Improved strength and toughness of polyketone composites using extremely small amount of polyamide 6 grafted graphene oxides

Polyketone (PK) composites were prepared by a solution casting method using 1,1,1,3,3,3-hexafluoro-2-propanol as a solvent and polyamide 6 grafted graphene oxides (PA 6-GOs) as filler materials. PA 6-GOs were obtained by in situ polymerization of ε-caprolactam using GOs having different amounts of oxygen functional groups. The PK composites containing only an extremely small amount of the PA 6-GOs (0.01 wt%) showed much improved mechanical properties compared to PK. This could be ascribed to the homogeneous dispersion of the graphene-based filler materials in the polymer and specific interactions such as dipole–dipole interactions and/or the hydrogen bonds between the fillers and the polymer matrix. For example, when 0.01 wt% of PA 6-GO having less oxygen functional groups was used as a filler for the composite, the tensile strength, Young’s modulus, and elongation at break of the composite increased by 35%, 26%, and 76%, respectively. When 0.01 wt% of PA 6-GO having larger content of oxygen functional groups and PA 6 was used, Young’s modulus decreased, while the tensile strength increased by 37%, and the elongation at break increased tremendously by 100 times, indicating that very tough polymeric materials could be prepared using a very small amount of the graphene-based fillers.