Diverse interfacial crystalline morphologies induced by poly (d-lactide) (PDLA) melt penetration process in multi-melt multi-injection molding (M3IM) system

In this study, poly (l-lactide) (PLLA) was penetrated by poly (d-lactide) (PDLA) in multi-melt multi-injection molding (M3IM) system, and a stable stereocomplex crystal (SC) band was obtained at the interface between the penetrated layer (PLLA) and the penetrating layer (PDLA). The relationship between the width of SC band and the injection velocity was investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), polarized optical microscopy (POM) and 2D-WAXD. It was found that a lower injection velocity leads to a wider and more stable SC band owing to the unique and the complex coupling action of external fields (shear field and temperature field, etc.) in M3IM system. The stable SC band endows the M3IM penetrated samples with enhanced mechanical performance compared to the conventional injection molding (CIM) sample, which shed a light into potential reinforcement of production in PLA manufacturing and application in barrier and unidirectional heat conduction.