Synthesis, characterization, thermal and mechanical behavior of polypropylene hybrid composites embedded with CaCO₃ and graphene nano-platelets (GNPs) for structural applications

In this study, ultra-fine graphene nanoplatelets (GNPs) were employed as nanofillers to reinforce a polypropylene (PP) matrix. This was done in conjunction with a polypropylene grafted maleic anhydride (PP-MAH) compatibilizer and calcium carbonate (CaCO₃), with the aim of improving the mechanical and thermal properties of the resulting hybrid composites. Formulations for the hybrid composites were fabricated by compounding the PP matrix with varying weight percentages of GNPs (x = 0.5, 1.0, 1.5, 2.0), 2 wt.% CaCO₃, and 5 wt.% PP-MAH using a twin-screw extruder followed by injection molding. This research thoroughly investigates the mechanical and thermal characteristics. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) results confirm the successful development of hybrid composites. The thermal stability, crystallization temperature, melting temperature, tensile strength, flexural strength, and impact resistance were evaluated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), universal testing machine, and low-velocity impact tester, respectively. The results indicated a significant improvement in the tensile strength of the PP matrix with the addition of GNPs, with the highest enhancement observed at 1.5 wt.% GNP loading, where the tensile strength reached a maximum of 40.54 MPa. This improvement was attributed to the proper interconnection, bonding, and compounding of PP with GNPs, thus leading to an increase in the load transfer efficiency.