Push–pull extrusion: A new approach for the solid‐state deformation illustrated with high density polyethylene

Abstract

AbstractThe crystalline state deformation of high density polyethylene has been examined at an extrusion draw ratio of 30 over a range of temperatures and pressures. The experiments involve combined pushing (extrusion) and pulling through a conical die. The pressure dependence of the extrusion rate through conical dies is given by a logarithmic relation and the temperature dependence by an activation energy of ∼95 kcal/mole. An equation established for the total applied force linearly relates the pulling and extrusion pressure components and represents a force balance at the die entrance and exit. Steady‐state extrusion, with or without pulling, was feasible in a pressure range beyond which fractures occurred owing to strain rate and shear or tensile failure. Under some circumstances the extrusion rate was increased by ten times. The mechanical properties and mode of deformation were not affected by pull load and fibers with a tensile modulus of 55 GPa were produced at T < 110°C.