Graphene-based polymer composite films with enhanced mechanical properties and ultra-high in-plane thermal conductivity

Graphene has very high electrical and thermal conductivities and thus is a promising candidate for use as a filler to enhance the conductivity of polymer composites. The main challenge is properly dispersing and aligning graphene nanoflakes (GNFs) within a polymer matrix. We report here a simple and scalable solution mixing and molding process to make such a composite film. These films were analyzed using SEM, ATR-FTIR, XRD, DSC, and TGA. An optical tensiometer and a laser flash analyzer were used to measure the water contact angle and in-plane thermal diffusivity of the films, respectively. The poly(vinylidene fluoride-co-hexafluoropropylene) composite films had an in-plane thermal conductivity (kappa) that reached a new record of similar to 25 W( )m(-1) K-1 at a GNF concentration of 20 wt%. The presence of GNFs had a noticeable effect on the surface morphology, crystal structure, and hydrophobicity of the polymer matrix. The tensile strength and Young's modulus of the composite films increased by the addition of GNFs up to 20 wt%. The composite films showed very high electrical conductivity due to the presence of highly conductive graphene layers. This manufacturing process ensured the in-plane orientation of graphene layers, which allowed the transport of phonons and electrons through the composite films.