Abstract
The equation of rubber elasticity proposed by the authors on the basis of the average network chain principle is applicable to explanation of uniaxial stress-strain behavior of rubber vulcanizates at large defor-mation for both the extension and the retraction curve of hysteresis cycle.But the plotted line is usually observed to deviate some what from a straight line at the point of small deformation region.The suthors considered this deviation as due to the internal viscosity of rubber vulcanizates and carried out to analyzed this problem molecularly by means of the three element viscoelastic and the pseudo crosslink network model. As a result of the analysis by means of the three element viscoelastic model, the parameter b or b which is introduced in the presented equation as a correction term is recognized as a value depending on the internal viscosity coefficient of vulcanized rubber and the strain rate of deformation. These dependencies were confirmed experimentally.
The correction terms b and b were also recognized experimentally to be proportional with the C2 term of the Mooney-Rivlin plot.
Then, the molecular meaning of the C2 term became more definite.
These experimental tendencies were also recognized in the case of a higher oil extended SBR vulcanizate. On the other hand, the difference between the values of b and b, and thixotropical properties as an example of hysteresis phenomenon cannot be explained by means of the viscoelastic model.
Then, the authors assumed an entanglement of network chain due to the intermolecular force as the secondary crosslink, and analyzed its change kinetically and could successfully explain the hysteresis phenomenon.
