Effects of stereo‐defect distribution on the crystallization and polymorphic behavior of β‐nucleated isotactic polypropylene/graphene oxide composites with different melt structures. Issue 6 (4th March 2019) - Jiang, Xi
Abstract : In this study, we have prepared two β ‐nucleated isotactic polypropylene/graphene oxide ( β ‐iPP/GO) composites with different stereo‐defect distribution (named NPP‐B and NPP‐A). The role of stereo‐defect distribution on the crystallization and polymorphic behaviors of samples with varied melt structures were investigated by scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC). It was found that NPP‐B (who with more uniform stereo‐defect distribution) prefers β ‐crystallization; while NPP‐A has a strong α ‐nucleation tendency and can hardly form β ‐phase; as fusion temperature decreases from 200°C to 168°C, the relative percentages of β ‐phase of NPP‐B and NPP‐A exhibit the same trends, suggesting that the β ‐nucleation efficiency is enhanced by the ordered structure effect (OSE) and causes β ‐crystallization even in NPP‐A. Moreover, the lower limiting temperatures of Region‐II of NPP‐B and NPP‐A are the same but their upper limiting temperatures are different, indicating the uniformity of stereo‐defect distribution also influences temperature window for OSE. Related mechanisms were discussed. POLYM. ENG. SCI., 59:1097–1104 2019. © 2019 Society of Plastics Engineers