Structural and physicochemical properties of melt-quenched poly(ethylene carbonate)/poly(lactic acid) blends

The effect of the melt-quench process on the thermal, structural and mechanical properties of partially miscible poly(ethylene carbonate) (PEC)/poly (lactic acid) (PLA) blends was investigated. The differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements found a largely amorphous phase of melt-quenched PEC/PLA blends, with crystallinity in the range 6-12%, depending on the PEC and PLA ratios. The high chain mobility of PEC reduces the cold-crystallization temperature of PLA for the melt quenched PEC/PLA blends by more 12 degrees C, as in the PEC60/PLA40 blend. Upon the rapid cooling, however, the morphology of PEC/PLA blend changes to enhance the toughness, especially for the PLA-rich blend. Addition of 10 wt% PEC to PLA slightly improved the tensile toughness, from 5.1 MJ/m(3) to 5.5 MJ/m(3), in which ductile PEC improves the toughness of PLA. SEM images of the quenched fracture cross-section of melt-quenched PEC/PLA blends confirmed that PEC and PLA are compatible, with a two-phase structure in which small PLA domains are distributed in the continuous PEC phase. This structure is responsible for the high interfacial adhesion in the sea-island morphology of PEC-rich blends, giving improved resistance to failure of PEC. (C) 2019 Elsevier Ltd. All rights reserved.