Hybrid GNPs/silane functionalised BN composite as TIM: Thermal, shear strength and moisture analysis

The rapid development of Thermal Conductive Adhesive (TCA) by using highly thermal conductive fillers like graphene nanoplatelets (GNPs) and boron nitride (BN) has heightened the need to hybridise both fillers in order to improve the thermal, mechanical and water resistance properties of the adhesive. The hybrid composites were prepared by varying the GNPs sizes, ratios, and silane coupling agent. The result indicates that hybrid GNPs15/fBN_KH560 composites exhibit the highest thermal conductivity (1.159 ± 0.02 W /mK) at a GNPs ratio of 0.75 compared to other composites. However, shear strength analysis shows a contradicting result where hybrid GNPs5 composites show a higher result than hybrid GNPs15 composites at all GNPs ratios. The difference is due to the size of the GNPs filler, where bigger fillers are preferable to transfer heat due to lower filler-polymer resistance, while smaller fillers are required to transfer stress due to the high effective surface area of the filler-polymer. The moisture analysis shows that hybrid GNPs15 composites absorb more water than the hybrid GNPs5 composite due to the lower filler loading and the wrinkling of GNPs15 filler that hinder its ability as a barrier against water. Consequently, the shear strength of hybrid GNPs15 composites is lower than hybrid GNPs5 composites for all GNPs ratios. It is also worth noting that the thermal and mechanical properties of hybrid composites containing fBN at all GNPs ratios are better than unmodified BN due to the well-dispersed filler, as depicted in the microstructure analysis.