In this work, the influence of the injection velocity profile on the crystalline phase molecular orientation of injection molded polypropylene samples has been evaluated. The molecular orientation has been evaluated both in the central and lateral positions on the surface of the injected tension specimens, using x-ray pole figures. The results demonstrated that the variations in molecular orientation of polypropylene crystallites were correlated to the different velocity profiles employed during the processing, showing that an increase in the velocity increases the orientation degree. It has been observed that the crystalline structure of the polypropylene molecules shows bimodal orientation and that the orientation degree at the lateral position is higher than that at the central position.
Molecular orientation; pole figures; x-ray diffraction; polypropylene; injection molding