Efficient fabrication of highly exfoliated and evenly dispersed high-density polyethylene/expanded graphite nanocomposite with enhanced dielectric constant and extremely low dielectric loss

A one-step melt mixing strategy based on the synergism of steam explosion and alternating convergent-divergent flow, is innovatively developed to fabricate high-performance high-density polyethylene (HDPE)/expanded graphite (EG) nanocomposites within 4 min, without any chemical reagents or complex pretreatments. A successful synergy of the external forces from surrounding elongational melts and the internal forces from steam explosion results in EG rapidly exfoliating into few-layer graphene and simultaneously dispersing in HDPE evenly. The thinnest exfoliated EG reaches two-layer graphene (1.4 nm). Benefit from excellent exfoliation and dispersion effect, the nanocomposites feature low melt resistance and relaxation time, good ductility. Furthermore, the nanocomposites obtain a greater increment of dielectric constant as more EG adding, but always maintain an extremely low dielectric loss (<0.01), exhibiting a potential for 5G communication materials. This strategy provides a promising pathway for industrially producing functional nanocomposites with high-content fillers and manufacturing nanosheets via melt-exfoliating 2D layered materials.