Enhancement of stereocomplex formation in poly(l-lactide)/poly(d-lactide) mixture by shear

The non-isothermal crystallization behavior of poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) blends under shear was investigated by in-situ polarized light optical microscopy (POM) and wide angle X-ray scattering (WAXS). Pulse shear for 5 seconds was applied to the melt during cooling. The effects of shear temperature and shear rate were systematically studied. It was found that the shear field could increase the nucleation density of stereocomplex crystal (SC), and accelerate the overall crystallization rate. The final crystallinity of SC increased to as high as ∼45% with a shear rate of 178 s−1 when the shear temperature was 150 °C. The onset crystallization temperature of α crystals increased by ∼10 °C. The final content of α crystals reduced with the increase of SC content. Multiple factors influence the crystallization of SC and α crystals, including the shear rate, shear temperature and the nucleating/confinement effect of SC on α crystals. [Display omitted] •The crystallization behavior of PLLA/PDLA equimolar mixture under shear field is investigated by in-situ WAXS.•The nucleation density and final content of stereocomplex are enhanced by shear field.•The final content of α crystal reduced with the increase of stereocomplex content.