Fabrication of high thermal conductive epoxy composite by adding hybrid of expanded graphite, iron (III) oxide, and silver flakes

Abstract

Thermally conductive epoxy adhesive composites have been fabricated by adding a tri-filler mixture of expanded graphite (EG), iron (III) oxide (Fe3O4), and silver (Ag) flakes with increasing concentration from 20 to 50 weight percent. The epoxy composite containing mixed filler of EG/Fe/Ag at 50 wt% has demonstrated diminutive higher thermal conductivity (TC) (4.85 W/mK) when compared to composite filled with EG/Fe hybrid (4.82 W/mK) at equivalent filler % which was about 25 fold improvement than epoxy unaided. The crystallography of the graphite flakes (GF), EG, neat epoxy, EG/Fe/Ag-epoxy, and EG/Fe-epoxy adhesive composites has been analyzed by X-ray diffraction (XRD) technique. The morphology of filler (EG and EG/Fe/Ag) and fractured surface analysis of corresponding epoxy composite has been carried out by scanning electron microscopy. The bonding strength through lap shear test of epoxy adhesives with the addition of 50 wt% of EG/Fe/Ag mixed and EG/Fe hybrid fillers has been displayed a decreased value as compared to neat epoxy. At the primary phase analysis of thermal dilapidation, the thermo-gravimetric analysis (TGA) concluded a negative effect on the thermal constancy of epoxy composites at higher assimilation (> 35 wt%) of EG, Fe3O4, and Ag mixed fillers. The damping factor (tan δ) (0.44 and 0.43) and glass transition temperature of composite demonstrated lower value (70 and 64 °C) when 50 wt% of EG/Fe and EG/Fe/Ag were added.