CNT-induced morphology and its effect on properties in PLA/PBAT-based nanocomposites

Melt mixed Poly(lactic acid) (PLA)/Poly(butylene adipate-co-terephthalate) (PBAT) 80/20 and 60/40 blends were modified with different CNT contents. Unfilled compositions were immiscible and combined good stiffness (Young's modulus > 2000 MPa), deformability (elongation at break > 150%) and, in the case of the 60/40 composition, notched impact strength higher than 100 J/m. The morphology of the unfilled 80/20 composition showed nano-sized, spherical PBAT particles finely dispersed within the PLA matrix, while the 60/40 composition showed an almost co-continuous morphology. In the case of the nanocomposites (NCs), the CNTs located in the minor PBAT phase because of their greater compatibility, producing larger, elongated PBAT domains more characteristic of co-continuous morphology. In addition, the CNTs created percolated networks and as a result, the NCs showed increased conductivity at CNT contents equal and higher than approximate to 1.5 wt%. Although Young's modulus did not increase significantly in the NCs and the yield strength decreased upon the addition of CNTs, the high deformability of the unfilled blends maintained up to 150% in all the compositions, and, in the case of the 60/40 blend, the impact strength increased up to 250 J/m, i.e. 20 times higher than that of pure PLA.