Constructing HighlyEfficient Thermally ConductiveNetworks in FFF-Printed PP/PA/BN Composites via Filler-Selective Localizationand Shear-Induced Alignment

Fused Filament Fabrication (FFF) offers a promising route for fabricating thermally conductive polymer composites, but high filler loadings often impair mechanical performance and processability. Here, an immiscible PP/PA6/BN ternary system was developed by integrating selective filler localization with FFF-induced domain alignment. Because of the stronger affinity between BN and PA6, BN platelets preferentially enriched in PA/BN-rich domains rather than dispersing randomly in the PP matrix. During FFF deposition, these domains were elongated and partially interconnected along the main raster direction, forming anisotropic thermal-transport pathways. Compared with compression-molded PP/PA/BN and binary PP/BN, the printed PP/PA/BN composite showed enhanced directional thermal conductivity while retaining mechanical integrity and printability. Morphological, WAXD/XRD, and rheological analyses indicate that thermal transport arises from BN orientation, PA/BN-rich domain interconnection, and multiphase interfacial effects. This work provides a morphology-regulation strategy for printable thermally conductive composites.