Research On Mechanical,Rheology Properties And Reinforcing&Toughening Mechanisms Of Graphene Reinforced Polypropylene Nanocomposites

As more and more attention to the problem of environmental pollution,iron and steel materials are replaced by polymer materials,the development of green environmental protection and excellent performance of polymer materials is more urgent.Polypropylene(PP)has the characteristics of no toxicity,no smell,no taste,heat resistance and corrosion resistance,but it still has many problems,such as lack of strength,high sensitivity to notch,large shrinkage and so on.Graphene(GNPs),as a new material,has excellent mechanical properties,but its research is still in its infancy.In order to improve the mechanical properties of PP,extend the application of GNPs and rich the theoretical system of GNPs,we prepared three different kinds of systems of GNPs reinforced PP composite materials with different sizes of GNPs,the mechanical properties of the composite were tested through tensile,bending and impact experiments.The rheological and extrudate swell behavior of the composites were tested and the mechanism of strengthening and toughening of PP by GNPs was systematically analyzed.The results are as follows:With the addition of GNPs,the mechanical properties of composites have been improved obviously.The elastic modulus of the composites with the increase of GNPs content increased after the stabilization of the rule,tensile elongation at break decreased with the increase of GNPs content.It was found that the GNPs with less sheet and larger specific surface area had a better effect on the tensile properties of the composites,and the presence of impurities could obviously reduce the tensile properties of the composites.Under the same GNPs content,the more layers,the thicker of GNPs,the impact performance of the composites was better.We observed GNPs evenly dispersed in PP by the SEM of impact profile,Obvious agglomeration was not observed.The mobility of PP was not changed by the addition of GNPs,and the shear viscosity of the composites decreased slightly.The addition of GNPs decreased the composite melt die swell ratio,which helps to improve the machining deformation of molding materials shrinkage.The tensile elastic modulus model and tensile strength model of GNPs reinforced polymer composites were established by introducing the interface strength factor,the influence of the size of GNPs and interface layer strength to the tensile elastic modulus model and tensile strength model of the composite was comprehensive considerated,more truly reflect the physical environment of GNPs reinforced polymer.The results show that the model can well describe the law of the enhancement of graphene.In the theory of reinforcement,the strength of the interface layer is the key factor for the enhancement of GNPs by PP,and the GNPs also plays a role in the framework of the composite materials.The toughening theory,interaction interface layer,formed by GNPs and PP with high specific surface area during fracture process of GNPs pulling out and bridging from PP induced crack deflection and the thrust process of the formation of a large number of micro cracks and the multiple crazing effect constitutes a theory of GNPs toughened PP.The results of this study is expected to broaden the application field of PP,promote the market-oriented of graphene and contribute to enrich the theoretical system of graphene,provide theoretical guidance for the design and application of polymer composite materials at the same time.