Biaxial Orientation of PLA/PBAT/Thermoplastic Cereal Flour Sheets: Structure-Processing-Property Relationships

This paper investigates the biaxial stretchability of polylactic acid (PLA)/poly (butylene adipate co-terephthalate) (PBAT)/thermoplastic cereal flour (TCF) ternary blends with a PLA/PBAT ratio close to 60/40 and a constant TCF content. A twin-screw extrusion process was used to gelatinize the starch and devolatilize the water in order to obtain a water-free TCF, which was then blended into a compatibilized or non-compatibilized PLA/PBAT matrix, introduced in the molten state. These blends were subsequently cast into sheets and biaxially drawn using a biaxial laboratory stretcher. The prepared ternary blends were found to present a typical ductile behavior. Scanning electron micrography highlighted dispersion and adhesion properties in the PLA/PBAT/TCF blends, where two different phases were observed. Moreover, the addition of the thermoplastic cereal flour did not significantly affect the biaxial stretchability of the PLA/PBAT blends but was found to lower the maximum stress before breaking. The modification of the interfacial tension between PLA and PBAT with the compatibilizer Joncryl before mixing with TCF had no effect on the durability of the PLA/PBAT/TCF sheet. Still, it slightly increased the maximum of nominal stress before failure.