Effect of nitrogen-doped graphene on morphology and properties of immiscible poly(butylene succinate)/polylactide blends

Plastic pollution has become a serious issue to the ecosystem, and biodegradable poly (butylene succinate)/polylactide (PBS/PLA) blends are regarded as the promising eco-friendly alternatives to replace the non-degradable plastics based on fossil fuels. Yet, the thermodynamically immiscible nature of PBS and PLA hinders their extended applications. In this contribution, nitrogen-doped graphene (NG) was introduced into immiscible PBS/PLA blends by melt compounding. The incorporation of NG in PBS/PLA (70/30 wt%) blends was observed to significantly improve the geometrical morphology and reduce the domain size of the dispersed PLA phase, indicating a compatibilization effect of NG on the immiscible blends. The TEM micrographs showed that the NG mainly dispersed in the PBS matrix while a small amount was located in PLA phase. When the NG concentration increased to 1.0 wt%, the NG filled PBS/PLA nanocomposites exhibited an obvious improvement in the storage modulus and loss modulus in comparison with the pristine PBS/PLA blend. The thermal stability of the PBS/PLA/NG nanocomposites was enhanced monotonously with an increase of the NG concentration, due to the barrier effect of NG and good interaction between the NG and polymer matrices. Moreover, the NG was noticed to act as a nucleating agent to significantly improve the PBS crystallinity without affecting the crystal forms of PBS and PLA. The tensile strength, tensile modulus and elongation at break of the blends could be enhanced by the low concentration of NG.