Internal Energy Contribution to the Elasticity of Natural Rubber

1969 ◽  
Vol 2 (4) ◽  
pp. 358-364 ◽  
Author(s):  
Mitchel Shen
Keyword(s):  
Natural Rubber ◽  
Internal Energy ◽  
Energy Contribution

Thermoelastic Behavior of Natural Rubber

1969 ◽  
Vol 42 (3) ◽  
pp. 835-849
Author(s):  
Mitchel C. Shen ◽  
Donald A. McQuarrie ◽  
Julius L. Jackson
Keyword(s):  
Statistical Theory ◽  
Natural Rubber ◽  
Temperature Coefficient ◽  
Internal Energy ◽  
Controlled Environment ◽  
Energy Contribution ◽  
Elongation Ratio ◽  
Chemical Effects ◽  
Nonequilibrium Conditions ◽  
Exact Derivation

Abstract Stress—temperature measurements of natural rubber were carried out up to the elongation ratio, α, of 2.0. An automatic stress relaxometer was constructed for this purpose which can be completely enclosed in a controlled environment. Experiments were so conducted as to minimnze possible chemical effects and nonequilibrium conditions. Relative internal energy contribution to stress, fe/f, is calculated as a function of α in terms of statistical and thermodynamic theories. Both of these yield similar results. It is shown that in the region of low strains (1.0<α<1.5),fe/f decreases rapidly with increasing α, but appears to remain constant at 1.5<α<2.0. This observation is not in agreement with the prediction of the current statistical theory of rubber elasticity, which stipulates that the energy effects are intramolecular and independent of deformation. Implications of these findings are discussed. It is suggested that perhaps at low strains the intermolecular interactions are large in comparison with intramolecular energies, but become relatively insignificant at higher elongation ratios. The temperature coefficient of unperturbed chain dimensions is also calculated from thermoelastic data. It is constant only in the region 1.5<α<2.0. Finally, a new, more exact derivation of the Elliott—Lippmann anisotropy factor in terms of the statistical theory is given in the Appendix.

Prediction of the internal energy contribution of polydimethylsiloxane during elongation

2012 ◽  
Vol 55 (11) ◽  
pp. 2433-2437
Author(s):  
SiMiao Wang ◽  
Juan Sun ◽  
XiaoZhen Yang
Keyword(s):  
Internal Energy ◽  
Energy Contribution

Internal Energy Contribution to the Elasticity of Natural Rubber

1970 ◽  
Vol 43 (2) ◽  
pp. 270-281 ◽  
Author(s):  
Mitchel Shen
Keyword(s):  
Natural Rubber ◽  
Elastic Stress ◽  
Tensile Elongation ◽  
Relative Energy ◽  
Rubber Elasticity ◽  
Energy Contribution ◽  
Constant Length ◽  
Shear Moduli ◽  
Energetic Stress ◽  
Apparent Strain

Abstract It has recently been noted by a number of workers that the relative energy contribution, fe/f, to the elastic stress of rubberlike materials appears to depend on the extension ratio at which thermoelastic measurements were carried out. This apparent strain dependence is in contradiction to the free energy additivity principle of the statistical theory of rubber elasticity. In this paper we resolve this problem by determining fe/f from the temperature coefficient of shear moduli. The shear moduli were not directly determined from measurements of shear, but calculated from tensile elongation data. This method circumvents the difficulty encountered in directly obtaining the relative energy contribution from stress—temperature data. Both constant length and constant stress thermoelastic measurements were used to obtain fe/f. A series of natural rubber samples, crosslinked in the presence of various amounts of n-hexadecane, were investigated. It is found that the relative energy contribution to the elasticity of natural rubber is 0.18. Changes in inter-molecular interactions, brought about by the incorporation of diluents, produce no variation in the value of fe/f. This observation supports the hypothesis that the energetic stress in rubber elasticity is wholly attributable to intrachain energies of the network chains.

Prediction of the internal energy contribution of polyethylene

2002 ◽  
Vol 47 (21) ◽  
pp. 1794-1796
Author(s):  
Juan Sun ◽  
Xiaozhen Yang
Keyword(s):  
Internal Energy ◽  
Energy Contribution
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