Improved mechanical and thermal properties of PLLA by solvent blending with PDLA-b-PEG-b-PDLA

In this article, two types of poly (d-lactide)-b-poly (ethylene glycol)-b-poly (d-lactide) (PDLA-b-PEG-b-PDLA) were added into PLLA matrix by solution casting method. The obtained films were characterized by wide-angle X-ray diffractomery (WAXD), differential scanning calorimetry (DSC), tensile testing and thermal gravimetric analyzer (TGA). Results indicated that the heat resistance of these blends could be improved when the amount of copolymer exceeded 30 wt%, because the high melting point stereocomplex was preferentially formed at that addition amount, whenever from solutions or from melt. Both the tensile strength and elongation at break of the blends were enhanced when 30 wt% copolymer was added, which were partly caused by the synergistic effects of stereocomplexation between enantiomeric PLAs and plasticization of PEG blocks. The blends showed higher thermal stability than neat PLLA at temperature above 370 °C. These results showed that the toughness and heat resistance of PLLA were improved, which made the application of PLA probable.