Thermal conductivity and shear strength characterisation of hybrid GNPs and silane functionalised BN as thermal conductive adhesive

The demand for high thermal conductivities and improved adhesion of thermal conductive adhesives has heighten the need for hybrid fillers with extraordinary properties, such as boron nitride (BN) and graphene nanoplatelets (GNP) especially at lower filler contents (<20 wt.%), particularly with silane-functionalised BN (fBN) and adhesion using the single lap joints approach. Thus, this study was conducted to measure the thermal conductivity and shear strength of hybrid GNP with BN or fBN at different filler sizes, GNP ratios, and silane coupling agents (KK550 and KH560). We observed that the hybrid GNP/fBN_KH560 composite at a ratio of 0.75 exhibited the highest thermal conductivity and shear strength with enhancements of 198.42% and 81.82%, respectively, attributed by the high compatibility between fBN_KH560 and the polymer matrix, proven by the lowest measured contact angle and Hansen solubility parameter difference. Despite the thermal conductivity value not surpassing that of the single-filled GNP composite, the hybrid composite at lower filler content was considered a success as it exhibited a synergetic effect when compared with single-filled BN or fBN; with the difference of 0.111. Besides, crack deflection, particle debonding and pull-out mechanism improved the shear strength and promoted cohesive failure in the hybrid composite.