Deformation of Sedimented Mats of Polyethylene Single Crystals

Abstract

By pressing the hot sedimented mats of polyethylene single crystals, fiber texture, in which chain axes are oriented in the direction of deformation, is formed through the following stages. The first, inter-lamellar slip develops because of the scarcity of tie-molecules, and at the same time, intralameller slip,i.e. slip and/or chain tilting result in a decrease of lamellar thickness and expansion of a unit cell. The second, locally concentrated slips occur in a mat instead of the homogeneous slip, and blocks of lamellar fragments rotate so as to decrease the thickness of a mat. Throughout these processes the lamellar crystallites behave as the structural units. The change of density of the mat is well explained by these modes of deformation. The increase of the unit cell dimensions by the deformation, which is anisotropic in the direction perpendicular to the chain axis, is observed. A qualitative discussion on slip is made.