Rubber elasticity on chemical relaxation

The applicability of the formula f ( t ) = n ( t ) RT (α − α −2 ) suggested by Tobolsky as the basis of chemorheology has been discussed. In this expression, f ( t ) is the stress after t hours, n ( t ) is the crosslinking density (mole/cc) after t hours, R is the gas constant, T is the absolute temperature, and α is the extension ratio. We have discussed the applicability of this formula, in another words, whether the degraded stress f ( t ) calculated from this formula would be consistent with the initial stress f t (0) of other polymer if the degraded crosslinking density values n ( t ) are equal to those of n t (0), the initial density values n (0) of other polymer. Natural rubber vulcanizates and SBR vulcanizates were used as samples in these experiments. Assuming n ( t ) = σ( t ) n (0), α( t ′) = 1, the applicability of the above formula was recognized from our experimental results.