Enhanced Crystallization Behavior and Stiffness-toughness Balance of Polylactide/Poly(propylene carbonate)/Nucleating Agent Blends

• The crystallization behavior and toughness of polylactide (PLA) were modified. • Poly(propylene carbonate) (PPC) had little effect on crystallization and toughness. • The addition of a hydrazide nucleating agent contributed to the dispersion of PPC. • The nucleating agent and PPC generated synergetic tailoring effect. Both poly(propylene carbonate) (PPC) and a hydrazide compound tetramethylenedicarboxylic di(2-hydroxybenzohydrazide) (TMBH) were selected to modify the crystallization behavior and stiffness-toughness balance of polylactide (PLA) simultaneously. For PLA/PPC binary blends, a sea-island phase structure could be observed and transformed to a bi-continuous structure gradually with the increase of PPC concentration. Due to the thermodynamic immiscibility, the addition of PPC had little nucleating effect on PLA during the cooling stage. As a result, tensile properties of PLA/PPC blends declined obviously with increasing PPC loadings. Otherwise, the addition of TMBH effectively enhanced the crystallization ability of PLA. Interesting ly, the dimension of both PPC domains and PLA crystals in ternary blends was much smaller than its binary counterparts under the same PPC concentrations due to the addition of TMBH. This contributed to the increase of tensile toughness and the occurrence of brittle-ductile transition as PPC content reached 40 wt%.