Unveiling the role of elongational flow: Toward enhanced ductility in biopolymer blends

In this work, the influence of the elongational flow on the microstructure and the ductility of a poly(lactic acid)/poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) blend was investigated. Anisotropic films were produced through cast extrusion and film blowing, and their morphology and mechanical properties were compared to those of an isotropic compression-molded sample. The results revealed that the application of the elongational flow is effective in inducing relevant modifications of the blend microstructure, passing from a droplet-matrix morphology for the isotropic sample to practically indistinguishable polymer phases in the anisotropic films. These processing-induced morphological alterations induced a brittle-to-ductile transition for both cast-extruded and blown films, which reached an elongation at break of 40 and 74 %, respectively.