Enhanced thermal conductivity of polypropylene/polyamide 6 composites via optimizing the selective distribution of h‐ BN and NH ₂ ‐ CNTs hybrid fillers within the co‐continuous structure

Abstract 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 (NH ₂ ‐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.