Influência do processamento e da alumina sintetizada por combustão nas propriedade do prolipropileno.

Abstract

This work was to evaluate the effect of the content of alumina filler, synthesized in the laboratory by combustion reaction, and of the processing on the properties of Polypropylene (PP). The synthesized alumina was characterized by X-Ray Diffraction (XRD), Energy Dispersive X-Ray Spectroscopy (EDX), granulometric distribution and Brunauer, Emmett and Teller (BET) technique. Furthermore the PP/Alumina composites, where prepared by extrusion followed by injection molding and characterized by XRD, Differential Scanning Calorimetry (DSC), mechanical properties (tensile and impact strength), flammability test, Scanning Electron Microscopy (SEM) and rheological properties. The results showed that the synthesized alumina has crystalline structure of the corundum type, 99.047% of Al2O3, agglomerates with an average diameter of 25,23 μm, particles with a size of 382 nm and it is microporous. With regard to composites, that alumina decreased the degree of crystallinity of PP and did not affect the thermal transitions (Tm and Tc). Mechanical properties results showed an increase in the elastic modulus and a decrease in the impact strength associated to a low degree of dispersion and high particles average size, confirmed by SEM. In the flammability test, the alumina delayed the burning time of the composites. It was also observed by the above mentioned techniques that the extrusion and injection processes made the PP more crystalline, more flammable and did not affect the mechanical properties, with exception of the elongation at break. In the rheological analysis, PP and the composites presented a shear thinning behavior, and the extrusion process and an increase in the alumina content led to a decrease in the apparent and complex viscosities, suggesting the occurrence of degradation of the PP matrix. The storage modulus of the composites increased with the increase in the alumina content, corroborating the results obtained by the mechanical properties.