Renewable Nanocomposites for Additive Manufacturing Using Fused Filament Fabrication

Additive manufacturing provides an opportunity to redefine sustainability for plastic products, as polyolefins, which dominate traditional plastics manufacturing, are generally unsuitable for 3D printing. One of the most widely used 3D printing technologies is fused filament fabrication (FFF), where a thermoplastic filament is melted and extruded to build the object layer-by-layer. The printing performance can be quantified in terms of mechanical properties and dimensional accuracy of the part. Here we demonstrate the ability to print high-quality parts via FFF using a biorenewable polyamide-11 (PA-11). The PA-11 monomer, 11-aminoundecanoic acid, is derived directly from castor beans by hydrolysis, methylation, and heat treatment of its oils. The elastic modulus and dimensional accuracy can be further improved by the incorporation of a natural nanofiller, sepiolite. The role of print orientation and filler content are systematically investigated, with elastic moduli greater than 1.1 GPa obtained for the optimal printing conditions. The addition of sepiolite tends to improve both the dimensional accuracy of the printed part and the elastic modulus. The mechanical properties are dependent on the print orientation, with a flat (XY) orientation leading to the highest moduli as well as ductile failure, while the elastic modulus when printed in the end-on (YZ) orientation is decreased by 10-30% with greater decrease as the sepiolite content increases. Moreover, the samples with an YZ orientation exhibit brittle failure, which is attributed to the deposition direction being perpendicular to the applied tensile load. These results demonstrate the potential of sustainable nanocomposites for additive manufacturing via FFF.