FDM 3D Printing of Flame-Retardant Polylactic-Acid-Based Composites with Electromagnetic Interference Shielding...

In this work, flame-retardant (FR) PLA-based composites exhibiting both good flame retardancy and electromagnetic interference (EMI) shielding were fabricated through combining melt blending with fused deposition modeling (FDM) 3D printing. Intumescent flame-retardant (IFR) fillers and graphene nanoplatelets (GNPs) were incorporated to construct a synergistic system, and the resulting structure-property relationships were systematically investigated. The optimal performance was achieved with 15 wt% IFR fillers and 3 wt% GNPs. The prepared composite exhibited a residual char yield of 14.3% at 700 °C, significantly higher than that of neat PLA. Regarding flame retardancy, the limiting oxygen index (LOI) increased to 32.5%, and the vertical burning level achieved a UL-94 V-0 rating. In the cone calorimetry test, both the peak heat release rate and total heat release were markedly reduced, attributed to the formation of a dense and stable char layer. For EMI shielding, the FR composite achieved a total shielding effectiveness (SE_T) of 20.6 dB in the X-band, with an absorption proportion exceeding 80%, indicating an absorption-dominated mechanism. Meanwhile, a well-established conductive network effectively enhanced the electromagnetic loss. Overall, the synergistic effect of IFR fillers and GNPs enabled simultaneous improvements in flame retardancy and EMI shielding in FR PLA-based composites, providing a feasible strategy for designing functional 3D-printed FR PLA-based materials.