ANALYSIS OF STRESS-STRAIN CURVE OF POLYETHYLENE FILMS BY TODA-LATTICE MODEL

Stress-strain curves of high density- and linear low density-polyethylenes and their blend films were analyzed by Toda-lattice model which has asymmetric interaction potential. Parameters in Toda-lattice model were experimentally determined from Young's modulus and Gruneisen parameter. Young's modulus was estimated from the initial slope of stress-strain curves, and Gruneisen parameter from the initial slope of ultrasonic velocity-strain curves. Using the parameters, we obtained the theoretical stress-strain curves at different temperatures for all the films. For all the films, the theoretical stress-strain curve was in good agreement with the experimental one except in the yielding region. Thus, nonlinear nature of polyethylene films can be ascribed mainly to the asymmetry of the interaction potential curve.