THERMAL CONTRACTION OF DRAWN POLYETHYLENE FILM - I - AN EMPIRICAL-EQUATION FOR TEMPERATURE-DEPENDENCE OF THERMAL-STRESS

Thermal stress and strain were measured during heating from 30 degrees C to 100 degrees C for drawn polyethylene films of various draw tempe ratures and ratios. Behavior of thermal strain was classified into thr ee types, and discussed in terms of structural change in polymer chain s during the drawing process. The Arrhenius plot was constructed for t he temperature dependence of thermal strain, and an inflection point w as observed in the plot over the temperature range studied. Temperatur e dependence of thermal stress showed the maximum value, which increas ed with draw ratio. An empirical equation for the behavior of thermal stress is derived using Boltzmann's superposition principle. Good agre ement was found between calculated and measured values of thermal stre ss.