Compósito híbrido constituído de partículas de granito e microfibras de eucalipto em matriz de polipropileno reciclado e pigmentado

Abstract

The development of sustainable composites materials, from recycled polymeric materials and waste from the wood industry and stone processing, allows reducing the volume of these by-products, minimizing impacts on health and the environment. Nowadays, polypropylene (PP) is the most recycled polymer in industry, while the furniture industry has increasingly used timber felled from sustainable forest plantations as a eucalypt. The powder tailing from the ornamental stone extraction and processing industry is commonly disposed of in the environment without previous treatment. Today, Brazil is one of the leading exporters of granite slabs worldwide which requires cutting, shaping, and finishing of ornamental and building stone blades. Thus, the technological option for the development of composite materials presents itself as a sustainable alternative for processing and manufacturing industries, enabling the development of new materials with special technical features. Composites made up of fibers and particles have been the focus of recent research in order to optimize the physical-mechanical properties of these materials. In this thesis, hybrid composites were prepared using untreated, alkalized and bleached eucalyptus microfibers with granite particles, respectively, as reinforcements in recycled polypropylene matrix (rPP). The thermoplastic matrix was characterized by differential scanning calorimetry (DSC), thermogravimetry (TGA), derivative thermogravimetry (DTG), Fourier transform infrared spectrometry (FTIR) and flow index (MFI). Eucalyptus microfibers were characterized by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). To characterized granite particles, SEM, EDS and X-ray diffraction (XRD) techniques were used. A single screw extruder and injection molding were used to manufacture the composites specimens. The mechanical characterization was performed through tensile, bending, Izod impact and Shore D hardness tests. Also, a statistical evaluation response by analysis of variance was made. The cross-sections of the samples submitted to mechanical tests were analyzed for morphology, microstructure and matrix-filler interface. Thermal, physicochemical, rheological, hygroscopic properties and the melting rate of the composites were also characterized. The experimental results showed an increase in the modulus of elasticity in traction and bending, stiffness and a reduction in toughness under impact with the incorporation of microfibers and granite powder in the matrix. Ductile-brittle fracture were observed, with ductile fracture present in tensile composites with eucalyptus microfibers and brittle fracture with the inclusion of fine granite particles. The effect of transcrystallization of polypropylene chains may have occurred on the surface of oxides of granite powder, probably nanometric. Delay in the polymer burning rate and lower water absorption of the composites were obtained with the addition of the inorganic fraction in the system. The results showed that powder granite particles can be incorporated into the polypropylene matrix associated with eucalyptus microfibers forming hybrid composites with potential application in structural engineering, such as transport and civil construction industries.