Effect of boron nitride addition on properties of vapour grown carbon nanofiber/rubbery epoxy composites for thermal interface applications

This work is focused on developing an epoxy-based hybrid composite using BN and VGCNF, with the main motivation of producing thermally conducting but electrically insulating composite thermal interface materials (TIMs). Various compositions of BN/VGCNF/rubbery epoxy hybrid composites were developed by 3-roll milling. The thermal conductivity of hybrid composites increases with increasing VGCNF content and electrical conductivity decreases with increasing BN content. SEM showed that BN inclusion inhibits VGCNF contacts resulting in more electrically insulating composites. Compression testing showed that BN inclusion produced stiffer composites than those produced with VGCNFs at equivalent loading. The thermal contact resistance of 6 wt.% BN/8 wt.% VGCNF/rubbery epoxy composite was 3.36 × 10-5 m2.K/W at a bond line thickness of 18 μm. Thermal contact resistance measurements showed that hybrid composites can offer better interfacial thermal transport at thick bond lines and this improves with increasing VGCNF content due to increased thermal conductivity imparted by VGCNF.