Influence of Draw Ratio on Crystal Morphology and Structure of β-Form of Isotactic Polypropylene

Abstract

The effects of the draw ratio (DR) on the polymorphic nature of β-iPP were investigated by polarized light microscopy (PLM), wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and differential scanning calorimeter (DSC). The iPP sheet is extruded through a slit die, and then the extruded sheets were hot stretched with the different draw ratio (DR). DSC and WAXD results indicate that the β-iPP content increase with DR increasing from 4.8 to 10.8. β-spherulites can be observed by PLM in the stretched specimen even at a lower DR (4.8). With increasing draw ratio, the relative amount of the β-cylindrites crystals gradually increased.