Rheological properties of graphene/nylon 6 nanocomposites prepared by masterbatch melt mixing

In this study, the rheological behavior of graphene/nylon 6 nanocomposites was investigated. Graphene-filled nylon 6 nanocomposites were prepared by diluting a graphene/nylon 6 masterbatch in a nylon matrix using melt compounding with a kneader mixer. Optical microscopic images of the graphene/nylon 6 nanocomposites showed good dispersion quality of graphene even at a high filler loading of 5 wt%. However, at the microscale, some agglomerates were also observed. Differential scanning calorimetry (DSC) results showed that the melting temperature (T_m) of graphene/nylon 6 composites increased as the concentration of graphene increased. The rheological properties and activation energy of graphene/nylon 6 composites were studied by rheometer under different temperatures and shear rates. Rheological results indicated that the viscosity dramatically increased as the concentration of graphene increased. Pure nylon 6 showed similar frequency dependencies and reached a Newtonian plateau at low frequencies. As for the graphene/nylon 6 nanocomposites, the viscosity curves displayed a much greater decrease with frequency and exhibited non-Newtonian (shear thinning) behavior, which was confirmed by flow behavior index (n) analysis. The viscous activation energy of nanocomposites decreased as the concentration of graphene increased, showing that the composites exhibited less temperature dependence at elevated temperature. Moreover, it is believed that the graphene/nylon 6 interactions increased with increasing graphene loading.