Lamellar morphologies in uniaxially-drawn banded spherulites of polyethylene

Abstract

A morphological study, using permanganic etching and with lamellar resolution, of the uniaxial drawing at 80°C of linear polyethylene containing banded spherulites has shown the response of the system to increasing draw ratios. Circular bands transform to increasingly eccentric ellipses to 30% extension but thereafter extend less than for affine change. Inhomogeneity in deformation develops with maximum response towards the ends of radii aligned along the draw direction and least for orthogonal radii. Dominant lamellae, which are initially S-profiled and non-planar flatten and their planes move towards the draw direction. Annealing experiments show that after drawing subsidiary lamellae melt and recrystallize at lower temperatures than dominant lamellae. This demonstrates that subsidiary lamellae are the more deformed and that there is a consequent spatial variation of mechanical properties typically of order 1 µm, the inter-dominant spacing.