MULTIAXIAL DEFORMATION OF POLYMER NETWORKS

We have developed a detailed molecular model for describing the response of a polymer network to multiaxial deformation. The approach allows one to explicitly calculate the strain energy density function W and its dependence on the strain invariants I. The results correctly describe the peculiar behavior of the strain energy derivatives observed experimentally at very low deformation and at high strains. The strong dependence of those derivatives on strain is attributed to slippage of molecular chains through entanglements. Our model predictions also clearly demonstrate the lack of physical meaning associated with the phenomenological Mooney-Rivlin equation.