On the plastic deformation of the amorphous component in semicrystalline polymers

Abstract

The molecular orientation of the amorphous component of semicrystalline high-density polyethylene (HDPE) induced by plane strain compression was studied by wide-angle X-ray scattering measurements utilizing the pole figure technique and separation of the scattering produced by the crystalline and amorphous components. It was found that the oriented amorphous component produced by large strain plastic deformation consists of domains of extended chain segments, closely packed in a two-dimensional pseudo-hexagonal aggregation, which are separated by less ordered regions. The deformation leads to the formation of a texture of the amorphous component which is common to the whole sample. In this texture, the direction of the chains coincides with the direction of flow, and one of the (100) pseudo-planes of the pseudo-hexagonal structure in every domain is perpendicular to the loading direction. It was suggested that the most important deformation mechanisms in the ordered amorphous component were the glide of the chain segments along their axes and the slip of the pseudo-planes of the ordered chains in the direction perpendicular to the chain axis, with resembling the crystallographic slip processes. Such a specific deformation of the amorphous layers most probably resulted from the strong constraint imposed by the slip deformation in the crystalline component to which the amorphous component is intimately connected.