Melt Crystallization of Constrained Polyethylene Chains in Uniaxially Drawn Film and Solution-Grown Lamellae

Abstract

When a uniaxially drawn polyethylene film was coated by evaporation of carbon in a vacuum, the deposited carbon layer fixed the texture and molecular orientation. Polyethylene single crystals were fixed at the fold surface on a carbon pedestal by carbon deposition. Since molecular chains of these samples were anchored on the carbon pedestal, their translational displacement on the pedestal, and longitudinal sliding along their axis, were largely restricted even when their thermal motions were activated at high temperatures. Consequently, the original molecular direction and the stacked lamellar morphology in drawn film, and the lozenge shape of polyethylene single crystals, were retained in the molten state. On crystallizing from melt, the stacked lamellar structure was reconstructed in the drawn film as double orientation was performed, and the c axis was parallel to the drawing direction, as the b axis was aligned preferentially parallel to the film surface. In single crystals, constrained chains crystallized in such a way that the b axis was kept in the lamellar plane, and their chain axis was tilted toward the long axis of the lozenge (the a axis) from the lamellar normal with an angle of 30°−54°.