Effect of processing technique on the transport and mechanical properties of graphite nanoplatelet/rubbery epoxy composites for thermal interface applications

Graphite nanoplatelet (GNP)/rubbery epoxy composites were fabricated by mechanical mixer (MM) and dual asymmetric centrifuge speed mixer (SM). The properties of the GNP/rubbery epoxy were compared with GNP/glassy epoxy composites. The thermal conductivity of GNP/rubbery epoxy composite (25 wt.% GNP, particle size 15 μm) reached 2.35 W m−1 K−1 compared to 0.1795 W m−1 K−1 for rubbery epoxy. Compared with GNP/rubbery epoxy composite, at 20 wt.%, GNP/glassy epoxy composite has a slightly lower thermal conductivity but an electrical conductivity that is 3 orders of magnitude higher. The viscosity of rubbery epoxy is 4 times lower than that of glassy epoxy and thus allows higher loading. The thermal and electrical conductivities of composites produced by MM are slightly higher than those produced by SM due to greater shearing of GNPs in MM, which results in better dispersed GNPs. Compression and hardness testing showed that GNPs increase the compressive strength of rubbery epoxy ∼2 times without significantly affecting the compressive strain and hardness. The GNP/glassy epoxy composites are 40 times stiffer than the GNP/rubbery epoxy composites. GNP/rubbery epoxy composites with their high thermal conductivity, low electrical conductivity, low viscosity before curing and high conformability are promising thermal interface materials.