Cost-effective Production of Antistatic Composite Filaments Using Expanded Graphite for Additive Manufacturing

This study presents the simple fabrication of antistatic composite filaments using expanded graphite (EG) as a conductive filler. EG was integrated into common thermoplastic polymers—PLA, PETG, FLEX 93A, ABS, ASA, and PP— using a single screw bench-top extruder with a simple particle loading technique to produce filaments with EG loadings up to 7.5%. Key processing parameters were optimised to minimise bubble formation and maintain a consistent filament diameter. Electrical resistivity measurements demonstrated that the addition of EG significantly reduced resistivity in all polymers, transitioning them from insulators to antistatic materials with volume resistivities ranging from 2.1 × 10¹¹ to 2.1 × 10⁸ Ω·cm, depending on matrix and loading. Morphological analysis revealed that EG was dispersed throughout the filaments; however, particle agglomeration occurred. Tensile tests showed material-dependent effects, with elastomeric FLEX 93A benefiting most from EG reinforcement, while PLA, ABS, and ASA displayed varying changes in strength and modulus. XRD was used to determine the relationship between EG loading and crystallinity for particle loading characterisation. These results validate the efficacy of expanded graphite for imparting reliable antistatic properties to additive manufacturing filaments without markedly compromising mechanical performance, enabling their use in sensitive electronics and safety-critical environments.