Relationships between Stress, Strain, and Molecular Constitution of Polymer Networks. Comparison of Theory with Experiments

Abstract

The theory recast in the preceding paper accounts for the relationship of the equilibrium stress to strain for elastomeric networks within probable limits of experimental error throughout the range of deformation accessible to experiment, including biaxial extension, pure shear, and torsion as well as simple elongation and compression. Effects of dilation by swelling on the stress-strain relationship are well reproduced by the same set of parameters: the reduced force [f*ph] for the equivalent phantom network, and κ and ξ that characterize the local constraints on fluctuations of junctions and their dependence on strain. Two of these three parameters appear to be related by κ[f*ph]½ = const, as follows from the premise that κ should depend on the degree of interpenetration in the network. Values of [f*Ph] deduced from elastic and swelling measurements agree approximately with “chemically” determined reduced forces given by ξkT/V0. It follows that one of the parameters is determinable independently and that discrete (“trapped”) entanglements do not contribute appreciably to the stress. © 1982, American Chemical Society. All rights reserved.