Toughening Biosourced Poly(lactic acid) and Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Blends by a Renewable Poly(epichlorohydrin-co-ethylene oxide) Elastomer

[Image: see text] A series of sustainable polymer blends from renewable poly(lactic acid) (PLA), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3,4)HB), and poly(epichlorohydrin-co-ethylene oxide) (ECO) elastomer were fabricated via a melt blending method to gain balanced physical performance. The interplay of the composition, mutual miscibility, and viscosity ratio of the pristine PLA, P(3,4)HB, and ECO elastomer resulted in diverse phase structures of the ternary blends. An excellent flexibility at an elongation of 270% was achieved for the PLA/P(3,4)HB/ECO (70/20/10) blend with a core–shell structure. The PLA/P(3,4)HB/ECO (70/10/20) blend with a phase-separated structure exhibited a high impact strength of 54 KJ/m(2), which is 25 times over that of the neat PLA. The relationship between the phase structure and physical performance of the blend was analyzed based on the compositions, surface tension, and physical characteristics of the neat components. Combining the compatibilization of the P(3,4)HB phase and ECO elastomer toughening played a crucial role in enhancing the mechanical properties of the blends.