Mechanical Enhancement And Interfacial Properties Between Graphene And Poly (methyl Methacrylate)

Graphene has been widely investigated as a promising candidate to reinforce the mechanical,thermal and electrical properties of graphene/polymer composite.The graphene-based nanocomposites have been widely used in industry.However,the studies on the structure-property relationship of graphene/polymer systems still under extreme conditions.In this paper,the pull-out processes were simulated to investigate the interafcial shear characteristics between monolayer of graphene graphene and polymethyl methacrylate(PMMA)matrix by using molecular dynamics simulation with ReaxFF reactive force field.The effect of defects and functionalization on interfacial shear properties were studied.Meanwhile,the interfacial enhancement mechanisms has also been revealed.The main contents show as follows:(1)The samples of graphene/PMMA composite systems were prepared by using the melting-quenching method.Meanwhile,the simulation method of pull-out process was determined.(2)We have simulated the processes of pulling graphene oxide out from PMMA matrix.The enhancement effect of functionalization on interfacial shear characteristics was investigated.The results shows that the interfacial shear strength between graphene oxide and PMMA increases with the increase of the edge coverage.Hoverer,further increase the surface coverage degree to about 6.48% leads to saturated shear strength.The interfacial binding strength(interaction energy)between graphene oxide and PMMA is the decisive factor to determine the interfacial shear characteristics of the interface.(3)We have simulated the processes of pulling defective graphene out from PMMA matrix.The enhancement effect of SW and DV defects on interfacial shear characteristics were analyzed.It was found that both two types of defects can notably enhance the interfacial shear strength and pull-out energy,which mainly attributed to the suface wrinkles of graphene caused by the defects.DV defect is more effective than SW defect in enhancing the interfacial shear properties of the defective graphene/PMMA composite systems.(4)We have simulated the processes of pulling functionalized graphene(FGr)with defects out from PMMA matrix.The effect of chemical functionalization of perfect graphene and defective graphene by hydroxy groups on interfacial shear characteristics were investigated.The results shows that after functionalization,the FGr without defect exhibits the strongest mechanical interlocking and interfacial shear strength in nanocomposites,while the FGr with SW defects is lower,and the FGr with DV defects is the worst one.This is because the hydroxy groups of different kinds of graphene exhibits different insertion behaviors,which dramatically influence the interfacial shear properties between FGrs and PMMA.