Zn²⁺-Doped Carbon Quantum Dots and Polycarbodiimide Comodified Polylactic Acid/Poly(butyleneadipate-<i>co</i>-terephthalate) Blends

Zn2+-doped carbon quantum dots (Zn-CDs) and polycarbodiimide (PCDI) were utilized as reactive compatibilizers to improve the material properties of polylactic acid/poly(butyleneadipate-co-terephthalate) (PLA/PBAT) blends. Extensive investigations were conducted to evaluate the mechanical, thermal, and rheological properties of the composite materials. In addition, the synergistic interaction of PCDI and Zn-CDs in PLA/PBAT blends was also explored. Notably, successful implementations of these PLA/PBAT blends in industrial grade fused deposition molding (FDM) pellet printers were achieved. The results unequivocally demonstrated that the incorporation of PCDI effectively improved the compatibility of PLA/PBAT blends, resulting in excellent mechanical properties. However, due to the poor melt flow behavior, its suitability for melt-printing applications is limited. This issue was resolved by introducing Zn-CDs into the PLA/PBAT blend system. The mechanical tests showed that the samples exhibited a tensile strength of 32.8 MPa under the synergistic effect of PCDI/Zn-CDs, while achieving a remarkable elongation at a break value of 728% and an increase in melt flow rates by 109%. The enhanced mechanism of PCDI/Zn-CDs was further analyzed through microscopic morphology. The reaction between PLA/PBAT terminal carboxyl groups and PCDI resulted in copolymer formation, enhancing the molecular chain entanglement and interphase interfacial adhesion. Moreover, the combination of Zn-CDs strengthened the intermolecular forces through hydrogen bonding and metal coordination, thereby imparting superior thermal properties for printing applications.