Large-format additive manufacturing of biodegradable reinforced TPS/PBAT composite blends

The increasing demand for sustainable materials in additive manufacturing (AM) has prompted the development of biodegradable composite blends suitable for large-format fused granular fabrication (LF-FGF). In this study, novel thermoplastic formulations based on thermoplastic starch (TPS), poly(butylene adipate-co-terephthalate) (PBAT) and calcium carbonate (CaCO3) were engineered and evaluated for printability, thermal stability, and mechanical performance. Two optimized formulations with different inorganic content (F1 and F2) were prepared via twin-screw extrusion using commercial masterbatches and characterized in terms of their starch, polymer, plasticizer, and filler contents. Spectroscopic and thermal analyses confirmed the structural integrity of all components post-extrusion. DSC and melt flow rate measurements revealed thermally stable processing windows (100–150 °C) and good flow behaviour suitable for LF-FGF. Both formulations were processed via injection moulding and LF-FGF, and mechanical testing was conducted on printed parts in two build orientations. F1 displayed superior toughness and dimensional fidelity, while F2 achieved the highest stiffness (E ≈ 300 MPa) due to higher CaCO3 content. Notably, F1 printed in the XY direction outperformed its injection-moulded counterpart in tensile strength, highlighting the advantage of layer-wise thermal relaxation in LF-FGF. A prototype latticework to separate spaces measuring 100 × 50 cm was successfully fabricated as a proof-of-concept. These results demonstrate the potential of tailored biodegradable TPS/PBAT/CaCO3 blends for scalable, sustainable manufacturing of large custom objects using pellet-based AM.