Thermal conductive epoxy adhesive composites filled with carbon-based particulate fillers: a comparative study

In this paper, different types of carbon-based fillers such as graphite powder (GP), expanded graphite powder (EGP), expanded graphite flakes (EGF), silane treated expanded graphite flakes (EGS) and exfoliated graphene nanoplatelets (GNPs) were used at 40 wt% loading level inside epoxy resin for comparative thermal conductivity enhancement analysis. Disc-shaped epoxy adhesive composite samples were manufactured by hand layup and mechanical mixing technique. The thermal conductivity (k) of epoxy composites was measured according to ASTM E1530 standard at 60 degrees C by steady-state heat flow meter technique. It was enhanced to 0.96 (similar to 5 times), 2.50 (similar to 13 times) and 3.21 W/mK (similar to 17 times) for 40GP + 0Ep, 40EGF + 60Ep and 40EGS + 60Ep epoxy adhesive composites at 40 wt.% of filler loading level inside low conducting (k similar to 0.194 W/mK) epoxy resin, respectively. From scanning electron microscopy, we observed the formation of the heat-conducting network through GP, EGF and EGS inside the epoxy matrix. The lap shear strength (LSS) of the epoxy adhesive joint was increased at 40 wt% of GP filler added epoxy adhesive but it decreased at 40 wt% EGF filler loading inside the epoxy resin. Introduction of EGF inside epoxy resin has influenced negative impact on TGA analysis (thermal stability) of epoxy adhesive than GP at initial stages of thermal degradation. This indicates the commercial use of these epoxy adhesives for heat dissipation application of electronic packaging industry.