Effect of epoxidized soybean oil on melting behavior of poly(l-lactic acid) and poly(d-lactic acid) blends after isothermal crystallization

The effect of epoxidized soybean oil (ESO) on homocrystallization (HC) and stereocomplex (SC) formation behavior of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) bends was investigated utilizing differential scanning calorimetry (DSC). Isothermal crystallization was performed on ESO/PLLA/PDLA blends with varying ESO contents (0, 5, 8, and 10 wt%) and temperatures (90 °C, 120 °C, and 150 °C) for a different duration (12.5, 25, and 125 min). It was found that the ESO could effectively inhibit HC crystallization and promote SC crystallization. For the sample without ESO (ESO-0), the isothermal crystallization temperature and duration had little effect on the melting behavior, whereas sample with 5 wt% ESO (ESO-5), HC crystallization decreased while SC crystallization continued to increase with increasing duration. Additionally, at higher crystallization temperatures with constant ESO content, the melting temperature of SC crystals did not significantly change, suggesting that ESO did not degrade PLLA/PDLA blends. These findings imply that ESO modifies crystallization kinetics, suppressing HC formation and enhancing SC formation, which could benefit for specific material properties and applications.