “peptizers” or chemical plasticizers of rubber, viz., mercaptobenzothiazole and o-o′-dibenzamidodiphenyl disulfide, require oxygen to be effective. A range of pure-gum rubbers has been compounded under nitrogen, and the physical properties after vulcanization compared with corresponding air-compounded rubbers. Some types of acceleration give vulcanizates whose physical properties are very sensitive to changes in the viscosity of the unvulcanized stock, decrease in viscosity giving decreased modulus. Other types of acceleration, notably “boosted” combinations which give high modulus vulcanization, are insensitive to stock viscosity changes over a wide range. This work forms part of a program of research undertaken by the Board of the British Rubber Producers' Research Association.

Some Properties of Vulcanized Rubber under Strain. Degree of Crystallization as Calculated from Temperature Coefficient of Elastic Tension

1951 ◽  
Vol 24 (4) ◽  
pp. 845-852
Author(s):  
B. B. S. T. Boonstra
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Thermodynamic Calculation ◽  
Energy Change ◽  
Thermodynamic Evaluation ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Calorimetric Measurements ◽  
Degree Of Crystallization

Abstract To elucidate the crystallization phenomenon in natural rubber and to investigate the applicability of thermodynamic calculation to measurements of the elastic tension as a function of temperature, it seemed necessary to check whether crystallization determined by x-ray analysis (and combined with density) lined up reasonably with the percentage of crystallization computed from the energy change found by applying thermodynamics to stretched vulcanized rubber) on stretching. Calorimetric measurements were desirable, as no accurate figures are available for the heat of crystallization of rubber crystallites. The heat of melting of rubber crystallites was determined to about 66 joules per gram, which is of the same order as that of isoprene. The spreading in the results was large; the determination is based on the degree of crystallization found by x-ray analysis of raw rubber. The heat of crystallization on stretching, found by thermodynamic evaluation of the elastic tension and its temperature coefficient, is combined with the value of 66 joules for the heat of melting of the pure rubber crystallites. The degree of crystallization calculated in this way agrees reasonably well with the direct x-ray measurements of Goppel and Arlman. Crystallization as determined by x-ray analysis and that responsible for the energy change on stretching are much the same. This also means that thermodynamic evaluation of the change of stress with temperature is justified if pufficient relaxation of stress has taken place.

Some Thermodynamic Properties of the Dimethylsulfoxide–Water and Propylene Carbonate–Water Systems at 25 °C

1974 ◽  
Vol 52 (5) ◽  
pp. 718-722 ◽  
Author(s):  
S. Y. Lam ◽  
R. L. Benoit
Keyword(s):  
Thermodynamic Properties ◽  
Vapor Pressure ◽  
Propylene Carbonate ◽  
Water Systems ◽  
Pressure Measurements ◽  
Free Energies ◽  
Carbonate Water ◽  
Enthalpies Of Mixing ◽  
Molar Excess ◽  
Vapor Pressure Measurements

Molar excess free energies of the systems dimethylsulfoxide–water and propylene carbonate–water have been calculated from static vapor pressure measurements at 25 °C. Enthalpies of mixing at low water concentrations have also been determined. Possible association interactions in these systems are discussed.

Acid Ionizations of Nitroalkanes in Aqueous Solution

1973 ◽  
Vol 51 (12) ◽  
pp. 1941-1944 ◽  
Author(s):  
Takeki Matsui ◽  
Loren G. Hepler
Keyword(s):  
Aqueous Solution ◽  
Carboxylic Acids ◽  
Equilibrium Constants ◽  
Free Energies ◽  
Methyl Substitution ◽  
Calorimetric Measurements ◽  
Acid Ionizations

Calorimetric measurements have led to ΔH0 values for ionization of nitromethane, nitroethane, 1-nitropropane, and 2-nitropropane in aqueous solution at 298°K. Combinations of these enthalpies with free energies from equilibrium constants for ionization have led to ΔS0 values for the ionization reactions. It is noted that the trend toward decreasing pK with methyl substitution in nitroalkanes is unusual compared to phenols and carboxylic acids. Similarly, correlations of ΔS0 with ΔG0 and ΔH0 are different for nitroalkanes than for other acids.

scholarly journals Studies on the Transport of Aromatic Solvents through Filled Natural Rubber

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Isaac O. Igwe ◽  
Obumneme E. Ezeani
Keyword(s):  
Particle Size ◽  
Weight Gain ◽  
Natural Rubber ◽  
Activation Energies ◽  
Free Energies ◽  
Snail Shell ◽  
Aromatic Solvents ◽  
Benzene Toluene ◽  
Powder Content ◽  
Shell Powder

The transport of three aromatic solvents (benzene, toluene and xylene) through snail shell powder filled natural rubber was studied at 313, 333, and 353 K by conventional weight-gain experiments. The effects of snail shell powder content, particle size, nature of solvent, and temperature on the transport characteristics of natural rubber were determined. The estimated Arrhenius activation energies for the processes of sorption, diffusion, and permeation showed that the activation energies were highest in xylene at all the filler contents investigated. The calculated enthalpies, and entropies of sorption were all positive for the solvents investigated. Similarly, the change in the estimated free energies of sorption were all positive; an indication of the non-spontaneity of the solubility of snail shell powder filled natural rubber in the aromatic solvents at 313 k.

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