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 degrees 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 approximate to 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 & times; 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.