The beta- and gamma-form distributions of isotactic Polypropylene injection molding controlled via melt vibration

The effect of melt vibration on the crystal form of isotactic Polypropylene (iPP) samples prepared by low-frequency Vibration-Assisted Injection Molding (VAIM) was investigated. The distribution of crystal forms through the thickness was investigated under different VAIM processing conditions, with Conventional Injection Molding (CIM) for comparison. Wide-Angle X-ray Diffraction (WAXD) showed that the content of beta-form crystals decreases from the surface to the core region in the CIM and VAIM samples. The beta-form distribution through the thickness is controlled by the VAIM processing conditions. The occurrence of gamma-form crystals was found in the VAIM samples produced at relatively low vibration frequency and relatively large pressure vibration amplitude.