Elaboration et caractérisation de matériaux multiphasiques à base de polylactide (PLA) et de polyhydroxyalcanoates (PHA)

Abstract : The objective of this PhD work is to provide a systematic and detailed study of the properties of PLA and PHA blends prepared by melt mixing. In particular, the rheological behaviour, the miscibility, the morphology, the mechanical properties and the influence of physical aging on the tensile properties of PLA/PHBV blends prepared in an internal mixer and by twin screw extrusion over the entire composition range were studied.The sensibility of PHBV to thermal degradation was highlighted, as well as the importance of the interfaces between PLA and PHBV on the rheological behaviour at low frequencies. The differential scanning calorimetry showed that the two polymers are immiscible. Two different types of morphologies (nodular and co-continuous) depending on blend composition have been observed by scanning electron microscopy and optical microscopy in reflection. The impact resistance of the PLA/PHBV blends with or without impact modifier was studied and the tensile properties of different blends containing PLA blended with PHBV, Lotader GMA, or PBAT were characterised. The addition of a small amount of dispersed phase in the initially brittle PLA matrix increases considerably its elongation at break. However, the obtained ductile properties decrease as the time between preparation of samples and their mechanical testing increases. A study of the influence of physical aging on the properties of PLA based blends was conducted and a qualitative model was proposed.
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Thibaut Gérard. Elaboration et caractérisation de matériaux multiphasiques à base de polylactide (PLA) et de polyhydroxyalcanoates (PHA). Autre. Ecole Nationale Supérieure des Mines de Paris, 2013. Français. ⟨NNT : 2013ENMP0021⟩. ⟨pastel-00874861⟩

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