PLA/PBAT/CaCO₃ Composites with Balanced Super-Toughness and Stiffness through Dynamic Vulcanization and Double Interfacial Compatibilization

The incorporation of biodegradable poly(butylene adipate- co -terephthalate) (PBAT) into poly(lactic acid) (PLA) is a simple method to improve the toughness of PLA; however, the toughening efficiency of PBAT is limited, and direct blending adversely impacts the stiffness of the material. In this paper, the surface of nano-CaCO 3 was modified with 3-Glycidoxypropyltrimethoxysilane (KH560) in order to prepare CaCO 3 - g -KH560. A two-step extrusion process using multifunctional epoxy oligomers (ADR) as cross-linking agents was used to prepare PLA/PBAT/CaCO 3 ternary blends with a subinclusion structure. In the first extrusion, ADR and CaCO 3 nanoparticles were mixed in PBAT. During the second extrusion, the epoxide groups cross-linked the PBAT dispersing phase, as well as co-cross-linked the PLA continuous phase at the PLA/PBAT interface. Fourier Transform Infrared Spectroscopy (FTIR) confirmed this speculation. Additionally, Dynamic mechanical analysis (DMA) and Scanning electron microscopy (SEM) analyses showed that the co-cross-linking reaction improved the interfacial compatibility of PLA/PBAT. Energy dispersive spectrometer (EDS) and Transmission electron microscopy (TEM) analyses confirmed the uniform dispersion of CaCO 3 in the PBAT phase. The synergistic toughening of ADR and CaCO 3 allowed for the notched impact strength and tensile strength of the prepared blend to reach 74.5 kJ/m 2 and 55.7 MPa (11 times and 1.3 times higher than PLA/PBAT with same ratio, respectively). Compared to elastomer toughening alone, the subinclusion structure improves the rigidity of the composite owing to improved interfacial interactions and a distinct energy loss mechanism. This paper provides a methodology for the preparation of PLA with balanced toughness and stiffness.