NONUNIFORMITIES IN HIGH-DENSITY POLYETHYLENE FILMS - CORRELATION BETWEEN THICKNESS, ORIENTATION FACTORS AND RECRYSTALLIZATION BEHAVIOR ON ANNEALING

Non-uniformities exist in films produced commercially by the film blow ing process and these variations should be borne in mind when techniqu es that monitor small areas are used to characterize films. Polarized infra-red spectroscopy is used to show variations in orientation facto rs in different areas of high-density polyethylene films, with more hi ghly oriented regions coinciding with thinner areas in the film. The t hinner areas deform less readily under load, while on annealing at 130 degrees C, these areas thicken more than do the thicker areas, the pr ocess being accompanied by the segregation of lower molecular mass mat erial into crystallites with a lower melting DSC endotherm.