Novel toughening mechanism for polylactic acid (PLA)/starch blends with layer-like microstructure via pressure-induced flow (PIF) processing

Polylactic acid (PLA) is an important bio-based polymer, however brittleness and high cost limits its wide application. Blending PLA with starch can greatly reduce cost however the blends become more brittle. In this paper, we report that layer-like microstructure along flow direction (FD) forms in PLA/starch blends via pressure-induced flow (PIF) processing. It can be found that impact and tensile strength for PLA/starch blends with the layer-like microstructure can be enhanced by 200% and 40% respectively. As indicated by the results of DMA and DSC, the confinement of molecular chain in amorphous phase of PLA and interphase between starch particles and PLA matrix for PIF samples significantly increases compared with non-PIF samples. The post-fracture surface of PIF samples was rougher, and the PLA sheets and deformed starch particles along FD can be clearly observed by SEM.

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► The PLA/starch blends after pressure-induced flow processing exhibits anisostropic and forms layered-like structure.
► PIF processing is a facile and green processing for the PLA/starch blends.
► Layered-like structure becomes more perfect with higher pressure.
► The impact and tensile strength increases by 200% and 40% respectively for PLA/starch blends with layered structure.