Rheology of complex biobased quaternary blends: Poly(lactic acid) [poly(ethylene oxide)]/poly(ether-b-amide)/poly(amide 11)

Abstract

Linear and nonlinear viscoelastic approaches are used to study multiphase biobased blends of poly(lactic acid), poly(amide 11), poly(ether-b-amide) (PEBA), and poly(ethylene oxide) (PEO) in a wide range of compositions. The novelty of this work resides in (a) the study of hybrid quaternary blends with droplet-matrix as well as cocontinuous morphology, (b) the effect of the PEO and PEBA blend components on the rheological properties, and (c) the investigation of the nonlinear viscoelastic regime for complex hybrid blends. Correlations are established between blend morphology and rheological behavior. Among the different linear rheological approaches, i.e., elastic modulus, complex viscosity, yield stress, Cole–Cole plots, Han plots, and Mavridish–Shroff or Booij–Palmen plots, the latter is the most sensitive allowing extraction of a relaxation time from the plot. The results correlate reasonably well with the different morphologies of the blends. Both, linear and nonlinear methods lead to compatible results, distinguishing among blends with droplet-matrix, partially continuous dispersed phase and fully cocontinuous morphologies. Moreover, for the first time, the analysis of the nonlinear parameter, Q0, allows a qualitative comparison of the interfacial areas of blends with a dispersed phase-matrix morphology at different continuity levels and those with cocontinuous morphology.