CHARACTERISTICS OF SOLID-STATE EXTRUDED POLYETHYLENE.

This paper describes the properties of solid-state extruded polyethylene as a function of two primary processing variables, extrusion temperature, and area reduction. The polymer was extruded in sheet form, giving a material having an orthotropic mode of orientation. Property data are presented for melting temperature and heat of fusion; sonic modulus, yield stress, and elongation at fracture; small-angle x-ray scattering; optical absorption coefficient; and morphology for material etched by ion bombardment at liquid nitrogen temperature. It is found that over the temperature range of about 90-120 degree C, where polyethylene can be successfully extruded to large area reductions, many properties of the extrudates show a surprisingly small dependence on extrusion temperature. A notable exception to this behavior is the elastic modulus, which increases significantly with increasing extrusion temperatures. In contrast to extrusion temperature, area reduction is found to have a major effect on nearly all properties of solid-state extruded polyethylene.