Recently, multifunctional polymer-graphene nanoplatelet (GnP) composites have demonstrated great promise as next-generation materials for energy management and storage, electromagnetic interference (EMI) shielding and heat dissipation components in electronic industries. However, the practical underpinning needed to economically manufacture graphene-based polymer composites is missing. Therefore, this dissertation aims to demonstrate how some of the challenges for efficient manufacturing of functional polymer composites, can be strategically tackled by using supercritical fluid (SCF)-treatment and physical foaming technologies.

In this PhD research, an industrial-scale technique for in situ exfoliation and dispersion of GnP in polymer matrices was developed and invented. This thesis also developed an in-depth understanding of the effects of cellular structures, GnPs’ orientation, arrangement, and exfoliation on the thermal/electrical conductivity, percolation threshold, dielectric performance, and EMI shielding effectiveness of the graphene-based polymer composites. In particular, it was demonstrated how SCF−treatment and physical foaming can significantly enhance thermal conductivity of polymer-GnP composites. The SCF-treatment and physical foaming exfoliated the GnPs in situ and microscopically tailored the nanocomposites’ structure to enhance the thermal conductivity. The research findings in this thesis have also demonstrated that the introduction of foaming and microcellular structure can substantially increase the electrical conductivity, EMI shielding effectiveness and can decrease the percolation threshold of the polymer-GnP composites. This research also presented a facile technique for manufacturing a new class of ultralight polymer-GnP composite foams with excellent dielectric performance. The generation of a microcellular structure provided a unique parallel-plate arrangement of GnPs around the cell walls. This significantly increased the real permittivity and decreased the dielectric loss.

This dissertation developed a fundamental understanding of structure-property relationships and new routes to microscopically engineer the structures and properties of graphene-based polymer composites for various application such as heat management (heat sink materials), EMI shielding, energy storage and capacitors (dielectric materials).