Deformation processes in polyethylene interpreted in terms of crystal plasticity

Abstract

The rolling texture of drawn polythene is interpreted in terms of slip and twinning processes characteristic of ordinary crystal plasticity in combination with the rubbery elasticity characteristic of macromolecular amorphous substances. The principal crystal plasticity elements operative are (100) [010] slip and (310) [130] and/or (110) [110] twinning. The observations appear to indicate that (110) [110] slip is a less easy mode of deformation than these, at least initially. Under more general deformation conditions, it appears that these modes predominate at small strain, tending to a texture with [010] aligned to the axis of extension, giving place to [001] slip processes, which align [001] and the molecular chains along the axis of extension when the strain is large. Under certain conditions a second crystalline phase also appears which in terms of general crystal plasticity would correspond to a martensitic type transformation and might arise through a regular sequence of stacking faults on {110} planes.