Additive manufacturing of PHBH and PBAT biopolymers via fused filament fabrication: a comparison between thermal and thermo-mechanical properties

This study aims to investigate the thermal and thermo-mechanical properties of poly(3-hydroxybutyrateco- 3-hydroxyhexanoate) (PHBH) and poly (butylene adipate-co-terephthalate) (PBAT) as sustainable alternatives for fused filament fabrication (FFF). Starting from commercial pellets, both biopolymers were processed into filaments using an extruder carefully controlling thermal parameters to ensure dimensional consistency. Filaments of PHBH and PBAT were subsequently used to produce several parts by using FFF. Thermal characterization was performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements to investigate the thermal behaviour of the two biopolymers, while their thermo-mechanical properties were assessed through dynamo-mechanical analysis (DMA) and tensile testing evaluating storage modulus, loss factor, elastic modulus, ultimate tensile strength, and elongation at break. The results evidenced that PHBH’s thermal stability slightly decreased progressively from pellet to filament extrusion up to the realization of printed components via FFF, with an important reduction of the degree of crystallinity. PHBH retains high stiffness and strength but remains brittle, limiting its use to applications where rigid components are required. On the contrary, PBAT maintains high thermal stability and thermal transitions quite similar during the whole processing with minor mechanical properties, which makes it useful for applications requiring high flexibility.