Fused Filament Fabrication with Engineered Polyamide-12-Cork Composites with a Silane Coupling Agent as an Interaction Promoter

For industrial-scale additive manufacturing (AM) to be successful, the adoption and innovation of sustainable materials made from biobased and renewable resources is vital. Herein, we explore the potential of using waste cork particles as a high-volume filler in nylon-12-based thermoplastic composites, with processing and performance characteristics optimized for fused filament fabrication (FFF) to create customized, lightweight engineered products. To generate engineering thermoplastic composites for FFF, we modified the cork with a silane coupling agent and melt-mixed it with nylon-12. A thorough evaluation was conducted on the impact of the volume fraction of the surface-modified cork filler on the viscoelastic and processing characteristics of the polymer melt. Using the optimized composition, filaments for 3D printing by FFF were produced, and their properties including thermal stability, crystallization behavior, filament extrusion morphology, and mechanical properties were evaluated. Scanning electron microscopy (SEM) was used on the tensile-fractured surface of the failure specimens to understand the mode of failure and correlate it with strength. Micro-CT was used as a nondestructive test to study the distribution of cork in the filament and the 3D-printed products. The surface roughness of the 3D-printed product was evaluated through digital microscopy. It was observed that (3-aminopropyl)triethoxysilane is an effective interaction promoter for nylon-12/cork composites. The melt rheology of nylon-12 and its composites exhibits non-Newtonian shear-thinning behavior and thermorheological complexity, with higher cork content further enhancing such shear-thinning characteristics. Considering processability, 3D printing capabilities, and final properties, a similar to 15 vol % cork content was observed to be optimal. It has been confirmed that 3D-printed nylon-12/cork composite products can offer superior mechanical properties, flexibility, and elongation at failure compared to compression-molded samples. This study provides valuable insights into the composite's feasibility for 3D printing and its potential applications.