Characterization of elastomeric network structures using the effects of swelling on stress-strain isotherms and the extents of swelling at thermodynamic equilibrium

Summary

Swelling has long been used in the study of elastomeric networks. In the case of stress-strain measurements on swollen networks, the most important observation was the decrease of the Mooney constant 2C₂, which is widely used to represent the magnitude of the departure of an observed stress-strain isotherm from that predicted by the simplest molecular theories. Swelling equilibrium data were generally analysed by the Flory-Rehner equation for affine networks simply to obtain a measure of the degree of cross-linking. The advent of model networks whose structures are well known and of a new theory due to Flory constitute great improvements for the study of rubberlike elasticity. In this, new context, swelling can be used to obtain additional important molecular information through both uniaxial extension of swollen samples and swelling equilibrium. In particular, the relation between the main parameter κ characterizing the local constraints on junction fluctuations in the Flory theory, the extent of swelling, and the molecular weight between cross-links can be probed.