Enhancing 3D printability of polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) based blends through melt extrusion based-3D printing

Abstract

Polyhydroxybutyrate (PHB) and poly (3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV) possess favorable biological properties such as biocompatibility and biodegradability, making them suitable for various applications. However, their utility is limited by a narrow processing window due to low thermal stability and challenges in manipulating filament size during extrusion, attributed to poor melt strength. These issues result in irregularities such as discontinuous flow and incomplete deposition of melted PHB, significantly affecting 3D printing outcomes. To address these concerns, this study explores blending PHB and PHBV with poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) to enhance its processability and printability. Thermal analysis of all blends revealed three distinct degradation steps occurring at approximately 300, 360, and 400ºC, corresponding to PHB or PHBV, PLA, and PBAT, respectively. Moreover, the melting temperatures of PHB, PHBV, PLA, and PBAT were measured around 176, 173, 152, and 121ºC, respectively. It was observed that the polymer blends exhibited lower crystallization temperature and degree of crystallinity compared to PHB or PHBV. Assessing their 3D printability, neat PHB and PHBV filaments experienced fusion issues, poor flow during extrudate deposition, and significant warping, leading to 3D printing failures. In contrast, the blends displayed enhanced flowability and successfully produced high-quality specimens. Scanning electron microscope (SEM) analysis highlighted a phase separation morphology in the blends, showcasing uniform dispersion of PLA and PBAT within the PHB matrix.