Development of nano-reinforced polypropylene with enhanced properties
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Date
2026-03-05
Authors
Ραγιά, Γεωργία
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Abstract
The present thesis investigates the development and characterization of nano-reinforced recycled polypropylene (rPP) systems aiming to improve their mechanical performance. Although recycled polypropylene offers significant environmental and economic advantages, its mechanical properties exhibit significant degradation compared to virgin material. The primary objective of this work is therefore to enhance the stiffness and strength of rPP through the incorporation of graphene related materials, thereby increasing its percentage in vPP/rPP blends without compromising overall performance. A series of reinforced rPP-based nanocomposites were fabricated using graphene nanoplatelets (GNPs) of different geometrical characteristics (C750, H5 and H15) at various weight fractions 0.8, 2.5 and 5%wt. The manufacturing process involved cryogenic pulverization of thermoplastic pellets, melt compounding through extrusion for filament production, pelletizing, and final specimen fabrication via compression molding. Processing parameters were carefully controlled to ensure dispersion stability and reproducibility. Mechanical characterization was conducted through tensile testing, while thermal behavior was evaluated using Differential Scanning Calorimetry (DSC). Scanning Electron Microscopy (SEM) was employed to examine fracture surface and nanoparticle dispersion. The results demonstrate that recycled polypropylene exhibits a marginal reduction in stiffness but a significant decrease in tensile strength compared to virgin PP. The incorporation of graphene nanoplatelets significantly improves mechanical performance at specific concentrations. In greater detail, 0.8 and 2.5%wt. C750 provided enhancement in tensile strength, while stiffness increased progressively with increasing filler content within the polymer matrix. Among the investigated formulations, the Blend 70 modified rPP demonstrated the optimal performance maintaining a balance between stiffness and strength. Overall, the study confirms that controlled nanoparticle reinforcement constitutes an effective strategy for restoring and upgrading the mechanical performance of recycled polypropylene, enabling increased recycled content in structural polymer applications while maintaining satisfactory thermal and mechanical behavior.
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Keywords
Recycled polypropylene, Graphene nanoplatelets, Polymer nanocomposites, Mechanical reinforcement, Structure-property relationships