Thermoelasticity of networks in swelling equilibrium

Abstract

Abstract A theoretical analysis of the thermoelastic behavior of polymeric networks in swelling equilibrium with excess diluent, using both the kinetic theory of elasticity and the Flory‐Huggins theory of mixing, is presented. Our calculations are restricted to the special case of diluents composed of a single constituent. The results are used to obtain the ratio of the energy component of the force f e to the total force f of rubber networks swollen in excess n ‐decane, and we find f e / f to be 0.17, which compares favorably with the value 0.18 reported for the unswollen network. Furthermore, f e / f is independent of elongation, in accordance with theory. The kinetic theory of elasticity is reasonably well obeyed in this highly swollen system although there remains a small contribution to the force from the C 2 term of the Mooney‐Rivlin phenomenological elasticity equation. It is not believed that this has an appreciable effect on f e / f .