Effects of Nano- and Micro-sized Calcium Carbonate on the Thermal and Mechanical Properties of Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) with Bi-continuous Phases.

The composites of poly(lactic acid)/poly(butylene adipate-co-terephthalate)/calcium carbonate (PLA/PBAT/CaCO₃) with nano-sized, micro-sized calcium carbonate particles, and both were prepared by using a twin-screw extruder. The effect of the CaCO₃ particles on the structure and properties of the composites were investigated comparatively by using DSC, SEM, XRD, FTIR, and TGA technologies and tensile testing. The interaction between nano-sized CaCO₃ particles and the PLA/PBAT matrix in PLA/PBAT/CaCO₃ composites retarded PLA crystallization, while 5 portions of micro-sized CaCO₃ particles were beneficial to PLA crystallization, and 10 portions of micro-sized CaCO₃ particles were unfavorable to PLA crystallization, which is attributed to the role of nucleation and cross-linking in blocking the movement of PLA molecular chains. The study of non-isothermal crystallization kinetics showed that the Jeziorny method indicated that the PLA phase crystallization dimension was slightly higher in this composite, and the Mo method showed that the PLA phase in this composite had a similar crystallization mechanism as that in the composite containing 5 parts of micro-sized CaCO₃ particles. Nano-sized, micro-sized CaCO₃ particles and both did not change the lattice parameters of PLA crystals in PLA/PBAT/CaCO₃ composites, but reduced the thermal stability of the composites. SEM micrographs showed that nano-sized CaCO₃ made PBAT dispersed in PLA in the form of grains, while micro-sized CaCO₃ made PBAT dispersed in PLA in the form of flakes. This study promoted the application of calcium carbonate in biodegradable plastics. [ABSTRACT FROM AUTHOR]