Résumé: This study examined the impact of incorporating graphene nanoplatelets (GnP) into high-density polyethylene (PE) to create nanocomposites, with and without a compatibiliser. We specifically focused on the impact of structural crystallinity on the mechanical properties of the nanocomposites. These nanocomposites exhibited a much higher Young's modulus compared with pure PE. Specifically, the Young’s modulus increased exponentially with the addition of a compatibiliser and linearly without it. One explanation for this exponential rise in Young's modulus is that the crystal's compacted polymer chain structure improved its stiffness, facilitating effective load transfer. Additionally, a poor distribution of GnP in the nanocomposites with a filler content of 0.5 and 1 wt.%, both with and without a compatibiliser, led to a decreased stress and strain at break. However, at higher filler contents, well-distributed GnP play a key role in enhancing stress and strain at break.

Résumé: The structural, rheological, thermal and mechanical properties of composites, constituted of a polyamide 12 filled with commercial graphene nanoplatelets and organically modified nanoclays, were investigated. Different graphene/clay ratios were used in order to better understand the role played by each kind of filler in the improvement of the end-use properties of prepared composites. With this aim in view, the dispersion state of fillers in ternary nanocomposites was evaluated in comparison with those of graphene PA and clay PA binary composites. Measured rheological and mechanical properties of ternary systems were discussed in comparison with those calculated as the sum of the contributions of graphene and clay in the PA matrix, underlining the combined roles of both fillers in the improvement of composite properties. On the other hand, structural and end-use properties of the 5 wt% graphene 5 wt% clay PA material were compared with those obtained in the past for the composite constituted with a high viscous polyethylene/maleic anhydride grafted polyethylene matrix filled with same commercial graphene nanoplatelets (5 wt%) and similar organically modified montmorillonite fillers (5 wt%). This comparison aimed at understanding the role played by the matrix in the dispersion states of both clay and graphene fillers, and consequently in the end-use properties of composites.

Résumé: Since the last decade, graphene nanoplatelets with their exceptional physical properties are used as fillers in thermoplastic blends. In this work, the influence of commercial graphene nanoplatelets on properties of a high density polyethylene, in solid and melt states, was investigated, in comparison with the one of organically modified montmorillonite fillers. The use of a compatibilizer, a maleic anhydride grafted polyethylene, led to a clay based nanocomposite, with some improved mechanical and rheological properties, but with disappointing mechanical properties at break. On the other hand, by reducing the viscosity during mixing, the added compatibilizer slightly lowered the degree of dispersion of high aspect ratio graphene particles, weakening the material. More interestingly, the nanocomposite constituted with both clay nanoplatelets and lamellar graphene particles exhibited better reinforcing characteristics, in melt and solid states. This result can be partially explained by the high viscosity of the clay based nanocomposite which helps in the separation of graphene particles during mixing.