EVOLUTION OF THE CRYSTALLINE TEXTURE OF HIGH-DENSITY POLYETHYLENE DURING UNIAXIAL COMPRESSION

The formation of an axially symmetrical texture in high-density polyethylene (HDPE) was studied through uniaxial compression at room temperature. The orientation of crystallographic axes was probed at various stages of the deformation process, up to an equivalent strain of 1.86, by means of WAXS pole figures. Additionally the lamellar orientation was studied using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The results of these structural and morphological studies demonstrated that the major deformation mechanism involved in plastic deformation of the crystalline parts of the sample was the (100)[001] chain slip. Other mechanisms that were detected as active in the crystalline phase were (100)[010] transverse slip, and, to a lesser extent, twinning and martensitic transformations. Plastic deformation of the crystalline phase was accompanied by deformation of the amorphous phase, mostly by shear of the interlamellar layers (interlamellar sliding). Such shear was found to be partially reversible, especially at lower strains. In contrast to other deformation modes, the deformation of HDPE by uniaxial compression does not induce fragmentation of the lamellar superstructure, at least in the strain range studied.