NON-LINEAR VARIABLE TEMPERATURE CREEP OF LOW-DENSITY POLYETHYLENE

Nonlinear creep of a thin-walled tube of low-density polyethylene in torsion during increasing and decreasing temperature is reported. This material was selected after verifying that its thermal expansion was stable. Results showed that creep was dependent on temperature history for both increasing and decreasing temperature. Nonlinear creep was described reasonably well by employing the Morland—Lee reduced time variable, together with a master creep curve. The master curve for a given stress was constructed from creep at different temperatures by horizontal shifts along the time axis. The temperature-history independence of creep during rising temperature previously reported for polyurethane is attributed to changes in moisture content. © 1978, The Society of Rheology. All rights reserved.