Stress–strain behavior in polymer networks containing nonlocalized junctions

Abstract

Two models of entanglement interaction in polymer networks are examined. One is based on Edwards’ principle of topological classification, the other on interstrand links which are free to slip along the strand contours. Relationships between stress and strain in simple elongation are developed for networks which contain such elements as well as permanent crosslinks. In each case departures from neo‐Hookean behavior are found. The apparent modulus decreases with strain in uniaxial tension and remains approximately constant in uniaxial compression as observed in real networks. If the network is expanded, such as would occur through addition of a swelling solvent, the departures from neo‐Hookean behavior become smaller, again as observed experimentally. It thus appears that chain entanglements, portrayed here by two different nonlocalized junction models, may account for many of the differences in behavior between real networks and predictions of the phantom network theories.