Ordered structure effects on β-nucleated isotactic polypropylene/graphene oxide composites with different thermal histories

In this paper, the influence of ordered structure effects (OSE) on crystallization behaviors of β-nucleated isotactic polypropylene/graphene oxide (β-iPP/GO) composites with different thermal histories, which crystallized at a slow cooling rate (called SLOW), fast cooling rate (called FAST) and medium cooling rate (called MED), respectively, was studied by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The ordered structure status of three samples before crystallization measurement was controlled by tuning the fusion temperature T(f) and melting time t(m). The results showed that for all samples, OSE would occur in an appropriate T(f) region (Region II). The OSE efficiency of MED was the highest, while that of SLOW were the lowest. It was also found that the crystallinity and crystalline perfection of SLOW were the highest, while those of FAST were the lowest. The effects of the melting time t(m) on the OSE were also investigated. At T(f) = 172 °C, the OSE efficiency of FAST reached the maximum at t(m) = 5 min, while that of SLOW reached the maximum at t(m) = 20 min. It was indicated that the OSE efficiency was affected by thermal history, and it could be improved by selecting the appropriate t(m). Related mechanisms concerning the roles of thermal history on the OSE behavior were proposed based on the results of DSC and in situ SAXS.