Fabrication of conductive polymer composites with segregated networks is an effective approach in electromagnetic interference (EMI) shielding. In this article, a simple strategy based on the addition of poly(ethylene oxide) (PEO), acting as a binder between carbonaceous nanofillers and poly(lactic acid) (PLA) particles, is proposed. The carbonaceous nanofillers were mixed with small amounts of PEO to prepare the masterbatch, and then the masterbatch was coated on the surface of PLA particles at an appropriate temperature. Finally, the coated PLA particles were hot-pressed to form the PLA-based carbonaceous nanocomposites with a segregated structure. The effects of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) on the electrical conductivity and EMI shielding properties of PLA-based nanocomposites, both in segregated and random structures, were compared. For all the nanocomposites, electrical conductivity is always higher in segregated structure than that in random structure. Moreover, the EMI shielding effectiveness (SE) in segregated structure is also higher than that in random structure for all the PLA/GNP nanocomposites and the PLA/CNT nanocomposites with 0.5 to 2 wt% of CNTs. However, for PLA/CNT nanocomposites with 4 to 6 wt% of CNTs, the EMI SE in segregated structure is lower than that in random structure, which is in sharp contrast to the situation of electrical conductivity, due to denser conductive networks in random structure compared to that in segregated structure as demonstrated by the scanning electronic microscopy results. This indicates that the mechanism of EMI shielding is different from that of electrical conductivity.

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Low-density polyethylene single-polymer composites (SPCs) reinforced with sandwiched ultrahigh-molecular-weight polyethylene woven fabric were prepared by insert injection molding. The process combines aesthetic and processing advantages. A processing temperature window (135–155°C) of a very short cycle time (less than 30 s) could be realized. The mechanical properties and morphologies of the samples were evaluated. The results suggested that the polyethylene SPCs were prepared successfully with concurrent increases in flexural strength (∼57%), tensile strength (∼164%), and impact strength (∼69%). The effects of different processing parameters including the nozzle temperature, injection pressure, injection speed, and the holding time were discussed. Numerical simulation results were used in the analysis.