Development and Characterization of 3D-Printable PA6/Oyster Shell Composites for Potential Oyster Spat Collector Applications

The growing accumulation of plastics in marine environments and their fragmentation into microplastics have increased the demand for durable and sustainable materials for aquaculture applications. Oyster shell waste is particularly attractive because it is an abundant by-product of shellfish aquaculture and consists predominantly of biogenic calcium carbonate (CaCO3), a mineral naturally associated with oyster habitats. This study investigates the feasibility of incorporating oyster shell powder into polyamide 6 (PA6) to produce 3D-printable composites for potential oyster spat collector applications. PA6 composites containing 10, 20, and 30 wt% oyster shell powder were compounded, extruded into filaments, and processed via fused deposition modeling (FDM). The materials were characterized with respect to processability, thermal and mechanical properties, moisture uptake, filler composition, and CaCO3 dissolution behaviour. All formulations showed good processability and were successfully printed into mechanically stable specimens. Increasing filler content increased stiffness but reduced ductility, while melting and crystallization temperatures remained largely stable but influenced enthalpy properties at higher filler loadings. Immersion experiments revealed partial dissolution of the mineral phase, indicating partial CaCO3 dissolution without visible degradation of the PA6 matrix. Overall, the results demonstrate the feasibility of highly filled PA6/oyster shell composites for additive manufacturing and provide a foundation for future studies addressing seawater exposure, oyster larval settlement and field-scale validation.