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

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 degrees 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 beta-crystal during the injection molding process, and annealing at 120-140 degrees C is also conducive to the formation of beta-crystal. A possible synergistic toughening mechanism of the incorporation of liquid-phase exfoliated G and annealing treatment was put forward.

Automated summary

This study investigates the incorporation of liquid-phase exfoliated graphene (G) nanosheets into isotactic polypropylene (iPP) matrix and the subsequent annealing treatment. The results show that the presence of G improves the crystalline structure of iPP and enhances the mobility of chain segments. The addition of well-dispersed G also has a positive effect on stabilizing the beta-crystal during the injection molding process.