Biopolymer Blends Based on Poly (lactic acid): Shear and Elongation Rheology/Structure/Blowing Process Relationships

International audienceThis study was dedicated to the blown film extrusion of poly(lactic acid),which mainly presents poor shear and elongation viscosities, and its blends. In order toenhance its melt strength, two main routes were selected (i) a structural modificationthrough chain extension and branching mechanisms by adding a reactive multifunctionalepoxide (named Joncryl) and (ii) blending with poly(butylene adipate-co-terephtalate),named PBAT in presence (or not) of Joncryl. The effects of the reactive agent on the shearand elongation rheology, morphological, and interfacial properties of the blends weresystematically investigated. A decrease of the interfacial tension has been also demonstratedaccording to the deformed drop retraction method (DDRM). Hence, the role of Joncryl as acompatibilizer was highlighted. Consequently, finer morphology of the dispersed phasewas obtained. Furthermore, the impact of the two modification routes on the blown filmextrusion ability of PLA has been studied. Based on the improved shear and elongationalrheological properties, a great enlargement of the blowing processing window of PLAmodified with Joncryl was demonstrated. Indeed, with the addition of Joncryl intoPLA–PBAT blends, a reduction of the instability defects has been detected. Finally,the induced crystalline structure and the thermo-mechanical properties of blown films wereshown to be improved