Experiments on the Elasticity of Dry and Swollen Networks: Implications for the Frenkel—Flory-Rehner Hypothesis

Torque and normal force measurements have been performed on cylindrical samples of dicumyl peroxide cross-linked natural rubber with the purpose of obtaining the first derivative of the (elastic) strain energy density function of the dry rubber. Similar rubber samples were swollen to equilibrium in different solvents and tested in uniaxial compression in the swollen state. We find that the dry-state properties can be used to predict the swollen-state properties by assuming, as did Frenkel, Flory, and Rehner, that the elasticity of the swollen network is unaltered by the presence of the solvent other than by (chain) deformation.