Compósitos de polipropileno reforçados com nanopartículas de alumina e fibras curtas de carbono

Abstract

In this investigation, composite materials based on polypropylene (PP) loaded with alumina nanoparticles (Al2O3) and reinforced with short carbon fibers (CF) were developed, aiming to obtain lightweight materials with high rigidity, mechanical strength and thermal stability, which can be processed in equipment commonly used in the polymer and automotive industries. For this purpose, polypropylene was processed with alumina, at levels defined through the response surface methodology inserted in Minitab software, in order to evaluate the effect of the incorporation of alumina and polypropylene grafted with maleic anhydride (PP-g-MA) used as a compatibilizer in some samples. The composites that presented the best mechanical properties, in this case, PP/PP-g-MA/Al2O3 hybrid composites were used with matrix and prepared using alumina content of 6% w/w and variable carbon fiber contents, between 10% w/w and 15% w/w. The composites were processed in a twin screw extruder, using a temperature profile from the feeding zone to the dosing zone of 200/210/190/190/190/190/200/220/220/230°C and screw rotation of 500 rpm. The preparation of PP/Al2O3 composites involved the development of a concentrate in a single screw extruder and subsequent dilution in a twin screw extruder. The temperature profile adopted was 180/200/200/200/200°C and the rotation speed was 35 rpm. The properties of the materials obtained were evaluated through several characterization techniques such as: mechanical tests in traction, thermogravimetry (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results obtained demonstrate that the hybrid composites show a tendency to increase stiffness at the cost of a significant loss of toughness with the increase in fiber content. In these materials, an increase in tensile strength is also observed. An increase in the modulus of elasticity was observed both in the hybrid composites and in the PP/Al2O3 composites. This increase, however, was more pronounced in the hybrid composites. The PP/Al2O3 and hybrid composites also showed an increase in tensile strength. The hybrid composites showed higher thermal stability than the PP/Al2O3 composites and lower melting and crystallization enthalpies. The micrographs obtained showed good interfacial adhesion between the alumina particles and the polymer, when the compatibilizer was used. In general, in this work, materials based on polypropylene were obtained with rigidity and mechanical strength superior to those presented by polypropylene.