A Study on the Orientation Effects in Polyethylene in the Light of Crystalline Texture Part 3 On the Effect of Applied Stress on the Molecular and Textural Orientation

Special sample types established and characterised in Parts 1 and 2 [ 1,2] were examined systematically under different modes of external deformation at constant temperatures. The structural changes recorded by means of wide- and low-angle X-ray patterns fully substantiated the bodily rotation of the otherwise unaltered crystallites in accordance with the interlamellar slip mechanism postulated in Parts 1 and 2, both in tension and under two modes of compression. Dimensional changes, however, were significantly in excess of those expected from the rotation of crystallites, but were uniquely correlated with this relation in the different samples under different conditions of deformation. This points to a unique structural and mechanistic interrelation between the crystallites and more compliant amorphous regions. As the X-ray long periods were unaffected by the deformation, the more extensible material cannot be identical to that associated with the lamellar periodicity, a fact which points to a previously unsuspected superlamellar regularity in the texture. A simple structural suggestion is made.