Influences of graphene nanoplatelet aspect ratio and thermal treatment on dielectric performances of poly(methyl methacrylate) composites

The dielectric property and percolated behaviour of polymer matrix composites largely depend on the morphology of conductive fillers and external stimulations especially when the composites are processed by melting blending and extrusion-injection way. In this study, the poly(methyl methacrylate) (PMMA) matrix composites incorporated by two kinds of graphene nanoplatelets (GNP), G5 and G150 with different aspect ratios (the ratio of diameter and thickness) are prepared to study the influence of GNP morphology on the dielectric performances close to percolation threshold (f(c)). After annealing at glass transition temperature (T(g)) for 1 h, the dielectric permittivities of PMMA/G5 and PMMA/G150 near f(c) increase 43 and 38%, respectively, while the dielectric loss change little. This improvement on the dielectric property is possibly attributed to the slight change of the distance between adjacent GNPs after annealing at T(g) which enables to arouse stronger polarisation by tunnelling effect