Dynamic rheological behavior and morphology of polylactide/poly(butylenes adipate-co-terephthalate) blends with various composition ratios

Polylactide (PLA)/poly(butylenes adipate-co-terephthalate) (PBAT) blends with various composition ratios were prepared via melt compounding using a twin-screw extruder. The dynamic rheological behavior and morphology of the blends were studied using a parallel-plate rheometer and a scanning electron microscope (SEM), respectively. The results showed that the shear-thinning tendency of blends became stronger with increasing PBAT content. Moreover, at low frequencies, the complex viscosity, storage modulus and loss modulus for blends with 20 wt% PBAT content were higher than that of other samples when PBAT content was less than 50 wt%. Based on SEM images, three distinct morphologies-spherical droplet, elongated fibrous structure, and co-continuous structure-were observed as the content of PBAT increased from 5 to 50 wt%. When the PBAT content reached 70 wt% and above, the morphology became droplets again, with PLA droplets dispersing within the PBAT matrix. In addition, the PLA droplets in the PBAT/PLA (80/20 w/w) blend were smaller and more regular than the PBAT droplets in the PLA/PBAT (80/20 w/w) blend, despite the same composition ratio.