Rheology and Morphology of Polyester/ Thermoplastic Flour Blends

Two maize flours (standard and waxy grades) were plasticized in an internal mixer with a constant amount of water and two glycerol contents. The resulting thermoplastic flours (TPFs) were characterized in dynamic oscillatory shear and creep/recovery rheometry. They displayed two different behaviors: the viscoelastic behavior of a high-molecular-weight polymer for the first one and a gel-like behavior for the second one. The TPFs were then mixed with a copolyester [poly(butylene adipate-terephtalate)]. All of the blends contained the same volume fractions and were prepared with the same mixing conditions. The morphology and rheological behavior of each blend were characterized. Different morphologies, ranging from cocontinuous to nodular, were observed. In fixed mixing conditions, the blend morphology was shown to be governed by the rheological behavior of the starchy phase and the plasticizer content. The gel-like behavior of the second TPF seemed to prevent droplet coalescence; this led to a very fine dispersion. The rheological behavior of each blend appeared to be linked to both the morphology and the rheological behavior of the two phases. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40222.