Impact of graphene concentration on crystallinity, rheological, and mechanical characteristics of a polypropylene copolymer

This study examines the impact of graphene nanoplatelets (GNP) on the properties of a CP442XP polypropylene (PP) copolymer. GNP was added in concentrations of 0.5%, 1%, and 2% by mass, alongside a 2% flake graphite blend. An objective of this work is to prepare the material using industrial equipment. Therefore, PP/GNP composite production involved twin-screw extrusion for mixing and injection molding to produce samples. Characterization as crystallinity by Differential Scanning Calorimetry (DSC), mechanical and thermal properties, morphology and rheological properties are investigated. Results indicate that 0.5% and 1% GNP enhance PP crystallinity, due to GNP particles acting as nucleation sites. However, 2% GNP reduced crystallinity, possibly due to poor dispersion. Besides that, the PP copolymer usually starts with a better impact strength, compared to a PP homopolymer. Mechanical analysis showed that 1% GNP in PP improves elasticity but reduces impact strength at higher concentrations, indicating a stiffer polymer matrix. Rheological analysis revealed that 1% GNP in PP lowers viscosity at shear rates of 10 to 100 1/s, suggesting less energy required for polymer processing. In summary, low GNP concentrations beneficially modify the mechanical properties and rheology of PP copolymers. Some properties are possible to achieve even using standard industrial equipment.