Sustainable biobased blends of poly(lactic acid) (PLA) and poly(glycerol succinate-co-maleate) (PGSMA) with balanced performance prepared by dynamic vulcanization

Biobased blends of poly(lactic acid) (PLA) and poly(glycerol succinate-co-maleate) (PGSMA) were fabricated by using a dynamic vulcanization strategy involving the simultaneous crosslinking and compatibilization of PGSMA within the PLA matrix on reactive extrusion. It was found that a balance between PLA/PGSMA compatibility and a low glass transition of PGSMA must be achieved in order to maximize the toughness of the blends. This was realized by setting the succinic acid to maleic anhydride content of the PGSMA synthesis to 1 : 0.75 : 0.25 mol glycerol : succinic acid : maleic anhydride, yielding a C=C bearing reactive PGSMA with a glass transition of -1.69 degrees C, as determined by differential scanning calorimetry. The dynamically vulcanized PLA/PGSMA blends achieved an interfacial adhesion of B = 0.744 according to the Pukanszky model, which was attributed to the formation of PLA-g-PGSMA copolymers as shown by FTIR analysis. PLA shear yielding induced by PGSMA debonding was the main factor responsible for enhanced toughness in both tensile and impact testing. With an increase in PGSMA content of the blends, the average size of the PGSMA phase increased from 0.469 up to 0.649 mm, as shown by SEM imaging. With this, a higher number of debonded PGSMA particles were able to induce plastic deformation of the PLA matrix leading to tougher blends. Biobased dynamically vulcanized blends containing 60/40 wt% of PLA/PGSMA displayed an increment in their elongation at break and notched Izod impact resistance of 53% and 175% as compared with the neat PLA material.