Desenvolvimento de compósitos de polipropileno com reforço híbrido de fibras curtas de carbono e grafeno para a indústria automobilística

Abstract

In this study, polymer composites based on polypropylene (PP) reinforced with graphene nanoparticles (GNP) and short carbon fibers (FCC) were developed, aiming to obtain materials with improved mechanical properties such as higher modulus of elasticity and tensile strength, in addition to high thermal stability. The composition of the composites was optimized through an experimental design using Minitab 19 software, aiming to identify the ideal combination of GNP and FCC contents. The composites were processed in a twin-screw extruder, under specific temperature and rotation conditions, to ensure homogeneous dispersion of the reinforcements in the polymer matrix. The characterization of the materials included mechanical tests (tensile, flexural), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results obtained demonstrated that the incorporation of GNP and FCC into PP promoted a significant increase in the elastic modulus and tensile strength of the composites, compared to the base polymer. These improvements in mechanical properties can be attributed to the efficient load transfer between the polymer matrix and the reinforcements, resulting from the high specific surface area of graphene and the stiffness of the carbon fibers. However, the incorporation of reinforcements into the polymer matrix also led to a reduction in the fracture toughness of the composites, indicating a correlation between stiffness and toughness. Thermogravimetric analysis revealed that the composites presented greater thermal stability compared to pure PP, indicating better resistance to thermal degradation. This improvement can be attributed to the thermal barrier provided by the graphene nanoparticles and carbon fibers. The micrograph obtained by SEM allowed visualization of the distribution of the reinforcements in the polymer matrix, evidencing the formation of a satisfactory interface between the phases, a crucial factor for obtaining superior mechanical properties. Thus, this study demonstrated the potential of PP composites reinforced with GNP and FCC for diverse industrial applications that require lightweight, rigid materials with high thermal stability. Among the samples analyzed, sample 7 (77.5% PP/20% FCC/2.5% GN) and sample 4 (75% PP/20% FCC/2.5% GN) demonstrated the best results. However, considering the cost-benefit ratio, sample 7, with a lower graphene concentration, is considered the best option.