Mechanical Characterization of Additively Manufactured Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) Biopolymer

ABSTRACT Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBH) is a biodegradable polyester with strong potential for marine and packaging applications common for thermoplastic polymers, yet its performance after being additively manufactured remains largely unknown. This study investigates the mechanical, density, and hardness properties of PHBH processed with fused filament fabrication (FFF) compared with injection‐molded benchmarks, with a focus on process–property relationships and useful information for design applications. FFF‐printed samples were produced under varying nozzle temperature, print speed, and layer height following a full‐factorial experimental design, and tested for elastic modulus, ultimate tensile strength, elongation at break, density, and Shore D hardness. Five replications of 27 factor combinations were used for the printed samples, in addition to the injection‐molded samples, for a total of 792 data points from 312 individual samples. Crystallinity values for the raw material and molded and printed samples were evaluated and found to not vary significantly for any of the samples. Compared with injection‐molded parts, FFF parts exhibited lower strength and elongation but comparable or higher modulus under certain conditions. In particular, the differences in properties were 5%–17% (with the exception of elongation) instead of 40%–70% seen with many other FFF materials. The differences were attributed to shorter thermal holding times in the extruder, layer‐wise deposition, and reduced consolidation. The density and hardness were generally lower in the printed parts, reflecting interlayer voids and limited polymer chain diffusion. The results highlight parameter combinations that improve interlayer bonding while avoiding thermal degradation, providing a processing window for reliable FFF production of PHBH. These findings support the viability of PHBH in additive manufacturing, enabling on‐demand fabrication of biodegradable components for short‐lifecycle and marine‐degradable applications.