Enhanced Mechanical Property of Polyamide-6/Graphite Sheet Composites with Segregated 3D Network Binary Structure for High Thermal Conductivity

Abstract

Segregated conductive polymer composites exhibit excellent electrical properties with a low percolation threshold. However, the mechanical properties of the segregated conductive polymer composites were always poor because the conductive fillers at the interfaces hinder polymer chain diffusion and thus lead to weak interfacial interaction between the conductive fillers and the polymer matrix. In this paper, polyamide-6 and polyamide-612 microspheres were synthesized via the in situ anionic ring opening of caprolactam and laurolactam. Segregated graphite sheets/polyamide-6(GS/PA6) and polyamide-612(PA612) composites with good mechanical properties were realized via high-pressure solid-phase compression molding. The microstructures of the composite samples were observed by scanning electron microscopy, which showed that the formation of a GS-conductive network at the PA6 granule interfaces in the segregated conductive structures and the adopting of PA612 considerably improved the interfacial adhesion of the composites. A superior impact strength of 5.1 kJ/m2 was achieved with 50 wt% PA612 loading owing to improvements in the interface compatibility between PA6 and GS. The composites possessed an ultralow percolation threshold, which was ascribed to the segregated network structure being successfully constructed inside the material. As for GS/PA6 composites, the combination of segregated GS-conductive networks achieved an ultralow percolation of 2.8 vol%. The percolation of 80PA6/20PA612-GS composites was slightly higher, measuring up to 3.2 vol%. Moreover, the thermal conductivity of the 80PA6/20PA612-GS composites increased from 0.26 to around 0.5 W/(m·K), which was 1.9 times larger than the pure polyamide.

3D Printing Interconnected Segregated Composites To Simultaneously Enhance Thermal Conductivity and Mechanical Properties

“…These methods encompass modifying the filler surface, hybridization and orientation of fillers, , as well as constructing a 3D segregated structure . The adoption of a segregated structure has proven its effectiveness in enhancing thermal conductivity in TPMCs while using lower conductive filler content over the past decade. − For instance, Liu et al fabricated the ternary composites of polystyrene/polypropylene/boron nitride (PS/PP/BN) composites with 3D segregated BN filler networks through a solution mixing, solvent etching, and hot-pressing approach. The resulting PS/PP/BN composite with 50 wt % BN loading achieved a TC of 5.57 W/mK.…”