Enhancement of crystallization and mechanical properties in isotactic polypropylene via adding liquid-phase exfoliated graphene

Abstract

In this work, liquid-phase exfoliated graphene (G) was introduced into isotactic polypropylene (iPP) via melt blending. Wide-angle X-ray diffraction measurements revealed that liquid-phase exfoliated graphene is a strong α-nucleating agent, making the iPP crystal grow preferentially on the (040) crystal plane. Differential scanning calorimetry and polarized optical microscopy results showed that the increase in both the nucleation density and crystal growth rate brings about the remarkable elevation of overall crystallization rate of iPP with the addition of liquid-phase exfoliated graphene. Moreover, remarkable enhancements in mechanical properties especially the toughness were obtained at low graphene loading. With the addition of 0.5 wt.% graphene, the impact strength and elongation at break of iPP increased by 103 % and 510 %, respectively. The significant enhancement of crystallization and mechanical properties of the composites could be attributed to favorable dispersion of liquid-phase exfoliated graphene in the iPP matrix. A possible toughening mechanism was proposed.