Unusual orientation phenomena in polyethylene interpreted in terms of the morphology

Abstract

In the first part of the paper various orientation phenomena of the drawing‐relaxation behavior are interpreted in terms of the changes occurring within the submicroscopic helices which form the spherulites. Not only drawing and relaxation but also the redrawing of the relaxed samples were followed, and it was shown that the observed anomalous orientation effects cannot be described in terms of tilts of planes with simple indices. However, by considering also the possible shapes of the submicroscopic units these orientation effects can be visualized. In the second part a new general type of orientation, the “row orientation” is introduced. This arises when crystallization takes place while the melt is flowing. Flow produces lines of high nucleus density, leading to growth of the crystallites in all directions perpendicular to the direction of drawing. This results in elongated aggregates of helices, and the alignment of these complex units produces a unique type of orientation which has been established from various angles.