Abstract
Although many theoretical and experimental equations have been proposed with regard to the elasticity of vulcanized rubber, a complete equation which can explain the stress-strain behavior at larege deformation has not yet been obtained.According to the network theory of rubber elasticity, the stress f is related to the extension ratio a in simple extension according to
f=vkT (α-1/α2)
which was derived by the calculation based on Gaussian distribution of its end-to-end distances of the chain. So the equation is not applicable to large deformation experimentally as well as theoretically.For large deformation, James and Guth derived an equation involving an inverse Langevin's function as follows:
f=vkTαm/3 {L-1 (α/αm)-1/α3/2L-1 (1/√α.αm)}
This equation was examined by several authors and found to be valid for large deformation but not for small one.On the other hand, Mooney and Rivlin proposed the following equation by the calculation of stored energy in material.f=2 (c1+c2/α)(α-1/α2)
This equation was proposed for large deformation, but it appears to be applicable experimentally only to small deformation.
In the present paper, the authors propose the following equation by the calculation of the entropy change of a chain having an average chain distance and discuss the conformity of these equations based on the experimental data of Trealoar's one.
f=kT (αm/2·1+α/αm/1-α/αm-1/α2)
