Soutenance de thèse : Hu QIAO

Environmentally Friendly Polylactide-Based Multiphase Systems: Processing-Structure-Property Relationship

Doctorant : Hu QIAO

Laboratoire INSA : IMP

École doctorale : ED34 : Matériaux de Lyon

The preparation of environmentally friendly multiphase materials by continuous melt mixing modification is an overall efficient and practical method to address the issues of polylactide (PLA). Investigating the effects of composition/structure on macroscopic properties/performance is essential in complex multi-component systems. This doctoral thesis focuses on an original strategy to manufacture the high performance PLA-based coextrusion multi-micro/nanolayers, where the coextruded constituents regarding PLA/PHBV blends and PLA/CNC biocomposites are studied separately. Starting with a fundamental study of PLA/PHBV biphasic blends over the entire range of compositions obtained by melt blending. The composition dependence of thermal stabilities, morphology, miscibility, rheology and dielectric properties of the blends are comprehensively investigated. Secondly, the ternary PLA-based nanocomposites incorporating PEG-coated CNC were prepared by a continuous extrusion method to enhance the dispersion of CNC. The effects of PEG/CNC mass ratio on CNC dispersion of and physical properties of PLA were highlighted. The dispersion of CNC, crystallization rate, crystallinity, elongation at break, as well as the oxygen transmission rate of the system were gradually improved with increasing the ratio, and their best values were obtained at a ratio of 5/1. Based on the above studies, we were finally able to fabricate the forced-assembly coextrusion multi-micro/nanolayer containing neat PHBV, and PLA/CNC-based composite manufactured by an industrial liquid feeding method. The increasingly suppressed crystallization and oriented lamellar/crystalline structure with increasing number of layers were revealed, accordingly resulting in a 64% reduction in OTR for the nanolayer. By establishing the processing-structure-property relationship, this dissertation provided a true understanding of how to enhance and/or induce the target properties/performance in the complex multiphase systems. The findings obtained in this work are dedicated to the development of innovative fabrication of high performance PLA-based eco-friendly materials for their advanced and broader applications.