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Additive Manufacturing of Polyamide 6/66 Copolymer Nanocomposites: Thermal and Flammability Properties

As one of the most commonly used methods of additive manufacturing (AM), fused filament fabrication (FFF) has drawn a great amount of interest in both industry and academia. The purpose of this study is to develop a flame retardant (FR) polyamide 6/polyamide 66 (PA6/66) nanocomposite with reduced flammability and enhanced thermal and mechanical properties, while simultaneously maintaining the printability for commercially available FFF machines. In this study, varying amounts of FR, thermoplastic elastomer (K), nanoclay (NC), and multiwall carbon nanotubes (MWNT) were melt compounded via twin-screw extrusion to prepare PA6/66 nanocomposite pellets. The flame retardant and thermal properties of these formulations were characterized using microscale combustion calorimeter (MCC) and thermogravimetric analysis (TGA). Based on MCC, it was found that formulations 2, 4, and 5 yielded best results, while formulation 3 and 2 gave best results in TGA testing. Finally, three FR PA6/66 formulations (2, 4, and 5) were down-selected, 3D printed via FFF, and used for flammability, thermal, and mechanical properties characterizations. Due to difficulties in 3D printing, only formulation 5 was successfully printed and tested. However, despite not being the best performing formulation, formulation 5 yielded promising results in UL 94 and tensile tests. Lastly, Micro-CT analysis displayed that formulation was much more porous in comparison to the neat PA6/66 system.