Blends PLA/PHA

     The work is focused on the preparation and characterization of blends of Polyhydroxyalkanoates (PHA) and Polylactide (PLA). Due to the rarefaction of fossil resources and the awareness of the necessity of reducing our footprint on the planet, there is a growing interest for materials made from renewable resources. Among these, the biomass-based polyesters such as PHA and PLA have an important place, particularly for the research of new applications and/or for the replacement of petrochemical-based polymers.

     The main goals of the work are the formulation and processing of blends of PHA and PLA, the fundamental understanding of the interaction mechanisms between the components, the prediction of the morphology of the final materials and the assessment of the mechanical properties of the composites. Rheology, rheo-optics and optical and electron microscopy will be the main tools used in this study.

      First, the properties of pure components and then of their blends in various proportions (prepared in an internal batch mixer) will be studied. The miscibility of the two components will be characterized by differential scanning calorimetry (DSC). The morphologies of the different blends will be observed and correlated with their rheological behaviour. The influence of the morphology on the mechanical properties of the materials will also be described.
      In a second part, a study of the compatibilization of the blends of PHA and PLA will be performed. The effect of adding a compatibilizer on the different properties and on the morphology of the blends will be evaluated.

PLA/PHA blend 50/50
Observation of a polished sample of a blend containing 50% of PLA and 50% of PHA (without compatibilizer) with a microscope in reflection. The bright phase corresponds to the PHA and the dark phase corresponds to the PLA.

PLA/PHA blend 70/30
Image of a fractured surface of a blend containing 70% of PLA and 30% of PHA, obtained with a Scanning Electron Microscope. One can observe nodules of PHA in the PLA matrix.
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