Coalescence in PLA-PBAT blends under shear flow: Effects of blend preparation and PLA molecular weight

Nofar M., HEUZEY M. C., CARREAU P. J., Kamal M. R., RANDALL J.

JOURNAL OF RHEOLOGY, vol.60, no.4, pp.637-648, 2016 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 60 Issue: 4
  • Publication Date: 2016
  • Doi Number: 10.1122/1.4953446
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.637-648
  • Istanbul Technical University Affiliated: Yes


Blends containing 75 wt. % of an amorphous polylactide ( PLA) with two different molecular weights and 25 wt. % of a poly[( butylene adipate)-co-terephthalate] ( PBAT) were prepared using either a Brabender batch mixer or a twin-screw extruder. These compounds were selected because blending PLA with PBAT can overcome various drawbacks of PLA such as its brittleness and processability limitations. In this study, we investigated the effects of varying the molecular weight of the PLA matrix and of two different mixing processes on the blend morphology and, further, on droplet coalescence during shearing. The rheological properties of these blends were investigated and the interfacial properties were analyzed using the Palierne emulsion model. Droplet coalescence was investigated by applying shear flows of 0.05 and 0.20 s(-1) at a fixed strain of 60. Subsequently, small amplitude oscillatory shear tests were conducted to investigate changes in the viscoelastic properties. The morphology of the blends was also examined using scanning electron microscope ( SEM) micrographs. It was observed that the PBAT droplets were much smaller when twin-screw extrusion was used for the blend preparation. Shearing at 0.05 s(-1) induced significant droplet coalescence in all blends, but coalescence and changes in the viscoelastic properties were much more pronounced for the PLA-PBAT blend based on a lower molecular weight PLA. The viscoelastic responses were also somehow affected by the thermal degradation of the PLA matrix during the experiments. (C) 2016 The Society of Rheology.