Surface Replicas of Drawn Polyethylene. III. The Morphology of Drawing with Neck Formation

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Abstract
During the first stage of plastic deformation before the neck formation the crystal lamellae are rotated into the position of maximum compliance to applied stress that causes the stress-strain curve to drop to the plateau characteristic for deformation with neck propagation. The plastic-flow pattern in the neck results in an asymmetry of strain momentum imposed on tie molecules which during annealing lets the lamellae on the sample surface rotate about an axis parallel to the surface and perpendicular to the draw direction. The temperature at which such a rotation starts increases with the draw ratio. Concurrently the c axis moves away from the draw direction. The rotation of lamellae in the surface layer is nearly prevented by keeping the sample at constant length during annealing and in the interior of the sample by the surrounding lamellae even if the sample is free to shrink. The difference in long period which depends on the temperature of drawing in bulk samples and on the thickness of original crystals in extremely thin films is most probably a consequence of different geometry of heat dissipation in both cases.

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