Material behaviourEffects of polyolefin elastomer and β-nucleating agent on morphological evolution of isotactic polypropylene under an intensive shear rate

The crystalline and oriented morphologies of isotactic polypropylene (iPP), polyolefin elastomer (POE), and β-nucleating agent (β-NA) blends molded by micro-injection were investigated using polarized light microscopy, scanning electronic microscopy, differential scanning calorimetry, wide-angle X-ray diffraction and small-angle X-ray scattering. Results showed that addition of POE and β-NA elevated the melting point and onset crystallization temperatures of the micro-injection molding (MIM) specimens as well as the thermal stability of oriented structures. Furthermore, POE induced the formation of perfect β-cylindrulites that are epiphytic and symmetrical on the surface of long fibrous crystals in the iPP/10%POE micropart. The elastomer also prevented the suppressive effect of intensive shear flow fields on the nucleating efficiency of β-nucleating agents toward the iPP matrix during MIM to a certain degree.