Melt rheology of polylactide/poly(butylene adipate-co-terephthalate) blends

Polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) were melt blended using a twin-screw extruder. The phase morphology of PLA/PBAT blends was observed by scanning electronic microscopy (SEM). The linear and non-linear shear rheological behaviors of PLA/PBAT melts were investigated by an advanced rheology expended system (ARES). The results show that PLA/PBAT blend is a kind of immiscible, two-phase system where PBAT disperses evenly in PLA matrix. Linear viscoelastic limits of PLA/PBAT melts are smaller than that of neat PLA melt. At lower frequencies, storage moduli (G′) of PLA/PBAT melts increase with PBAT content. PBAT content has no significant effect on loss moduli (G′′) of PLA/PBAT melts, but the relaxation moduli of the melts increase with the introduction of PBAT. At the same time, the incorporation of PBAT results in a gradual increase of the melt viscosity and a decrease of flow activation energy. Besides PBAT causes a decrease of flow index n, which is in conformity with the more serious shear-thinning tendency of PLA/PBAT melts.