Shape memory performance of bio-based polyester blends 4D printed by Fused Granulate Fabrication (FGF)

With the rise of advanced manufacturing technologies such as Fused Granulate Fabrication (FGF), the influence of processing routes on the shape-memory behavior of bio-based polymers remains poorly understood. This study investigates poly(hydroxybutyrate) (PHB)/poly(lactic acid) (PLA)/poly(butylene succinate- co -adipate) (PBSA) biopolyester blends 3D-printed using FGF under varied programming conditions to establish structure–process–property relationships relevant to 4D printing. Comparing compression-molded and printed samples revealed how fabrication and printing-induced orientation affect morphology, mechanical properties, and the shape memory effect (SME) response. PLA75-PBSA25 demonstrated superior mechanical performance (strength ≈40.00 MPa, modulus ≈1.10 GPa) and SME efficiency, achieving nearly perfect shape fixity (Rf ≈ 100%) and high recovery (Rr ≈90.0%). Based on combined SME and mechanical performance, the blends can be ranked as: PLA75-PBSA25 > PHB25-PLA50-PBSA25 > PHB33-PLA33-PBSA33 > PHB50-PLA25-PBSA25 > PHB75-PBSA25. Programming temperature had a significant influence on SME: cold programming resulted in incomplete fixation, hot programming caused partial loss of recovery due to plastic deformation, while warm programming (60 °C) yielded the most balanced and repeatable performance. 3D-printed samples retained SME efficiency within 10.0% of that of compression-molded counterparts. Layers printed parallel to the deformation direction exhibited slightly higher recovery than those printed at 90°. Cyclic testing confirmed that PLA75-PBSA25 retained stable SME performance over 15 cycles, while other blends exhibited moderate fatigue. Overall, optimized phase compatibility and warm-programming conditions enabled the reliable synthesis of SME, identifying PLA75-PBSA25 as a promising material for durable 4D-printed shape memory applications.