Balancing performance of epoxidized soybean oil (ESO)/poly(lactic acid) composites: Synergistic effects of carbon nanotubes and tannic acid-induced crosslinking of ESO

Highly tough and biobased epoxidized soybean oil (ESO)/poly(lactic acid) (PLA) blends were formulated through in-situ formation of tannic acid-crosslinked ESO (TA-c-ESO) oligomer as a dispersed phase with PLA matrix by dynamic vulcanization technique. To repair the sacrificial strength of the blends and endow the composites with electrical conductivity, different concentrations of CNTs, i.e., 0.5 to 10 wt%, were incorporated into the TA-c-ESO/PLA blends to prepare CNT/TA-c-ESO/PLA nanocomposites. The added CNTs selectively localized within the PLA matrix, leading to a reduced size of TA-c-ESO phase. The synergistic effects of CNTs and TA-c-ESO phase on the tensile properties, thermal stabilities, crystallization characteristics, and electrical properties of the nanocomposites were fully investigated along with the understanding of CNT reinforcing and TA-c-ESO toughening mechanism. The formation of TA-c-ESO phase significantly increased the fracture elongation and tensile toughness of the blends, while the incorporation of CNTs resulted in increased tensile strength, tensile modulus, and storage modulus of the nanocomposites; the combination of this two effects contributed to the obtained ternary composites with balanced mechanical properties and favorable electrical conductivity.