Enhanced crystallization behavior and stiffness-toughness balance of polylactide/poly(propylene carbonate)/nucleating agent blends

Both poly(propylene carbonate) (PPC) and a hydrazide compound tetramethylenedicarboxylic di(2hydroxybenzohydrazide) (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. Interestingly, 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%.

Automated summary

Both PPC and TMBH were used to modify the crystallization behavior and stiffness-toughness balance of PLA. A sea-island phase structure was observed in PLA/PPC blends, which gradually transformed into a bi-continuous structure with increasing PPC concentration. The addition of PPC had little nucleating effect on PLA, resulting in a decrease in tensile properties. On the other hand, the addition of TMBH effectively enhanced the crystallization ability of PLA. The dimension of PPC domains and PLA crystals in ternary blends was smaller than their binary counterparts due to the presence of TMBH, leading to improved tensile toughness and brittle-ductile transition.