Morphology and performance relationship studies on biodegradable ternary blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polylactic acid, and polypropylene carbonate

A biodegradable ternary blend fabricated from polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polypropylene carbonate (PPC) with a good balance of stiffness and toughness via optimizing the composition ratio and morphological structure is, to the best of the authors' knowledge, reported here for the first time. The optimal blend formulation is comprised of 20% PLA, 40% PHBV, and 40% PPC, which possesses a tensile strength measuring 44 MPa and an elongation at break measuring at 215%. Thermal performance analysis revealed an HDT value of 72 °C. The Harkins equation predicts that the three immiscible polymers formed a complete wetting morphology, which was confirmed by scanning electrical microscopy. As the PPC content of the ternary blends is increased, the material undergoes morphological transition from droplet to co-continuous structure, resulting in significant improvement of elongation at break (approximately 40 times higher than that of the PLA–PHBV binary blend). Excellent stiffness and over 200% elongation at break make these sustainable ternary blends feasible for use in packaging as substitutes for certain non-biodegradable petroleum-based single use plastics.