Reinforced epoxy composite adhesives of expanded graphite (EG) and graphene nanoplatelet (GNPs) were prepared by hand layup and mechanical mixing method. Disk-shaped epoxy composite samples with EG and GNP mixtures in varying ratios were prepared to measure the thermal conductivity (TC) enhancement. Thermal characterization testing data showed high thermal conductivity enhancement with three different hybrid filler concentrations of 10, 25, and 35 wt%, respectively. The highest thermal conductivity of 3.6 W/m K was obtained for an epoxy adhesive composite having 30 wt.% EG and 5 wt.% GNP which was tested by guarded heat flow meter technique. This significant improvement in thermal conductivity can be attributed to the lowering of overall thermal interface resistance due to small amounts of nanofiller (GNP) improving the thermal contact between the primary microfillers (graphite). The synergistic effect of this hybrid filler system is lost at higher loadings of the GNP relative to expanded graphite. The structure of the graphite flake, GNP/epoxy, EG/epoxy and hybrid EG/GNP/epoxy composites was investigated by XRD. The EG prepared by acid intercalation and abrupt thermal expansion showed good compatibility with GNP and the epoxy resin. From scanning electron microscopy photographs, the formation of conducting network observed through the expanded graphite and GNPs in a low conducting epoxy matrix. The thermal decomposition temperature of the composite increased to 450 and 615 °C with the addition of 10 and 35 wt% of hybrid EG/GNP inside epoxy matrix, respectively. LAP shear strength of single and hybrid filled epoxy adhesive decreased at 35 wt.% loading than neat epoxy.

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Thermal management is an important parameter in an electronic packaging application. In this work, three different types of fillers such as natural graphite powder (Gr) of 50‐μm particle size, boron nitride powder (h‐BN) of 1‐μm size, and silver flakes (Ag) of 10‐μm particle size were used for thermal conductivity enhancement of neat epoxy resin. The thermal properties, rheology, and lap shear strength of the neat epoxy and its composite were investigated. The analysis showed that the loading of different wt% of Gr‐based fillers can effectively increase the thermal conductivity of the epoxy resin. It has also been observed that the thermal conductivity of the hybrid filler (Gr/h‐BN/Ag) reinforced epoxy adhesive composite increased six times greater than that of neat epoxy resin composite. Further, the viscosity of hybrid filler reinforced epoxy resin was found to be increased as compared with its virgin counterpart. The adhesive composite with optimized filler content was then subsequently subjected to determine single lap shear strength. The degree of filler dispersion and alignment in the matrix were determined by scanning electron microscopy (SEM) analysis.

the Amalgomer CR showed the highest fluoride release among all the experimental dental restorative materials.