Abstract
Functional filaments for the FDM (Fused Deposition Modeling) 3D printing process are available on the market in a wide variety, including materials with enhanced strength, heat resistance, chemical stability, and thermal or electrical conductivity. The latter are particularly interesting due to their broad range of applications, spanning printed electronics, smart textiles, and electromagnetic shielding components. Most conductive filaments use common polymers such as PLA, ABS, or PETG mixed with conductive fillers, but reaching high conductivity typically requires high filler content, which makes the filaments brittle and difficult to print.
This research focuses on a novel type of electrically conductive filament consisting of hot-melt adhesives and multi-walled carbon nanotubes. It was found that such electrically conductive adhesives retain their flexibility and have good printability, but their behavior strongly depends on the composition. The addition of carbon nanotubes alters the thermal characteristics and, in some cases, decreases the degradation temperature, which may limit their suitability for the FDM process. The electrical properties were further influenced by processing parameters such as flow rate and nozzle temperature, which altered the CNT orientation, as confirmed through high-resolution scanning electron microscopy. Mechanical and electrical evaluations were performed on specimens cut from 3D-printed boxes made using a Prusa MK4 printer. Finally, the conductive filaments were printed under optimized conditions into mesh structures, which were subsequently used as interlayers in a carbon-fibre reinforced polymer to reduce through-thickness electrical resistivity caused by the insulating nature of the thermoset polymer matrix.
The research leading to these results received funding from the National Centre for Research and Development through the LIDER XV (GA: LIDER15/0151/2024) and the Small Grant Scheme 2014–2021 (GA: NOR/SGS/3DforCOMP/0171/2020-00).