Improving Dispersion and Mechanical Properties of Polypropylene/Graphene Nanoplatelet Composites by Mixed Solvent-Assisted Melt Blending

To improve the dispersion of graphene nanoplatelet (GNP) in polypropylene (PP), GNP was exfoliated in a mixed solvent of p-xylene and N,N-dimethylform-amide (DMF) and the exfoliation of GNP was maintained by the addition of a compatibilizer before the melt blending. The concentration of the dispersed GNP in various ratios of the mixed solvents was measured in order to confirm the effect of the mixed solvent on the pre-treatment process. As a compatibilizer for the composite, pyrene-functionalized maleic anhydride-grafted polypropylene (Py-PP) was synthesized. The dispersion state of the composites was analyzed by the three dimensional non-destructive X-ray micro-computed tomography (3D micro-CT). The improved dispersion of GNP resulted in a significant enhancement in the mechanical properties. Young's modulus of PP composites with 2 wt% GNP has increased by 43% compared with that of PP. These results are attributed not only to the improved interfacial interaction between PP and GNP, but also to the homogeneous dispersion state of the GNP in the matrix.