Abstract
The relation between the properties and the structure of two sorts of rubber vulcanizates was studied.
Here, two sorts of rubber vulcanizates are that cured by a normal method which is called DC-sample and that cured by a special method, or a solution cured one which is called SC-sample.
The latter sample is considered to have less entanglements than the former one, and then this seems to be an approximate phantom network rubber vulcanizate.
The difference between both samples was remarkably observed by following measurements (a physical stress relaxation in N2 at room temperature, a stress-strain behavior, X-ray diffraction patterns, a birefringence-extension experiment, Mooney-Rivlin plots, and a chemical stress relaxation).
It is known that the parameter h in eq. (1) is unity for a phantom network rubber, while h is zero for an affine network rubber.
G=(n-hμ)κT(1)
Here, G: shear modulus, n: the number of main chains between crosslinks per unit volume (crosslinking density), μ: the number of crosslinks, κ: Boltzmann constant, T: absolute temperature, h: an index of the degree of fluctuation of crosslink site.
For DC-sample, h was found to be approximately a half. This indicates that the degree of fluctuation is approximately medium between affine deformation and phantom deformation for DC-sample.
The simple relation f(t)/f(0) (relative stress)=n(t)/n(0) (relative network chain density) was established for SC-sample, while the complicated relation was found for DC-sample.
