Self-reinforced composites based on polypropylene fiber and graphene nano-platelets/polypropylene film

Self-reinforced polymer composites (SrPCs) have many advantages such as light weight, easy recyclability, improved bonding, and low cost. However, the enhancement of mechanical properties of SrPCs is generally restricted by the composite structure and the narrow processing temperature window. The combination of graphene and self-reinforcing mechanism is a potential method to realize a significant improvement in the mechanical properties of polymer composites. It is necessary to study the self-reinforcing mechanism on adjusting the orientation of graphene, so as to reduce the amount of graphene and improve the mechanical properties. This paper presents SrPCs that combine polypropylene (PP) fibers and graphene nano-platelets (GnPs)/PP composite films through film stacking. The unidirectionally arranged PP fibers form narrow channels which facilitate the orientation of GnPs during the impregnation process. The prepared GnPs/PP SrPCs were characterized in comparison with neat PP. At a very low GnPs content of only 0.019 wt%, the tensile strength and modulus of PP were increased by 152% and 186%, respectively, and the interfacial adhesion force of PP SrPCs was improved by 280%. Numerical simulation was successfully conducted to evaluate the processing temperature and the mechanism of graphene orientation in the film stacking process. It proved that the GnPs were highly oriented over the region of unidirectional fibers by the flow field. This new technical method can be potentially used in the industrial manufacturing of economical graphene/polymer nanocomposites with superior mechanical properties.