Enhanced thermal conductivity of polypropylene/polyamide 6 composites via optimizing the selective distribution of h‐BN and NH2‐CNTs hybrid fillers within the co‐continuous structure

Achieving high thermal conductivity in composites with low filler content is a major challenge in current research. In this paper, polypropylene (PP) and polyamide 6 (PA6) were used as polymer matrix, and the hybrid thermal conductive filler, formed by hexagonal boron nitride (h‐BN) and aminated carbon nanotubes (NH2‐CNTs), was integrated into matrix for the fabrication of thermal conductive composites (PP/PA6/h‐BN and PP/PA6/h‐BN@CNTs) via two‐step melt blending technology. The thermal conductive fillers were selectively distributed in a phase of the polymer matrix with a co‐continuous structure, forming a thermal conductive path with a three‐dimensional network structure. The results show that when the content of h‐BN reaches 25 wt%, the thermal conductivity of the PP/PA6/h‐BN and PP/PA6/h‐BN@CNTs composites was 199% and 300% higher than that of PP/PA6, respectively. Through testing the volume resistivity of the composites, it was confirmed that PP/PA6/h‐BN@CNTs composites maintain good electrical insulation. Both composites demonstrated remarkable thermal conductivity and outstanding electrical insulation. This research provides a facile way to prepare highly thermal conductivity polymer composites with excellent processing performances and electrical insulation. Highlights h‐BN@CNTs hybrid fillers with sandwich structure were prepared. A two‐step blending method was used to control the selective distribution of hybrid fillers in a phase of the polymer matrix with a co‐continuous structure. The hybrid filler formed a thermal conductive path with a three‐dimensional network structure in the collective. PP/PA6/h‐BN@CNTs composites demonstrated remarkable thermal conductivity, outstanding electrical insulation and favorable processing performances. Schematic diagram of microstructure of PP/PA6/h‐BN@CNTs composites.