Étude de l'évolution de morphologie sous écoulement contrôlé de nanocomposites à base de charges carbonées

Abstract

In this work, blends of two immiscible polymers presenting a co-continuous morphology, namely polypropylene (PP) and polystyrene (PS), were filled with graphene (GnP). The PP/PS/GnP composites were prepared by melt extrusion. They were then subjected to extensive characterization, including rheological, morphological, and electrical analyses. To obtain precise data on the electrical and rheological properties of these composites, we used a rheometer coupled to a dielectric-rheological device (DRD). To study the evolution of the properties of PP/PS/GnP composites under the influence of controlled flow, two types of tests were carried out: a time sweep (simulating thermal annealing) at a temperature of 200°C for one hour, and a steady shear test at shear rates of 0.05▯ and 1▯. These two tests were then preceded and followed by a small-amplitude oscillatory shear test to assess the impact of shearing and annealing on material morphology. The results reveal a clear reduction in electrical and rheological percolation thresholds for PS/PP/GnP composites compared with pure graphene-filled polymers (PS/GnP and PP/GnP). The incorporation of GnP also led to a drastic reduction in the domain size of the PP/PS/GnP co-continuous morphology, indicating morphology refinement. In addition, the electrical conductivity of the PS/PP/GnP composites increased by an order of magnitude during the first few minutes of annealing, and then stabilized, revealing the evolution towards the formation of a more robust graphene network during annealing. It was also demonstrated that GnP could stabilize the morphology of a cocontinuous blend, even under the application of high strain.

Date	24 Jan 2024
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Nicole R. Demarquette (Supervisor) & Éric David (Co-supervisor)