Annealing induced high‐impact toughness of injection molded isotactic polypropylene filled with liquid‐phase exfoliated graphene

摘要

Abstract Favorable dispersibility of graphene (G) nanosheets in isotactic polypropylene (iPP) matrix is a keypoint that affects its toughening effect. In this work, a very low level of liquid‐phase exfoliated G was incorporated into iPP, and the iPP/G composite samples were further annealed at moderate temperature (120–140°C) for 3 h. It was found that liquid‐phase exfoliated G exhibits favorable dispersibility and efficient heterogeneous nucleation ability, significantly reducing the size of iPP spherulites. Characterization of the changes in microstructure of iPP and iPP/G composite upon annealing reveals that the presence of G promotes the perfection of crystalline structure and enhances dramatically the mobility of chain segments in the amorphous region of iPP during the annealing treatment. Moreover, the addition of this kind of well‐dispersed G may be favorable for the stabilization of β‐crystal during the injection molding process, and annealing at 120–140°C is also conducive to the formation of β‐crystal. A possible synergistic toughening mechanism of the incorporation of liquid‐phase exfoliated G and annealing treatment was put forward.