The thermal behavior of polylactide with different d-lactide content in the presence of dissolved CO2

Abstract

The crystallization behavior of polylactidewith different D-lactide content (1.5, 4.6, and 10.1%.) was investigated in the presence of dissolved CO2 by using a high-pressure differential scanning calorimeter. The PLA's crystallization rate was significantly increased with the dissolved CO2 and by reducing the D-lactide content. However, the PLA with a high D-lactide content did not reveal any crystallization during non-isothermal and isothermal melt crystallization, even under 60 bar CO2 pressure. On the other hand, the final crystallinity of the other two PLA samples differed at various CO2 pressures and at different cooling rates. Thiswas due to the resultant effects of CO2's plasticization and the density of the crystal nuclei on the PLA's molecular mobility, a phenomenon consistent with our earlier investigations of PLAs with different branching degrees and with PLA nano/microcomposites. Moreover, the plasticizing CO2 molecules depressed the crystallization and glass transition temperatures of the PLA samples similarly.