INTRINSIC CHAIN STRESS MODEL FOR THE MOONEY EFFECT IN SWOLLEN NETWORKS

The concept of the axial force exerted by a given chain in a network loses its clear physical significance in the presence of interchain noncovalent interactions because the chain is subject to forces along its length as well as at its ends. The concept of intrinsic chain stress is a generalization of the concept of chain force which retains its significance in the presence of noncovalent interactions and reduces to the concept of chain force in their absence. In a recent paper we have applied the intrinsic chain stress concept to an idealized network model and have shown that it implies a nonhydrostatic stress contribution by the noncovalent interactions that varies with deformation because of the change in chain orientation. Furthermore, it was shown that, as a consequence, the stress-strain relation in a simple extension of this model exhibited the strain-softening or Mooney effect characteristic of dry rubberlike solids. In this paper, the analysis is extended to swollen networks and it is shown that the model predicts a decrease in the magnitude of the Mooney effect with a degree of swelling that is characteristic of real systems. © 1990, American Chemical Society. All rights reserved.