Modification of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/Poly(lactic acid) Blends by In-Situ Reactive Melt Processing for Sustainable Packaging Application

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biopolyester produced by bacterial biosynthesis that has the potential to replace commodity plastics. However, poor melt strength and a narrow processing window limit its packaging application. In this work, commercial and pilot-scale PHBV is biosynthesized from fermented dairy manure using mixed microbial culture, extracted with dimethyl carbonate, and purified. Blends of the purified PHBV with poly(lactic acid) (PLA) were reactive melt-processed with triallyl isocyanurate (TAIC; 0.2–0.3 wt%), Joncryl (0.1–0.5 wt%), and talc (0.1 wt%), followed by injection molding. Rheological, thermal, and mechanical properties were studied and compared with modified commercial PHBV/PLA blends. The formulation containing 0.3% TAIC/0.3% Joncryl/0.1% talc showed the highest complex viscosity, indicating improved processability. Thermal analysis showed a broadened processing window for the laboratory PHBV/PLA blend but a reduction for the commercial blend. Molar mass analysis indicated considerable thermomechanical degradation, particularly in the laboratory blend. FTIR and gel fraction analysis were consistent with limited network formation in the commercial blend, whereas the laboratory blend showed no measurable gel fraction, with property improvements mainly attributed to enhanced chain entanglement. Differential scanning calorimetry showed reduced crystallinity in both blends. Mechanical testing showed reduced stiffness in both blends. Reactive melt processing enhanced the PHBV/PLA processability for sustainable packaging applications.