DENSITY CHANGES ON DRAWING BY SOLID-STATE EXTRUSION OF HIGH-DENSITY POLYETHYLENE

This communication reports the density change during drawing by solid-state-extrusion for a large range of initial morphologies, varying from folded-chain to extended-chain crystals, of HDPE. Data are presented which show that the highest draw ratio achieved was 16 before observable fracture. Such high draw is not attainable by conventional tensile drawing - the highest previously reported is 8. Extrusion at 90 degree C produced the largest decrease density on draw yet reported, 1. 4%. The decrease is smaller, 0. 4-0. 7%, for extrusion draw temperatures (90 and 100 degree C) the final densities of extrudates remain lower than the undrawn extended-chain polyethylenes. The smaller decrease at the higher extrusion temperature suggests that 90-100 degree C is near the upper limit for deformation temperature to avoid significant annealing.