Fibrous Structure Formation in Cold-Drawing of Polyethylene

Abstract

Rods of spherulitic, linear polyethylene were cold-drawn at 60 and 100°C and the morphology of the drawn material, particularly the necked portion, was characterized by light and electron microscopy and by wide- and small-angle x-ray scattering. The drawing proceeded by neck formation and propagation at a draw ratio of 10. Further extension or creep beyond the neck produced draw ratios up to 20. Neck formation was characterized by spherulites deforming essentially in concert with the macroscopic deformation, becoming elongated and oriented and, thereby, defining a gross fibrous structure. Very early in the process of neck formation, small disruptions appeared within the spherulites. Similar to crazes in amorphous materials, these disruptions measured a few microns long, perpendicular to the direction of deformation, and a fraction of a micron thick. The disruptions increased in size and number as drawing progressed, dominated the structure at the higher draw ratios, and oriented to define a fine, fibrillar structure. These observations are contrasted with the rather different results obtained in an earlier, similar study of the cold-drawing of nylon 66.