Blending PHBV with P(3HB- <i>co</i> -4HB) for superior thermal stability, mechanical strength, and environmental degradation

Polyhydroxyalkanoates (PHAs) hold significant potential as sustainable alternatives to fossil-based plastics because of their bio-based origin and inherent biodegradability. Poly-3-hydroxybutyrate-<i>co</i>-3-hydroxyvalerate (PHBV) is a well-known commercial member of the PHA family characterized by good mechanical resistance and thermal behavior similar to that of some conventional polymers, such as polypropylene. However, its high crystallinity and fragility limit its application. Poly3-hydroxybutyrate-<i>co</i>-4-hydroxybutyrate (P(3HB-<i>co</i>-4HB)) is a new commercial copolymer containing a 4-hydroxybutyrate (4HB) segment that provides increased flexibility because of its amorphous phase. In this study, PHBV and P(3HB-<i>co</i>-4HB) were blended by extrusion, varying the percentage of P(3HB-<i>co</i>-4HB) to improve the PHBV properties without losing the PHA assets and potentializing the insertion of this biopolymer in the market. The results indicate that the impact energy required for fracture was increased in the polymer blends. These blends exhibited greater thermal stability than pure PHBV, with no significant changes observed in the melting and crystallization temperatures. Furthermore, blending was found to reduce shrinkage in injection-molded samples. The degradation in the soil increased with the highest P(3HB-<i>co</i>-4HB) content. Through 3D printing, it was observed that the blends led to an increase in the melt flow index and a reduction in warpage in the printed objects, thereby facilitating the processing of these materials. Consequently, incorporating P(3HB-<i>co</i>-4HB) into PHBV has emerged as a promising strategy to address the inherent limitations of PHBV. This approach not only enhances the mechanical properties and thermal stability but also improves the overall processability, thereby expanding the potential applications of this biopolymer blend.