| Abstract: | Precision determination of high density polyethylene unit-cell dimensions are reported. The crystallographic analysis was carried out on pressure crystallized and subsequently solid-state extruded samples respectively, by means of x-ray photographic and diffractometric procedures. In all cases the crystal data was derived from a large number of independent reflections. It was shown that the unit-cell dimensions and the corresponding crystallographic densities of all the specimens are invariant with respect to either crystallization pressure or nominal draw ratio. The effects of deformation on macroscopic density are attributed, therefore, to changes of the degree of crystallinity and to an increase of the density of the amorphous phase. This interpretation is consistent with the experimental data in the framework of the two-phase model of polymer morphology. |
