A ternary blend of entirely biodegradable polymers, namely polylactide (PLA), poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV), and poly(butylene succinate) (PBS), was first melt-compounded in an effort to prepare novel fully biodegradable materials with an excellent balance of properties. The miscibility, morphology, thermal behavior, mechanical properties, and thermal resistance of the blends were investigated. DMA analysis revealed that PHBV and PLA showed some limited miscibility with each other, but PBS is immiscible with PLA or PHBV. Minor phase-separated structure was observed from SEM for all the blends composition except PHBV/PLA/PBS 60/30/10 blend, which formed a typical mixture of core-shell morphology. The morphologies were verified by analysis of the spreading coefficients. Excellent stiffness-toughness balance was achieved by ternary blends of PLA, PHBV, and PBS. Significant enhancement of the toughness and flexibility of PLA was achieved by the incorporation of PBS and PHBV without sacrificing the strength apparently. Both the stiffness and toughness were improved for PHBV in the ternary blends with PHBV as matrix. The crystallization of the PLA and PBS were enhanced by presence of PHBV in the blends, while the crystallization of PHBV was confined by PLA and PBS phases. Moreover, the thermal resistances and melt flow properties of the materials were also studied by analysis of the heat deflection temperature (HDT) and melt flow index (MFI) value in the work.

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