CRYSTALLIZATION TEMPERATURE EFFECT ON THE SOLID-STATE RHEOLOGY OF A HIGH-DENSITY POLYETHYLENE UNDER COMPRESSION

The plane-strain compression test provides quantitative data on the po lymer rheology in homogeneous large deformation at constant strain-rat e, and on the friction shear stress between the film and the dies. Thi n HDPE films with a homogeneous morphology were formed by quenching or isothermal crystallization. The structure was modified by varying the crystallization temperature over a wide range: 118 degrees C less tha n or equal to T-c less than or equal to 130 degrees C. A mechanical mo del with a pressure-dependent rheology and two friction laws was teste d. The rheological parameters are different in tension and in compress ion. The occurrence of brittle fracture under compression depends on t he crystallization temperature, but the rheological parameters are alm ost independent of the crystallization conditions.