Study on epoxy resin based thermal adhesive composite incorporated with expanded graphite/silver flake hybrids

Abstract

In this paper, two types of fillers such as expanded graphite flakes (EG) of 20 μm particle size and silver flakes (Ag) of 10 μm particle size were used for thermal conductivity (TC) enhancement of neat epoxy resin. Mix and heat based simple method were used to produce hybrid thermal filler which was reinforced in epoxy for composite formation. Disc-shaped epoxy composite samples with different hybrid filler formulations were prepared by hand layup and mechanical mixing technique. The thermal conductivity of single (EG) and mixed (EG/Ag1) hybrid epoxy adhesive composites was measured according to ASTM E1530 standard at 60 °C. It was increased to 2.511 (˜13 times) and 3.42 W/mK (˜17 times) than neat epoxy at 30 wt.% loading level inside the epoxy matrix, respectively. This indicates the commercial use of this adhesive formulation for thermal interface materials application. From scanning electron microscopy (SEM), we observed the conducting network formation through EG and EG/Ag hybrids inside the low conducting epoxy matrix. The lap shear strength (LSS) of epoxy resins with the incorporation of 30 wt% EG/Ag was decreased as compared with neat epoxy.TGA analysis showed that the introduction of Ag inside epoxy hybrids has influenced more negative impact on the thermal stability of epoxy composite at initial stages.