Amorphous orientation and its relationship to processing stages of blended polypropylene/polyethylene fibers

Abstract

Abstract Changes in the molecular orientation, melting behavior, and percent crystallinity of the individual components in a fibrous blend of isotactic polypropylene (iPP) and high‐density polyethylene (HDPE) that occur during the melt extrusion process were examined using wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystalline orientation of each component was found using Wilchinsky's treatment of uniaxial orientation and described by the Hermans–Stein orientation parameter. The amorphous orientation was found by resolving the X‐ray diffraction pattern in steps of the azimuthal angle into its iPP and HDPE crystalline and amorphous reflections. The utility of DSC and WAXD analyses to capture the effects of small differences in processing, and the use of these results as fingerprints of a particular manufacturing process were demonstrated. Major increases in the melting temperatures, percent crystallinities, and molecular orientations of the iPP and HDPE components occurred during the main stretching stage of the melt extrusion process. The annealing stage was found to have little to no effect on the melting behavior and molecular orientation of these components. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008