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

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.