Texas State University – San Marcos: FDM 3D Printing with Polyamide 6 / Nanographene Filaments

Researchers from the Ingram School of Engineering at Texas State University-San Marcos recently published their findings on polyamide 6 nanographene composites. Outlined in ‘Electrical and Mechanical Properties of Fused Filament Fabrication of Polyamide 6 / Nanographene Filaments at Different Annealing Temperatures,’ we find out more about electrostatic charge dissipation in relation to temperature changes with the use of specific materials.

Nanographene particles can reduce electrical resistivity as well as generate conductive networks. These composites also promise the benefits of parent polyamide 6, offering good mechanical properties for FDM 3D printing—in this case, using a Lulzbot TAZ 6 3D printer.

The research team turned to conductive plastics because—unlike nonconductive plastics—they can act as a shield from electromagnetic interference (EMI).

Lulzbot TAZ 6 Printer and Printed Tensile Samples

“Conductive plastics are dependent on the material thickness, dispersion of the additive, and the conductivity of the additive. An advantage of using a conductive plastic instead of a coating is that the EMI shielding is integral to the part and cannot be removed by abrasion,” explained the researchers.

Nonconductive polymers also do not offer what is often necessary protection from electrostatic discharge (ESD); for example, industries that produce semiconductors or medical devices must ensure the protection of sensitive electronics. Conductive polymers can also be used to make packaging for such devices, capable of diminishing electrical charges. Both Polylactic Acid (PLA) polymer and reduced graphene oxide (r-GO) are suitable for making electrical components like circuit boards due to their conductivity—allowing them to improve on other materials like copper wire.

A variety of nanomaterials are also used for making nanocomposites capable of dissipating electrostatic charge, like 4 wt% PA12/carbon black nanocomposites. These materials may also be made with polyamides that are durable enough for space, combined with other additives. Graphene nanoplatelets are another alternative, composed of flat carbon nanosheets—offering good quality and better affordability.

3D printing during this study was not seamless. Despite the disadvantages of using SLS, the research team encountered issues with print quality, prompting a change from PA11 to PA6 due to availability. The interlaminar separation was still present, resulting in both air pockets and further electrical resistivity. Due to the findings in this study, the researchers suggested the use of an IR light ‘mounted ahead of the extruder.’ Localized heat could prove to be more effective in adhesion of layers.

Ultimately, the researchers performed tensile tests on the neat PA6, and with 3 wt%, 5wt%, and 7 wt% NGP and annealed at 80°C, 140°C, and 200°C. Both tensile strength and elasticity fell as they added NGP—except for the 200° annealed specimens.

Tensile Testing Setup and Tested Specimens.

“SEM was used to verify the dispersion and morphology of filament samples that were annealed at 80°C and not annealed. The filaments showed good dispersion on all samples by using twin screw extrusion. It is unknown if annealing changed morphology as it was not a change observed in the SEM images. Some specimens were not flat. Heating profiles could be investigated to decrease warpage,” concluded the researchers.

Ultimate Tensile Strength for Annealing Temperatures and Wt.% NGP.

Elastic Modulus for Annealing Temperatures and Wt.% NGP.

The use of composites continues to expand, and with FDM 3D printing as a common method due to ease in use, affordability, and accessibility—from lignin biocomposites to thermoplastic magnetics, glass, and more.

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Tensile Testing Summary of Not Annealed and Annealed at 80°C, 140°C, and 200°C FFF 3D Printed PA6/NGP.